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ENGINEER COURSE 
 
 IN 
 
 TOPOGRAPHY 
 
 THE GENERAL SERVICE SCHOOLS 
 
 FORT LEAVENWORTH, KANSAS 
 
 1921-22 
 
 THE GENERAL SERVICE SCHOOLS PRESS 
 
 Fort Leavenworth, Kansas 
 
 6-20-22— 2M 
 
 1922 
 

 LI3RARY OF CONGRESS 
 
 RECEIVES 
 
 . OCT 9 1923 
 
 DOCUMENTS D1V1&ION 
 
PREFACE 
 
 This pamphlet has been prepared by the Engineer Sub- 
 section with the object of presenting in convenient form 
 the data necessary for the course in Topography at The 
 General Service Schools. The material has been obtained 
 from other army publications and from lectures and con- 
 ferences prepared by the engineer instructors during the 
 courses of 1919-1920-1921. 
 
 The course in Topography at The 'General Service 
 Schools is not a course of instruction in methods of topo- 
 graphy, but is a course of application of topographical 
 methods to the military art. This pamphlet is printed in 
 limited numbers for use as a text at The General Service 
 Schools. 
 
 H. A. Drum, 
 
 Assistant Commandant. 
 Approved : 
 
 H. E. Ely, 
 
 Commandant. 
 
TABLE OF CONTENTS 
 
 Chapter I— INTRODUCTION: equipment needed; measured course 
 for determining length of stride; model scale for alidade. 
 
 Chapter II — MAP READING: title; co-ordinates; scales; compass; 
 contours; shelter from artillery fire; orientation; aeroplane pho- 
 tographs; practical exercises. 
 
 Chapter III— USE OF INSTRUMENTS: methods; standard sketch- 
 ing equipment; azimuths; distances; elevations; slope equivalent; 
 details of making a sketch; indoor exercises in use of instruments; 
 practical exercises. 
 
 Chapter IV— APPLIED MILITARY SKETCHING: road sketch, 
 railroad, stream, woods, camp, outpost, place, landscape; combined 
 sketching; rates of sketching; data; practical exercises. 
 
 Chapter V— AIRPLANE MAPPING: present state of development; 
 statement of uses of airplane photographs; advantages and limi- 
 tations; use in reconnaissance and mapping large areas; battle 
 maps; general maps; interpretation and restitution; interpreta- 
 tion of enemy works. 
 
 Chapter VI— MAPPING LARGE AREAS: United States mapping or- 
 ganizations; present status as to maps; grid system in United 
 States; system of mapping large areas; system for United States 
 Army; organization for 10,000 square miles per month; assistance 
 by aeroplanes. 
 
 Chapter VII— MAP REPRODUCTION: Classification of methods; de- 
 scription, blue print, brown print, neo-cyclostyle, Ellam duplicator, 
 hectograph, Dorel process, lithography; reproduction outfit with 
 division, corps, army, general headquarters; mobile plant; A. E. 
 F. results, 1st Army, 2d Army, general headquarters; assistance 
 by staff officers; issue schedule of maps for A. E. F. infantry divi- 
 sion; summary of work done by base plant at general headquar- 
 ters. 
 
CHAPTER I 
 
 Introduction 
 
 1. The following equipment will be needed for the 
 work in topography : 
 
 Colored and black pencils Buy from Book Dept. 
 
 Erasers 
 
 Leavenworth 3" sheet 
 
 Gettysburg 3" sheet 
 
 Alidade " " 
 
 Pace tally " " 
 
 Celluloid sheets " " 
 
 Hand level or clinometer — Issued from instrument room on memoran- 
 dum receipt. 
 
 Sketching case — Issued from instrument room on memorandum re- 
 ceipt. 
 
 W. D. Pamphlet of Conventional Signs — To be drawn from Library. 
 
 G. S. S. Pamphlet on Conventional Signs — To be drawn from Library. 
 
 Paper protractor Issued from instrument room. 
 
 Co-ordinate scale Issued from instrument room. 
 
 Three-inch scale of meters, yards and miles__ Issued from instrument 
 room. 
 
 Celluloid paper should always be available for work in 
 field in case of rain. This work proceeds in all kinds of 
 weather, and celluloid paper is not injured by the rain. 
 
 2. The following equipment should always be brought 
 to lectures and conferences in topography : 
 
 Colored and black pencils. 
 
 Erasers. 
 
 Leavenworth sheet 3" map. 
 
 Gettysburg sheet 3" map. 
 
 Alidade. 
 
 Sketching board. 
 
 Pamphlets on Conventional Signs. 
 
 This pamphlet. 
 
 Protractor. 
 
 Co-ordinate scale. 
 
 Three-inch scale of meters, yards and miles. 
 
 It is advisable to form the habit of bringing the tripod 
 with the sketching case, as otherwise it may be forgotten 
 later when there is field work. 
 
 l 
 
2 TOPOGRAPHY 
 
 3. The following distances have been measured along 
 Grant Avenue for use in determining length of stride : 
 
 Beginning on the west walk of Grant Avenue on a line 
 with the south side of the converter station (small building 
 south of Post Exchange), thence south to southwest wing 
 of arch bridge over Corral Creek. Distance from begin- 
 ning, 6,009 feet. 
 
 Thence south to southwest corner of Grant and Metro- 
 politan Avenue (curb at former saloon) . Distance from be- 
 ginning 8,750 feet. 
 
 This entire course should be paced down and back by 
 members of the class to determine the length of stride to 
 be used in the sketching work. 
 
 It is necessary that this pacing be done so that the 
 length of stride is known before the beginning of field work. 
 
 After the length of stride has been determined, it will 
 be necessary to obtain from the instrument room an alidade 
 and a ruled scale corresponding to the length of stride. This 
 ruled scale will be pasted on the alidade. 
 
 4. For rapid work the differences of elevation for one 
 degree of slope for the distances given should be shown on 
 each side of the alidade. To obtain the total difference of 
 elevation with any degree of slope for a fixed distance, mul- 
 tiply the number of degrees by the difference of slope for 
 1 degree marked on the same line as the distance. 
 
 5. The three drawings herewith show the usual scales 
 on the three sides of the alidade. 
 
CHAPTER II 
 
 Map Reading 
 
 1. Each complete map, in addition to the map proper, 
 should show all the information necessary for map reading. 
 On a finished map this generally consists of the following : 
 
 (1) The title, consisting of : 
 
 (a) Name of organization under whose auspices it is made, 
 
 as Corps of Engineers, U. S. Army; 8th Corps Area; 
 1st Division; etc. 
 
 (b) A statement showing what the map represents, i.e., its 
 
 'particular feature or purpose, if any, as position sketch. 
 
 (c) The locality. (This and the preceding item may be in- 
 
 terchanged.) 
 
 (d) Its sources, as surveyed by, etc.; compiled from, etc.; 
 
 reduced from, etc. 
 
 (e) Under whose direction, if any. 
 
 (f) By whom. 
 
 (g) The date. 
 
 (h) Linear scale, generally in inches to the mile. 
 
 (i) Representative fraction. 
 
 (j) Graphic scale, generally in miles or thousands of yards 
 
 and fractional parts thereof, 
 (k) Contour interval. 
 (1) Scale of slope equivalents (frequently omitted). 
 
 (2) Notes showing: 
 
 (a) Reference or datum plane for elevations. 
 
 (b) Miscellaneous. 
 
 (3) Arrows showing true and magnetic azimuth, and 
 magnetic declination. 
 
 (4) Legend, if necessary. 
 
 (5) Latitude and longitude of projection lines. 
 
 (6) A key map showing other sheets, if map is one of 
 a series of sheets; or references in margins to adjacent 
 sheets of such a series. 
 
 Plate II shows a specimen title suitable for military 
 sketching. The title should, when practicable, be placed in 
 the lower right hand corner. 
 
MAP READING 5 
 
 1ST DIVISION 
 Position Sketch 
 
 Of Area 
 northwest of 
 
 Fort 5 am Houston, Texas 
 Showing Sector of '2d Brigade 
 by 
 
 Capf. A 1st Inf 
 
 February 21,1920 
 
 Scale: 6=1 mile R.Fi:i0-S6O 
 
 lOO 50 O lOO 200 SOO AOO 500 Yards 
 
 i.ii 1 1 ■ 1 1 1 r i _i i i i 
 
 V. I.-IOFr: 
 1 L! I ?! I 3' ,f,5-,6-,7-|OX 
 
 Note :- Elevations are above mean see level, 
 
 based on (J 3 Geological Survey data . 
 
 Plate II 
 
 2. The following suggestions will be of assistance in 
 map reading: 
 
 (a) Note the title, purpose, kind (sketch, survey, etc.), 
 authorship, and date of the map, with a view to estimating 
 its probable accuracy and usefulness for your particular 
 purpose. 
 
 (b) Note the meridian on the map and associate it 
 with the local meridian. 
 
 Note the declination of the compass, and the relations 
 between the true meridian and the grid lines if any. 
 
 (c) Note the scale of the map (see par. 12). If only 
 the R. F. is given, the number of inches to the mile may be 
 calculated by dividing 63,360 by the denominator of the 
 R. F. ; thus, if the R. F. is 1 : 80,000, then the scale in inches 
 to the mile is 63,360 :80,000, or 0.792 inches to the mile. 
 
 If there is no scale, look for some other indication of 
 distance. It may possibly be found in local names, as Three 
 Mile Creek, Two Mile House, etc.; in roads uniformly 
 spaced; in city blocks, which are usually about 100 yards 
 on the shorter side; railroad stations or sidings, the dis- 
 tances apart of which may be taken from time tables; in 
 the spacing of co-ordinate grid lines; in the spacing of 
 
6 TOPOGRAPHY 
 
 parallels of latitude (assume roughly 69 miles to each de- 
 gree, or 1.15 miles to each minute of latitude). 
 
 (d) If the map is contoured, note the contour intervals 
 and the scale of slope equivalents. If the contours are not 
 numbered, decide which are the high and which the low 
 ones. Closed contours are much more likely to be elevations 
 than depressions, especially if several are concentric. If the 
 contour interval is not given, it will be difficult to get any 
 clue to it unless isolated elevations appear on the map. If 
 the ground is accessible, the contour interval may be de- 
 termined by actual measurement of gradient. 
 
 (e) Note all topographical and cultural signs and asso- 
 ciate them in mind with the advantages or disadvantages 
 for military operation. Note the legend, if any. 
 
 (f ) Note the system of co-ordinate grids if any — the 
 spacing of the grid lines, the co-ordinate numbers, and 
 whether meters or yards are used. If the map is not 
 gridded, but is provided with meridians and parallels of 
 latitude, points may still be definitely located by stating 
 their positions with reference to these meridian and latitude 
 lines. 
 
 3. The study of a map is much facilitated by the use 
 of a relief map, or of photographs made from relief maps. 
 Relief maps also furnish a quick and easy (but somewhat 
 approximate) means of solving visibility problems, by the 
 use of a minute electric lamp. The lighted and shaded 
 areas show at once what terrain is visible from the point 
 at which the lamp is located. The best way to study a map 
 is by work with the map, on the ground. 
 
 4. Co-ordinates : — The system of co-ordinates adopted 
 at these schools is based on squares 1,000 yards to a side. 
 There are two groups of maps in general use, viz., the 
 Leavenworth Group and the Gettysburg Group. In the 
 Leavenworth Group, the lines 350 and 750 run through 
 the school tower. In the Gettysburg Group, the lines 350 
 and 750 run through the Gettysburg Central Square. The 
 origin of these co-ordinates is not defined, but it is taken 
 somewhere to the south and west of the mapped area so 
 that all co-ordinates will be positive in sign. The French 
 
MAP READING 7 
 
 before the war used Treves, Germany, as an origin, but in 
 order to avoid negative readings, changed to an indefinite 
 point 500 kilometers to the west and 300 kilometers to the 
 south. 
 
 5. All maps used for problems in these schools are di- 
 vided into squares, one thousand yards on a side on the 3- 
 inch maps and five thousand yards on a side on the 1-inch 
 maps. Lines creating this division are numbered succes- 
 sively from left to right and from bottom to top. These 
 lines form the basis for the system of co-ordinates. 
 
 Briefly stated, the system of co-ordinates is used to 
 find the location of a point by co-ordinates expressed in 
 thousands of yards, dropping off the figures not necessary 
 for accuracy, and then writing the figures beside each other, 
 properly pointed off, X co-ordinate first, the two co-ordi- 
 nates being separated by a .dash. A number of pairs of 
 co-ordinates written one after another would be set apart 
 by commas between the pairs. 
 
 The following example will illustrate the above: 
 The co-ordinates of a certain point to three decimal 
 places are: 
 
 X = 197.783 
 
 Y = 262.724 
 
 For ordinary purposes, locations to closer than the 
 nearest 100 yards (tenth of a thousand yards) are unneces- 
 sary. Consequently for ordinary purposes, the co-ordinates 
 of the point are expressed thus : 
 
 X= 197.8 
 
 Y = 262.7 
 
 The methods of writing the above point as required at 
 this school are 197.8—262.7 for 1", 2", 3", 4", 6" map. 
 
 The 12" map is supposed to represent the ground itself, 
 thereby giving reality to indoor problems requiring the use 
 of the terrain. It, therefore, has no co-ordinate grid 
 printed on it, as the ground has no co-ordinates. 
 
 6. In work requiring their constant use co-ordinates 
 are frequently abbreviated, when there can be no confusion 
 
% TOPOGRAPHY 
 
 as to general location, by omitting the tens and hundreds. 
 Thus, point (197.8—262.7) may be written point 78.27. 
 This method of abbreviation is in general use by the Field 
 Artillery. In all work at these schools co-ordinates are re- 
 quired to be written out in full. 
 
 7. In designating a line of co-ordinates, the co-ordinates 
 of sal; en t points in the line should be written one after 
 another, separated by commas, thus, line 358.7 — 761.2, 
 358.9—761.6, 359.2—761.9, 359.6—762.4, 360.4—762.9. A 
 square may be designated by the word "square" followed by 
 the co-ordinates of its southwest corner with the decimals 
 omitted, thus: "square 342 — 7-U." 
 
 8. Conventional Signs: — For the purposes of this 
 course, conventional signs will be used as indicated in the 
 War Department pamphlet Conventional Signs, United 
 States Army Maps. This is the only official pamphlet on 
 the subject. As it does not give all the signs which will be 
 needed for this course, the pamphlet of special signs issued 
 here will be used until such time as another War Department 
 publication designates conventional signs to cover the school 
 requirements. 
 
 9. In military mapping, and particularly in field 
 sketching, the exclusive use of conventional signs is fre- 
 quently impracticable, and a written designation or descrip- 
 tion by words is often more intelligible and more quickly 
 recorded. These verbal designations or descriptions are 
 often cause of much confusion due to their indefinite char- 
 acter; where conventional signs are prescribed they should 
 be used. 
 
 10. A method of expediting sketching is seen on many 
 maps, viz., to surround an area with a narrow border of the 
 proper sign and leave the middle blank. The pamphlet of 
 conventional signs shows special signs which are often used 
 for rapid sketching work. 
 
 11. Scales: — All maps are drawn to scale; that is to 
 say, one unit of length on the map always represents a cer- 
 tain number of the same units on the ground. This scale 
 may be represented on the map in one or more of three 
 ways: 
 
MAP READING 9 
 
 (a) By words, as 3 inches = 1 mile. This system is followed 
 in the United States and in practically all parts of Great Britain. 
 
 (b) By a ratio shown as the representative fraction (ab- 
 breviated R. F.), which gives the ratio of a unit of length on the 
 map to a similar unit on the ground. For example, the R. F. of 
 a l"-to-the-mile map is 1:63,360, since 1" on the map equals 1 mile 
 on the ground, or 63,360 inches. The R. F. is the only method 
 of giving the scale which will permit it to be understood by all 
 peoples, regardless of their unit of length. 
 
 (c) By a graphical scale, usually given on American and 
 English maps in miles or thousands of yards and fractions thereof. 
 Other nations use kilometers and fractional parts. An impor- 
 tant advantage of a graphical scale is that in case the map has 
 been reduced or enlarged from another map the scale is still true, 
 which is not the case for the other methods of representing the 
 scale. 
 
 12. Scales of Standard Maps: — The map scales 
 adopted as standard for use by the military forces of the 
 United States are as follows: 
 
 1:20,000 (approximately 3 inches=:l mile), fire control map, 
 or training map, for detailed trenches, enemy organization, artil- 
 lery objectives. Limited areas only will be covered on this scale. 
 
 1:62,500 (approximately 1 inch = l mile, tactical map, for 
 general use in open warfare. 
 
 1:250,000 (approximately 1 inch = 4 miles), strategic map, 
 for general study of theater of operations, supply system. 
 
 1:500,000 (approximately 1 inch = 8 miles), general map. 
 
 1:1,000,000 (approximately 1 inch = 16 miles), general map~ 
 
 1:2,500,000 (approximately 1 inch = 40 miles), geographical', 
 map of the U. S. 
 
 1:7,000,000 (approximately 1 inch = 110 miles), geographvcat 
 map of the U. S. 
 
 13. Scale of Special Maps: — The use of maps of 
 scales larger than 1 :20,000 for general military purposes 
 is to be discouraged, and such maps will not be used in 
 training unless specially authorized by the War Department. 
 When, however, for special purposes it becomes necessary 
 to show detail which cannot be shown on maps to 1 :20,000 
 scale, either 1 :10,000 or 1 :5,000 may be used. Except for 
 some engineering and construction purposes, maps of scale 
 larger than 1 :5,000 will rarely, if ever, be needed by the 
 military forces. In general, the various scales will be used 
 as follows : 
 
 (a) 1:62,500. — For route maps of extended marches, or of 
 marches of large commands using several roads. 
 
 (b) 1:20,000. — For ordinary route sketches and extended 
 marches, or of marches of large commands using several roads. 
 
 (c) 1:10,000. — For position and outpost sketches. 
 
 (d) 1:5000. — For maps used in the war game, discussion of, 
 operations at maneuvers, and in siege operations. 
 
10 TOPOGRAPHY 
 
 14. The scales heretofore most commonly used for mili- 
 tary sketching are as follows : 
 
 3" = 1 mile, for mounted sketching or route sketches in gen- 
 eral. 
 
 6" = 1 mile, for area, position, outpost or other sketches made 
 on foot. 
 
 12" = 1 mile may be used when greater detail is required. 
 
 While the above scales differ from those adopted for 
 War Department maps they will still continue to be used 
 until it is possible to replace them. 
 
 15. It is not practicable to have prepared under War 
 Department supervision, in the field, all the maps required 
 for military use, and consequently the maps of some of the 
 several civil agencies of the Government engaged upon sur- 
 vey work have been adopted as standard for such use. 
 
 16. A.R. No. 100-15, 1920, which covers the subject of 
 maps and map making, classifies maps for use of the mili- 
 tary forces as Standard and Special. 
 
 Standard maps are those which, whether geographic 
 or topographic in character, are ordinarily made in time of 
 peace, as an element of preparedness, or for the commercial 
 development of the country. They are printed in quantity 
 for general uses. 
 
 Special maps are those especially made for special pur- 
 poses. The purpose ordinarily is to show, as to a particular 
 area, certain details not found on standard maps thereof. 
 Special maps may be topographic maps to special scales, 
 or may be produced by drawing or printing on standard 
 maps, the data desired to be made available. 
 
map reading 11 
 
 17. Table of Map Scales Used by Various Nations : 
 
 
 i* 
 
 00 
 
 i* 
 
 
 R. F. 
 
 l"Sa 
 
 
 Country 
 
 
 - =~ 
 
 ~ ~ ^ 
 
 
 
 
 R,S g 
 
 
 
 
 <*"S^ 
 
 
 1 '5000 
 
 12 
 
 1-12 
 
 
 1 10,000 
 
 6 
 
 1-6 
 
 
 1 20,000 
 
 3 
 
 1-3 
 
 United States 
 
 1/62.500 
 
 1 
 
 1 
 
 
 1 125,000 
 
 1-2 
 
 2 
 
 
 1 250,000 
 
 1-4 
 
 4 
 
 
 1 6,000,000 
 
 1-16 
 
 16 
 
 
 1/5,000 
 
 12 
 
 1-12 
 
 • 
 
 1 10,000 
 
 6 
 
 1-6 
 
 
 1/20,000 
 
 3 
 
 1-3 
 
 
 1/50,000 
 
 1 1-4 
 
 4-5 
 
 France 
 
 1 80,000 
 
 4-5 
 
 1 1-4 
 
 
 1/100,000 
 
 3-5 
 
 1 3-5 
 
 
 1/200,000 
 
 1-3 
 
 3 
 
 
 1/320,000 
 
 1-5 
 
 5 
 
 
 1 500 000 
 
 1-8 
 
 8 
 
 
 1/600,000 
 
 1-10 
 
 10 
 
 
 1/1,000,000 
 
 1-16 
 
 16 
 
 
 1/10,000 
 
 6 
 
 1-6 
 
 
 1/31,680 
 
 2 
 
 1-2 
 
 Great Britain (does not 
 
 1 63,360 
 
 1 
 
 1 
 
 include maps they 
 
 1/125,000 
 
 1-2 
 
 2 
 
 used in France and 
 
 1 253,440 
 
 1-4 
 
 4 
 
 Belgium) 
 
 1/1,000,000 
 
 1-16 
 
 16 
 
 
 1 25.000 
 
 2 1-2 
 
 2-5 
 
 
 1/100,000 
 
 3-5 
 
 1 3-5 
 
 Germany 
 
 1 200,000 
 
 1-3 
 
 3 
 
 (not complete) 
 
 1 1.000,000 
 
 1-16 
 
 16 
 
 
 1/20,000 
 
 3 
 
 1-3 
 
 Japan 
 
 1 100,000 
 
 3-5 
 
 1 3,-5 
 
 (not complete) 
 
 1 100.000 
 
 3-5 
 
 1 3-5 
 
 Mexico (maps of Mex- 
 
 1/4,530,000 
 
 1-72 
 
 72 
 
 ico are inaccurate) 
 
 18. U.S. Geological Survey sheets are generally 1 :62,- 
 500 (about 1"=1 mile) and 1:125,000 (about \"=1 mile). 
 The 1 : 62,500 sheets cover 15' of latitude and 15' of longi- 
 tude. 
 
 For the Progressive Military Map, the United States, 
 Portq Rico, and Hawaii have been divided into a series of 
 numbered sheets, the highest number being 825. Each sheet 
 is divided into 8 sub-sheets, thus : 
 
 N— I, N— II, N— III, N— IV, 
 S— I, S— II, S— III, S— IV. 
 
 Most of these sub-sheets are drawn to a scale 1 :62,500 
 covering 30 minutes of longitude and 15 minutes of lati- 
 tude. 
 
12 TOPOGRAPHY 
 
 19. The correct designation of maps now used in prob- 
 lems, conferences, etc., at these schools is given below : 
 
 General Map, Gettysburg-Antietam, 1" = 10 miles. 
 
 General Map, Gettysburg-Antietam, 1" = 5 miles. 
 
 Gettysburg-Antietam Map, 1:21120; sheets are designated by 
 name as "Taneytown sheet." 
 
 Gettysburg-Antietam Map, 1:5280; sheets are designated by 
 letter and number as Sheet A-5. 
 
 Pennsylvania and Maryland Geological Survey Map, 1:62500; 
 sheets are called "Taneytown quadrangle," etc. (Two states in 
 name as boundary crosses the quadrangle.) 
 
 General Map, vicinity of Leavenworth, 1"=15 miles. 
 
 Map of Fort Leavenworth and Vicinity, 1:21120; sheets are 
 designated by name, as "Boling sheet," etc. 
 
 Map of Fort Leavenworth and Vicinity, 1:5280; sheets are 
 designated by letter and number, as sheet E-3. 
 
 Kansas-Missouri Geological Survey Map, 1:62500. There 
 are four separate sheets called: Leavenworth and Vicinity; 
 Leavenworth Quadrangle; Smithville Quadrangle; Platte County, 
 Missouri. 
 
 Geological Survey Map, Leavenworth and Vicinity, printed 
 in black, 1:62500. 
 
 Kansas-Missouri special, printed in black, 1:62500. 
 
 Road Map of Fort Leavenworth, Kansas, and Vicinity, 
 1:62500. 
 
 Road Map of Easton, Kansas, and Vicinity, 1:62500. 
 
 Map of Part of Kansas and Missouri, Geological Survey, 
 printed in black, 1:125000. 
 
 For example, the following might appear at the begin- 
 ning of a problem : 
 
 MAPS: Gettysburg-Antietam Map 1:21120, Taneytown, 
 Kingsdale, Bonneauville, Gettysburg sheets. 
 
 20. Compass : — The compass does not point to the north 
 pole. It points to the magnetic pole, which is in the northern 
 part of British America (Canada) . However, along a mean- 
 dering line running near Charlestown, Cincinnati, and Sault 
 Ste. Marie, the compass points to the north pole, while 
 pointing at the same time to the magnetic pole. East of 
 this line the compass points west of true north ; west of the 
 line the compass points east of true north. 
 
 The following should be remembered : The direction 
 of an object, expressed in degrees from the north measured 
 round to 360° with the hands of a watch, is the azimuth of 
 the object. As there are two norths used, true and mag- 
 netic, there are two azimuths used, called true and magnetic 
 azimuths. In military work the azimuths alivays, unless 
 otherwise stated, refer to true azimuths, that is, to the azi- 
 muths measured from true north. 
 
MAP READING 13 
 
 21. A knowledge of the peculiarities of the compass is 
 necessary to map reading. At Fort Leavenworth, if you 
 are ordered, while in the field to change the direction of your 
 advancing line so that it will move in the direction 37° 54', 
 you do not advance in the compass direction 37° 54'. You 
 remember that the order refers to map north (that is, true 
 north) and that the magnetic declination at Fort Leaven- 
 worth is 9° east; you subtract 9° from 37° 54' and advance 
 in the magnetic direction 28° 54'. In other words, in this 
 longitude, you subtract the magnetic declination from the 
 true north in order to get the compass reading; and vice 
 versa, you add the magnetic declination to the compass read- 
 ing to get the true north. In Europe you do just the oppo- 
 site. 
 
 22. The following rules are easy to remember : 
 First, west of the line of no magnetic declination (as 
 
 at Leavenworth), where declinations are east: 
 
 (a) Add to the magnetic, to get the true. 
 
 (b) Subtract from the true, to get the magnetic. 
 
 Second, east of line of no magnetic declination (as at 
 Gettysburg and in Europe), where declinations are west, 
 do just the opposite, viz. : 
 
 (a) Subtract from the magnetic, to get the true. 
 
 (b) Add to the true to get the magnetic. 
 
 Verify these rules from a sketch or mental picture. 
 
 23. The mean magnetic declination for any map can 
 usually be found indicated on the sheet. A common method 
 of indicating it is to draw an arrow with a full arrowhead 
 pointing to true north, another arrow pointing to magnetic 
 north with half a head drawn on the right or left hand, 
 according as the declination is east or west, and to in- 
 scribe the declination either in the space between the lines 
 or on the magnetic meridian. This declination changes 
 from year to year, but the declination marked on the map 
 is accurate enough for all practical purposes. 
 
 24. Contours: — The best way to learn to read con- 
 tours, and later to draw them, is to practice the drawing of 
 contours on a sketch where the critical points are given 
 and with the actual ground in sight. By this means, one 
 learns just what are the critical points, how they should be 
 selected in the field and how a failure to properly select 
 
14 TOPOGRAPHY 
 
 them will lead to a false representation of the ground, how 
 to read at a glance differences of elevation, and how in 
 sketching to draw in the contours by looking at the ground 
 itself. 
 
 25. The War Department is the only organization 
 which appears to have adopted any logical scheme of con- 
 tours ; foreign maps and Geological Survey maps have cer- 
 tain contours to certain maps, but they represent no fixed 
 scheme of slopes for different maps. Of course they rep- 
 resent difference of elevation, but a glance at foreign con- 
 toured maps does not show, without calculation, the slope of 
 the ground. On the other hand, the War Department maps 
 have a fixed relation of contours so that the number of 
 contours shows the slope, regardless of the scale of the 
 map. Thus for the 3" map, we have 20-foot contours 
 (3X20=60) ; for the 6" map, we have 10-foot contours 
 (6X10=60), that is, twice as many contours for the same 
 difference of elevation ; but as the 6" map has twice the lin- 
 eal dimensions of the 3" map covering the same territory, we 
 have the same number of contours for the same lineal dis- 
 tance on the paper ; for the 12" map we have 5-foot contours 
 (12x5=60), that is, four times as many contours for the 
 same difference of elevation, but as the lineal dimensions 
 of the map are four times as great as on 3" map for the 
 same territory, we have the same number of contours for 
 the same distance on the paper. For the War Department 
 maps the following contour intervals are prescribed: 
 
 Feet 
 
 1/62,500, vertical interval, normally 20 
 
 1/20,000, vertical interval 20 
 
 1/10,000, vertical interval 10 
 
 1/5,000, vertical interval 5 
 
 Consequently with War Department maps, except the 
 20-ft. contour, 1 : 62500 maps, anyone can know at a glance, 
 without reading the contour intervals, whether the ground 
 is very steep or rolling or flat, but for exact differences of 
 elevation he must look at the contours. In some foreign 
 maps, hachures show the character of the slope, and the 
 hill tops have elevations, but this method obscures the map 
 and lacks the exactness of that of contours. 
 
 With a contoured map it may help in map reading to 
 take a colored pencil, and trace the important contours. 
 
MAP READING 15 
 
 Also it may help if the map is shaded, grading from white 
 on the level to darkest on the steepest slopes. 
 
 26. The critical points of a terrain are in the stream 
 lines and the ridge lines; for at those points the contours 
 change their direction most rapidly. A few critical points 
 with known elevations along stream lines and on ridge lines 
 are of more value in drawing contours than are a greater 
 number of points not critical. 
 
 27. Figure T-l shows a map with the critical points 
 marked and the elevations shown. The problem is to draw 
 contours at 10 feet vertical intervals, with no other data 
 than that given. The first step is to locate the points where 
 desired contours cross the main stream line. As there are 
 no falls between elevation 790 and elevation 850, it is as- 
 sumed that the slope of the stream between these points 
 is nearly uniform, becoming, however, a little steeper as the 
 stream is ascended. Under this assumption the crossing 
 points of contours 800, 810, 820, 830, and 840 are at once 
 interpolated by eye on the main stream between 790 and 
 850. By interpolation between these,, the elevations of 
 the points where each of the tributary ravines enter the 
 main stream are secured. Between these latter points and 
 the heads of the ravines, the elevations of which are given, 
 the points where the contours cross each of the ravines 
 are marked. 
 
 28. Each point shown along the ridge lines was chosen 
 as being a critical point, that is, a point where the slope 
 or direction of the ridge changes. From point to point 
 along the ridge lines, it is assumed that the slope is uni- 
 form. The points where the intervening contours cross 
 the ridge lines have, therefore, been interpolated. The re- 
 sult of interpolation along stream and ridge lines is shown 
 in Figure T-2. As a rule, the ridges and spurs of eroded 
 hills point in the general direction of the junctions of the 
 streams which have eroded them. Therefore, interpola- 
 tions have been made in these directions. 
 
 29. The contours are now drawn in by joining the 
 arrowheads in streams with the corresponding elevation 
 on the ridge lines. See Figures T-2, T-3, and T-4 for the 
 successive steps. 
 
16 topography 
 
 30. Characteristics of Contours. 
 
 (1) All points on any one contour have the same elevation. 
 A contour is a level line. 
 
 (2) Every contour closes on itself, either within or beyond 
 the limits of the map. In the latter case the ends of the con- 
 tour line will run to the edge of the map. 
 
 (3) A contour which closes within the limits of the map in- 
 dicates either a summit or a depression. In a depression there will 
 usually be found a pond or a lake. If there is no water, the 
 depression must be indicated in some way to differentiate it 
 from a summit. The usual method is to hachure the inner side 
 of the depression contour. 
 
 (4) Contours never split and never cross each other except 
 in the case of an overhanging cliff, in which case there must 
 be two distinct intersections. These cases are not common. 
 
 (5) Contours are spaced equally to represent a uniform slope. 
 If the slope is a plane surface (i.e., if it has no irregularities 
 due to erosion or other cause) the contours are parallel and 
 straight. 
 
 (6) In crossing a valley the contours run up the valley on 
 one side; turning at the stream, run back on the other side. In 
 crossing a ridge the contours run to the ridge line and, turning, 
 run back on the other side of the ridge. 
 
 (7) Contours are always at right angles to the lines of 
 steepest slope. They, therefore, cross the stream lines and the 
 ridge lines at right angles. 
 
 (8) The contours are farther apart at the top and bottom 
 of an eroded hill than near the middle, because in these portions 
 the slope is somewhat flatter. 
 
 (9) Contours are usually closer together near the sources of 
 streams — as a stream is usually steeper near its source. This 
 is not always so. A stream may have at its source a very flat 
 collecting basin, a lake, or pond. 
 
 (10) The smaller the stream, the steeper the slope in the 
 usual case. Hence, contours are usually closer together on tri- 
 butaries than on main streams. 
 
 (11) Bad shaping of contours is usually due to illogical in- 
 terpolation between critical points. The drainage lines and ridge 
 lines are master lines of contours. Interpolate along the drain- 
 age lines first, beginning on the main lines and going to the 
 tributaries. Then search out the ridge lines and interpolate along 
 the lines of the ridges. 
 
 (12) If one has difficulty in tracing out a particular contour, 
 he may be helped by imagining himself to be walking along the 
 contour. If he starts out with low land on his right hand, he 
 will always have low land on his sight hand as long as he walks 
 that contour in that direction, and vice versa. 
 
 31. Figure T-5 shows an attempt at contouring, where- 
 in each of the above characteristics are violated. 
 
 Each number on the figure show the particular charac- 
 teristic which has been violated at that point. 
 
 1-1 shows the same contour crossing the same stream 
 twice; this is impossible. 
 
 2 shows a contour ending within the limits of the 
 map ; it cannot be done. 
 
MAP READING 
 
 17 
 
 3 shows a closed contour within the limits of the map. 
 Evidently, it is a depression contour, but there is nothing 
 to show that it is of a different nature from any of the 
 other closed contours, all of which represent tops of hills. 
 
 4 shows a contour which splits ; this is unreasonable 
 because there is no overhanging cliff and there is only one 
 such intersection or split. 
 
 5-5 shows unequal spacing and hence unequal slope, but 
 it is probable that the slope here is not unequal. 
 
 6-5 shows contours going straight across a small valley ; 
 no such valleys exist. 6a indicates that a man could walk 
 straight from one stream to another on a level line ; such 
 conditions never exist. 
 
 7 shows a contour not at right angle to steepest slope. 
 
 8-8-8 shows contours closer together at top and bottom 
 of a ridge ; this is possible but not probable. 
 
 9-9-9 shows contours closer together at the mouth of 
 the stream; this is possible, but not probable. 
 
 10-10-10 shows that the larger stream has the greater 
 slope, which is not probable. 
 
 11-11 shows bad shaping of contours due to illogical 
 interpolation between critical points. 
 
 12-12 shows the same contour twice on the same slope. 
 This means that a man could walk to the right, continue 
 along the contour, and then come back above his original 
 position and still be on the same level. 
 
 32. Figures T-6 to T-12 are critical points for sketches. 
 It is advisable to practice on these figures so as to secure 
 facility in drawing contours and in understanding the mean- 
 ing of contours. 
 
 33. Shelter from Artillery Fire: — The following 
 table shows in round numbers the angle of fall of 75-mm. 
 projectiles for different ranges. 
 
 
 Shell 
 
 Shrapnel 
 
 
 Range in meters 
 
 Approx. 
 
 Approx. 
 
 
 
 angle of jail 
 
 angle of fall 
 
 
 1.000 
 
 2° 
 
 2" 
 
 
 2,000 
 
 4° 
 
 4° 
 
 
 3.000 
 
 8° 
 
 7" 
 
 
 4,000 
 
 13° 
 
 12° 
 
 
 5.000 
 
 20° 
 
 17° 
 
 
 6.000 
 
 27° 
 
 24° 
 
 
 7.000 
 
 37° 
 
 32° 
 
 
 8.000 
 
 51° 
 
 41° 
 
 
18 
 
 TOPOGRAPHY 
 
 By means of the above tables problems may be worked 
 out showing whether certain positions are protected by the 
 conformation of the ground from fire of 75-mm. guns. This 
 table will be referred to in problems. 
 
 34. The following table shows the relation between 
 vertical and horizontal distances for slopes mentioned in 
 above table. 
 
 Slope in 
 degrees 
 
 2 
 
 29 
 
 horizontal to 
 
 4 
 
 14 
 
 horizontal to 
 
 8 
 
 7.1 
 
 horizontal to 
 
 9 
 
 6.3 
 
 horizontal to 
 
 11 
 
 5.3 
 
 horizontal to 
 
 13 
 
 4.5 
 
 horizontal to 
 
 16 
 
 3.5 
 
 horizontal to 
 
 20 
 
 2.7 
 
 horizontal to 
 
 26 
 
 2.0 
 
 horizontal to 
 
 29 
 
 1.8 
 
 horizontal to 
 
 33 
 
 1.55 
 
 horizontal to 
 
 87 
 
 1.35 
 
 horizontal to 
 
 39 
 
 1.25 
 
 horizontal to 
 
 40 
 
 1.2 
 
 horizontal to 
 
 46 
 
 1. 
 
 horizontal to 
 
 50 
 
 1. 
 
 horizontal to 
 
 51 
 
 1. 
 
 horizontal to 
 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 vertical 
 1.04 vertical 
 1.2 vertical 
 1.25 vertical 
 
 35. The following rule of thumb for converting degrees 
 of slope to per cent of slope is fairly accurate up to ten 
 degrees : 
 
 Multiply degrees by % to get per cent. 
 
 36. Visibility : — A problem frequently arising in map 
 reading is that of determining what points are visible from 
 a given point. 
 
 The simplest and most satisfactory method consists in 
 drawing a profile of the surface of the ground between the 
 two points and then drawing the line of sight. If it touches 
 any point of the surface as shown by the profile, the two 
 points are not mutually visible. 
 
 However, this method is long and tedious. A compari- 
 son of the gradients between the two points and between one 
 of them, lower most convenient, and intermediate points 
 higher than the lower point is the method employed. A 
 gradient to an intermediate point from the lower point 
 steeper than the gradient between the two points under in- 
 vestigation will mean non-visibility. Generally it is possible 
 by inspection of the map to find two or three intermediate 
 obstacles whose elevations are the deciding factors as to the 
 
MAP READING 19 
 
 miftual visibility or non-visibility of the two points. Then, 
 simple calculations will show in every case whether the two 
 points are mutually visible. 1st: take the higher point, find 
 its distance from the lower point, divide this by its eleva- 
 tion above the lower point. 2d: take the higher point and 
 each of the obstacles in turn, find the distance from the 
 higher point to each obstacle, divide this by the elevation of 
 the higher point above the obstacle. If the quotient of the 
 1st (distance between higher and lower points divided by 
 the difference of elevation) is in every case greater than the 
 quotient of the 2d (distance from higher point to obstacle 
 divided by the difference of elevation), then the two points 
 are mutually visib]^. Thus, to determine whether or not 
 the bridge near Frenchman's is visible from hill 1065 (point 
 346.9 — 749.2, on 3" Map) or is concealed by intermediate 
 ground. Take the elevation as 1,065. The distance is 5700 
 feet, difference of elevation 266 feet, quotient 21.4. Along 
 the line of sight, we find the 960-foot contour on the flank of 
 Sentinel Hill to be an obstacle ; distance is 2700 feet, differ- 
 ence of elevation 105 feet, quotient 25.7. The 1st (21.4) is 
 less than the 2d (25.7) ; therefore the two points are not 
 mutually visible. 
 
 37. When a relief map is available of the territory, 
 problems in visibility are much simplified. An immense 
 number of visibility studies were made by us in France by 
 using a little electric bulb on a relief map in a dark room. 
 By placing the lighted bulb on any point on the map, the 
 whole of the map was marked by shadows or lighted areas. 
 The lighted areas correspond- to the visible areas for an ob- 
 server at the same point on the ground — the light, in prin- 
 ciple, taking the same place of the eye of the observer. The 
 lighted and shaded areas were copied on maps and sent out 
 for use of the troops, especially the artillery. With well 
 made relief maps this method is very accurate. The diffi- 
 culty in the use of this method lies in the fact that the pro- 
 duction of relief maps is such a complicated process. With 
 relief maps the application of the method is unlimited. In 
 France by the use of a number of lights we made maps show- 
 ing the following: 
 
 (a) The maximum ground behind our lines which could be 
 seen from the system of German observation posts. 
 
20 TOPOGRAPHY 
 
 (b) Maximum amount of ground which could be seen from 
 all of our system of posts. 
 
 (c) Same as (a) and (b) above for balloons. (In the case 
 of balloons, the little light is suspended above the map at the 
 proper point to represent the balloon.) 
 
 (d) In case of advance by us, where to find the best points 
 for observation posts. 
 
 (e) Whether or not the objective lines for an attack were 
 properly located from a visibility standpoint. 
 
 38. Orientation : — The reading of maps is not wholly 
 an indoor occupation. The general, in a comfortable and 
 well lighted room, plans his battles from his map ; but the 
 regimental officers read their maps in the field, often in the 
 rain, and have the problem of correlating the map with the 
 ground. The first thing they must do, is # to orient the map ; 
 or, in other words, lay the north of the map to the north on 
 the ground. By using the compass, find the north, and then 
 point the arrow on the map indicating north in that direc- 
 tion ; if no north is indicated on the map it is a fairly safe as:- 
 sumption that the top is north. If mo compass is available, 
 use the North star at night or the sun in the daytime, 
 roughly figuring that the sun is in the east at 6:00 AM, 
 the southeast at 9 :00 AM, south at noon, the southwest at 
 3 :00 PM, and the west at 6 :00 PM. 
 
 39. The following are methods of orientation : 
 
 First method. — Take a map with the magnetic meridian 
 marked upon it. Set up a sketching board on its tripod. Put 
 the map on the board. Shift it until the magnetic meridian on 
 the map becomes parallel to the meridian line of the needle 
 . trough. Pin the map down with thumb tacks. Orient the sketch- 
 ing board later. 
 
 Second method. — Using a compass, but not the sketching 
 board. Lay the map on the ground. Lay the sight line of the 
 compass along the magnetic meridian of the map. Rotate map 
 and compass together until the needle points north. If sight line 
 of compass has been kept along magnetic meridian of map, the 
 map is oriented. 
 
 Third method. — No compass or no magnetic meridian; true 
 meridian given; .position unknown. Point the hour hand of your 
 watch (held face upward) at the sun, if in the northern hemis- 
 phere. The line drawn from pivot to the point midway between 
 the outer end of the hour hand and XII on the dial will point 
 toward the south. Shift your map to correspond. This will give 
 a very rough orientation. 
 
 40. Now, having oriented the map, always keep it 
 oriented. Do not move the map, but move around the map 
 if it is desired to get at it from a new angle. To locate 
 yourself accurately on the map select some distant point on 
 
MAP READING 21 
 
 the ground which you recognize on the map, draw a line 
 through the point on the map toward the corresponding 
 point on the ground ; repeat this process with other similar 
 points. The intersection of the two lines thus drawn on the 
 map will be the observer's map position. This method is 
 called resection. The method is more accurate as the in- 
 tersection approaches a right angle. 
 
 Practical Exercises in Map Reading 
 
 NOTE : — (L) after the number of the exercise indicates that the Leavenworth 
 area and the 3" map of the Leavenworth Group are used: (G) similarly indicates 
 that the Gettysburg area and the 3" map of the Gettysburg Group are used. 
 
 Practical exercises consist in working out in a section 
 room or in the field practical problems which illustrate the 
 points in the preceding discussion. Briefly, they consist of 
 questions in map reading, drawing in contours and making 
 sketches. 
 
 Compass 
 
 1 (L) . At Fort Leavenworth does the compass point 
 east or west of true north ? 
 
 2 (L) . What is the magnetic declination at Fort Leav- 
 enworth ? 
 
 3 (L). You have received an order to attack in the 
 direction, 35°. What will be your compass direction of at- 
 tack? 
 
 4. In writing an order, will you give a direction by 
 its true or magnetic azimuth? 
 
 5 (L) . You are an observer in the school tower, and 
 wish to write to your superior the direction of an object. 
 Its magnetic azimuth is 342°. What azimuth do you write 
 him? 
 
 6 (L). Having a magnetic needle, how do you orient 
 a map by using it? 
 
 7. You have a watch and the sun is shining. How do 
 you find north? 
 
 8 (L) . What is the azimuth of the line joining 348.0 
 —755.0 and 349.0—756.0? Give it as you would write it 
 in an order. 
 
 9 (L) . What is its magnetic azimuth? 
 
 10 (L). You are in command of an organization and 
 receive a message from your commanding officer to attack 
 
22 TOPOGRAPHY 
 
 in the direction 340°. The magnetic declination given on 
 your map is 8° 23' E. What compass direction would you 
 follow? 
 
 11 (L). You are preparing the orders for a small at- 
 tack, and find that the direction of attack is parallel to a 
 line joining points 345.0—752.0 and 346.0—753.0. What 
 direction will you write in your order as the direction of 
 attack ? 
 
 12 (L). You are in command of a battery and one of 
 your observers on Sentinel Hill (346.35 — 750.0) reports that 
 a body of enemy, estimated at a platoon, are resting along- 
 side the main road about 3,000 yards to the north of him 
 — magnetic azimuth 359°.- You have the location of the ob- 
 server plotted on your map. What will be the true azi- 
 muth of the line you will draw from the position of your 
 observer in order to locate the enemy? 
 
 13. You are in command of a company and have sent 
 a trained officer out to find the azimuth of a certain straight 
 road. You receive a message from him that it is 13°. Will 
 you assume that he has sent in the true or magnetic azi- 
 muth? 
 
 14. You are in command of an American regiment serv- 
 ing in a foreign country. You are scheduled to attack and 
 the order says in the direction 327°. Upon looking at a map 
 it is found that the declination is given on it at 13° W. 
 What will be the reading of your compass after you have 
 set it to give the direction of attack? 
 
 15 (L). You are holding a section of a battle line along 
 ridge running through 355.0 — 747.0. An order comes to you 
 to attack in the direction 342°. What do you set your com- 
 pass? 
 
 Contours 
 
 1. What is contour interval on the 3" map? 
 2 (L). What is the nature of the contour surrounding 
 point 344.38—752.35? 
 
 3. Do two contours ever cross? If so, what is repre- 
 sented? 
 
 4. The contour interval is 20' on a 3" to a mile map. 
 To have the contours spaced the same distance apart on 
 any given slope, what should be contour interval on a 2" 
 map of the territory? 
 
MAP READING 23 
 
 5 (L). In which direction does the water flow in the 
 stream passing near 343.5 — 748.6? 
 
 6 (L). Which is higher, Sentinel Hill or Bell Point? 
 
 7 (G). What is the name given to the class of contours 
 similar to the one running through point 353.75 — 746.25? 
 
 8 (G). In which direction does the water flow in the 
 stream running near 355.1 — 743.6? 
 
 9 (G). What is the highest point on the road between 
 Gettysburg and Germantown? The lowest? 
 
 Conventional Signs 
 
 1 (L) . What does the conventional sign at each of 
 following places represent: 
 
 (a) At 351.8—758.4? 
 
 (b) Vicinity 345.3—755.1? 
 
 (c) At 343.15—756.4? 
 
 (d) At 345.65—751.75? 
 
 (e) At 344.94—755.77? 
 
 2 (L). What does the map show to be the character 
 of the country in the vicinity of the following points : 
 
 (a) Vicinity 348.0—757.15? 
 
 (b) Vicinity 351.5—755.0? 
 
 (c) Vicinity 351.3—754.0? 
 
 (d) Vicinity 344.8—754.4? 
 
 (e) Vicinity 347.3—757.5? 
 
 3 (L) . In going southwest to water from house marked 
 Tramel at 351.9 — 756.15, what does the map show to be 
 the artificial features passed over? 
 
 4 (L) . Are they roads or trails which pass through the 
 following points? If roads, are they improved or unim- 
 proved ? 
 
 (a) 351.58—754.0? 
 
 (b) 344.0—753.8? 
 
 (c) 350.0—756.15? 
 
 5 (L). What is the character of the ground as shown 
 by the contours surrounding point 348.5 — 752.45? Sur- 
 rounding point 345.9—752.8 ? 
 
 6 (L). You are on the road at point 350.55 — 751.86, 
 leading a patrol of four men, when you are fired on by rifle 
 fire from a southwesterly direction. Where would you take 
 cover ? 
 
24 TOPOGRAPHY 
 
 7 (L). You are marching a platoon south along the 
 road at 347.7 — 750.45 when you are suddenly shelled from 
 the west with high angle fire. Where would you go for 
 shelter ? 
 
 8 (L). The ground in the vicinity of point 344.4 — 752.3 
 is indicated on the map as meadow land and flat. What 
 is the objection, if any, to camping there? 
 
 9 (L). Your aeroplane had stalled and you were forced 
 to land at point 349.8 — 754.6. Where is the nearest place 
 you might find assistance? 
 
 10 (G). You are ordered to interrupt the York Turn- 
 pike running northeast out of Gettysburg. Where would 
 be the best place to do it? 
 
 11 (G). Is there underbrush in the woods at 352.89 — 
 747.63? 
 
 12 (G). You are on a horse and turn out of column for 
 twenty minutes to ride to top of hill 571 (356.85—743.53). 
 Can you see anything from the top of the hill ? 
 
 13 (G). What vegetation is shown at the following 
 points ? 
 
 (a) At 356.1—750.3? 
 
 (b) At 356.45—742.55? 
 
 (c) At 352.30—748.50? 
 
 (d) At 357.7—745.8? 
 
 (e) At 349.35—745.75? 
 
 14 (G). Is it a cut or fill at 348.2—750.9? At 355.25 
 —748.6? 
 
 15 (G). What two types of fences are most prevalent 
 on map? 
 
 16 (G). Are there any evergreen trees on the forest 
 on Culp's Hill? 
 
 17 (G). What natural feature is shown at 351.58 — 
 748.24? 
 
 18 (L). You are with your company in the open at 
 347.2 — 747.6 when high angle mortar shells begin dropping 
 very close to you. Where do you go? 
 
 19 (L). What is the shortest road distance between 
 354.3_744.86 and 354.2—742.8? 
 
 20 (G). You are at crossroads 348.25 — 746.4 in charge 
 of a truck train and have orders to proceed to point 350.1 — 
 745.5 with the utmost dispatch. It has been raining. Which 
 way do you go? Why? 
 
MAP READING 25 
 
 21 (L). The enemy has been shelling with gas the 
 area between Merritt and Pope Hills and Metropolitan 
 Avenue. Where will the gas be most dangerous ? 
 
 22 (G). Considering gas alone, is it better to take 
 position at 351.5—749.5 or 351.1—748.8? 
 
 Co-ordinates 
 
 1. You are defining a line by co-ordinates. The fol- 
 lowing are points on this line, given in order from right to 
 left. Write them as they would be written, in an order. 
 
 (1) X = 346.75, Y = 752.62 
 
 (2) X = 345.52, Y = 753.05 
 
 (3) X = 344.18, Y = 754.32 
 
 2 (G). What are the co-ordinates of the top of Round 
 Top? 
 
 3 (G). What are the co-ordinates of the church, south 
 of the road at Two Taverns (east side of Gettysburg sheet) ? 
 
 4 (G). Designate by co-ordinates the wire fence run- 
 ning south from name B. D. Snyder (southeast corner Get- 
 tysburg sheet). 
 
 5 (G). What are the co-ordinates of Penn College in 
 northwestern Gettysburg ? 
 
 6. How far is it between points 344.0—756.0 and 346.0 
 —756.0 ? 
 
 7. How far is it between " 354.9— 748.0 and 355.0— 
 749.0? 
 
 8. What is the distance between 354.7 — 745.6 and 356.4 
 '_746.7? 
 
 9 (G). What is the shortest road distance, expressed 
 in meters, between the crossroads at Two Taverns and point 
 354.74—741.62? 
 
 10 (G). Most crossroads on the map are numbered. 
 Were these numbers arbitrarily assigned or do they follow 
 a system? If a system is followed, what is it? 
 
 Scales 
 
 1. You have counted your strides on a course 5105 feet 
 long, extending from A to B. The number of strides counted 
 from A to B was 1008 ; on return from B to A you took 
 1034 strides. What is the length of your stride in inches? 
 
 2. How many such strides to a thousand yards? 
 
26 TOPOGRAPHY 
 
 3. On a six-inch to the mile sketch, how many inches 
 on the map will be equal to 792 of the strides determined in 
 Question 1 above? 
 
 4. The scale of a map is 1 centimeter=l kilometer. 
 What is the R.F. of the map ? 
 
 5. What is it expressed in inches to a mile ? 
 
 6. A map is photographed so that the distance between 
 any two places on the photograph map is four times the 
 same distance on the original map. The R.F. of the original 
 was 1:20,000. What is the R.F. of the photograph? 
 
 7. You are in command of a regiment in the enemy's 
 country. The map issued to you is to scale 1 :25,000. What 
 is the scale expressed in inches to a mile? 
 
 8. What is the best method to represent the scale of 
 a map designed for use by people of all races ? 
 
 9. What is the R.F. of a map whose scale is 6" to 1 
 mile? 
 
 10. In order to reproduce a map quickly it was photo- 
 graphed. You have a copy of this photograph. On the map 
 are shown a R.F. and a graphic scale. In using the map 
 which will you use? 
 
 11. What is the scale of a map expressed in inches to 
 miles when its R.F. is 1:600,000? 
 
 12. You have made a sketch and found that your pace 
 scale was incorrect. With incorrect scale map was drawn 
 with R.F.=1:10,000. A known distance of 80 yards scales 
 100 yards on your map. What is the correct R.F. ? 
 
 Orientation 
 
 1 (L). You are at point 349.0 — 749.2 and have your 
 location plotted on the map. Your compass is broken and 
 you have no watch. How would you orient your map? 
 
 2 (G). The enemy has just been forced back behind 
 Gettysburg from his former lines well to the east. You 
 have been given the mission of locating his abandoned 
 dumps. You have found one at 352.57 — 749.17. Your com- 
 pass is out of order and it is a cloudy day. How will you lo- 
 cate the position of the dump on your map ? 
 
 3 (L). You are in the very thick woods along Quarry 
 Creek somewhere northwest of the National Cemetery. The 
 enemy is about 200 yards north of your position. You want 
 
MAP READING 27 
 
 artillery assistance. How do you locate yourself so that 
 you can report your exact position to the assisting artil- 
 lery? 
 
 Visibility 
 
 (Disregard trees, buildings, etc., unless otherwise stated.) 
 
 1 (L). Assume the school tower is 940' above the 
 datum of your map. Can an observer in the tower see a 
 company at point 348.0—748.65 ? 
 
 2 (L). Can he see a troop of cavalry on the road at 
 point 347.2—747.65? 
 
 3 (L). Assume ail trees are 60' high and that if ob- 
 serving from a wooded area, the observer can get a good 
 view by climbing up 60' in a tree. With the above assump- 
 tion can an observer on Sentinel Hill (center of map) see 
 infantry at 343.68—753.1? 
 
 4 (L). Assume same conditions as above, can he see 
 Plum Hill (346.2—755.9) ? 
 
 5 (L). Disregard trees, etc. Can an observer at 346.0 
 — 747.6 see a squadron of cavalry on the road at point 345.5 
 —750.38? 
 
 6 (G). Disregarding trees, buildings, etc., can the point 
 on road at 350.63—750.0 be seen from top of Wolf Hill? 
 
 7 (G). Can Little Round Top be seen from Wolf Hill? 
 Can Round Top be seen? 
 
 8 (G). Disregard trees, etc. Can point 349.0—747.36 
 be seen from point 350.1 — 747.5? 
 
 9 (G). Considering all natural features would a com- 
 pany of infantry at point 353.2 — 750.8 be visible from hill 
 612 (354.0—750.3) to the southeast? 
 
 10 (L). Considering natural features. Your battal- 
 ion is at 343.6 — 753.2. Can you be seen from the top of 
 Sentinel Hill ? 
 
 Field Exercises in Map Reading 
 
 1 (L) . Place sketch on board with the magnetic meri- 
 dian on the sketch parallel to the compass needle when the 
 compass reads north. 
 
 2 (L). Orient your map, assuming the compass is 
 broken. 
 
28 TOPOGRAPHY 
 
 3 (L). Assuming the compass reading to the school 
 tower is 45°, what is the true azimuth to it? 
 
 4 (L) . What is the true azimuth to the wireless tower? 
 
 5 (L). You are an observer at this point and wish to 
 write to your commander the azimuth of a line which by 
 your compass is given as 54° 51'. What do you write in 
 your message? 
 
 6 (L) . Without looking at the map, what is the differ- 
 ence in elevation between this point and Merritt Lake? 
 
 7 (L). Looking at the map, what is it? 
 
 8 (L). Without looking at the map, how far is it to 
 the line of barracks north of here? 
 
 9 (L). Look at the map ; how far it is? 
 
 10 (L). Without looking at the map, what do you es- 
 timate is the difference in elevation between this point and 
 the top of Engineer Hill? 
 
 11 (L): Look at the map; what is the difference in 
 elevation ? 
 
 12 (L). What do you estimate the distance between 
 the wireless station and the school tower to be? Figuring 
 from the map, what do you find it to be? 
 
 13 (L). Looking at the map, is the hill in the vicinity 
 of point 347.0—749.3 visible from here? 
 
 14 (L). Without looking at the map, is it visible? 
 
 15 (L). Using map only; could an observer in the 
 vicinity of point 346.15 — 747.65 see a patrol at this point? 
 
 16 (L). Check answer by the ground. 
 
 17 (L). Take outline sketch given you and draw in 5' 
 contours, looking at the ground and using the elevation 
 given on the sketch. 
 
CHAPTER III 
 
 Use of Instruments 
 
 1. All sketching consists in placing on paper in their 
 approximate relative positions the natural and artificial 
 features of the terrain. A point B is fully located in rela- 
 tion to a point A when its azimuth and horizontal distance 
 from A and its vertical distance above or below A are 
 known. The fundamental operations of sketching are the 
 determination by rapid and approximate methods of the first 
 two of the above named co-ordinates, and also of the third 
 when the relief of the terrain is to be shown. 
 
 2. There are three general methods of sketching: 
 
 (a)' Compass and notebook method, in which the sketch is 
 drawn up later from the notes and partial sketches made in the 
 field. 
 
 (b) Compass and drawing board method, in which the sketch 
 is made in the field, azimuths being obtained by compass and 
 drawn on the sketch by protractor. 
 
 (c) Oriented drawing board or plane table method, in which 
 the sketch is drawn directly on the board, which is oriented either 
 by compass or backsight. 
 
 3. The Engineer Department issues a standard recon- 
 naissance equipment as follows, based solely on the plane 
 table method: . 
 
 Equipment 
 
 1 alidade. 1 holder, timing pad. 
 
 1 board, sketching. 1 pace tally. 
 
 1 chest, sketching outfit. 1 pencil pocket. 
 
 1 clinometer, service, with case. 1 tripod, wood, folding. 
 
 1 compass, prismatic. 
 
 Supplies 
 
 12 celluloid sheets. 16 pencils, drawing, H. 
 
 4 erasers, rubber. 4 pencils, green. 
 
 6 pads, timing. 4 pencils, red. 
 
 72 paper sketching board sheets. 3 protectors, pencil point. 
 
 4 pencils, blue. 3 tape, adhesive, rolls. 
 
 This is the equipment used in these schools. 
 
 29 
 
30 TOPOGRAPHY 
 
 4. The approved distribution is one standard equipment 
 to each regimental and battalion headquarters of infantry, 
 cavalry, and field artillery, and three to each engineer tool 
 wagon giving six per foot company or three per mounted 
 company. Headquarters of higher engineer units and divi- 
 sion or chief engineers not attached to engineer units re- 
 ceive normally three such standard equipments, but divi- 
 sion and other engineers may receive a larger number upon 
 requisition. 
 
 5. Alidade: — The alidade supplied is a three-sided 
 ruler. It is used for three purposes : 
 
 (a) For use as a sighting vane. 
 
 (b) For use as a measuring scale. The three sides are blank, 
 and scales of various kinds are pasted on these three sides. The 
 scale most in use is the 3" scale of strides. In Chapter I, there 
 is shown a set of scales that has been found suitable for the 
 three sides of an alidade. 
 
 (c) To determine differences of elevation from the scales 
 of slopes provided. It is found most convenient to lay off on the 
 scale of the alidade (see the plate of scales shown in Chapter I), 
 the differences of elevation corresponding to a difference of 1 
 degree of elevation. To find the difference of elevation for any 
 distance for more or less than 1 degree, it is sufficiently accurate 
 to multiply by the proper number. Plate V shows a scale of 
 differences of elevation for 1 degree for distances marked on many 
 different scales. 
 
 6. Clinometer : — The clinometer is the instrument for 
 obtaining difference of elevation; it measures slopes. 
 
 7. Clinometers are all based on the establishment of 
 a horizontal reference line by the spirit level or by the plum 
 bob. Trie line of sight is in a vertical plane with the refer- 
 ence line and makes an angle with it equal to the slope be- 
 tween the eye-piece of the instrument and the point upon 
 which the sight is taken. A scale of degrees or grades is 
 placed on the instrument so as to measure the slope and is 
 usually read in reconnaissance instruments at the same 
 time that the line of sight is adjusted on the distant point. 
 
 8. As the slope is usually desired between two points 
 on the ground itself it is necessary to sight upon a point 
 above the distant point a distance equal to the height of the 
 eye above the ground at the time of taking the sight or to 
 make proper allowance for the height of the eye above the 
 ground in calculating the difference of elevation of the 
 two ground points. 
 
USE OF INSTRUMENTS 
 
 31 
 
 Plate V 
 
32 TOPOGRAPHY 
 
 9. The clinometer often needs adjustment. It should 
 be tested as follows : 
 
 Mark two points, say 50 feet apart. Put clinometer 
 sight on one point and read angle of difference to second 
 point. Put clinometer sight on second point and read angle 
 of elevation to first point. Add the two numerical values, 
 regardless of sign, and divide by 2 ; the quotient is the 
 true reading. For example, if first reading is 2 degrees 
 and second reading 1 degree, the correct reading is H 
 degrees. Put clinometer sight line on first point, sight to 
 second point, and adjust clinometer until it reads l.V de- 
 grees; or if the clinometer does not permit of adjustment 
 apply the index error with its proper sign to each reading. 
 
 10. Sketching Board and Tripod form simply a small 
 plane table. The tripod has been found to be not only a 
 great convenience but is necessary to secure the accuracy 
 inherent in the plane table method. 
 
 11. Azimuths are measured in degrees of arc from 
 to 360, beginning with zero at the north, and passing 
 clockwise, through the east (90 degrees), south (180 de- 
 grees), and west (270 degrees), to the north again. 
 
 In work with compass, azimuths are usually referred 
 to the magnetic north as zero; they are called magnetic 
 azimuths. For accurate maps and surveys, azimuths are 
 referred to the true north and may be called "true azi- 
 muths," or simply "azimuths." In military operations 
 true azimuths are generally used at division and higher 
 headquarters (sometimes grid azimuths, when gridded 
 maps are used), and magnetic azimuths between division 
 headquarters and lower units, and in lower units. The full 
 names, viz., magnetic, grid, or true azimuth, should be 
 stated ; in military work the azimuths always, unless other- 
 wise stated, refer to the true north. 
 
 12. There are other ways of expressing azimuths 
 adapted to special conditions or circumstances. In astro- 
 nomical work and tables the azimuth is reckoned from the 
 south, through W., N., and E., 360° to south again. 
 
 In navigation, azimuths are reckoned from the mari- 
 ner's compass, and are called bearings. The dial is divided 
 into 32 points and each point into quarter points. 
 
USE OF INSTRUMENTS 33 
 
 In land surveys bearings are used to indicate direction 
 rather than azimuths. They are referred to the cardinal 
 points of the quadrant in which they occur usually naming 
 the north point or the south point first, thus N 85° W., S. 
 70° E. 
 
 13. The Compass is the standard instrument for the 
 determination of azimuths in topographical reconnaissance. 
 Compasses for sketching and general military use are of 4 
 types : 
 
 Prismatic compasses. 
 Box compasses. 
 Watch compasses. 
 Trough compasses. 
 
 Trough compasses indicate the magnetic north but are 
 not graduated to show azimuths. Prismatic, box, and watch 
 compasses are so graduated that when used as intended 
 for the particular type, they will read magnetic azimuths. 
 
 14. Magnetic Declination: — The angle which the 
 needle makes with the true north at any place is called the 
 declination of the needle or magnetic declination at that 
 place (east declination if the needle points east of true 
 north ; west declination if the needle points west of true 
 north). For latitudes of 60° or less, the declination is ordin- 
 arily between limits of 20° east and 20° west, being taken 
 now as 9° east at Fort Leavenworth, and 7° west at Gettys- 
 burg. 
 
 15. Periodic changes in declination take place, viz. : 
 Daily (5' to 15' of arc) ; lunar (less than 1'") ; annual (less 
 than 1') ; and secular (a long slow swing covering many 
 years). Only the last is large enough to be even noticed 
 in military sketching or map reading. In the United States, 
 all east declinations are now gradually decreasing, and west 
 declinations increasing, at a rate of about 3' per year. Even 
 the secular variation is not of importance except for exact 
 surveying. 
 
 In addition to the periodic variations, there are irregu- 
 lar variations, uncertain in character, due to magnetic 
 storms or to local attractions such as iron ore in the hills 
 or steel rails on a railway track. 
 
 16. The declination of the compass may be determined 
 with sufficient accuracy for military sketching or guiding 
 by 3 methods : 
 
34 
 
 TOPOGRAPHY 
 
 1. Plotting the shadow of the sun at noon; 
 
 2. Observing the magnetic azimuth of the sun or of some 
 star at rising and setting; 
 
 3. From Polaris. 
 
 17. The dip of the compass is the tendency of one end 
 of the needle to be drawn downward out of the horizontal 
 plane because of the location of the magnetic poles beneath 
 the earth's surface. The dip is overcome by the use of a 
 small adjustable counterweight, placed on the southern end 
 of the needle in the northern hemisphere, and on the north- 
 ern end in the southern hemisphere. 
 
 18. Distances in sketching may be determined by the 
 following methods : 
 
 (a) Pacing on foot. 
 
 The length of a man's pace is about 30 inches. A stride 
 is 2 paces. On level ground careful pacing will give dis- 
 tances correct to 3 per cent or less. The length of the pace 
 decreases on slopes, more rapidly on ascending slopes than 
 on descending. The table below shows the necessary cor- 
 rection for great accuracy. However, such accuracy is 
 rarely required in sketching. 
 
 Slope, degrees 
 
 Ascending 
 
 Equivalent 
 Horizontal 
 
 Descending 
 
 6 
 
 90.4 
 
 100 
 
 95.6 
 
 10 
 
 78.7 
 
 100 
 
 91.5 
 
 15 
 
 69.3 
 
 100 
 
 87.4 
 
 20 
 
 58.5 
 
 100 
 
 80.8 
 
 25 
 
 49.1 
 
 100 
 
 68.2 
 
 30 
 
 35.8 
 
 100 
 
 51.4 
 
 NOTE : — Both the shortening 01 the pace and the reduction to the horizontal 
 are allowed for this table. 
 
 (b) Pacing mounted. 
 
 The step of the average horse is 33 inches at a walk ; 44 
 inches at a trot. 
 
 (c) Timing a horse. 
 
 The speed of the average horse is 1 mile in 16 minutes 
 at a walk, 8 minutes at a trot. 
 
 (d) Recording the number of revolutions of a wheel 
 by odometer or tallying. 
 
 (e) Speedometer. 
 
 (f) Intersection or resection and location on the map. 
 A point may be located by intersection by taking azimuths 
 to it from two known points. The unknown point will lie 
 at the intersection of the plotted azimuths. An observer 
 
USE OF INSTRUMENTS 35 
 
 at an unknown point may locate himself by taking azimuths 
 to two known points, provided the board be oriented. From 
 the known points, plot the corresponding back azimuths 
 and they will intersect at the point of observation. 
 If it is not possible to orient oneself or to take azi- 
 muth readings, an observer at an unknown point may 
 still locate the point by resection on three known points, 
 as follows : Fasten a piece of transparent paper on the board. 
 Mark a point on it anywhere to represent the station and 
 draw a ray to each of the three known points. Place 
 the transparent paper on the sketch and shift the 
 paper until each ray passes through the proper known point 
 as already located on the sketch. Prick the point of inter- 
 section of the three rays through to the sketch, and the pin- 
 hole will give the location of the position occupied. 
 
 (g) Estimating. 
 
 An expert sketcher should be able to estimate dis- 
 tances with less than 10 per cent error to about 600 yards, 
 and within 15 per cent up to a mile. Objects seem nearer 
 than they really are: 
 
 1. When the sun is behind the observer and the object is in 
 the bright light. 
 
 2. When seen over a body of water, snow or level plain. 
 
 3. When seen below the observer. 
 
 4. When in high altitudes and very clear atmosphere. 
 
 Objects seem farther away than they really are: 
 
 1. When up a steep hill from the observer. 
 
 2. In poor light such as fog. 
 
 3. When seen across undulating ground. 
 
 Objects are distinguishable to average eyes at the fol- 
 lowing distances : 
 
 9 to 12 miles, church spires. 
 
 5 to 7 miles, windmills. 
 
 2 to 2i miles, chimneys. 
 
 2000 yards, trunks of large trees. 
 
 600 yards, individuals of a column. 
 
 500 yards, individual panes of glass in windows. 
 
 400 yards, arms and legs of dismounted men. 
 
 The average distance between street railway and tele- 
 phone poles is usually 100 feet. In a large portion of the 
 United States the land is divided into sections, and the 
 hedges and fences are usually 440 or 880 yards apart. 
 
36 TOPOGRAPHY 
 
 19. In surveys and large scale mapping, distances are 
 obtained by more accurate methods — by steel tape or chain, 
 transit and stadia, or triangulation. 
 
 20. Elevations are determined by instruments which 
 measure the total difference of elevation by spirit level and 
 rod, by barometers which indicate directly the difference 
 or by instruments which show the gradient or slope and the 
 difference in elevation is then obtained by calculation. 
 
 21. The difference of elevation by spirit level and rod 
 is generally obtained only in accurate work. However, the 
 clinometer can be set at zero and then used as a level, though 
 the results are not very accurate. 
 
 22. Barometers are instruments which show by direct 
 reading the results of differences of air pressure. The 
 aneroid barometer is graduated so as to show the elevation 
 in feet; other barometers require much calculation after 
 reading the instrument. Due to atmospheric changes baro- 
 metric levelling requires complex adjustment to secure 
 even approximate results. 
 
 23. The slope method of determining differences of 
 elevation is the one in general use in sketching. 
 
 24. Slopes are usually expressed in degrees (plus for 
 rising grades and minus .for descending) ; or in per cent, 
 i. e., the rise or fall in feet for each 100 feet horizontal dis- 
 tance. They may also be expressed as follows : 
 
 The foot-rise per mile; as "the grade is 50 feet," or "a 50- 
 foot grade." 
 
 The number of feet vertical per foot horizontal; 3s 1 on 1, 
 6 on 1. 
 
 25. In reconnaissance work, slopes may be determined 
 directly by the use of : 
 
 1. The gravity clinometer; 
 
 2. The Abney or spirit-level clinometer; 
 
 3. The locater level (a hand level with object glass grad- 
 uated in degrees or per cent) ; 
 
 4. The slope board and plumb line. 
 
 26. For ordinary sketching, the following rough rules 
 are sufficiently accurate for determining differences of ele- 
 vation on slopes of not more than 10°. 
 
 (a) When slope is given in degrees take product of hori- 
 zontal distance .0175, and the number of degrees in the slope; 
 
 (b) When slope is expressed as a grade in per cent take 
 product of grade by horizontal distance and divide by 100. 
 
USE OF INSTRUMENTS 37 
 
 27. Elevations may also be shown by profiles. In pro- 
 files, as well as on relief maps, it is usual to adopt a vertical 
 scale larger than the one for horizontal distances. The ratio 
 of the two scales is called the vertical distortion or exag- 
 geration. Ten or 20 feet to the inch is a common scale for 
 profiles ; if the horizontal scale is 3" to the mile, the result- 
 ing distortions are 176 and 88 times. Both horizontal and 
 vertical scales should always be written below profiles. 
 
 28. Contours: — Differences of elevation are shown by 
 writing on the sketch numbers corresponding to elevations 
 (in feet) , by hachures, or by contours. These have already 
 been discussed in a minor way in Chapter II. Contouring 
 is hereinafter discussed in so far as is deemed necessary for 
 assistance in sketching. 
 
 29. The most difficult part of sketching is the repre- 
 sentation of ground forms by continuous contour lines. This 
 arises from the fact that contours are on the ground imag- 
 inary lines, and their location on the map requires the de- 
 termination of all three co-ordinates — azimuth, distance, 
 and difference of elevation — of points. 
 
 The shore line of a quiet lake with no outlet, may be 
 considered a contour line. As one walks around the lake 
 in the direction of the hands of a clock, he always has water 
 on his right hand and ground on a higher elevation on his 
 left hand. If one desires to follow the above line, he will 
 have to turn to the left arid walk up every valley to get 
 around the head of the water line, cross the valley line at 
 right angle, and then turn to the right, again following down 
 the other side of the valley to get around the point of the 
 hill or spur which lies between that valley and the next. 
 His course will bend back at every little drainage line, cross 
 it, and turn again on the other side to get around it. We see 
 then that valley contours go in pairs, that is, there is al- 
 ways one of the same elevation on each side of the valley. 
 They form a sort of V which opens out in the direction of 
 water flow; point of the V upstream. Similarly the spur 
 contours go in pairs. They form a sort of U which opens 
 out to higher ground up the spur. 
 
 The typical contour, then, is a wavy line, alternately 
 salient and re-entrant, a series of V's for the valleys and U's 
 for the spurs. If then the extreme points of the V's and 
 
38 TOPOGRAPHY 
 
 U's are determined and these points are connected by a curv- 
 ing line, opening out gradually as we go down stream from 
 the points of the V, and rounding out to the point of the U, 
 we get a line which will roughly represent the contour of 
 the ground for the particular elevation. In other words the 
 head of the V's or the points where the contour crosses 
 the stream, and the points of the U's or the points where 
 the contour crosses the line of the watershed between two 
 valleys are essential control points for the drawing of any 
 contour line ; and having these points well located, the con- 
 tour between them can be drawn in by looking at the ground 
 in the field. 
 
 It is evident that it will not be practicable to locate the 
 points where each contour crosses each stream or ridge 
 line. No map can show every change of form of the ground. 
 Certain points of the ground are, however, form-controlling. 
 Between these form-controlling points, the assumption is 
 made that the ground slopes uniformly. The effort there- 
 fore should be to locate the form-controlling points, and 
 having drawn these in, intervening ones may be spaced 
 uniformly. 
 
 30. These form-controlling points are called critical 
 points. They are along the valleys and on the watersheds, 
 because the bottoms of valleys and tops of ridges are the 
 lines where opposite slopes meet, and therefore the con- 
 tours themselves change direction most rapidly at their 
 crossing of these lines — the ridge lines and the valley lines. 
 Indeed at the valley lines and the ridge lines the contours 
 begin to turn in an opposite direction. Of course, the forms 
 of the ground change at numberless places not in the bot- 
 toms of the valleys and on the tops of the ridges, but these 
 changes are not very great. 
 
 31. Having placed on the map the critical points, it is 
 assumed that the slopes are uniform between these points, 
 and points of same elevation as the contour lines are inter- 
 polated. After this interpolation, we have on the sketch 
 the critical points whose elevations have been determined, 
 and a number of intervening points whose elevations have 
 been interpolated. Now, if we have the ground in view, 
 we may, with a fair degree of truth sketch the contours on 
 the map. 
 
USE OF INSTRUMENTS 39 
 
 32. In sketching, it is always best, if time permits, to 
 complete the circuit of an area, make the map close by ad- 
 justing the circuit and by a corresponding adjustment of 
 the critical points, and then go over the terrain again and 
 with the critical points as a guide draw in the contours 
 while looking at the terrain itself in order to show on the 
 sketch minor changes in terrain which are not obtained by 
 the critical points and the interpolated elevations. This 
 means simply that the control of the map should be com- 
 plete and in satisfactory adjustment before the details are 
 added. Should time be lacking it may be necessary to put 
 in the details as the control is taken, in such a case an ad- 
 justment of the control will require an adjustment of all 
 the details. 
 
 34. A little practice with a contoured map will be of 
 advanta-ge in obtaining an appreciation of the critical points 
 in drawing contours. An area on a map should be selected 
 with many changes of directions of stream lines and with 
 contours not uniformly distant apart. Then a piece of trans- 
 parent paper should be placed over the area, and critical 
 points selected and marked with their elevations on the 
 transparent paper. The paper should then be removed from 
 the map, and effort should be made to reproduce the con- 
 tours of the map without looking at it. 
 
 35. The vertical interval between contours of a cone 
 system is constant. The distance between contours on a 
 map varies with the slope of the ground. The steeper the 
 slope of the ground the closer together are the contours on 
 the map. The slope of the ground can be obtained from the 
 distance apart of the contours on the map to scale and the 
 known vertical, interval of the contours. A scale may be 
 constructed which, applied to the distance between con- 
 tours on the map, will indicate the slope of the ground. The 
 tangent of 1° is approximately .0175. If I is the vertical 
 interval in feet and R is the representative fraction, then 
 the distance apart in inches on the map of contours for a 
 one degree s^pe of the ground is 
 
 12 I x R 
 .0175 
 
40 TOPOGRAPHY 
 
 This applied to a map of one inch to one mile with a verti- 
 cal interval of 60 feet gives 
 
 12 X 60 
 
 = .65 inch. 
 
 .0175 X 63360 
 
 A scale may be obtained by multiplying the distance for one 
 degree by the number of degrees and will be approximately 
 correct up to slopes of 10°. Such a scale is called a scale of 
 slope equivalents. 
 
 36. Details of Making a Sketch : — Set up the board 
 at the point of beginning, station A. Free the needle. Turn 
 the board until the needle comes to a rest along, the 
 middle line of the needle trough. The board is now oriented. 
 Clamp the board by tightening the screw under the center 
 of the board. It is unnecessary to clamp very tightly. Place 
 a pin at any point of your paper to represent station A. Draw 
 a triangle around the pin and write the elevation (generally 
 given) of station A. Place the alidade on the board, press- 
 ing it against the pin. Select a well defined object or a 
 critical point to the right, left, or rear, pivot the alidade 
 on the pin, and sight on the object. Draw a ray to the 
 point; then measure the difference of elevation. Write 
 with light pencil at end of ray the name of object and the 
 -degrees of elevation. Plot the distance to the object; then 
 determine the difference of elevation by multiplying the 
 difference of elevation on the alidade corresponding to 1 
 degree for the distance by the number of degrees measured. 
 Add this difference (algebraically) to the elevation of sta- 
 tion A and write the elevation opposite the point plotted. 
 Erase the ray. 
 
 Similarly sight on other objects which can be best 
 sketched from station A, and plot them on the sketch. 
 
 Draw in the stream lines, the ridge lines, and the na- 
 tural and artificial features of the terrain. If it is not ex- 
 pected to make a second trip over the terrain, due to lack 
 of time, interpolate elevations on the sketch and now draw 
 contours in accordance with the actual form of the ground. 
 
 37. Finally, look ahead, select a suitable point for the 
 next station, a point from which much sketching can be 
 done, sight on it, draw the ray, measure the degree or per 
 
USE OF INSTRUMENTS 41 
 
 cent of elevation, set pace tally at zero, loosen clamp screw, 
 tighten the needle, pick up the equipment, and start pacing 
 to station B, which is best chosen when an extended view 
 of the terrain can be obtained therefrom. 
 
 38. On the way to station B, do not be diverted into 
 setting up unnecessarily on the road. It is generally possi- 
 ble to select a good station from the last station, and it is 
 rarely worth the time to set up to sketch some data on the 
 way. If deemed necessary, it is sufficient to stop for a min- 
 ute, read the pace tally, make a side drawing of the special 
 data at the distance as shown by the pace tally, clearly 
 identifying it by noting on it the number of paces of the 
 pace tally, then proceed on the way, without setting back the 
 pace tally. 
 
 39. Arrived at station B, set up as described for sta- 
 tion A. Sight back to station A and measure the angle 
 of elevation as a check. Calculate from the alidade the 
 difference of elevation, add it (algebraically) to the eleva- 
 tion of station A, write it down on the sketch at station B, 
 and then proceed as before. Sight to points that are to 
 appear on the map. Plot them as before. Sight to points 
 which were also sighted from station A with a view of ob- 
 taining their positions by intersection (being unable to pace 
 or estimate them from station A). Plot them at intersec- 
 tions, measure and calculate the differences of elevation, 
 and write in the proper elevation for each point. Draw the 
 terrain, with contours if necessary, sight to distant points 
 for later location by intersection from other stations ; finally 
 select station C, sight on it, draw ray, measure angle of 
 elevation, pick up equipment, and proceed to next station. 
 
 40. Should the route lead the sketcher back to the 
 starting point the traverse will close if the work has been 
 accurately done. If it, in such case, does not close, the 
 amount of failure to do so will indicate the accuracy of the 
 work. If the failure to close is so great as to indicate blun- 
 der the blunder must be found and corrected. If it is such 
 as to be accounted for by the lack of accuracy in the methods 
 employed and is so great as to distort the sketch then the 
 sketch may be adjusted by the ordinary method, which is: 
 draw a line from the final location of the initial point to its 
 first location and displace each traverse station, to- 
 
42 TOPOGRAPHY 
 
 gether with all points located therefrom, in the direction of 
 this line and by a proportional part of it determined by the 
 ratio of the traversed distance to the station in question 
 to the whole traversed distance of the circuit. 
 
 41. Indoor Exercises in Use of Instruments may be 
 used with advantage to acquire facility in use. For rainy 
 days, and to save time, they are very useful; but they can- 
 not take the place of work in the field. 
 
 For indoor work, the student is furnished a chart as 
 shown on small scale in Plate VI, and is given such informa- 
 tion as he would acquire in the actual operation of sketch- 
 ing in the field. He is then required to make the sketch 
 with this information, and draw in the contours and other 
 features just as he would do in actual field work. 
 
 42. The following problem is an example of indoor work 
 in sketching: 
 
 Scale 6 inches to 1 mile. 
 
 10 foot contours. 
 
 Length of stride 72 inches. (Assumed as 72 inches in order 
 to use yard scale as stride scale.) 
 
 All clinometer readings to ground line unless otherwise 
 stated. Height of eye 5 feet. 
 
 Magnetic declination, 9° East. 
 
 Directions are given by reference to a co-ordinate point to- 
 wards which the object is located as seen from the station. By 
 the use of the station and the given co-ordinate point the alidade 
 may be placed in the direction of the object which is to be located 
 as it would be done by sighting in the field. 
 
 Sketch to be drawn on a gridded sheet similar to Plate VI. 
 
 Eequired : 
 
 Sketch west half of area bounded by Somers Road on 
 west, Franklin Road on north, Charles Pike on east, and 
 Somerville — Sunflower Road on south. Use traverse data 
 below ; and make sketch include 200 yards outside traverse 
 which 200 yards is given in data. 
 
 A traverse will be run from A, intersection of Somers- 
 ville — Sunflower Road (west and east) with Somers Road 
 (to north), north along Somers Road to Franklin Road, 
 thence east along Franklin Road 1200 yards to high ridge 
 in eastern part of area, thence south to Somersville — Sun- 
 flower Road, thence west to A. This will give a good road 
 on which to pace a base for constructing the map, will com- 
 pletely cover the area, and will provide a closed traverse for 
 checking the work. 
 
300 301 
 
 /ndoor Exercise in Jke tching 
 
 764 
 
 76S 
 
 76 Z 
 
 761 
 
 760 
 
 30O 
 
 301 
 
 Plate M 
 
 ion 
 
 764 
 
 763 
 
 76Z 
 
 761 
 
 30£ 
 
 76<T 
 
44 TOPOGRAPHY 
 
 Set Up at A 
 
 A is located on the sheet at co-ordinated point 300.68 — 
 760.90. Known elevation at A is 167 feet. Road runs in a 
 westerly direction toward Somersville, straight as far as 
 visible, about 500 yards, direction towards co-ordinate point 
 300.00 — 761.05. Same road runs in an easterly direction, 
 straight as far as can be seen, about one-half a mile, direc- 
 tion towards point 302.00 — 760.60. Somers Road runs 
 northward direction towards point 300.75—762.00, to Bend 
 B, estimated about one-half -a mile distant. 
 
 Farmhouse of John Somers is in northeast corner of 
 road intersection. 
 
 Land east of Somers Road (as far as visible, about one- 
 half mile) , and north of Somersville — Sunflower Road (about 
 500 yards), is plowed. 
 
 South from A is a knob (Al), direction towards point 
 300.65 — 760.00, distance estimated 900 yards, slope read- 
 ing plus | degree. 
 
 A spur extends northwesterly from this knob to point 
 A2, direction towards point 300.17 — 760.00, distance from 
 A estimated 500 yards, slope reading plus f degree. 
 
 West of A is a head A3 of a dry stream running north- 
 eastwards. The point A3 in is direction of co-ordinate point 
 300.00 — 760.97, distance estimated 35 1 yards, slope reading 
 zero. This same dry stream crosses the Somers Road at 
 A8, distance estimated 400 yards north of A, slope reading 
 minus J degree. 
 
 Northwest of A is a knob A4 (running north and south) 
 direction towards point 300.00 — 762.20, distance esti- 
 mated 700 yards, slope reading plus J degree. 
 
 Northeast of A is a flat knob A5, direction towards 
 point 302.00 — 761.90, distance estimated 1 mile, slope read- 
 ing plus £ degree. 
 
 A6, the saddle between A5 and A2 is in the direction of 
 A5 from A, distance from A estimated 125 yards, slope 
 reading minus one degree. 
 
 At a point A7, 450 yards eastward of A, the Somersville 
 Road crosses a dry stream running towards the northeast, 
 slope reading minus J degree. 
 
USE OF INSTRUMENTS 45 
 
 Sketch in the topography including the contours so far 
 as may be done from the above data. 
 
 The next station will be in the direction of B. A sight 
 towards it has already been taken above. 
 
 This ends set up at A. 
 
 Traverse Towards B 
 
 Stop at A8 but do not set up. 
 
 The distance of A8 from A is found to be 205 strides. 
 This checks very closely the estimated distance given above. 
 The dry stream from A3 to A8 is noted to be practically 
 straight, and just beyond A8 this stream bends towards the 
 north passing about one hundred yards east of B. 
 
 Continue Traverse Towards B 
 
 Stop at A9, northern edge of plowed field, but do not 
 set up. 
 
 Distance from A to A9 is 250 strides. Northern edge 
 of plowed field as far as visible about \ mile extends in the 
 direction towards point 302.00—761.13. 
 
 Continue Traverse Toivards B 
 Total distance- A to B is found to be 375 strides. 
 
 Set Up at B ' 
 
 Backsight towards A, slope just a little above zero 
 (about 3 feet). 
 
 Correct location and elevation of B to conform to the 
 correct distance given above. 
 
 The road ahead runs towards co-ordinate point 300.40 
 — 763.00 as far as point C (intersection with Franklin Road) 
 about | mile from B (plot direction carefully as probably 
 next station will be towards C), slope reading to C is zero. 
 On east side of road at B is farmhouse with mail box 
 marked "Henry Somers." 
 
 From B, hill A4 is found to be in the direction of point 
 300.00—761.37. The intersection of this line with the direc- 
 tion line from A checks fairly closely the estimated dis- 
 tance of A4 from A given above. 
 
 The top of hill A5 cannot be seen very clearly from B, 
 A5 appears to be in the direction of point 302.00 — 761.75, 
 
46 TOPOGRAPHY 
 
 and the slope reading about plus | degree. The intersection 
 of this line with the direction given from A indicates that 
 the estimated distance of A5 from A was too great by about 
 400 yards. Correct location and elevation of A5. 
 
 To the northwest, in the direction of point 300.00 — 
 762.35, is a lone tree Bl, estimated distance 400 yards from 
 B, which marks end of the flat spur extending northwards 
 from hill A4 ; slope reading zero. To the northeast is a 
 round knob B2, direction towards point 302.00 — 762.60, es- 
 timated distance 1000 yards, slope reading plus \ degree. 
 
 A saddle connecting B2 with A5 cannot be clearly seen 
 from B. 
 
 To the northeast, towards point 301.90 — 763.00, is point 
 B3 the lower end of a wide spur running down from B2, 
 distance estimated 500 yards, slope reading zero. 
 
 To the north towards point 301.40 — 763.00, distance 
 estimated 300 yards, the dry stream A3-A8 bends to the 
 west of north. 
 
 Northeast of B, towards point 302.00—762.10, is B4, 
 the foot of a draw leading towards the saddle between B2 
 and A5, distance estimated 400 yards, slope reading minus 
 I degree. 
 
 Sketch in so much of the topography including contours 
 as can be done from the above data. 
 
 The next station will be in the direction of C (a sight 
 towards it has already been taken). 
 
 This ends set up at B. 
 
 Traverse Towards C 
 
 Stop and set up at B5, on Somers Road 300 strides 
 north of B. 
 
 Short Set Up at B5 
 
 Slope reading B5-B is zero. 
 
 To northeastward, towards point 302.00 — 762.70, is 
 B5a, the southwest corner of woods W (large trees, no un- 
 derbrush) , distance estimated 200 yards. The western edge 
 of woods W runs a little east of north. The southern edge 
 of woods W extends past B5b, which is towards point 302.00 
 — 762.35, distance estimated 500 yards, slope reading zero. 
 
 A draw extends from just south of B5a through B5b. 
 
USE OF INSTRUMENTS 47 
 
 The dry stream from A3-A8 passes just east of B5a 
 and continues on to the west of north. 
 
 From B5 the direction of B3 is towards point 302.00 — 
 761.60. The intersection of this line with the direction 
 given above from B checks fairly closely the estimated dis- 
 tance of B3 from B. 
 
 From B5, the direction of Bl is towards point 300.00 — 
 761.20. The intersection of this line with the direction given 
 from B, checks closely the estimated distance of Bl from 
 B. 
 
 About 200 yards ahead, at point B6, the road crosses a 
 dry stream running from the southwest towards the north- 
 east, slope reading B5-B6 minus f degree. 
 
 End of set up at B5. 
 
 Continue Traverse Towards C 
 Stop and set up at B6, 365 strides from B. 
 
 Short Set Up at B6 
 
 The dry stream through B6 comes from the direction 
 of point 300.00 — 761.90, and continues to the northeast to- 
 wards point 300.85 — 763.00. About 100 yards northeast of 
 B6 it is joined by the stream from A3-A8-B5a. 
 
 End of set up at B6. 
 
 Continue Traverse to C 
 Distance from B to C is 645 strides. 
 
 Set Up at C 
 
 Backsight to B, slope minus Vg of 1 degree. 
 
 Correct location of C to conform to correct distance. 
 
 The Somers Road ends at C where it runs into the 
 Franklin Road which runs eastwards towards point 302.00 
 — 762.66, as far as D, estimated more than 1000 yards dis- 
 tant, slope reading zero. To the west, the Franklin Road 
 runs in prolongation of the above towards Westport. 
 
 To the northwest, towards point 300.00 — 763.13, is 
 point CI, head of a dry ravine running towards the north- 
 east; distance of CI from C estimated 250 yards, slope read- 
 ing minus 1| degrees. 
 
48 TOPOGRAPHY 
 
 About 400 yards southwest of C, towards point 300.00 
 — 762.50, is C2, slope reading C-C2 is plus I degree. The 
 crest of a spur runs from C2 through C to the northeast 
 towards C3. The direction of C3 is towards point 302.00 — 
 764.00, distance from C estimated 700 yards. Slope reading 
 C-C3 is minus f degree. 
 
 Hills A5 and B2 are concealed from C by woods W. 
 
 Sketch in so much of topography including contours 
 as may be done from the above data. 
 
 Sketch now looks like figure T 13 in back of Topography, 
 except it is twice as large as that given in the figure. 
 
 The next station will be in the direction of D (sight to 
 D already taken). 
 
 This ends set up at C. 
 
 Traverse Towards D 
 
 Stop and set up at C4 where the dry stream from B6 
 crosses the Franklin Road 180 strides east of C. 
 
 Short Set Up at CU 
 
 Slope reading C4-C is plus \ degree. 
 
 C4a, northwest corner of woods W, is towards point 
 301.35—762.00, distance estimated 150 yards. The north- 
 ern edge of the woods parallels the Franklin Road. The dry 
 ravine through C4 runs practically straight from B6 and 
 continues to the northeast towards point 301.60 — 764.00. 
 
 End of set up at C4. 
 
 Continue Traverse Toivards D 
 Distance from C to D is 585 strides. 
 
 Set Up at D 
 
 Backsight to C, slope reading minus Ye of 1 degree. 
 
 Correct the location and elevation of D. From D the 
 Franklin Road continues eastward towards point 302.00 — 
 762.70, straight for about a mile. 
 
 From D, knob B2 (previously sighted from B) is to- 
 wards point 301.75 — 762.00, slope reading plus 1 degree. 
 The intersection of this line with the direction plotted from 
 B shows that the estimated distance of B2 from B was 
 
USE OF INSTRUMENTS 49 
 
 about 175 yards short. Correct the location and elevation 
 of B2. 
 
 From D, C3 is towards point 300.25—764.00. The in- 
 tersection of this line with direction of C3 from C shows 
 that the estimated distance of C3 from C was a little too 
 great. 
 
 Slope reading to Dl, a point about 300 yards to the 
 east on Franklin Road where the road begins to run down 
 hill is minus | degree. 
 
 D2, on the downward slope to the north, is towards 
 point 301.90 — 764.00, distance estimated 300 yards, slope 
 reading minus 1 degree. 
 
 The eastern edge of woods W is on the line towards 
 point 301.20—762.00. The northeastern corner, D3, is esti- 
 mated to be about 150 yards from D. 
 
 The next station will be in the direction of E which is 
 towards point 301.54 — 762.00, distance estimated 250 yards, 
 slope reading plus § degree. 
 
 Sketch in so much of topography including contours 
 as may be done from the above data. 
 
 This ends set up at D. 
 
 Traverse Towards E 
 
 Distance D-E is 125 strides. This checks the estimated 
 distance above. 
 
 Set Up at E 
 
 Backsight to D, slope reading is minus 1| degree. 
 
 The point E is on a small spur extending westwards 
 into woods W from north end of knob B2. 
 
 To the southwest of E is El, the southeast corner of 
 woods W, direction towards point 300.60 — 762.00, distance 
 estimated 200 yards. 
 
 The next station will be located in the direction of F 
 which is on spur between B2 and B3, direction from E is 
 towards point 301.54 — 762.00, distance estimated 250 yards, 
 slope reading zero. 
 
 Sketch in so much of topography including contours 
 as may be done from the above data. The sketch should now 
 look like figure T14 in the back of pamphlet on Topography, 
 except it is twice as large as that given in the figure. 
 
 This ends set up at E. 
 
50 TOPOGRAPHY 
 
 Traverse Toicards F 
 
 Distance E-F is 130 strides. This checks the estimated 
 distance to F. 
 
 Set Up at F 
 
 Backsight towards E, slope reading minus f degree. 
 
 From F, former station B is towards point 300.00 — 
 761.10. This line passes through station B as plotted on 
 the map. This indicates that no errors have been made in 
 running and plotting traverse from B to E (Note: Station 
 A cannot be seen from F). 
 
 From F, B2 is in the direction of point 302.00—762.78 
 and B3 is in the direction of point 300.00 — 761.55. This 
 checks the former location of those points. 
 
 From F, hill A5 is in the direction of point 302.00 — 
 761.20, slope reading zero. Intersection of this line with 
 the direction of A5 from A now definitely locates A5. The 
 rough intersection formerly made from station B is found 
 to be very close. 
 
 The draw from B4 starts at Fl ; direction of Fl from F 
 is towards point 301.47 — 761.00, distance estimated 400 
 yards, slope reading minus 1 degree. To the southeast of 
 F is F2 which is the head of a dry ravine running towards 
 the northeast; direction of F2 from F is towards point 
 302.00—761.50, distance estimated 350 yards. F2 is about 
 the same height as Fl. 
 
 East of F is F3, another point in the dry ravine from 
 F2, direction from F is towards point 302.00 — 762.10, dis- 
 tance estimated 475 yards, slope reading minus 1 degree. 
 
 The next station will be in the direction of G which is 
 on spur between A5 and A, direction of G from F is towards 
 point 301.47 — 761.00, distance estimated 600 yards, slope 
 reading minus i degree. 
 
 Sketch in so much of topography including contours 
 as may be done from the above data. 
 
 This ends set up at F. 
 
 Traverse Towards G 
 Distance F-G is 330 strides. 
 
USE OF INSTRUMENTS 31 
 
 Set Up at G 
 
 Backsight to F, slope reading zero. 
 
 Correct the location of G. 
 
 From G, station A is in the direction of point 300.00 — 
 760.30, and station B is in the direction of point 300.00 — 
 761.68. These lines pass through those stations respec- 
 tively. This indicates that the running and plotting of the 
 traverse is correct. 
 
 From G, A5 is towards point 302.00—761.90. This 
 checks the former location of A5. 
 
 South of G is Gl, northeast corner of plowed ground 
 mentioned under A above, direction from G is towards point 
 301.47—761.00, distance estimated 330 yards. From Gl 
 the northern edge of the plowed ground runs toward A9, 
 and the eastern edge runs due south. 
 
 South of G is G2, point in dry ravine from A7, direc- 
 tion toward point 301.57 — 761.00, distance estimated 500 
 yards, slope reading minus l ! i-, degree. 
 
 Southeast of G is G3, another point in same dry ravine 
 as G2, direction towards point 302.00 — 761.10, distance es- 
 timated 550 yards, slope minus 1% degree. 
 
 The next station will be at H which is south of G on 
 the Somerville — Sunflower road, direction from G is to- 
 ward point 301.41 — 760.00 (the intersection of this line 
 with the road locates H), slope reading minus i degree. 
 
 Sketch in such topography including contours as may 
 be done from the above data. 
 
 This ends set up at G. 
 
 Traverse Toivards H 
 
 Stop at Gl and G2. 
 
 Gl is found to be 165 strides. 
 
 G2 is found to be 250 strides from G. These check 
 the former estimated distances to Gl and G2. The direc- 
 tion of A7 and G3 are noted to be very close to that already 
 plotted. 
 
 Continue Traverse Towards H 
 
 Distance G-H is found to be 430 strides. This checks 
 very closely the above location of H by intersection. 
 
52 TOPOGRAPHY 
 
 Set Up at H 
 
 As far as can be seen, about 800 yards, the road to 
 Somerville continues directly in prolongation of the section 
 already located. 
 
 On road to east of H a dry ravine crosses the road at 
 HI, distance estimated 300 yards, slope reading minus -\ 
 degree. This dry ravine comes from a little west of south 
 through HI and continues on and appears to join the G2- 
 G3 ravine about 200 yards east of G3. 
 
 Southeast of H is H2, end of spur running down from 
 Al, direction of H2 from H is toward point 301.60—760.00, 
 distance estimated 200 yards, slope reading is zero. 
 
 From H, hill Al is in the direction of point 300.65 — 
 760.00, and spur A2 is in the direction of point 300.00 — 
 760.30. The intersection of these lines with the directions 
 formerly given from A checks very closely the estimated 
 distances from A. 
 
 Sketch in as much of topography including contours 
 as may be done from the above data. Sketch should now 
 look like Figure T15 in the back of Topography, except that 
 it is twice as large as the sketch in that figure. 
 
 This ends set up at H. 
 
 Traverse Towards A 
 
 Distance H-A is 400 strides. This checks very closely 
 the location already plotted. This indicates that no ap- 
 preciable error has been made in running and plotting the 
 traverse. 
 
 End of Data 
 
 Place title and name on sketch. 
 
 Practical Exercises in Use of Instruments 
 
 1. From station A, you take a clinometer reading to 
 the ground line at B. The height of your eye is five and 
 one-half feet above the ground at A. The clinometer read- 
 ing is two degrees down. The distance to B is paced off 
 and found to be 200 strides (60 inches each). Is B higher 
 or lower than A, and how much ? 
 
USE OF INSTRUMENTS 53 
 
 2. A hill a half-mile away has a clinometer reading, 
 from station A, of plus six degrees. The elevation of sta- 
 tion A is 1480 feet. What is the elevation of the hill? 
 
 3. The distance to a wireless tower, as plotted by you 
 on your sketch, is 550 yards. The clinometer reading to 
 the mound at the base of the tower is | degree descending. 
 The reading to the top of the tower is 3i degrees ascending. 
 What is the height of the tower? 
 
 4. A man climbs a tower at A and reads the slope to a 
 crqssroad B. The clinometer reads minus 4^ degrees. He 
 descends 70 feet to the ground and reads again to the same 
 point. The reading is now minus ^ degree. About how 
 many yards away is the crossroad? 
 
 5. Your elevation at A is 770 feet. Clinometer reading 
 to ground at crossroad E is plus 2 degrees, distance 1000 
 yards, and from A to base of flagstaff at F is plus 3 degrees, 
 distance 1500 yards. (Height of eye, 60 inches.) What is 
 elevation of crossroad E? Of base of flagstaff F? 
 
 6. Marks have been put on two posts, A and B. Sight- 
 ing from A to B, your clinometer reads minus £ degree. 
 From B to A, the reading is minus H degrees. What is the 
 correct reading from A to B ? 
 
 7. Does the instrument read too high, or too low, and 
 how much? 
 
 8. How will you correct in the future for this error in 
 your instrument — 
 
 (a) On plus readings? 
 
 (b) On minus readings? 
 
 9. Location of a Point by Intersection: — (Use 
 blank grid sheet.) Locate on a sheet of paper the point A 
 at 301.0 — 763.0. Your sketching board is set up at A and 
 oriented. (True north at top of paper.) Scale of sketch 
 to be 6" to the mile. You sight ahead to a new station B, 
 which is on the line from A to co-ordinate 305.0 — 764.0. 
 Draw in this line of sight. You sight on a hill on your right 
 with a flagstaff (F) on line from A to co-ordinates 305.0 — 
 760.0. Draw in this line of sight. (The distance to F is 
 estimated as 600 yards, but it is probable you can get 
 another sight later from the new station B.) You then pace 
 off the distance from A to the new station B, and find it to 
 
54 TOPOGRAPHY 
 
 be 360 strides (72 inches each). You set up your board, 
 plot your new location B, and then sight on flagstaff F, which 
 lies in the direction B to co-ordinate 304.0 — 760.0. Locate 
 the flagstaff F on the sketch. What is its general direction 
 from B? How many yards from A to F? From B to F? 
 
 10. Location of a Point by Resection on Two Known 
 Points: — (Use blank grid sheet.) 
 
 Captain E, who is making a six-inch-to-the-mile sketch, 
 finds himself at an unknown point, C, which he needs to 
 locate. He has on his sketch the locations of two prominent 
 points, A and B, both visible from C. A is at 301.0 — 761.1; 
 B is at 303.3 — 762.0. Orienting his board at C, Captain 
 E sights at and draws in lines of sight towards A and B. 
 On his sheet the line CA has an azimuth of 195°; the line 
 CB has an azimuth of 120°. How many yards is C from B? 
 
 11. Location by resection on three points: (Use blank 
 grid sheet and tracting paper.) 
 
 On his sketch (6" equal 1 mile) Captain E has three 
 prominent points. A at 300.5—764.2, B at 302.0—764.2, C 
 at 304.1 — 763.7. All are visible from his present unknown 
 location X. Setting up his sketching board (unoriented, as 
 his compass is broken), Captain E puts a sheet of tracing 
 paper on the board over his sketch, puts in a pin near the 
 middle and calls this point (X) . (Put tracing paper over 
 grid sheet and plot X near center of sheet.) He draws 
 rays to A, B, and C. Ray XA has an azimuth of 297° ; ray 
 XB, of 355° ; ray XC, of 45°. 
 
 1. Locate X on the sketch. 
 
 2. How many yards from X to A ? From X to B ? From 
 X to C? What is the general direction from A to X? 
 
 3. The elevation of B to 592. The slope reading X— B 
 is 3 degrees down. The slope reading X — A is 1 degree up, 
 X — C, 1 degree down. Disregarding height of eye, what are 
 elevations of points X, A and C ? 
 
 12. Place a sheet of tracing paper over area of 3" 
 Leavenworth sheet bounded by Millwood Road, Kickapoo 
 Road, Atchison Pike, Co-ordinate 343.0. Select 21 critical 
 points and write their elevations in proper place ; put noth- 
 ing else on tracing paper. Set aside map. Draw in 20-foot 
 contours. Place on map and compare result. 
 
USE OF INSTRUMENTS 55 
 
 13. Drawing of road sketch in room from data given 
 (use blank grid sheet) . Scale 6" to 1 mile. Vertical inter- 
 val, 10 feet. This problem, uses compass for practice. 
 
 NOTE No. 1 : — Unless otherwise stated, all ground in this prob- 
 lem is meadow land. 
 
 NOTE No. 2: — All slope readings are taken at the height of the 
 eye; that is, all lines of sig'ht are taken on a point (in the air) which 
 is above the object a distance equal to the height of the observer's eye. 
 
 NOTE No. 3:— Strides are 60 inches. 
 
 NOTE No. 4: — All roads are unimproved earth roads. Special 
 data such as size of rails on railways, character of houses for defense, • 
 etc., are omitted (for brevity in description). 
 
 Set Up at A 
 
 A is a point on road with co-ordinates 301.2 — 760.3 on 
 the gridded sheet. Known elevation of A is 875 feet. 
 
 Al, road with magnetic azimuth 78 degrees, distance to 
 top of ridge estimated 600 yards, difference of elevation 
 estimated plus 7 feet. 
 
 A2, same road as above (fenced in and discontinued on 
 western side of road) with magnetic azimuth 258 degrees, 
 distance to ridge top estimated 350 yards, slope plus 4 de- 
 grees ; two wooden houses at top of ridge. 
 
 A3, road with magnetic azimuth 170 degrees, distance 
 100 yards, difference of elevation estimated minus 10 feet. 
 
 A4, along edge of ridge, magnetic azimuth 275 degrees, 
 distance estimated 200 yards to edge of woods, 400 yards 
 to top of ridge, slope plus 6 degrees. 
 
 A6, smoke stack, magnetic azimuth 66 degrees, location 
 to be obtained by intersection later. 
 
 Sketch in, by looking at terrain: 
 
 (a) Ravine from station, magnetic azimuth 258 degrees, 200 
 yards long, 10 feet deep. 
 
 (b) Ravine from station, magnetic azimuth 263 degrees, 150 
 yards long, 8 feet deep. 
 
 (c) Corn on right; meadow at left; wire fences. 
 
 Sight station B, magnetic azimuth 350 degrees. 
 End of set up at A. 
 
 Traverse Toward B 
 
 Stop at A7, bottom of stream line, 125 strides, estimated 
 5 feet below A. Stream line comes from magnetic azimuth 
 290 degrees (made up of two stream lines joining 200 yards 
 
56 TOPOGRAPHY 
 
 away with magnetic azimuths of 320 degrees and 240 de- 
 grees), turns at this point (where it crosses the road) and 
 continues with magnetic azimuth 67 degrees, distance 400 
 yards, estimated difference of elevation 15 feet. Woods, 
 magnetic azimuth 270 degrees, distance 400 yards, differ- 
 ence of elevation estimated 50 feet ; ridge top estimated 600 
 yards, slope plus 4^ degrees ; meadow land to left, corn to 
 right. 
 
 Continue Traverse Toivards B 
 
 Meadow land to left, corn to right; A to B, 240 strides. 
 
 Set Up at B 
 
 Backsight to station A, slope, minus f degree. 
 
 Bl, woods, magnetic azimuth 270 degrees, distance 30 
 yards, slope plus 15 degrees. 
 
 B2, along low ridge line to stream line junction, mag- 
 netic azimuth 90 degrees, estimated distance 550 yards, 
 slope minus 2| degrees ; stream line through A7 joins stream 
 line with magnetic azimuth 310 degrees, new stream con- 
 tinues with magnetic azimuth 110 degrees. 
 
 A6, smoke stack, 82 degrees magnetic azimuth ; slope 
 to its estimated foot, minus one-fifth degree. 
 
 Sketch in, by looking at terrain : 
 
 (a) Large brick wall inclosure around smoke stack, estimated 
 square with sides 300 yards long, walls 70 feet high, buildings 
 in center and along south wall. 
 
 (b) Road from this inclosure, magnetic azimuth 270 degrees, 
 to road junction with road from magnetic azimuth 120 degrees, 
 distance estimated 350 yards; road then continues with mag- 
 netic azimuth 340 degrees. 
 
 (c) Railway 20 yards beyond main road and parallel to it, 
 crossing road from brick inclosure. 
 
 Sight station C, magnetic azimuth 10 degrees. 
 End of set up at B. 
 
 Traverse Toward C 
 
 Stop at B3, bottom of stream line, 210 strides, estimated 
 20 feet below B. Stream line runs magnetic azimuth 90 de- 
 grees for 200 yards, then runs to stream junction at B2. 
 To left of road at B3, stream line enters woods, magnetic 
 azimuth 260 degrees, distance estimated 200 yards, dif- 
 ference of elevation estimated plus 50 feet. Ridge top es- 
 
USE OF INSTRUMENTS 57 
 
 timated 500 yards, slope plus 5 degrees. Meadow land to 
 right. 
 
 Continue Traverse Toward C 
 
 Stop at B4, B to B4, 300 strides ; woods to edge of road 
 on left, top of ridge invisible, slope plus 10 degrees. 
 
 Continue Traverse Toward C 
 
 Woods at edge of road to left; corn to right; B to C 
 452 strides. 
 
 Set Up at C 
 
 Back sight to B, slope, minus 1 degree. 
 
 CI, railway, magnetic azimuth 20 degrees, 55 strides, 
 difference of elevation estimated minus 10 feet. 
 
 C2, center of railway cut 10 feet deep, 100 yards long, 
 magnetic azimuth 90 degrees, 45 strides, top of cut es- 
 timated minus 7 feet. 
 
 C3, direction of road, magnetic azimuth 165 degrees. 
 
 C4, woods at edge of road, magnetic azimuth 270 de- 
 grees, top of ridge invisible, slope plus 10 degrees. 
 
 C5, railway from point 1200 yards with magnetic azi- 
 muth 97 degrees, to a point 500 yards with magnetic azi- 
 muth 110 degrees, then curves in general direction of mag- 
 netic azimuth 320 degrees. 
 
 C6, old earth road, magnetic azimuth 20 degrees, crosses 
 one railroad at 55 strides, second railroad (continuation of 
 curve) at 150 strides. 
 
 C7, woods at head of stream line, magnetic azimuth 
 90 degrees, estimated distance 300 yards, estimated dif- 
 ference of elevation minus 60 feet. 
 
 Sight station D, magnetic azimuth 330 degrees. 
 
 End of set up at C. 
 
 Traverse Toward D 
 
 Woods on both sides, slope down on right, up on left, 
 C to D, 215 strides, actually about 210 strides as road bends 
 slightly to right of straight line C — D. 
 
 Set Up at D 
 
 Draw in road C — D, bending somewhat to right of 
 straight line C — D. 
 
58 TOPOGRAPHY 
 
 Backsight to C, slope minus 3£ degrees. 
 
 Dl, woods to right, magnetic azimuth 40 degrees, slope 
 minus 6 degrees for at least 200 yards. 
 
 D2, woods to left, magnetic azimuth 220 degrees, slope 
 plus 8 degrees for at least 100 yards. 
 
 Sight station E, magnetic azimuth 335 degrees. 
 
 End of set up at D. 
 
 Traverse Toward E 
 
 Woods on both sides until beginning of cut, then 
 meadow land. Slope down on right, up on left until be- 
 ginning of cut. At stride 140, wood road comes from mag- 
 netic azimuth 100 degrees, crosses road DE, and continues 
 with magnetic azimuth 300 degrees. D to E, 260 strides, 
 actually about 250 strides, as road bends about half way to, 
 say 20 yards to left of straight line D — E. 
 
 Set Up at E 
 
 Backsight to D, slope, minus 3 degrees. 
 
 Draw in road D— E, bending to left of straight line 
 D — E about 20 yards at stride 125. 
 
 E is located in center of cut at top of ridge; cut 100 
 strides long, 20 feet high at center; rocky ledges. 
 
 El, direction of ridge, magnetic azimuth 30 degrees, 
 slope plus 1 degree for 500 yards. 
 
 E2, direction of nose, magnetic azimuth 260 degrees, 
 slope zero for 150 yards. 
 
 E3, direction of ridge, magnetic azimuth 167 degrees, 
 slope zero for 700 yards. 
 
 E4, stream line, magnetic azimuth 300 degrees, slope 
 minus 6 degrees. 
 
 E5, wooded hill top, magnetic azimuth 333 degrees, 
 location to be obtained by intersection later, slope zero. 
 Sight station F, magnetic azimuth 335 degrees. 
 End of set up at E. 
 
 Traverse Toward F 
 
 Woods and slope down on left; meadow and slope up 
 on right, E to F 260 strides. 
 
USE OF INSTRUMENTS 59 
 
 Set Up at F ' 
 
 Backsight to E, slope, plus 5 degrees. 
 
 Fl, railway 15 yards from F on side toward E, mag- 
 netic azimuth on left 210 degrees for at least 600 yards; 
 magnetic azimuth on right 42 degrees for 300 yards where 
 road bends to right around nose of hill. 
 
 F2, railway 20 yards beyond F, magnetic azimuth on 
 left 213 degrees for about 500 yards where it bends to right ; 
 magnetic azimuth on right 46 degrees for 300 yards where 
 it bends to right around nose of hill. 
 
 Sight station G, magnetic azimuth 277 degrees. 
 
 Traverse Toward G 
 
 One hundred strides, road to right, magnetic azimuth 
 55 degrees, road junction at this point estimated 30 feet 
 below F. 125 strides, stone house 50 feet to right and wood 
 house 30 feet to left, estimated 30 feet below F, point being 
 on road and at foot of slope to top of hill to north ; 175 strides 
 stone school house 100 feet to right 30 feet up hill side, 
 wood house 20 feet to left, cultivated land to left, cultivated 
 land to right except on steep wooded hill side. 
 
 335 strides to G. 
 
 Set Uv at G 
 
 Backsight to F, slope, plus 2 degrees. 
 
 G2, hill sighted from E, has a long flat top, 55 degrees 
 magnetic azimuth to southern end. 
 
 G3, 10 degrees magnetic azimuth to northern end. 
 
 G4, 55 degrees, 200 yards, estimated difference of eleva- 
 tion plus 40 feet, point where slope changes, thereafter be- 
 ing more rapid rise to top of hill. Corn to south and 
 southwest, orchard and brush on other side of road. 
 
 Sight station H, magnetic azimuth 317 degrees. 
 
 Traverse Toward H 
 
 175 strides, road coming in on left from magnetic azi- 
 muth 245 degrees, trees on both sides of this road, brick 
 house at end, distance 200 yards, estimated difference of 
 elevation minus 5 feet below G. 
 
60 TOPOGRAPHY 
 
 175 strides, 2 wood houses on right of road, on edge of 
 road. Corn on left, brush and meadow on right. 
 350 strides to H. 
 
 Set Up at H 
 
 Backsight to G, slope plus § degree. 
 
 Stream line from 176 degrees magnetic azimuth crosses 
 road at H, going 355 degrees to large creek 375 yards. 
 
 HI, farm road to wood house, 68 degrees magnetic 
 azimuth, 250 yards to wood house, estimated plus 50 feet 
 difference of elevation. 
 
 H2, north edge of flat hill, 60 degrees magnetic azimuth, 
 distance found by intersection of line G — G3 with H — H2. 
 
 H3, small knoll on left, 270 degrees, 100 yards, differ- 
 ence of elevation plus 37 feet. 
 
 H4, wooden house 400 yards farther along road which 
 has a general direction of 317 degrees magnetic azimuth, 
 and crosses large creek at 375 yards, estimated difference 
 of elevation where road crosses creek minus 15 feet. 
 
CHAPTER IV 
 
 Applied Military Sketching 
 
 1. Military sketching aims at showing the features of 
 the terrain that are of special importance to the operation 
 that the sketch is intended to serve, — camp, march, or en- 
 gagement. The features that are usually important in all 
 sketches, whether these features are natural or artificial, 
 are: those which affect the movement of troops and trans- 
 port both on and off the established lines of travel; those 
 which affect the observation of both friendly and enemy 
 troops from the ground and from the air; and those which 
 affect the fire of the various arms. 
 
 2. The ability to produce a satisfactory sketch signifies 
 not only the necessary topographical skill, but also a know- 
 ledge of military operations in general as well as informa- 
 tion as to the immediate operation that is to be undertaken 
 on the terrain to be mapped or sketched. Even with the 
 most exact knowledge of the information that the sketch 
 should show, limitations as to time and as to how much 
 detail a sketch of the scale adopted can show restrict the 
 amount and the kind of data that will be placed upon the 
 sketch. Those features which, in the judgment of the 
 sketcher, have a material bearing on the operations to be 
 undertaken are the features to show. 
 
 3. Military Sketches or Reconnaissances May be 
 Classified as follows : 
 
 Road sketch, 
 
 Reconnaissance of a railroad, 
 
 Reconnaissance of a stream or river, 
 
 Reconnaissance of woods or forest, 
 
 Reconnaissance for a camp or cantonment, 
 
 Reconnaissance for a position (position sketch), 
 
 Outpost sketch, 
 
 Place sketch, 
 
 Panoramic or landscape sketch. 
 
 61 
 
62 TOPOGRAPHY 
 
 Sketches may also be classified as mounted sketches 
 or foot sketches, and as combined sketches or individual 
 sketches, depending on the methods by which they are 
 made. 
 
 4. A Complete Road Sketch should show data on the 
 following subjects: 
 
 The road: Gradients, especially the steepest; net 
 width of roadway; if paved, width, kind and condition of 
 paving; width and depth of side ditches, and whether wet 
 or dry ; if not paved, character of soil, sand, clay or gravel ; 
 kind of fences and width between them ; telegraph and tele- 
 phone lines. The sketch should also show where the road 
 is in embankment or in cutting; where wagons cannot 
 double or pass, and where foot troops cannot march along 
 the side between the wagon track and the fences. 
 
 Bridges: Material of piers and abutments; type and 
 material of superstructure, as girder, truss, arch, suspen- 
 sion, wood, steel, stone, etc. ; width of roadway, and clear 
 headroom; safe load. Of bridges over the road, clear width 
 and height; for bridges over streams, the nearest bridges, 
 above and below, and whatever information can be obtained 
 about them. 
 
 The country : Character of cultivation or natural vege- 
 tation ; areas and density of adjacent timber ; marshes and 
 fords, kinds of fences, nature of soil; general configuration 
 of surface, especially high hills, long ridges or valleys, bluffs 
 or slopes too steep to scale, and practicable routes to their 
 crests. 
 
 Streams crossed: Name, width, depth, character of 
 bottom, fordability, and surface velocity in swiftest current 
 (velocity in miles per hour or noted as sluggish, moderate, 
 quick, or swift) ; elevation of high-water marks in relation 
 to the road ; which bank is the higher at crossing and above 
 and below, and how much; accessibility of water for stock; 
 fords at or near crossing, length, depth and steepness of 
 approaches; levees or embankments, height and thickness 
 on top ; if navigable, to what distance above and below and 
 for what class of vessels — steamers, flatboats, rowboats. 
 
 Town and villages passed through: Name, location on 
 map, and population ; names of streets to be traversed ; ma- 
 
APPLIED MILITARY SKETCHING 63 
 
 terial, as stone, brick, frame, log ; location of railway depots, 
 post, telegraph, and telephone offices ; of drinking fountains 
 and watering troughs; of elevators, storehouses or other 
 accumulations of food or forage ; of blacksmith, wagon, and 
 machine shops. 
 
 When ordered to make a complete examination of a 
 town or a village, note beside the foregoing, location and 
 size of principal buildings, halls, court and school houses, 
 churches, banks, jails, and their ownership ; sources, maxi- 
 mum quantity, quantity and distribution of water supply; 
 sanitary conditions and disposal of wastes ; location of rail- 
 roads, depots, freight houses, sidings, etc. ; condition and 
 width of roads entering from surrounding country, and 
 names of places to which they lead ; location and extent of 
 open spaces, and of large buildings standing apart; loca- 
 tion and extent of high ground within range, especially 
 that from which streets can be enfiladed. 
 
 Railroads crossed : Name, gage, single or double 
 track; sidings and loading platforms at point of crossing; 
 crossing (at grade, over, or under) ; distance and name of 
 nearest station each way. 
 
 Telegraph and telephone lilies:' Location of central 
 offices, of batteries ; where the lines lead ; condition, number 
 of wires. 
 
 5. A Complete Reconnaissance of a Railroad should 
 furnish the following data : 
 
 The line : Local name, terminal points and distances 
 between stations and other points; gage; single or double 
 track ; condition of roadbed, ties, and rails ; drainage and 
 liability to overflow or washouts ; facilities for repair ; con- 
 dition of right of way for marching troops along the line. 
 
 Tunnels and bridges : Number and location ; dimen- 
 sions ; strength of bridges ; means of destroying and repair- 
 ing; of blocking traffic. 
 
 Rolling stock : Number and nature of engines and 
 cars available ; capacity for transporting troops between 
 given points; facilities for constructing armored trains, as 
 spare rails, steel plates, old boilers, etc. ; location and capa- 
 city of shops and store yards. 
 
64 TOPOGRAPHY 
 
 Stations : Name and location ; facilities for entrain- 
 ing and detraining troops with wagons and horses; plat- 
 forms on through line and sidings ; ramps ; sidetracks, num- 
 ber and capacity ; turntables ; water tanks ; fuel supply ; stor- 
 age facilities ; derricks or cranes, crossovers for teams and 
 pedestrians. Facilities at hand for hospitals, camps, de- 
 pots ; for feeding men, heating coffee, watering horses dur- 
 ing temporary halts. 
 
 Other communication*: Telegraph lines; number and 
 location of stations, number of wires; connections; parallel 
 highways, roads, rivers, or canals; means of access from 
 same to railroad; junctions and crossings of other lines; 
 relative elevation ; facilities for laying temporary switches 
 and sidings at stations or between crossing lines. 
 
 Defensibility: Heights commanding line of road; de- 
 fense of stations ; defense of road and telegraph lines against 
 raiding parties ; structures exposed to demolition ; defense 
 and attack of same; defiles and river crossings. 
 
 6. Reconnaissance of a Stream or River: — The 
 banks are designated as right or left' if on the right or left 
 hand as facing down stream. Data required for complete 
 reconnaissance. 
 
 The valley: General configuration, heights of limit- 
 ing ranges, and positions of passes or roads crossing them ; 
 commanding ground from which a stretch 'of the channel of 
 considerable length can be enfiladed by artillery; forest 
 growth on or near banks ; soil and cultivation of the valley ; 
 roads parallel to river, and means of access to them from 
 the river. 
 
 The stream: Its width, depth, and velocity; naviga- 
 bility, as for steamboats, flatboats, rowboats, rafts, and 
 head of navigation for each ; nature of obstructions to navi- 
 gation and possibility of removing or avoiding them ; season 
 of high and low water ; average rise and fall ; rapidity of 
 rise and fall, and causes; amount of drift; character of 
 banks and relative command. Quality of water; amount 
 and kind of sediment borne; usual period and thickness of 
 ice. 
 
 Tributaries and canals: Width, depth, navigability, 
 and means of crossing. Nature and purposes of canals; 
 
APPLIED MILITARY SKETCHING 65 
 
 dimensions and lifts of locks ; time for lockages ; means of 
 destroying locks and effect of destruction ; floating plant 
 found. 
 
 Bridges and fords : As in road report. Also, for 
 bridges, note position of the channel and navigable width 
 between piers; height of arches and lower chords above the 
 water at different stages ; dimensions and operation of draw 
 spans. Note the exact position of fords and the marks on 
 both banks by which they may be found ; length, width, and 
 nature of bottom ; velocity of current ; position of deep holes ; 
 aids to crossing. Note nature of approaches to bridges and 
 fords ; width of roadway, slopes, soil, effect of weather and 
 traffic. Note especially the defensibility of bridges and 
 fords. 
 
 Ferries, boats and other means of crossing: Position 
 of ferries; approaches and practicability for horses and 
 loaded wagons ; sizes, number, and kinds of boats ; method 
 of propulsion, sites for military bridges or ferries ; char- 
 acter of site for construction, use and defense ; proximity of 
 islands and tributary streams ; approaches and slope of 
 banks ; width of river and maximum surface velocity of 
 current; materials for the construction or repair of boats, 
 bridges, or ferries. 
 
 Inundations : Places suitable for inundations by dam- 
 ming or obstructing a narrow bridge span, or by cutting a 
 levee or dike. Note raised roads on ground liable to natural 
 or artificial inundations and the safest route to follow by 
 known landmarks when the road is overflowed. An exten- 
 sive inundation 2 feet deep on level ground is a serious ob- 
 stacle unless the roads are very sound and marked by trees, 
 posts, etc. Even when so marked, a dip in the roadbed of 
 3 or 4 feet may render the road impassable. A railroad bed 
 is soon washed out even by a slight overflow. 
 
 7. Reconnaissance of Woods or Forest: — Note all 
 roads and paths, and all hills, ravines, and streams within 
 the wood or striking the edges ; kinds of trees, density and 
 growth; underbrush, prevalence of vines, marshy or large 
 open spaces; practicability of forming new roads by cut- 
 ting ; creation of obstacles by felling trees ; if there are no 
 roads, traverse the shortest practicable path between the 
 
66 TOPOGRAPHY 
 
 point of entrance and point of exit, and mark bowlders or 
 blaze trees, set stakes, or otherwise indicate this path, and 
 also give compass bearings of the route to be followed. Note 
 the exterior forms of the woods, whether parts of the edge 
 flank other parts; connection with the neighboring pieces 
 of wood by scattered trees or clearings ; undulations of the 
 ground that would give cover to attacking force or to de- 
 fenders. 
 
 8. A Reconnaissance for a Camp or Cantonment : — 
 Site : Location, elevation, and area ; sanitary features, 
 
 such as drainage, dryness, and general character of top soil ; 
 proximity of swamp ground or stagnant ponds. 
 
 Communications: Sufficiency of existing roads and 
 paths, maximum grades, probable condition under heavy 
 traffic and in bad weather, location and kind of materials 
 available for improvement or repair, railroad or water com- 
 munication and terminal facilities of same. 
 
 Water and fuel: Location, kind and quantity of fuel 
 at hand; quality and quantity of water; facilities for filling 
 water carts, for watering animals and for washing and bath- 
 ing; nature of supply, as wells, springs, running streams, 
 and its reliability. 
 
 Shelter and conveniences : Proximity of trees, brush, 
 wood, hay, and straw for huts and bedding ; of markets ; of 
 towns and villages. 
 
 Defensibility : Location of outposts and guards ; loca- 
 tion and character of defensive positions in or near the 
 camp ; force required to hold positions which may command 
 the camp. 
 
 9. An Outpost Sketch is a sketch made from the 
 friendly outpost. It is principally a sketch of the enemy's 
 position, and may simply cover ground in front of an outpost 
 line or it may serve to extend a road or position sketch 
 toward the enemy farther than the farthest point which 
 can be reached by the sketcher. The outpost sketch may 
 also include certain parts of the friendly outpost, in which 
 case it does not differ in that terrain from a position sketch. 
 
 Since it is impossible to proceed beyond certain points 
 in the outpost, all terrain beyond these points, in fact the 
 greater part of the outpost sketch, must be ascertained by 
 
APPLIED MILITARY SKETCHING 67 
 
 intersection. For this purpose, it is necessary to sketch 
 from at least two points in the outpost. 
 
 An outpost sketch must show as much of the enemy's 
 terrain and dispositions as is practicable or desirable. Special 
 consideration must be given to the following points : 
 
 Landmarks, especially such as can be used by the artillery 
 for adjustment and by the infantry for ranges. 
 
 Woods, ravines, houses, etc., which may be used to conceal 
 the enemy. 
 
 Roads, trails, etc., which may be used by the enemy for com- 
 munication. 
 
 Telegraph and telephone lines. 
 
 All hostile works which may be of use to patrols or in 
 planning and executing an attack should be located as ac- 
 curately as means will permit. This should include the fol- 
 lowing : 
 
 Hostile machine guns. 
 
 Hostile outguards. 
 
 Enemy batteries, being specially careful to state whether 
 positions are known or unknown. 
 
 Enemy lines, position, length, direction, etc. 
 
 Enemy observation posts, balloons, etc. 
 
 Enemy movements, written or marked on the sketch as may 
 be necessary. 
 
 General character of the terrain, such as contours, etc. 
 
 Character of our own terrain, as much as may be desired. 
 
 10. Position Sketch : — A reconnaissance for a position 
 usually includes the selection of the position or a recommen- 
 dation as to a proper selection (see also text-books on fortifi- 
 cation) . The object of the sketch must be kept in mind and 
 the features that most influence the considerations which 
 call for the map must be shown or indicated. 
 
 The principal object of such a reconnaissance is to ob- 
 tain the data for putting the troops on the most favorable 
 positions that the ground affords. An officer with troops who 
 is furnished the sketch should be able to go on the ground 
 and follow the lines as shown ; therefore such details of the 
 terrain as will be readily recognizable must be shown on 
 the map, in addition to the military features. The military 
 features shown by the sketch should include the following : 
 
 Natural and artificial features of the position, particularly 
 those related to cover, shelter, command, dead spaces, and ob- 
 stacles. 
 
 The field of fire, including ranges to or location of impor- 
 tant targets. 
 
68 TOPOGRAPHY 
 
 Depth of the position. 
 
 If desired, most suitable locations for lines of defense, etc. 
 Nature of flanks. 
 Communications. 
 
 Positions in front of the line which are suitable for outposts. 
 Artillery positions. 
 
 Possible positions from which the enemy can secure advan- 
 tages of command, enfilade, and ground observation. 
 
 11. A Place Sketch is a sketch of an area, made by 
 a sketcher from one point of observation. The directions 
 and data for elevations may be measured as in any other 
 sketch, but the distances (and consequently the elevations) 
 are obtained by estimation or by comparison with known 
 distances. For some reason, the sketcher is limited to one 
 point, as would be the case in an observation tower on a por- 
 tion of the outpost of which the tower was the only point 
 from which a sketch could be made. 
 
 A place sketch will show such information as is specially 
 needed for the mission. If for an outpost, it will show the 
 data required for an outpost sketch ; if for a position, it will 
 show the data required for a position sketch, etc. 
 
 12. A Panoramic Sketch is a pictorial representation 
 of a certain portion of the terrain, as seen from a given 
 point, drawn on the principle of perspective; the more 
 important features of the landscape being so emphasized 
 that they may be identified with certainty. It differs from 
 a map in that objects are portrayed as if viewed from a 
 definite point on the earth's surface, instead of from an 
 infinite distance above it; furthermore the features of the 
 ground are, as far as possible, shown as they appear, in- 
 stead of by means of standard conventional signs. 
 
 13. Object of Panoramic Sketch: — A panoramic 
 sketch is used in war : 
 
 (1) To provide firing data for artillery and machine guns. 
 
 (2) To furnish graphical information of enemy front line 
 activities. 
 
 (3) To assist observers at fixed observation posts in deter- 
 mining the map locations of enemy activities. 
 
 It will be seen from the foregoing that the panoramic 
 sketch serves, essentially, as a means of identifying and lo- 
 cating targets for the indirect fire (immediate or eventual) 
 of artillery and machine guns. Therefore the information 
 it shows should be so exact that battery and machine gun 
 
APPLIED MILITARY SKETCHING 69 
 
 company commanders may rely upon it for the computation 
 of firing data. 
 
 14. The Mil: — As the information furnished by a 
 panoramic sketch is largely employed in indirect fire., it 
 is desirable that the angular unit used in panoramic sketch- 
 ing should be identical with the one used in fire control. 
 This unit is the mil. However, if ruler with mils is not 
 available, the direction may be given in degrees as deter- 
 mined by a compass. 
 
 In all panoramic sketching, a battery commander's 
 ruler (called B.C. ruler) or a musketry rule will be found 
 of great assistance. 
 
 15. Time Element: — The panoramic sketch may be 
 made in a few minutes by a scout during a reconnaissance ; 
 or it may be made by an observer from a permanent ob- 
 servation post, in which case an abundance of time will be 
 available. Whoever makes the sketch must bear in mind 
 that the sketch is to be used by another person, either by 
 the higher commander in his study of the sector, by the 
 battery or machine gun company commander in his conduct 
 of fire, or by future observers at the same post ; hence, cer- 
 tain accepted fundamentals as to identification, informa- 
 tion and technique must be observed. 
 
 The type of sketch that is to be made will depend upon 
 the time element. Occasionally time is the all-important 
 element, as when the sketch must be quickly ready to as- 
 sist a battery or machine gun company commander in the 
 rapid preparation of fire; hence rapid methods of calibra- 
 tion of the paper with regard to the landscape will be em- 
 ployed. When positions are stabilized, the sketcher will 
 use instruments in making measurements of all horizontal 
 and vertical angles and will, accurately, place the points so 
 located on the paper, according to some adopted horizontal 
 .and vertical scale. Such a sketch will- be almost photo- 
 graphic in its exactness. 
 
 16. Panoramas and Perspective Sketches: — A 
 sketch made deliberately with exact instruments and cover- 
 ing all of the terrain visible from a given observation post 
 is often called a panorama. The sketch made by the scout 
 during the reconnaissance of a position sometimes is known 
 
70 TOPOGRAPHY 
 
 as a perspective sketch. There is really little distinction 
 between them, one sketch grading into the other according 
 to the time employed on it. Blank sheets should be fur- 
 nished the sketcher for either type of sketch. These sheets 
 should contain a series of parallel vertical lines and a 
 series of parallel horizontal lines. By adopting "a certain 
 scale for the space between the vertical lines; e.g., 100 
 mils, it will be possible to make a series of sketches all to 
 one scale, which, when pasted together end to end, will 
 give the sketcher a complete panorama. On the other 
 hand the lines on the paper lend themselves to the more 
 hurried methods of calibration as will be explained later. 
 
 17. There are two essentials of a panoramic sketch 
 which must stand out with particular prominence; first, 
 clearness of identification; second, information furnished. 
 Accuracy is another essential. 
 
 Identification'. — The sketcher must remember that If 
 the person using his sketch cannot identify the terrain 
 represented, then his work is valueless. Hence the sketcher 
 must neglect nothing that will add to the certainty of 
 identification. Of course the sky line is likely to be the 
 greatest aid to identification of the sector and hence should 
 not be omitted, although the objects thereon may be far out 
 of artillery range. Objects in the mid-distance and fore- 
 ground also should be included when they will aid in this 
 step although they may have no particular military value. 
 Lastly the data to be entered at the bottom of the page, 
 showing the place where the sketch was made and indicat- 
 ing the orientation, are essential to the identification of 
 the sector. 
 
 Information-. — The object of the sketch is to convey 
 information. Hence, although the sketch may be a work 
 of art; and although the one who picks it up may have no 
 difficulty in identifying the sector; yet if that sketch does t 
 not show the features of the terrain that are of importance 
 in the military situation existing, it is valueless. That the 
 information furnished should be accurate is self-evident; 
 otherwise the sketch loses much of its value. 
 
 Drawing : — While drawing is not so important as some 
 other things in sketching, the sketcher must remember cer- 
 
APPLIED MILITARY SKETCHING 71 
 
 tain fundamentals. First, the sketch must not be obscured 
 by unimportant details. That is, the important features 
 must be emphasized at the expense of the unimportant. 
 Hence it is just as important to know what to leave out as 
 it is what to put in. Whatever is done, the sketcher must 
 not attempt to show the sector by a mass of shading such 
 as might be employed for artistic effect in a picture. Such 
 a procedure will hide essential details rather than empha- 
 size them. The fewer lines that can be used to convey the 
 desired information, the better the work. 
 
 However the drawing need not prove troublesome. 
 Any man who can handle a pencil well enough to make an 
 area sketch can make a satisfactory panoramic sketch, re- 
 gardless of whether or not he has any of the instincts of an 
 artist. More often than not he will make a more valuable 
 sketch than the trained artist because he will not be tempted 
 to make a pretty picture and so hide military information. 
 
 18. Technical Devices : — Since the sketch must enable 
 the user to identify the sector quickly, it should convey to 
 the eye a rough picture of the terrain as it actually is seen. 
 To secure this picture a few technical devices should be 
 employed. 
 
 System of 'parallel lines: — First of these technical de- 
 vices is the principle of perspective. This is a means of 
 making use of the fact that distance to the eye is indicated 
 by the angle which an object of given height subtends at the 
 eye. The greater the distance the smaller the angle and 
 hence the smaller the object appears to the eye. Thus a 
 row of objects of a given height extending into the distance 
 apparently will grow smaller as the distance becomes greater 
 until they finally vanish into a point on the horizon. In 
 order to get the same effect of distance or depth in a sketch, 
 the following principles of perspective should be applied. 
 
 Parallel lines, if prolonged appear to come together or 
 vanish at a point called the vanishing point. Perhaps the 
 commonest example of vanishing of parallel lines is to be 
 found in the track of a level railroad. 
 
 Parallel lines not horizontal, vanish in a point above 
 or below the horizon. 
 
 Parallel lines also parallel to the plane of the picture 
 are drawn parallel in the sketch. 
 
72 TOPOGRAPHY 
 
 19. Consecutive ci'est lines : — The effect of distance 
 can be given in a mechanical way by varying the weight of 
 line. Since objects seen close at hand are large and clear 
 and decrease in size and clearness as they recede from the 
 observer, this principle must be applied to sketching. The 
 nearest features must be the largest and the heaviest of 
 line, while they should become smaller and lighter of line 
 until the most distant crest line is reached, which must be 
 the faintest of all. 
 
 20. Broken lines : — By refraining from actually join- 
 ing intersecting crest lines, a further technical means is 
 employed of giving the effect of depth to the sketch. This 
 gives the effect of haze found on distant slopes. 
 
 21. Ground Slopes and Forms: — One of the funda- 
 mental requirements of a good sketch being clearness, it 
 is essential that all useless details be omitted. On the other 
 hand the general slopes and configurations of the ground are 
 of military importance and the question arises as to how 
 to show this ground form without detracting from the 
 clearness of the sketch. This is effected by using the nat- 
 ural and artificial features that exist on the ground, drawn 
 to conform to the principles of perspective. 
 
 The position and shape of a road may indicate a rise 
 over a crest in the foreground, a gentle slope to a turn, and 
 finally a gradual rise to a crest, where it disappears. A 
 telegraph line would bring out the same facts. (See Plate 
 VII.) These features are of military importance and there- 
 fore must be shown, but, by means of these features the 
 configuration of the ground also is indicated without intro- 
 ducing useless lines or detracting from the clearness of the 
 drawing. In the same way the form of the hills may be 
 brought out by a few lines flowing in the direction of slope. 
 In the case of the wooded hill (Plate VII) the lines are short 
 and irregular, representing the tops of trees, while in the 
 bare hill the lines are smoother. 
 
 The tendency of the average sketcher, upon completion 
 of his sketch, is to attempt to add to the general artistic 
 effect by introducing shading of various descriptions. This 
 should not be done, for the only result accomplished is to 
 detract seriously from the clearness of the work. It should 
 
APPLIED MILITARY SKETCHING 
 
 73 
 
 be borne in mind that the panoramic sketch is not a land- 
 scape drawing, but is a skeleton chart, devoid of everything 
 of no military value, in which clearness is one of the prime 
 essentials sought. Therefore, unless the sketcher is thor- 
 oughly familiar with shading and its use, it should be elim- 
 inated. 
 
 22. Conventional Signs: — Since simplicity and clear- 
 ness is the key-note of a good sketch, the simplest possible 
 
 f.j*. i 
 
 
 ^»~s.. 
 
 BAR.E 
 
 
 Plate VII 
 
 symbols to represent natural and artificial features should 
 be used. For this reason conventional symbols or signs 
 are employed that are easily and quickly made, and which, 
 by slight variations, represent and identify features found 
 in any given locality. For the purpose of rapid identifica- 
 tion of features depicted, it is necessary to make the con- 
 ventional signs look as much like the features they repre- 
 sent as possible. 
 
 Possibly the features most commonly met in a landscape 
 are tree groups. They should be represented by an ir- 
 
1 \ TOPOGRAPHY 
 
 regular line for the tops and a more or less straight line 
 for the near edge. Care should be taken to make the ir- 
 regular line ve«ry irregular to prevent its confusion with the 
 lines of the sketch such as hills, crests, lines, etc. (Plate 
 VIII, Fig. 1.) 
 
 23. Control: — The inexperienced sketcher examining 
 a landscape is confused by the many details that meet his 
 eye. Important and unimportant features are so numer- 
 ous and mixed together that it seems a hopeless task to 
 pick out and recognize the simple framework on which 
 the whole is built. It is necessary, therefore, that the eye 
 be trained to separate a landscape into its main mass groups, 
 disregarding details, and bounding these masses by a single 
 line so that the relative position and size of the masses, 
 both vertically and horizontally, shall form the framework 
 of the whole. The lines bounding hills, mountains, crests, 
 and tree groups, and their intersections with each other, 
 form such mass groups; and once having recognized these 
 main bondary lines, and having plotted them in their rela- 
 tive horizontal and vertical relation, the sketcher has a 
 framework that is complete, after which important details 
 may be inserted quickly in their correct positions. A sim- 
 ple method of recognizing these mass groups is to half close 
 the eyes and examine the country, when these groups will 
 become immediately apparent. 
 
 24. Detailed Operatic us of Making the Sketch: — 
 Equipment: The following equipment is used: 
 
 1. Compass. 
 
 2. Field glasses. 
 
 3. B. C. ruler or a musketry rule. 
 
 4. Penknife. 
 
 5. 1 medium hard (2H) and 1 medium soft (2B) pencil. 
 
 Colored pencils may be used. 
 
 6. Eraser. 
 
 7. A map of the terrain to be sketched, from which the 
 
 names of villages, destination of roads and railway 
 lines, names of rivers, streams and mountains may be 
 obtained, and ranges to prominent features measured 
 by scaling. 
 
 8. Sketching pad of smooth paper. This paper preferably 
 
 should be ruled in faint lines in some convenient manner 
 as a guide and aid to the sketcher. 
 
 Locations of the sector : — The first step necessary is to 
 determine, by actual inspection, the limits of the sector. 
 If the sector has been plotted on a map previously it is neces- 
 
APPLIED MILITARY SKETCHING 
 
 75 
 
 sary for the sketcher to orient himself and determine the 
 sector limits accurately from the map. Having located the 
 limits of the sector, the sketcher measures it with a B.C. 
 ruler, musketry rule or some other instrument for meas- 
 uring horizontal angles. Since the panoramic sketch is 
 
 Treai i Underbr uih 
 
 Re 
 
 e Po" 
 
 fe ' i<J 
 
 lie 
 
 .!**= 
 
 K r 
 
 Target 
 
 
 
 
 
 
 Ronqs(yds) 
 
 5000 
 
 4J500 
 
 2 150 6000 .^000 
 
 3 mi 
 
 3000 
 
 Def (mils) 
 
 c 
 
 HO 
 
 i.00 ISO 2B0 
 
 340 
 
 ,5lO 
 
 5 ketch made 
 from point 
 (343.0-747.0)- Map 
 Weother:clear 
 
 Fig. 2 
 
 / 
 
 Panoramic Sketch 
 
 o/ front of 
 
 1-jt Division 
 
 Drawn under the direction of Ma f Oen A 
 
 5 oopm tOJepf,/°i9 
 
 by Mej X 
 
 Plate VIII 
 
 drawn to a definite horizontal scale it is necessary to deter- 
 mine this scale before proceeding. The artillery sketching 
 pad is divided into eight vertical zones between the two 
 limiting vertical lines. Hence if the sector measures 800 
 mils, the distance between any two adjacent vertical lines. 
 
76 TOPOGRAPHY 
 
 will represent 100 mils; if the sector is 400 mils, the dis- 
 tance between adjacent vertical lines will represent 50 mils, 
 etc. For a pad ruled in any similar convenient manner 
 the scale of the sketch may be determined. 
 
 It is essential that data giving location of sector and 
 sketching point be recorded immediately, for the impor- 
 tant reason that unless this information is shown, the sketch 
 is of slight value to anyone else attempting to use it. Casual- 
 ties among sketchers and observers are frequent and it 
 should be mandatory on all sketchers to complete these 
 data, as soon as the sector to be sketched has been deter- 
 mined. The sketch thus becomes valuable at once to others 
 as soon as any military information appears on it, and in- 
 creases in value in proportion to the completeness and ac- 
 curacy of this information. 
 
 Orientation of the sketch : — Just as a map must, in 
 order to make it of any value, have indicated upon it the 
 points of the compass, so must a panoramic sketch have 
 some indication of direction. In the latter case this indi- 
 cation is only an approximation and serves more for identi- 
 fication of the country than a correct designation of direc- 
 tion. At the bottom of the sketch an arrow indicating the 
 magnetic north should be drawn. Its direction is deter- 
 mined in the following manner : 
 
 Turn the sketching pad into a horizontal position. Sight 
 along any vertical line at or near the center until this line, 
 if prolonged will pass through the exact point on the land- 
 scape through which it passes in the sketch. The sketch is 
 now oriented. 
 
 Holding the pad in this position place a compass on it at 
 the bottom of the sketch and allow the needle to come to rest. 
 
 Through the position of the compass draw an arrow par- 
 allel to the compass needle. Note the place from which the 
 sketch is made, the name of the sketcher, date, weather, as 
 regards visibility and the hour of the day. 
 
 This last point is important as the visibility changes 
 from day to day and from hour to hour, hence unless indi- 
 cated, an officer who was using a sketch of a particular sec- 
 tor might imagine that he was in the wrong area unless he 
 knew that the condition of visibility had changed. If time 
 
APPLIED MILITARY SKETCHING 77 
 
 permits, a sketcher may choose the hour of the day when the 
 visibility is best for the area before him. Thus early morn- 
 ing is best for a sector to the east while shadows of late after- 
 noon will serve to bring out successive ridges in an area to 
 the west. 
 
 Examination of the sector: — Before proceeding fur- 
 ther, examine the sector with and without glasses. The 
 ground should be studied in an effort to get a clear mental 
 picture of the formation and to separate it into its fundamen- 
 tal mass groups ; the foreground mass of defilading screen, 
 successive crests, the background or horizon. Glasses often 
 will disclose crests, hollows, etc., capable of hiding targets 
 which otherwise might be overlooked. A little study will 
 separate the important from the unimportant details and 
 the sketcher then is ready to proceed along definitely 
 thought out lines, to conform to the object of the sketch. 
 
 Selection of reference 'point and horizontal control: 
 — In order to make the horizontal scale of practical value, 
 an origin of horizontal measurement must be selected from 
 the terrain and must be plotted and indicated on the sketch. 
 A sketch without a clearly indicated reference point is an- 
 alogous to a map without means of orientation. The ref- 
 erence point may or may not be in the sector included by 
 the sketch. It should preferably be in the sector, but 
 owing to the fact that the reference point must be a dis- 
 tinct, easily identified point, it is possible that a given sec- 
 tor may be devoid of any point that could fulfill these condi- 
 tions. In this case such a point should be selected as close 
 to either limit of the sector as possible and an arrow, labeled 
 reference point, drawn immediately above the sketch point- 
 ing in the direction of this reference point. The point 
 selected should further be described briefly as, "Reference 
 point, lone pine tree on sky line," etc." Under normal con- 
 ditions a suitable point can be chosen in the sector and 
 indicated directly on the sketch. Since it is the origin of 
 horizontal measurements, its angular designation will be 
 zero, a fact which further identifies it. 
 
 In the selection of a reference point, the following con- 
 siderations should govern: 
 
78 TOPOGRAPHY 
 
 (a) It should be easily seen and identified even under un- 
 favorable conditions of visibility, hence, not too far away (as 
 a distant mountain-peak on the sky line) . 
 
 (b) It should be of such a character that it cannot be 
 entirely destroyed by artillery fire. 
 
 The most suitable reference points during the late war 
 were found in the middle distance, preferably, features of 
 the terrain, such as a small hill of distinctive shape, a well 
 denned crossroads or road fork, the point where a road 
 crossed a crest, or the intersection of a stream with a road 
 or railroad, etc. These were found to satisfy all condi- 
 tions better than houses, towers, chimneys, trees or dis- 
 tant mountains. 
 
 By means of the plotted reference point and the ver- 
 tical guide lines, a basis of horizontal control is established. 
 By actually measuring with the mil ruler the horizontal 
 deflection of important points from the reference point, 
 these points may be plotted horizontally on the sketch in 
 their true rciuiion. This reference point preferably should 
 be placed on one of the vertical lines of the sheet. 
 
 Vertical control : — Vertical control, while not so im- 
 portant as the horizontal must be considered by the sketcher 
 if he would avoid distortion. Unless some line of vertical 
 control is adopted a sketcher often will enlarge the vertical 
 scale of one side of his sketch, due to the amount of detail 
 which appears there, while the other side, being without 
 military features, may be compressed. Usually it is cus- 
 tomary for the sketcher who is not using instruments to 
 choose a vertical control line to which he will refer all other 
 elevation, the reference being wholly by eye. 
 
 In choosing the vertical control line for the sheet, it 
 should be placed so as to leave the greater part of the area 
 of the sheet for the showing of most important targets. To 
 properly portray the details of the ordinary terrain a cer- 
 tain amount of exaggeration of the vertical relations is de- 
 sirable, otherwise successive crest and tree lines will be so 
 crowded as to make the picture obscure. Ordinarily the 
 sketcher who has adopted a vertical control line need not 
 concern himself with the need of exaggeration, since he will, 
 unconsciously, exaggerate in the course of his drawing. 
 
APPLIED MILITARY SKETCHING 79 
 
 If, however, the sketch is to be a true panorama 
 in which the site of each target is desired, the vertical re- 
 lations of the several points to be noted may be obtained 
 and the points plotted on the sheet in their proper relation 
 according to an adopted vertical scale. Some schools ad- 
 vocate a vertical exaggeration of two to one. This amount 
 is excessive and the sketcher should be cautioned against 
 too great an exaggeration, lest he make his sketch gro- 
 tesque and add to the difficulty of identification. 
 
 Framework: — The deliberate method consists simply 
 of plotting a few important or critical points by means of 
 the horizontal and vertical control. With these points es- 
 tablished, the framework can then be drawn in through 
 them by reference to the terrain. Typical critical points 
 are crests of hills, intersections of crests, houses, limiting 
 points of roads, limits of tree groups, etc. Through these 
 plotted points draw the outline of the terrain. 
 
 In the hasty method the pad is held vertically in front of 
 the eye. By looking over the top of the pad at the landscape, 
 and at the same time moving the pad to or from the 
 eye, a point will be reached at which the two limiting ver- 
 tical lines of the pad will intersect, if prolonged, the cor- 
 responding limits of the sector. Holding the pad here the 
 sketcher draws in lightly, at the extreme top of the sheet, 
 the sky line and as many other important points as possible, 
 comparing the outline directly with the country as he 
 glances over the top of the pad. This procedure automa- 
 tically locates the framework horizontally. When com- 
 pleted, the pad is lowered into a comfortable horizontal 
 position and the framework so drawn is carried down into 
 its proper position on the sheet, especial attention being 
 given to locating the framework correctly by means of the 
 vertical control. 
 
 This method is much more rapid than the other and 
 after a little practice equally accurate results can be ob- 
 tained with it. It has the advantage of eliminating con- 
 stant identification of plotted points with corresponding 
 ground points, and the consequent loss of time. 
 
 The framework by either method should be done 
 lightly with a hard pencil. If time permits it can be gone 
 
80 TOPOGRAPHY 
 
 over later and corrected where necessary. More atten- 
 tion can then be paid to characteristic shapes and forma- 
 tion, and to relative vertical relations. The principles 
 of perspective also should be applied. 
 
 By using a sheet of transparent celluloid, the same 
 size as the sketching pad blank, ruled in the same manner 
 as the blank and attached at right angles to the pad, the 
 sketcher may calibrate his sketch, simply by looking through 
 the celluloid, and noting on which line or in which space 
 each feature falls. It is a simple matter, then to sketch 
 those features in the same areas on the paper. 
 
 Filling in : — With the framework established it is a 
 comparatively simple operation to fill in with those details, 
 the importance of which is governed by the purpose of the 
 sketch. Time being a factor, and the object being prin- 
 cipally to locate targets, the framework is sufficient and 
 no unneccessary time should be spent on filling in, and the 
 framework itself should be only a rough approximation. 
 Time and the object sought govern the amount of detail 
 shown, and it is here that the knowledge of what to omit 
 makes itself manifest. 
 
 Speed and simplicity are gained in locating details by 
 plotting limiting points on the framework and then draw- 
 ing in the details between these points. Points where 
 roads, telegraph lines, fences, etc., appear and disappear 
 over crests, horizontal limits of tree groups and settle- 
 ments, are features that can be located this way. Simple 
 points may be located by referring them to points on the 
 sky line under which they are vertically situated. 
 
 With the soft pencil the sketcher should go over the 
 drawing and vary the weight of lines in it, bearing in mind 
 that the weight of line and size of objects decrease uni- 
 formly as they recede from the observer, the lightest lines 
 being the objects seen furthest away. Usually the immedi- 
 ate foreground is unimportant and little time should be de- 
 voted to it. . 
 
 Designation of targets and important points : — When 
 a target is plotted on the sketch its deflection from the ref- 
 erence point and range from the sketcher's position as well 
 as the target designation, should be entered in an appro- 
 
APPLIED MILITARY SKETCHING 81 
 
 priate place on the sheet. Vertical lines are drawn from 
 the top of the sheet and terminate in an arrowhead in 
 the exact point on the sketch where the point in question 
 is located on the ground. Directly at the top of the line 
 the description of the point so located is written diagonally, 
 so that it can be read with the sketch held in a normal 
 position. Conventional signs for targets should not be used. 
 They serve only to add unnecessary detail to the sketch and 
 destroy clearness. Since the right of the target as viewed 
 by the observers is the point on which firing data are com- 
 puted, the vertical line should indicate the location of the 
 right of the target, and if further identification is necessary, 
 its width in mils may be indicated. This woud mean then, 
 that the arrowhead locates the right of the target, and that 
 the target extends to the left of this point so many mils. 
 Simplicity in designation of targets can be accomplished 
 by using definitely understood abbreviations; e.g., "I" for 
 infantry deployed, "A" for artillery in position, etc. The 
 reference point always should be indicated as such and 
 may further be given its corect name if known. For quick 
 identification the line to this point may be made heavy or 
 doubled. According to the judgment of the sketcher and the 
 purpose of the sketch, any information may be shown such 
 as names of hills, mountains, farms, villages, destination 
 of roads and railroads, location of bridges, trestles, cul- 
 verts, etc. The sketcher is governed only by consideration 
 of the relative military importance of the points shown or 
 omitted. 
 
 On the sketch, directly under the description of the 
 indicated point or object, should be shown its range. The 
 range is either estimated or measured. (See Plate VIII, 
 Fig. 2.) 
 
 Elimination of unessentials : — The sketcher must re- 
 member that he is busied in making a map, a military 
 record which is to be used by others. Therefore he should 
 ask himself constantly, "What value has this sketch at this 
 moment to another person?" With this question before 
 him the sketcher should be able to resist the temptation to 
 draw unessentials, and so put down only data of value, re- 
 cording such items in turn according to their imDortance. 
 
82 TOPOGRAPHY 
 
 COMBINED SKETCHES 
 
 25. The methods of combined sketching were developed 
 at The General Service Schools several years ago and an 
 interesting account of these methods, including the advan- 
 tages to be gained in their use, can be found in the School 
 Library in a book entitled "Individual and Combined Sketch- 
 ing" by Cole and Stuart. 
 
 26. To appreciate the advantages of the combined 
 sketch, one must keep clearly in his mind the distinction 
 between such a sketch and a combination of individual 
 sketches. In the latter case a given area is assigned to 
 each individual party and this area is sketched indepen- 
 dently of all other parties. The results are then submitted 
 to the draftsmen who adjust existing difference along the 
 border line between the sketches in the office without any 
 personal knowledge of the ground. Where a network of 
 control lines exist with established elevations along each 
 line, or sufficient time is available to establish such a net- 
 work, each individual party may be assigned to an area 
 bounded on all sides by the control lines and there is then 
 no necessity for any two or more parties combining their 
 work in the field. 
 
 However, when there is no network of control or it is 
 not sufficient to enable the draftsmen to make an intelligent 
 adjustment and time is not available for the establishment 
 of the necessary control, the advantages to be gained by 
 requiring individual parties to adjust their work with ad- 
 joining parties in the field is apparent. The following cases 
 should be considered : 
 
 1. Where certain control lines already exist but the control 
 is not sufficient for adjustment in the office. 
 
 2. Where no control lines exist. 
 
 For example, certain railway surveys and road maps 
 may exist giving a fair amount of flat control through the 
 entire area. These roads or railways may then be made 
 the boundary lines between parties ; and adjoining parties, 
 working together along these lines, may establish joint ver- 
 tical control and also adjust all horizontal features along 
 the line. 
 
APPLIED MILITARY SKETCHING 83 
 
 Or again, a single railway may be taken as a base line 
 from which all parties start. 
 
 The control may be so well established that it may not 
 be necessary for some adjoining parties to adjust their 
 work in the field while quite desirable for others to do so. 
 In such a case, part of the sketch, may be a combination of 
 individual sketches, but the other part becomes a combined 
 sketch just as soon as adjustment is made in the field by 
 two adjoining parties. 
 
 27. In the case where no control exists, good results 
 cannot be expected unless all the sketchers have had much 
 experience, have worked together before, and the work is 
 thoroughly organized. 
 
 While either two or three sketchers may be assigned 
 to one party in a position or area sketch, it is thought quite 
 desirable that three be assigned if for no other reason than 
 to keep in touch with the other two members of the party. 
 If the man doing the actual sketching is worried all the 
 time about finding another member of his party it is bound 
 to detract from his efficiency, and failure of the two to 
 get together at the outer limits of the sketch results in an 
 incomplete sketch. 
 
 28. The following method of making a position sketch 
 is one that has been used by The General Service Schools 
 in past years. It is not presented as the only method, as 
 there are various ways of organizing the work to accomplish 
 tha s:;me rssult. 
 
 Assume that a general line has been sketched such as 
 (C C). (Plate IX.) The position sketch is in charge of an 
 officer designated as the topographical officer, who selects 
 a base line such as (A-a-B), so that areas whose sides are 
 perpendicular to the base line will include the general line. 
 The total depth of area to be mapped will depend on the 
 time and number of sketchers available. If the sketchers 
 are skilled in their work and the terrain is not very diffi- 
 cult, the entire area may be divided 'into parts one-half mile 
 in length and two miles in depth and the work can be exe- 
 cuted by fifteen parties in a day. Each small area, such as 
 (a t s's) is assigned to a party of three, one chief of party 
 and two sketchers. The topographical officer proceeds with 
 
84 
 
 TOPOGRAPHY 
 
 X 
 
APPLIED MILITARY SKETCHING 85 
 
 all the parties to the point A where the most distant visible 
 point of the base or control line, as (a), is pointed out to 
 all chiefs of parties. Sketcher No. 1 of the first party, de- 
 signated as party (A), determines the magnetic bearing of 
 the line (A a) from which the magnetic bearing of the lines 
 perpendicular to it is determined and begins sketching along 
 line A A'. The chief of party A paces off a distance of a 
 half mile along the line (A a). All topographers except 
 sketcher No. 1 of party A follow the chief of party A. The 
 elevation of the point A is determined by the topographical 
 officer by an aneroid barometer. The aneroid barometer 
 is preferable for this work, but if not available the eleva- 
 tion of point A must be assumed and the relative elevations 
 determined by the clinometer. This latter method is rather 
 tedious if no known elevation can be seen, but is not so diffi- 
 cult if sights can be secured on points of known elevation. 
 When the chief of party A reaches the point (m) one-half 
 mile distant from A, he halts with his No. 2 sketcher and 
 No. 1 of the next party, designated as party B, and marks 
 the point by a stake or selects some natural object in the 
 near vicinity, such as a hill or fence post. 
 
 The topographical officer then gives to the chief of party 
 A the magnetic bearing of his right boundary and the ele- 
 vation of the point (m) . The chief of party B starts pacing 
 off the distance from (m) to a point (n) one-half mile dis- 
 tant from (m), accompanied by his sketcher No. 1 and 
 sketcher No. 1 of party C. The same process continues 
 until (a) is reached where the bearing of the line (a B) is 
 determined by the topographical officer and the number of 
 wedge shaped areas is also determined by him. The wedge 
 shaped areas are assigned to a selected party and the 
 methods followed from (a) to (B) are similar to those de- 
 scribed from (A) to (a). 
 
 Meanwhile, at the point (m), sketcher No. 1 of party 
 B in company with sketcher No. 2 of party A, sketches along 
 the line (m m') and extends the sketch 300 yards on each 
 side. It is in' material whether sketcher No. 1 of party B 
 or sketcher No. 2 of party A does the actual sketching, but 
 it should be done by the best sketcher of the two, the other 
 acting as assistant. When these two have proceeded along 
 
86 TOPOGRAPHY 
 
 the line (m m') for a distance of two miles, which would 
 scale a distance of 12 inches on the map (assuming the 
 scale of the map as six inches to a mile), the sketch is cut 
 apart along the line (m m') , which is merely the cutting line 
 of the sketch. It is not necessary that the sketchers follow 
 the line (m m') on the ground, but they should so direct 
 the traverse as to secure in the most convenient manner, 
 reliable data for 300 yards on each side of the line (m m')- 
 After the sketch is cut- apart each of the sketchers takes 
 the part of the sketch assigned to his party, and from the 
 point (m') sketches along the outer boundary of his area. 
 In the meantime the chief of party B having run the care- 
 ful traverse from (m) to (n), gets in touch with'both of 
 his sketchers so that when the outer boundary is reached 
 he may assemble the two without delay at a point about half 
 way between (m') and (n')» When they assemble, the 
 chief of party will have a plotted traverse showing the dis- 
 tance between the parallel line (m m') and (n n') and the 
 sketchers of his party will each have a sketch of a strip of 
 topography 300 yards wide along each side of the area. 
 These two sketches are then placed one over the other so 
 that the distance betweerrthe outer edges at all points scales 
 a half mile according to the scale of the sketch. A knife 
 cut is then made down through the center so that there is no 
 overlapping and the pieces secured in position by thumb 
 tacks and rubber bands. The party then proceeds back to- 
 ward the base or control line ^connecting up the contours 
 and topographical features and adjusting differences. The 
 sketch having been completed according to this method, will 
 "at accurately along its edge with adjoining sketches on both 
 sides, and all are ready for combination without any altera- 
 tion whatever. Before turning in the sketch of his area 
 at the appointed assembly place, the chief sketcher secures 
 the two parts of his sketch in position with fasteners or 
 binding tape. When turned in each sketch should also have 
 a margin of at least an inch on each end so that they can all 
 be pasted together without interfering with the portion on 
 which the actual sketch exists. 
 
 When turned in, it is only necessary to place all the 
 sketches with their edges together in their proper relative 
 
APPLIED MILITARY SKETCHING 87 
 
 positions and secure them at each end with binding tape. 
 It is not necessary to trace this work for blue printing if 
 the field work has been done properly. 
 
 29. The question is principally one of organization. 
 Each sketcher, upon being given his area, should be given 
 also the co-ordinates of the points where he will meet the 
 adjacent sketchers, the times he will meet them, and the 
 common boundaries which they will sketch together. He 
 must fulfill these appointments, no matter what the condi- 
 tions of his work; afterward, if time permits, he may do 
 other important Work on his area. 
 
 30. In combined road sketching it is often impossible 
 to know ahead of tfme just what are the co-ordinates of 
 points on the connecting roads along which two sketchers 
 are to meet ; in fact, it is often the case that it is not known 
 that the road itself actually exists. In such cases, each 
 road sketcher will be given bounding areas in which he is 
 to sketch every road, these areas being made so that they 
 will overlap several hundred yards. Each sketcher will 
 then proceed to the limits of his area, and if it has been 
 impossible to designate the co-ordinate at which he will 
 meet the adjacent sketcher, and time of meeting, he will 
 place a card in a conspicuous place on the side of the road, 
 showing his ideas as to the co-ordinate of the card and his 
 elevation (if elevations are being obtained). The adjacent 
 sketcher will similarly sketch to his boundary; except that 
 if he finds the card of the other sketcher, he will stop at 
 that point and will endeavor to adjust his sketch to the co- 
 ordinate and elevation of the other sketcher. If unable to 
 do so, he will make a note on his sketch that this is the 
 point where he found the card, defers any adjustment and 
 proceeds with this work, it being unnecessary, however, for 
 him to proceed farther along this same road. The overlap- 
 ping of several hundred yards in the area designated to be 
 sketched by each sketcher is necessary in order that the 
 card of the first sketcher will surely be found by the second 
 sketcher. 
 
 The following is an organization which has worked 
 well in peacetime, based on covering 3 main parallel roads : 
 
88 
 
 TOPOGRAPHY 
 
 Directors 
 
 Principal Sketcher (main 
 road) 
 
 Asst. to Prin. Sketcher 
 
 Asst. Sketchers (crossroads) 
 
 Total enlisted (all 
 mounted) i 
 
 Officer in charge 
 
 Party A 
 
 Right flank 
 
 road 
 
 Party B 
 Center road 
 
 Party C 
 
 Left flank 
 
 road 
 
 Total 
 
 3 
 3 
 12 
 
 21 
 1 
 
 31. In an unmapped country combined sketching may 
 be utilized to furnish a rough map in the shortest practica- 
 ble time. Without control of some kind the work of inde- 
 pendent parties can never be made into an harmonious 
 whole. The effect of the combination of parties is to supply 
 in some degree the absence of control. In mapping exten- 
 sive areas by independent parties before control is estab- 
 lished the work of these parties is likely to be entirely 
 wasted; if the combined sketch system is used the work 
 may be adjusted to an accurate control when such control 
 is obtained. 
 
 32. Rates of Sketching: — A good sketcher, under 
 average conditions, can sketch in one day: 
 
 On foot : 
 
 1 square mile of area. 
 10 miles of road. 
 
 Mounted : 
 
 15 miles of road (in emergency 20 to 25 miles). 
 
 33. The following data is of use in reconnaissance work : 
 Water — Approximate daily requirements : 
 
 1 gallon per man on march. 
 
 5 gallons per man in camp. 
 
 6 to 10 gallons per animal on march and camp. 
 
 (The above figures apply to water taken from streams, 
 where animals are watered at the streams, and cooking 
 water carried. In estimating the daily supply for perma- 
 nent or semi-permanent camps, where water is piped to 
 kitchens, bath houses, etc., the requirements will be 25 to 
 30 gallons per man and 10 to 15 gallons per animal, depend- 
 ing on climatic conditions.) 
 
APPLIED MILITARY SKETCHING 89 
 
 Estimating quantity of water in stream: BxDxVX 
 10,800=gallons in 24 hours. B=average width, D=aver- 
 age depth, V=average velocity (all in feet). 
 
 34. Practicability of slopes. Slopes from 0° to 5° are 
 practicable for maneuvering all arms, singly or combined. 
 
 On slopes from 10° to 15° all arms can be moved up or 
 down. 
 
 Slopes from 15° to 30° are practicable for small de- 
 tachments only. 
 
 On slopes from 30° to 45° foot troops can move with 
 difficulty. 
 
 War material can be dragged up any slope. 
 
 Slope fractions Degrees Operations 
 
 1/50 
 1/20 
 1/12 
 
 1 
 3 
 
 1/10 
 
 6 
 
 1/8 
 
 1/7 
 1/6J 
 
 7 
 8 
 9 
 
 1/6 
 1/4 
 1/3 
 1/2 
 1/1 
 
 14-15 
 18| 
 
 ,26 
 
 45 
 
 Maximum for railroads. 
 Maximum for first-class roads. 
 
 Practicable for all arms. Somewhat difficult for cav- 
 alry to charge descending. 
 Maximum for cava'ry charge in mass ascending. In- 
 fantry in close order descends with some difficulty. 
 Cavalry can descend at a trot. 
 Not practicable for heavily loaded vehicles. 
 With few exceptions it is impossible for heavily 
 leaded trucks to climb grades exceeding 16 per cent 
 (about 9°), even when the road surface is hard 
 ti . ood condition. 
 Fie'd artillery can no longer maneuver. 
 
 mm up to which all arms can move. 
 i ight vehicles can ascend. 
 
 ■ .' and mules can ascend or descend. 
 Foot troops can ascend or descend aided by bands. 
 
 35. The minimum width of usable roadway for a two- 
 way road is 18 feet. 
 
 36. Fords, Practicable Depth : 
 
 2 to 3.5 feet deep for infantry. ~] 
 
 4 to 4.5 feet deep for cavalry. [ Depending on current and 
 
 3 feet deep for artillery. nature of bottom. 
 2.3 feet deep for wagons. 
 
 37. Strength of Ice: 
 
 Three inches thick will support small groups of men. 
 
 Four and one-half to 7 inches thick will support cavalry 
 and light guns. 
 
 Eight to 12 inches thick will support heavy guns and 
 wagons. 
 
 38. Stream Flow: 
 
 Velocity in miles per hour=0.7 of velocity in feet per 
 second. 
 
90 . TOPOGRAPHY 
 
 Practical Exercises in Applied Military Sketching 
 
 See any of the recent problems at The General Service 
 Schools, Fort Leavenworth, Kansas. Each of these prob- 
 lems required a certain kind of sketch under certain military 
 conditions. The results of the problems showed that nearly 
 all officers possess a general knowledge of the methods of 
 sketching, but not so many possess the ability to show in a 
 limited time the military features required by a special 
 sketching mission. 
 
CHAPTER V 
 
 Airplane Mapping 
 
 1. Aerial photography has reached a stage of develop- 
 ment where it is of distinct value in military operations both 
 in providing information of enemy works and operations, in 
 reconnaissance work, and in furnishing data on which to 
 base new or revise old topographic maps. 
 
 Owing to the fact that good topographic maps already 
 existed of the western battle front in the World War,' no 
 new surveys of it had to be made and aerial photography 
 was principally devoted to detecting enemy works and evi- 
 dences of his operations. The information thus obtained 
 was supplied to organizations principally by making addi- 
 tions to the existing maps and by distributing great num- 
 bers of the photographs. 
 
 Under these conditions, airplane mapping, which had 
 been developed to some extent in the United States and 
 abroad before the World War, did not receive as much at- 
 tention as the intelligence use of photographs, although the 
 Germans claim to have mapped large areas of terrain on the 
 eastern front by airplane photography. Since 1917 the 
 Corps of Engineers, the Air Service and the Geological Sur- 
 vey have been working conjointly on the development of 
 methods and instruments for airplane mapping and have 
 brought the subject to a point of practical application to 
 military mapping. 
 
 The use of aerial photographs is still limited to only 
 a portion of the work of complete topographic mapping; 
 primary control and contouring of the ground are still ne- 
 cessary, and the efforts made so far represent pioneer work 
 in which the influence of the experimental stage enters to 
 a high dgree. 
 
 2. Aerial photography has four distinct and valuable 
 uses in military operations: 
 
 91 
 
92 TOPOGRAPHY 
 
 (a) In map making. 
 
 (b) In reconnaissance. 
 
 (c) In supplementing battle and operation maps, to guide 
 
 organizations in an attack. 
 
 (d) To give information of enemy works and operations. 
 
 GENERAL LIMITATIONS ON AERIAL PHOTOGRAPHS 
 
 Application of Aerial Photography to Military 
 Sketching 
 
 3. An aerial photograph is a photograph of the ground 
 taken from the air. It may be either oblique, or vertical. 
 An oblique photograph is one taken from a low-flying ma- 
 chine or captive balloon, with the axis of the camera making 
 an acute angle with the ground. It is used for giving a 
 panoramic view of the ground, and is of little use in map- 
 ping. A vertical photograph is one taken with the axis of 
 the camera perpendicular (or approximately so) to the: 
 surface of the ground. It is usually taken in war time from 
 an altitude of from 8000 to 15000 feet. For the best re- 
 sults, photographs taken in time of peace are usually taken 
 under 6000 feet. 
 
 In addition to its other uses, the vertical aerial photo- 
 graph is used in mapping. Such a photograph has the fol- 
 lowing advantages: 
 
 (1) It is the best means of securing fresh topographical in- 
 formation about territory in enemy possession. 
 
 (2) It is sensibly free from errors due to the personal equa- 
 tion of the topographer. 
 
 (3) It is the most rapid means of securing such topographical 
 information as is shown on the picture. 
 
 (4) It is the least expensive method (in human life) for se- 
 curing a record of our own works in territory subject to enemy 
 fire. 
 
 The vertical aerial photograph has the following dis- 
 advantages : 
 
 (1) As the position of the camera and its orientation at the 
 moment of exposure is never accurately known, aerial photographs 
 must be employed without these data. No practicable means of 
 determining them in the office has yet been devised. 
 
 (2) It is extremely difficult to hold the camera directly ver- 
 tical, and slight deviations from this position cause considerable 
 distortions in the record. 
 
 (3) No data as to the relative elevations of objects on the 
 ground can be secured from the photographs except some slight 
 information from the images of the shadows. 
 
 (4) Objects hidden to the observer in the machine, whether 
 by clouds or by overlying terrestrial objects, such as forests, etc., 
 are equally hidden in the photograph. 
 
 (5) All aerial photographs are subject to special errors of 
 distortion. 
 
AIRPLANE MAPPING . 93 
 
 The most important advantages are the completeness 
 and accuracy of detail and the speed of getting features 
 which are tedious to draw or difficult to reach. 
 
 Speed of Work 
 
 4. A single sketcher with good control can put in the 
 detail in diversified country of about one square mile per 
 day. 
 
 A single photograph from a tri-lens camera taken from 
 an altitude of 10,000 feet can cover an area of about 10 
 square miles. Due to the necessity, explained below, of 
 taking a large number of overlapping photographs, the area 
 covered by a single plane in one flight is not much over 
 35 square miles. 
 
 Actual cases : 
 
 An area 15 x 20 (300 sq. miles) required 22 strips of 33 photos 
 each (7" x 9") or 726 photos. 9 hours flying time for photo- 
 graphs or 4 flying days. 
 
 Atlantic City Mosaic — 35 sq. miles. 
 Flying time— 2a hours. 
 Total time in field — 4 days. 
 Time in laboratory and in assembling mosaic — 2 weeks. 
 
 Camp Benning — 150 sq. miles. 
 Flying time — 10i hours. 
 Number of photos — 619. 
 
 Time spent in field to take and finish photos— 41 days. 
 Time spent in assembling mosaic — 1 month. 
 
 In the 8th Corps Area 17,000 square miles were map- 
 ped between April and August, 1921. The personnel con- 
 sisted of seven officers, ten enlisted men and two civilian 
 photographic developers. Four planes were operated. 
 
 5. The cost of topographic surveying without airplanes, 
 excluding control, will average about $50.00 per sq. mile. 
 
 The cost of getting topography by airplane photography 
 after control has been obtained by other means averages 
 about $10.00 per sq. mile. This cost is not comparable with 
 the above as no data on vertical relief is obtained. 
 
 The comparative cheapness of the airplane photograph 
 method is an advantage since most maps, even those for 
 military purposes, are made in time of peace, when cost 
 has to be considered. 
 
94 TOPOGRAPHY 
 
 Disadvantages 
 
 Principal disadvantages in use of airplane photography 
 in mapping are due to the lack of control and errors of dis- 
 tortion. 
 
 Lack of Control: — No method has yet been devised 
 of registering the positions of the airplane when the pho- 
 tograph is made. 
 
 Control points, which will register in a photograph, 
 must be established by ordinary methods of terrestrial sur- 
 veying. Without control previously established airplane 
 photographs though they may be valuable for reconnais- 
 sance purposes, are useless for map making. 
 
 Distortion : — The principal errors of distortion are 
 due to inclination of the camera and to differences of eleva- 
 tion in the terrain. 
 
 No method has been devised for keeping the axis of 
 the camera vertical or for registering the amount of in- 
 clination. 
 
 If the axis is not vertical the photograph will be dis- 
 torted exactly as the photograph of a tall building taken 
 from near its base. 
 
 Distortion due to relief arises from the fact that points 
 at different elevations, equally distant from each other, will 
 not be projected at equal distances on the photographic 
 plate. A simple geometric figure will show this. 
 
 Uses of Airplane Photographs 
 
 G. Reconnaissance: — Airplane photography has a 
 very valuable field of usefulness in the reconnaissance of 
 roads, streams, and large uncharted areas where the prin- 
 cipal object is to get the character of the road or terrain, 
 and the lack of control is unimportant. 
 
 With the ability to photograph a strip of country from 
 2 to 6 miles in width and from 50 to 75 miles in length, it is 
 possible to make an excellent road reconnaissance ahead of 
 a marching column. 
 
 No absolute control is needed other than the road fol- 
 lowed or towns passed over. The photographs will show 
 the width, and possibly the character of the road; the 
 bridges, whether standing or destroyed, width of streams at 
 
AIRPLANE MAPPING 95 
 
 crossings, fords along side of roads and the general nature 
 of the topography for a distance of from 1 to 3 miles on 
 each side of the road. 
 
 Flying can be done in the morning, photographs devel- 
 oped and mounted in the afternoon and ready that night for 
 issue to advance guard or column commanders. A map 
 would be preferable, but the making of a map from photo- 
 graphs requires several days. 
 
 A number of valuable route reconnaissance maps have 
 recently been made in the 8th Corps Area. In some cases 
 the flight followed a railway, the survey notes of^which were 
 available. In other cases a rough survey of the route to be 
 followed was made by using a compass and speedometer. 
 In other cases the mosaic was controlled simply by different 
 towns, the location of which was known. 
 
 A reconnaissance of a stream will show its width, char- 
 acter of banks, whether steep or wooded, and location of 
 fords. 
 
 A reconnaissance of large unmapped or incompletely 
 mapped areas, such as might be found in Mexico, will give 
 a good idea of the general character of the terrain and will 
 be valuable even though the exact location of the various 
 features cannot be determined. 
 
 7. For Battle Use : — Vertical and oblique photographs 
 issued to organization commanders in conjunction with bat- 
 tle or operations maps are useful aids in orienting and 
 guiding organizations in an attack. 
 
 About 40,000 such photographs were issued by G2, 
 First Army, for the St. Mihiel attack down to and including 
 platoon commanders. That their use was not more success- 
 ful was due to lack of instruction in their interpretation and 
 use, and to lack of time. 
 
 Issuance of photographs to small units is too much of 
 a detailed task for the army. They should be supplied by 
 the division. 
 
 8. Map Making: — Airplane photographs are used in 
 mapping to correct and revise old maps, fill in existing maps 
 and make new maps. 
 
 In the last case, making new maps, some existing map, 
 i.e., some control is absolutely necessary. 
 
96 TOPOGRAPHY 
 
 9. Relief: — No practicable method has yet been dis- 
 covered of getting elevations from vertical photographs. 
 The Germans and French have developed complicated meth- 
 ods involving minute measurements but they are not prac- 
 ticable for military purposes. The general character of re- 
 lief, however, can be determined from stream lines, shad- 
 ows, location of woods, bends in roads and curves in rail- 
 ways. 
 
 10. Control: — It is necessary to have a guide map on 
 which courses to be flown to obtain the photographs can 
 be marked. From the air the pilot identifies points on the 
 terrain which correspond with the courses and uses them 
 to maintain proper directions during flights. It is generally 
 necessary in order to insure that no gaps occur and to re- 
 duce distortion due to inclination, to have the photographs 
 overlap on all sides. The prints are then brought to the 
 same scale, if necessary, fitted and adjusted to the control, 
 the overlapping parts cut away and the remainder mounted 
 together to form a mosaic. 
 
 11. Cameras: — The cameras in use in our service are 
 a single lens automatic camera and tri-lens non-automatic. 
 The latter consists of three cameras, one central and two 
 side cameras inclined in opposite directions at an angle of 
 35 degrees to the central camera. This camera was designed 
 especially for mapping purposes and has a field about three 
 times as large as that of the single lens automatic type 
 
 12. Transforming: — The side pictures of an inclined 
 lens camera are distorted with reference to the central pic- 
 ture. By projecting the negatives onto a plane making the 
 same angle with the negative that the side cameras make 
 with the central axial camera, the resulting prints will be 
 the same as though the axes of all the cameras were paral- 
 lel. This process is called transformation. If it were pos- 
 sible to register the tilt of a camera, distortion due to lack 
 of verticality could be eliminated by transformation. 
 
 Interpretation and Restitution 
 
 13. A photograph print furnished to an organization 
 must be interpreted : i.e., some one must decide what the 
 various objects shown on the photographs really are. The 
 
AIRPLANE MAPPING 97 
 
 interpretation of houses, open roads, schools, rivers, boun- 
 daries of woods and swamps, trace of open trenches, etc., 
 usually presents no difficulty to any topographer. On the 
 other hand, the interpretation of objects hidden by other 
 natural objects, such as roads in a forest, etc., is frequently 
 very difficult. The interpretation of military features, 
 which have been specially prepared on the ground to resist 
 interpretation (camouflaged) involves difficulties which can 
 usually be solved only by experts, and is a problem in mili- 
 tary intelligence, and not in topography. 
 
 The location on a map of the various features on the 
 photograph, after they have been interpreted, is termed 
 restitution. Restitution is a branch of topography. Where 
 restitution is done in great haste, with a view to getting 
 information into the hands of troops rapidly, it is a branch 
 of sketching. 
 
 14. Control of Restitution: — Theoretically, given 
 the elevation at which the vertical photograph of a flat sur- 
 face was taken, and the optical characteristics of the camera 
 (i.e., the focal length) the scale of the photograph, con- 
 sidered as a map, could be calculated. Since the altitude of 
 exposure is known only approximately, the axis of the cam- 
 era is rarely vertical and the surface photographed is never 
 flat, an accurate calculation is impracticable. In sketching, 
 the scale would be determined by measuring the straight 
 line distance between two control points, and comparing it 
 with the actual horizontal distances between these points 
 on the ground. Even this scale will be inaccurate, owing 
 to errors of distortion. It is, however, usually accurate 
 enough for sketching purposes. Several control points if 
 available should be used to obtain an average value for the 
 scale. 
 
 The selection of control points should be made from the 
 best available existing map of the area photographed, and 
 those used in determining the scale should be chosen as 
 near the centre of the area as possible. Because their 
 images are usually definite on the picture and their loca- 
 tions are generally accurate on maps, pronounced features 
 along railroads and roads such as crossings and roadforks 
 are the most satisfactory control points. It is impossible 
 
98 TOPOGRAPHY 
 
 to use a restituted photograph in topography, unless at 
 least two control points can be located. 
 
 15. Methods of Restitution: — Owing to errors of 
 distortion which make the scale of a photograph variable 
 in different parts of the picture, it is insufficient merely to 
 reduce or enlarge the picture to the scale of the sketch. 
 There are three methods of transferring data from the pho- 
 tograph to the map, the graphical, the optical, and the pho- 
 tographic. Only the graphical method is adapted to sketch- 
 ing. 
 
 In the graphical method four control points are se- 
 lected on the photographic print which can be identified on 
 the map. These points are connected by straight lines form- 
 ing a quadrilateral. By drawing the diagonals, four tri- 
 angles are formed, and these triangles can be again divided 
 into as many small triangles as will be found necessary for 
 the amount of detail desired. The same number of lines 
 and figures must be drawn on both photograph and map. 
 The features on the photograph are then transferred to the 
 map. 
 
 Knowing the scale both of the map and the photograph, 
 compilation work is comparatively simple. The sketcher 
 measures the perpendicular distance, on the photograph, 
 from a point to the nearest triangle boundary, and the dis- 
 tance along the triangle boundary to the nearest intersec- 
 tion. He converts these distances to the scale of the map, 
 measures them back in reverse order, and locates the point 
 on the map which corresponds to the point on the picture. 
 After a few points have been thus located, the remaining 
 features in the triangle can usually be drawn in freehand. 
 
 16. Interpretation : — In examining an airplane pho- 
 tograph it should be held so that the shadows fall toward 
 you and also away from the source of light (lamp or win- 
 dow) . If it is held so that the shadows fall away from the 
 eye the relief is apt to appear reversed — a cut will look like 
 a fill. Having the source of light in the same relative posi- 
 tion as the sun when the negative was exposed will assist 
 in bringing out the relief. 
 
 Interpretation is facilitated by a study of a map of the 
 terrain covered by the photograph. If none is available, try 
 
AIRPLANE MAPPING 99 
 
 to get a map and photographs of adjacent similar terri- 
 tory. 
 
 The Use of Airplane Photographs to Obtain Informa- 
 tion of Enemy Works and Operations : 
 
 17. This use of air photos is commonly considered an 
 intelligence function though, as a matter of fact, it is largely 
 a matter of map making. The restitution of enemy works 
 for purposes of artillery fire, planning attacks, etc., which 
 may be considered a tactical use, is trfie mapping. The 
 comparative study of the restituted works to discover 
 changes in appearance of front line works, and evidences of 
 concentrations, etc., in rear areas, a strategic use, from 
 which the enemy's intentions and operations may be de- 
 duced, is intelligence work. 
 
 18. In interpreting photographs of enemy works the 
 expert depends on four main characteristics : 
 
 (a) Shadows, showing- especially trenches. 
 
 (b) Marks of use, such as tracks, blasts, etc. 
 
 (c) Marks of construction, such as spoil banks, felled trees, 
 
 etc. 
 (cl) Differences, as compared with previous photographs. 
 
 The camouflage operator endeavors to nullify such 
 characteristic features. He does not attempt to render the 
 objects invisible, but he does attempt to make the object 
 cause no change in the appearance of the terrain. He uses 
 nets to overcome the shadows, covers up tracks and blasts 
 or prevents the making of same, covers or disguises spoil 
 banks, etc., and endeavors to prevent any differences of ap- 
 pearance in the terrain. 
 
 However, although camouflage operators covered the 
 object, there are certain characteristic features as discussed 
 below, which show certain enemy activities ; and careful 
 reading of aeroplane photographs gives results of very great 
 military assistance. Plates III and IV show an aeroplane 
 photograph actually taken in France, and its interpre- 
 tation. 
 
 19. The degree of certainty with which enemy batteries 
 may be located by aeroplane photographs depends on the 
 perfection of the camouflage and the character of the ter- 
 rain. Verified locations in France during the World War in- 
 
100 
 
 TOPOGRAPHY 
 
 Plate III 
 
AIRPLANE MAPPING 
 
 101 
 
 'Wire 
 ^'\ZA859 JO 9/6 8000' Lens JO' 
 
 PL.te IV 
 
102 TOPOGRAPHY 
 
 dicate that the percentage of batteries located by this means 
 varied from 20% to 70% of those present. 
 
 In reading airplane photographs, there is great diffi- 
 culty in determining the meaning of certain signs on the 
 photograph. Actually, it is often impossible to interpret 
 the meaning of certain signs as seen on the photograph ; 
 but the specialist who is engaged in interpreting the photo- 
 graph has at hand all of the information concerning the 
 particular section, such as reports of fire of batteries from 
 a certain vicinity, the reported presence of machine guns 
 in a wood, the presence of heavy guns in a ravine. By com- 
 bining this information with a careful study of the indefin- 
 ite signs on the photograph, it is possible to come to fairly 
 correct results. 
 
 20. Aviation Fields: — Hostile airdromes may be re- 
 cognized on photographs by the following indications : 
 
 (a) Hangars. 
 
 (b) Preparation of the ground. 
 
 (c) Landing "TV or small smoke fires, giving the direction 
 
 of the wind. 
 
 (d) Machines on the ground. 
 
 21. Batteries: — Casemated or underground battery 
 emplacements are always easy to distinguish on the photo- 
 graphs, on account of the shadows from the projections, 
 provided the shadows are not hidden by camouflage. 
 
 The different color of excavated earth in comparison 
 with the ground immediately around an emplacement makes 
 the spoil very noticeable. The enemy knows that, as the 
 importance of a position may be determined by the amount 
 of excavated earth, it is desirable to transport all earth to 
 a distance before scattering it. Gun positions very care- 
 fully camouflaged, have been discovered because the cut turf 
 was noticed in the territory immediately surrounding them. 
 In the winter time the enemy has to throw snow over the 
 uncovered section of ground. 
 
 In wooded country, especially if the woods are of any 
 extent, batteries are difficult to locate with accuracy owing 
 to the fact that just when conditions are most favorable 
 for air photography (i.e., the spring and summer), the leaves 
 and natural cover are thickest. Camouflage with fresh 
 
AIRPLANE MAPPING 103 
 
 branches and undergrowth is a simple matter, and tracks 
 which can be seen entering a wood are soon lost inside it. 
 
 An orchard or a hedge can completely conceal a bat- 
 tery if the occupants take sufficient precautions to avoid 
 circulation marks, blast marks, etc. 
 
 Pieces installed in caves or in the midst of partially 
 ruined houses blend with the white ruins and it is difficult 
 to distinguish them. 
 
 22. When batteries are forced to retire, the enemy 
 sometimes constructs emplacements of the normal type in 
 the new positions, but during extensive operations it is 
 common for guns to come into action in the open without 
 protection of the guns themselves or for the battery per- 
 sonnel. In this case, one would expect to find the battery 
 near a road or in a position where the natural features of 
 the ground give a certain amount of protection. 
 
 23. When the tactical situation necessitates the rapid 
 installation of batteries on terrain that presents no cover, 
 the enemy sometimes neglects to conceal them. They frankly 
 accept the hardship of fire and dispense with all attempts 
 to assure efficient protection for the personnel and materials. 
 If the photograph is taken at a great height, however, the 
 battery itself is rarely discernible in the photograph of 
 the target. At a lower altitude, the effect of camouflage 
 is the same, viz., the battery cannot always be discerned 
 directly. 
 
 24. Battery positions are indicated directly by the regu- 
 larity of the work, the blast marks, and the smoke. The 
 enemy avoids placing his shelters in regular groups, and 
 tries to eliminate abrupt changes in the angle of slope be- 
 tween the camouflage and the surrounding ground, and to 
 eliminate conspicuous shadows. All regular geometrical 
 forms are avoided as much as-possible in the construction of 
 the works. The blast of a piece traces a clear, very char- 
 acteristic mark in front of the muzzle of the gun, especially 
 if it is firing at a low elevation. When the snow is on the 
 ground, it is particularly difficult for the enemy to cover 
 the area melted by the heat of the blast. To avoid blast 
 marks in dry weather, the guns are sometimes placed where"' 
 they will fire across a road or under a tree. 
 
104 TOPOGRAPHY 
 
 25. Battery positions are indicated indirectly by marks 
 on the surrounding ground, of which the principal are tracts 
 and paths. Practically the first thing that is noticed on the 
 photograph is the system of tracks. Most often the artil- 
 lery is revealed by the radiating tracks. Tracks which end 
 abruptly in a fan-shape are clearly discernible. At each 
 track end, there appear clearly emplacements in semi-cir- 
 cular form. From this it results that the approach roads 
 may be effaced to at least 300 meters in rear by plowing 
 or harrowing, or other means. 
 
 Because of the number and importance of tracks the 
 enemy makes an extraordinary attempt to suppress the 
 traces. A common means of hiding tracks made by men 
 is to make the troops follow the borders of cultivation — the 
 perimeter of fields. Every path that cuts across a field in 
 any one direction shows up conspicuously on the aeroplane 
 photograph, and in following its trace, we can arrive at the 
 work to which it leads. 
 
 A feature with batteries in exposed positions is a 
 covered trench leading from an adjacent road or trench, 
 enabling personnel and ammunition to enter the battery 
 without leaving tracks above ground. 
 
 When a path stops abruptly or becomes narrow when 
 it has been broad, we find, in the vicinity of the point where 
 it changes form, something whose presence necessitates im- 
 portant circulation. If the nature of the ground and the 
 distance from the front are favorable for an artillery posi- 
 tion, we report the possible presence of a battery. 
 
 26. It is evident that on photographs false batteries 
 are at the very first glance easy to distinguish from real 
 positions, if care is not taken. This is especially true when 
 it is considered sufficient to build false emplacements, and 
 leave the surrounding ground as it is, especially behind the 
 position so that the false position on the photograph ap- 
 pears to be deprived of movement. That is why it is strictly 
 necessary that, behind each false battery, tracks should be 
 kept fresh by making supply trains pass over them from 
 time to time, as often as possible, preferably after a rain, 
 and in a direction previously decided upon. A haphazard 
 circulation of traffic behind the position without following 
 
AIRPLANE MAPPING 105 
 
 a pre-determined road does not deceive the enemy suffi- 
 ciently. Smoke is sometimes produced to simulate kitchens, 
 false telephone lines are installed, and blast marks made. 
 
 At the end of an existing wagon road, as often as pos- 
 sible, a false battery with radiating wheel tracks is installed. 
 The foot path leading from the false battery to the position 
 occupied need not be direct. 
 
 The enemy construct few dummy batteries. Those that 
 exist are generally recognized by the too clear indication 
 of the blast marks, and of the artificial paths. 
 
 However, one finds in the enemy lines many reserve 
 emplacements, for the most part unoccupied, which serve. 
 the same purpose as false batteries. 
 
 Machine Guns may be looked for : 
 
 (a) Where an angle occurs in the trench system, or a trav- 
 erse is constructed so as to bring fire to bear on the flank. 
 
 (b) Within easy reach of a communication trench, with dug- 
 outs for the team close at hand. 
 
 The covered emplacement may be discovered by a V- 
 shaped mark in the forward edge of the parapet, where the 
 latter has been cut away to allow the gun to traverse. At 
 the back of this "V" or close beside it in the trench, if the 
 emplacement is entered from the side, may be found a dark 
 spot similar to a dugout entrance. 
 
 The open emplacement takes the form of a square tray 
 or concrete platform let into the parapet. It varies in ap- 
 pearance according to the altitude of the sun, and may 
 show up either as a white mark with a dark edge or as a 
 comparatively dark square. The latter is hard to distin- 
 guish from the many dark cuts in the parapet, which may 
 be sentry posts or firing recesses. 
 
 Outside the trenches, the search requires a minute ex- 
 ploration of the whole terrain in which tactical reasoning 
 plays an important part. 
 
 Railways: — Light railways usually follow contours 
 and defilading ground, and may sometimes be discovered 
 by the fact that they lead into trenches which have no 
 traverses and sharp corners. It is very difficult to establish 
 the presence of light railway along a road, as it is generally 
 constructed near a ditch and under trees. The railway 
 
106 TOPOGRAPHY 
 
 may often be discerned at corners of the road and under 
 roads, where it is necessary for the lines to leave the road 
 or to make a more gradual curve. 
 
 Standard gage roads are never successfully camou- 
 flaged, but sidetracks for the cars are placed from 500 to 
 1000 meters from the nearest freight yard to distract at- 
 tention from the important unloading point. 
 
 Sometimes the narrow gage railways (particularly the 
 0.60-m.) are camouflaged by tunnels or roofs of branches, 
 but result is not deceptive. 
 
 The railway spurs that lead from a main line to allow 
 the long distance railway artillery to fire, are camouflaged 
 with special care. Before and after the spur is in use the 
 tracks are often covered with dirt covered tarpaulins, the 
 excavation in the bank is concealed with a slanting screen 
 of branches, a number of false spurs are constructed to dis- 
 tract attention, and the gun and carriage are carefully con- 
 cealed beneath a large screen of nets with interwoven 
 branches. 
 
 27. Reserves: — One should distinguish between the 
 troops in reserve, who are kept immediately behind the com- 
 bat position or near the second position, and the troops 
 in rest, in the re^-r. 
 
 The supports, or reserves, are placed : 
 
 In shelters opening along trenches or communication trenches. 
 In shelters hidden, opening behind a feature of the terrain 
 
 or sunken road. 
 In groups of shelters forming real caverns in the open or in 
 
 the woods. 
 In old quarries. 
 In tunnels. 
 In organized caves (rarely). 
 
 The only indications of a reserve emplacement are: 
 
 The spoil, sometimes transported some distance away by a 
 
 narrow gage road of 0.60m. or 0.40m. 
 The circulation. 
 
 The paths leading up to the position. 
 The entrances, ventilation, chimneys, etc. 
 
 (b) Troops in rest are found: 
 
 In camps in the open, but defiladed from terrestrial and 
 
 balloon observation. 
 In camps in the woods. 
 In villages. 
 
AIRPLANE MAPPING 107 
 
 The indications are : 
 
 The presence of barracks. 
 Paths disappearing into woods. 
 Paths for training horses. 
 
 Proximity of exercise grounds, works for hand grenadiers, 
 firing positions. 
 
 28. Roads, Paths, Tracks, Etc.: — A study of tracks 
 will often reveal the following points: 
 
 Roads in use (by parallel or divergent tracks in their vicin- 
 ity). In wet weather it is possible to distinguish the 
 character of the road, whether paved or unpaved. 
 
 The main communication trenches in use (by tracks running 
 alongside, made by carrying parties at night) . 
 
 Many tracks on both sides of trenches often indicate that 
 trenches are in bad condition. 
 
 Dumps. 
 
 Billets and hutments (especially in woods). 
 
 Active battery positions. 
 
 Headquarters. 
 
 Wire which is almost invisible, and gaps through it. 
 
 Patrol paths. 
 
 Observation posts. 
 
 In villages, houses which are important centers. 
 
 Advance listening posts. 
 
 Fortified shell holes. 
 
 In quiet parts of the line, the appearance or gradual 
 disappearance of tracks will often give valuable information 
 as to the enemy's activity in any particular locality. 
 
 During the artillery preparation new tracks leading to 
 a group of dugouts under bombardment are sure signs that 
 the dugouts have not been absolutely destroyed or that 
 they have been reoccupied. 
 
 The appearance of tracks varies with weather condi- 
 tions; sometimes they show up as white lines of varying 
 thickness, sometimes as darker ones. 
 
 29. Organized Shell Holes are of two distinct forms : 
 
 (a) Shell holes, real or artificial, placed in echelon, in stag- 
 gered formation surrounding machine gun emplacements outside 
 the trenches. 
 
 (b) Shell holes, often square, which often seem shallow, 
 grouped in pairs, usually on high ground for drainage purposes. 
 
 These organizations, which one can only study on large 
 r-~ale photographs, are disclosed by the spoil which is some- 
 times scattered in nearby holes, by the organization itself, 
 by tracks, by the material left on the side or in the holes, 
 
108 TOPOGRAPHY 
 
 by a visible entrance to a shelter at the bottom, or by a 
 segment of communication trench prolonged underground. 
 
 30. Shelters are indicated by the following character- 
 istics : 
 
 During construction: 
 
 (a) The digging and the spoil. The excavation, often con- 
 cealed by camouflage, reveals concrete shelters, the spoil from 
 which is visible around the hole or carried off some meters to. 
 the rear to form a large pile, or transported some distance by 
 narrow gage. The spoil from a mine-gallery shelter is gen- 
 erally disposed around the two entrances (which appear as black 
 points visible at the end of the works). 
 
 (b) By the narrow gage railway transporting the concrete. 
 
 After construction: 
 
 (a) Traces of the entrance (shadow or small notch in the 
 parapet or bench). Often the entrances of one concrete type 
 are between two traverses. 
 
 (b) The ventilation chimneys. 
 
 (c) The trace left by the narrow gage railways. 
 
 (d) The spoil and sometimes the path made by its evacua- 
 tion. 
 
 Any unusual amount of spoil should be scrutinized care- 
 fully, as it may indicate subterranean work. 
 
 31. Supplies: — Dumps are discovered by the piles of 
 material, tracks, roads or even railways leading to the 
 dumps. 
 
 Supply centers are determined, first, by deciding as to 
 their proper location, second, by searching the vicinity for 
 railways, roads, tracks, etc. 
 
 Supply depots will be found where standard gage rail- 
 way changes to narrow gage ; also at switches, warehouses, 
 etc., along tracks. 
 
 32. Trenches are identified on photographs by the 
 characteristic line of traverse and fire-bays, showing up as 
 dark and light lines, varying with the direction of the light. 
 
 Dummy or incomplete trenches can be identified by the 
 comparative absence of shadow. 
 
 The extent to which spoil on the parapet or parados is 
 conspicuous depends on the nature of the soil and the new- 
 ness of the work. 
 
 33. Trench Mortars : — Light trench mortars are often 
 fired from open emplacements to allow a rapid change of 
 
AIRPLANE MAPPING 109 
 
 position, and it is difficult to distinguish the appearance of 
 these emplacements from that of latrines and dump pits. 
 One difference, which is by no means universal, is that 
 trenches leading to trench mortar emplacements are more 
 often zig-zag or traversed than are trenches leading to 
 latrines. 
 
 Medium and heavy trench mortar emplacements are 
 casemated and much more conspicuous. They can gen- 
 erally be recognized by an almost square, dark mark in the 
 center of a mound or a ring of earth. This square mark 
 is the top of the funnel up which the mortar fires, and 
 differs in appearance according to the angle of light. 
 
 34. Barbed Wire shows up on a photograph as a broad 
 line varying in tone from light gray to almost black, accord- 
 ing to the newness of the wire and the contrast with the 
 color and texture of the ground. The tracks made by work- 
 ing parties are often visible along either side of a belt. 
 
 As ground becomes cut up by bombardment, wire be- 
 comes increasingly difficult to distinguish. . 
 
 The absence of signs of wire on a photograph must 
 not necessarily be taken to mean that no wire exists. Oblique 
 photographs will often reveal wire which does not cast 
 enough shadow to show up on a vertical photograph. 
 
 Wire is very often the earliest indication of a new line 
 of defense. 
 
CHAPTER VI 
 
 Mapping Large Areas 
 
 1. There are many organizations engaged in mapping 
 for the United States. The following is a list of them : 
 
 U. S. Coast and Geodetic Survey. 
 
 U. S. Geological Survey. 
 
 General Land Office. 
 
 Topography Branch, Post Office Department. 
 
 Bureau of Soils. 
 
 U. S. Reclamation Service. 
 
 Bureau of Public Roads. 
 
 Bureau of Indian Affairs. 
 
 Mississippi River Commission. 
 
 U. S. Lake Survey. 
 
 International (Canadian) Boundary Commission. 
 
 Forest_ Service. 
 
 U. S. ilydrographic Office. 
 
 Corps of Engineers, U. S. Army. 
 
 2. The .Corps of Engineers of the .United States Army 
 is in charge of the map work for the United States Army, 
 because of the army regulations which prescribe, among 
 their duties—* 
 
 "Reconnoitering and surveying for military purposes, in- 
 cluding the laying out of camps; the preparation of military 
 maps of the United States and its possessions, including co-opera- 
 tion with other Government and private agencies, and in field 
 operations of maps of the theatre of operations." 
 
 3. It will be noticed that these regulations state that 
 the Corps of Engineers will co-operate with other Govern- 
 ment and private map agencies. As a result of this co- 
 operation, particularly with the Coast and Geodetic Survey 
 and with the Geological Survey, the Corps of Engineers 
 has been able to obtain maps of our coast lines, borders and 
 interior localities. These maps will be very useful in case 
 of hostilities. 
 
 4. In addition to the map making organizations men- 
 tioned above, the Corps of Engineers has been assisted by 
 the Army through progressive military maps ; however, the 
 
 110 
 
MAPPING LARGE AREAS 111 
 
 results obtained by this work vary so greatly that the gen- 
 eral advantage is doubtful. 
 
 Present Status as to Maps 
 
 5. On the eastern coast there are fairly good maps from 
 Maine to Jacksonville, Fla., covering the whole section of 
 the coast line, except the coast of North Carolina. 
 
 6. On the western coast, there are fairly good maps 
 covering every section of the coast except the mountainous 
 country west of Puget Sound and this would not be of any 
 military importance. There is a map of the northern coast 
 line of this section, which is the only part that would be 
 useful. 
 
 7. Along the northern boundary, there are fairly good 
 maps, covering about 50 per cent of the border ; in the other 
 50 per cent there are still unmapped a few small sections 
 and the large sections of Maine, Michigan, Minnesota and 
 North Dakota. 
 
 8. Along the southern boundary, there are fairly good 
 maps, except of that portion of Arizona west of Nogales ; 
 and as this is a desert country, it is not deemed of great 
 importance, though efforts are being made to map it in the 
 near future. Incidentally, there are maps of certain small 
 areas across the boundary in ,Mexico, but these maps are 
 not reliable. 
 
 9. It is noticed on looking over the portions of the 
 country which have been mapped by the Geological Survey 
 that certain states such as West Virginia, New York, Massa- 
 chusetts and Pennsylvania are completely covered, whereas 
 Michigan and Louisiana have practically not been mapped 
 at all by the Geological Survey. This is due to the fact 
 that the Geological Survey has generally an appropriation 
 which must be aided by appropriations by the state. In coal 
 states, such as West Virginia, the state has made the nec- 
 essary appropriations. 
 
 10. In Hawaii, there is an excellent map of the Island 
 of Oahu to the scale of 1 : 18,000 ; this will be made 1 :20,000. 
 
 11. In Alaska there are practically no military maps. 
 In Panama, the Coast and Geodetic Survey have published 
 reliable charts of the Pacific and Atlantic coasts on either 
 
112 TOPOGRAPHY 
 
 side of the Canal. War Department maps, scale 1 :62500, 
 have been made of the coasts and waters adjacent to each 
 entrance and maps on a scale of 1 :21120 are available cov- 
 ering nearly the entire Zone, and considerable territory ad- 
 joining it on each side of the Isthmus. 
 
 12. In the Philippines, the United States Army has 
 mapped about f of the Island of Luzon. The only unmapped 
 portion consists of inaccessible mountains and useless coast 
 line on the east coast. Considerable work has been done 
 towards mapping the rest of the Philippine Islands. This 
 was indexed by the same system as the Progressive Mili- 
 tary Map of the United States. The scale to be used was 
 1:62,500 and 1,125,000 at first; but most of the sheets seem 
 to have been made to scale 1:63,360 (1 inch) or 1:126,720 
 (i inch). 
 
 Map Sheets and Scales 
 
 13. The earth is round and the map sheets are flat. 
 One cannot show accurately even a small portion of the 
 round earth on a flat sheet. However, there is a system 
 called "polyconic projection," wherein the surface of the 
 sphere is projected on the surface of a cone tangent to the 
 sphere and the cone is rolled out, or developed, on a plane. 
 The distortion is small for points near the circle of tan- 
 gency; therefore to avoid great distortion and still be able 
 to represent considerable surface of the sphere a number of 
 cones tangent along adjacent circles of latitude are used, 
 hence the term polyconic. The Geological Survey sheets 
 are made on this system. There is a straight central line 
 representing the central meridian of the sheet. The four 
 boundaries of the sheet are parallels of latitude or meridians 
 of longitude. They appear to be straight lines also, but 
 they are not. By careful measurement, one will find that 
 the northern boundary is a little shorter than the south- 
 ern boundary. Likewise, one will find that all four boun- 
 daries are slightly curved. 
 
 14. The U. S. Geological Survey sheets are polyconic 
 and generally 1:62,500 (about 1"=1 mile) and 1:125,000 
 (about i"==l mile). The 1:62,500 sheets cover 15' of lati- 
 tude and 15' of longitude. 
 
MAPPING LARGE AREAS 113 
 
 15. Grid System in the United States: — The sys- 
 tem of map co-ordinates used by the U. S. Army is based 
 on 1000-yard squares or grids. The whole of the United 
 States is divided into seven zones, each 8 degrees of longi- 
 tude in width, but with an additional h degree at each side 
 for overlap on the adjacent zone. The following table shows 
 the designation of the several zones across the United 
 States, with their central meridians and the meridians which 
 limit the zones : 
 
 Designation 
 
 Central meridian 
 
 Limiting meridians 
 
 A 
 
 73° 
 
 68° 30'— 77° 30' 
 
 B 
 
 81° 
 
 76° 30'— 85° 30' 
 
 C 
 
 89° 
 
 84° 30'— 93° 30' 
 
 D 
 
 97° 
 
 92° 30'— 101° 30' 
 
 E 
 
 106° 
 
 100° 30'— 109° 30' 
 
 V 
 
 113° 
 
 108° 30'— 117° 30' 
 
 G 
 
 121° 
 
 116° 30'— 125° 30' 
 
 The only exception, so far as limiting meridians are 
 concerned, is the strip over Maine to the eastward of longi- 
 tude 68° 30' which is included in the grid tables for zone 
 A, though it is more than 4° 30' to the eastward of the cen- 
 tral meridian of the zone. 
 
 An origin of co-ordinates for each zone is arbitrarily 
 selected southwest of the area covered by the zone, so that 
 the co-ordinates for all points will be positive. The point 
 selected as the arbitrary origin is 1,000,000 yards west 
 and 2,000,000 yards south of the intersection of the central 
 meridian of each zone with the parallel 44° 30' of latitude. 
 The vertical co-ordinates run from about 600,000 yards at 
 the west boundary of each zone to 1,400,000 yards at the 
 east boundary, the 1,000,000 co-ordinate line co-inciding 
 with the central meridian. 
 
 The horizontal (Y) co-ordinates run from about 500,000 
 at 28° N. latitude to 3,000,000 at about 49° N. latitude. 
 
 Points on the overlaps between zones will have a dif- 
 ferent set of co-ordinates for each zone. The two grid sys- 
 tems may be placed in different colors on maps of the over- 
 lapping areas. 
 
 16. Grid Azimuths: — Owing to the converging of 
 meridians, any line on the earth's surface (except at the 
 central meridian of the zone) will make a different angle 
 
114 TOPOGRAPHY 
 
 with the grid meridian from the angle it makes with the 
 geographic meridian. At points west of the central meri- 
 dians, the grid azimuths are greater than geodetic or true 
 azimuths; at points east of the central meridians they are 
 less. The differences vary from zero at the central meridian 
 to about 3i degrees at the eastern or western edges of the 
 respective zones. 
 
 further details regarding the above system may be 
 found in Special Publication No. 59, U. S. Coast and Geodetic 
 Survey, "Grid System for Progressive Maps in the United 
 States." 
 
 17. System of Mapping Large Areas: — A complete 
 system of mapping large areas consists of: 
 
 (a) Preparation of skeleton projection sheets, involv- 
 ing two steps : 
 
 1. Securing of data. 
 
 2. Production of skeleton projection sheets. 
 
 (b) Field work, involving three steps: 
 
 1. General control. 
 
 2. Local or transit traverse control. 
 
 3. Sketching in. 
 
 (c) Making final sheets, involving two steps: 
 
 1. Drafting of final maps by transfer from field sheets. 
 
 2. Printing or reproduction of maps. 
 
 18. The securing of data consists in finding all possible 
 available information. There is practically no large area 
 in the world in which maps have not been made of at least 
 some small portions. There are generally railroad surveys 
 which can be used. Often, astronomers have worked out 
 accurately certain local points, all of which can be obtained 
 for use in mapping the area. 
 
 19. The production of field sheets consists simply in 
 (a) deciding on the size of the field sheet; (b) putting on 
 it all of the available accurate data; (c) putting on it also 
 all of the control data secured by our own mappers; (d) 
 furnishing as a memorandum all of the data which may be 
 useful but is not known to be accurate. 
 
 20. If a country has never been mapped at all, it is nec- 
 essary to secure control, for the control of a map is like 
 
MAPPING LARGE AREAS 115 
 
 the steel framework for a modern skyscraper. By control, 
 is meant the accurate location of certain points, say 100 
 miles apart for primary control and 10 miles apart for sec- 
 ondary control. This has been done in the past by expand- 
 ing triangulation from a base line measured to the highest 
 attainable accuracy, and using the most refined instruments 
 of precision in measuring the angles. An area of large ex- 
 tent is covered by two sets of triangles, primary, with sides 
 up to 30 miles long, and secondary with sides up to 10 miles 
 long. 
 
 21. Control within the triangulation and tied thereto 
 or for small areas not covered by triangulation is often es- 
 tablished by traverse lines. These lines may be run with 
 a high degree of accuracy, and with fair speed, and with a 
 number of parties in the field, cover considerable area. Such 
 method of control is what may be expected in military sur- 
 veys. 
 
 22. For hundreds of years, it has been possible to find 
 by astronomy quite accurately the latitude of a place, but 
 not the longitude. Lately, however, the telegraph, and still 
 more lately, the wireless, are being used until it is now pos- 
 sible for a survey party equipped with a theodolite, a wire- 
 less receiving outfit, and an ephemeris (astronomical tables) 
 to locate itself in the middle of a desert or mountainous 
 country a thousand miles away from any other human be- 
 ing. The finding of the longitude of a point consists in find- 
 ing the exact time when a star or the sun passes the meri- 
 dian of the place; and then finding by calculation, using the 
 ephemeris, the difference between this time and the time 
 the star or sun passes the meridian of Greenwich. A clock 
 is set with say Greenwich time and taken out into the field ; 
 the time is observed by this clock when the star or sun 
 passes the meridian of the place ; the difference, with cal- 
 culated corrections, gives the longitude. It all depends on 
 the clock, which has errors which are very small but vary 
 from day to day. The daily error is so small that it can be 
 assumed proportionate and calculated and compensated for ; 
 the error for several days cannot be assumed as propor- 
 tionate and cannot be so calculated, consequently the cal- 
 culated longitude is not exactly correct. Lately, wireless 
 
116 TOPOGRAPHY 
 
 helps a great deal, because the clock error can be determined 
 each day ; and we need only consider the daily error, which 
 as stated above is assumed as proportionate to the whole 
 day and is so small that the result is quite accurate. In run- 
 ning the Mexican boundary lines, a clock was used and was 
 fairly satisfactory; but the clock gradually accumulated 
 varying errors while being packed around over the rough 
 country ; and when the party arrived at a telegraph station, 
 they had to refigure all their observations in order to adjust 
 for the errors of the clock, and even then they had to as- 
 sume that the errors were proportionate to the time since 
 the clock error was last determined. 
 
 23. Having acquired primary control, it is then neces- 
 sary to run a series of secondary triangles called "secondary 
 triangulation," in order to provide a second set of known 
 points closer together and more convenient for detailed 
 use. If the country is difficult and the map need not be 
 exceedingly accurate, this second set of known points may 
 be determined in latitude and latitude astronomically, or, 
 if conditions warrant, by traverse. This second set of 
 known points should not be more than 10 miles apart and 
 preferably less than that. 
 
 24. Before the sketcher starts to work on an area, he 
 must have points closer together even than 10 miles, be- 
 cause with sketching instruments, it is not possible to make 
 a series of sketches covering an area 10 miles square which 
 will be accurate enough. Consequently, a series of traverse 
 lines is run connecting these points of the secondary trian- 
 gulation. Branch traverse lines may be run so as to give 
 as close a net of control as the circumstances demand. 
 
 25. By these means, we secure a control net or frame- 
 work on which may be hung in their proper relation the de- 
 tails determined by the methods of sketching. 
 
 26. In the general system of control, transit traverse, 
 and sketching, as noted above, it is necessary to adjust the 
 triangles and transit lines. The curvature of the earth 
 makes this necessary, and in addition there are always cer- 
 tain errors in closing a triangle. The sum total of the de- 
 grees of a measured triangle will never be exactly 180 de- 
 grees. In such case, the difference is not applied to the last 
 
MAPPING LARGE AREAS 117 
 
 angle determined; but the total difference is divided out 
 among all the angles of the triangles, or series of polygons. 
 Similarly, if the lines are not the proper length, the adjust- 
 ment is made on all of the lines and not simply on the last 
 line. 
 
 27. All of the control points having been plotted on the 
 field sheet as previously stated, the transit and sketching 
 parties are assigned certain sections for work. In the as- 
 signment of areas for sketching parties it is advisable to 
 make the division with some regard to the roads and trails 
 that give accessibility to the areas rather than by an arbi- 
 trarily adopted set of dividing lines. 
 
 28. The sheets furnished the field parties should be of 
 uniform size adapted to the equipment, sketching board, 
 plane table, etc., that is to be used. These sheets should 
 have upon them the control, and all other data that can be 
 reliably placed on them at the office issuing them. Any 
 other data on hand which might be of use to field parties 
 should be issued to them; 
 
 29. A central party controls transit and sketching 
 parties. It is assigned its area, given its field sheets, and 
 sent out into the field. The transit parties run their transit 
 traverses ; central party checks and plots their work and 
 turns over the field sheets to the sketching parties. These 
 fill in the areas, then the central party checks and co- 
 ordinates the field sheets and sends them to the main office 
 for final check before being turned over to the printing 
 and reproducing outfit. 
 
 30. The two steps in making final sheets are the trans- 
 fer of field data with good drafting and then the printing 
 of the maps. Each field sheet must fit with its adjacent 
 sheet. The work of adjusting the field sheets of adjacent 
 field parties is done in the central office with the assistance 
 of representatives of the field parties where necessary. Ad- 
 jacent sheets from one field party should require no adjust- 
 ment for concordance by the central office. The central 
 office has much preliminary work to do when topography 
 is taken from airplane photographs. 
 
 31. The transfer force has much special work when we 
 use aeroplane photographs. Also, the transit work of the 
 
118 TOPOGRAPHY 
 
 field parties must always be checked. Altogether, the- 
 transfer force has much to do even before it begins the 
 drafting. 
 
 32. The printing of the maps is an art in itself. It 
 requires special equipment and special men. In France, the 
 29th Engineers did this work. They were very specially 
 selected men, and they did the work so well that most peo- 
 ple thought it was easy to do. 
 
 System for the United States Army 
 
 33. In case the Army of the United States should oc- 
 cupy a new country which has been unmapped, it would 
 be advisable to promptly commence making maps of the 
 country. The system followed should be as stated above; 
 if such a system is not followed, there are always unneces- 
 sary difficulties. This system was followed in Hawaii and 
 in the Philippines, and it worked out very well. However, 
 in Cuba we used a very different system. It appeared that 
 for certain reasons is was necessary to begin the field work 
 of sketching without delay. Consequently the sketchers 
 were hurried out into the field before control had been ob- 
 tained of the country. As a result, the. sketching parties 
 made sketches which, in some cases, could not even be ad- 
 justed by expert draftsmen in accordance with the actual 
 distances as developed later, when the primary and secon- 
 dary control were obtained. In most cases it was possible 
 to adjust these sketches, but where this could not be done, 
 it was necessary to have a sketching party go all over the 
 work again. 
 
 34. In map work by the army it is best to follow the 
 approved system and apply the available agencies to the 
 accurate work. Consider each of the steps of the approved 
 system, and see how to apply it to the army. 
 
 35. Securing of Data: — This would be done by the 
 engineers on the staff of the general headquarters and at 
 other headquarters. Most of the data is obtained from 
 books or from records in the capital city of the country. In 
 Cuba, practically all of the data was secured in Havana ; in 
 one case, railway data was secured from the headquarters 
 in the United States of this particular railway. 
 
MAPPING LARGE AREAS 119 
 
 36. Production of Field Sheets: — This will be done 
 by the reproducing company of the topographical engineer 
 battalion. It might be done at one central headquarters 
 by all of these companies working together, or each battalion 
 might work at some central point in its own district. 
 
 37. Control: — This work would require expert map- 
 pers. For this purpose, the survey company of the topo- 
 graphical engineers would be used and they should start 
 at once. These men securing primary control would also 
 be the ones to secure secondary control. It is estimated 
 roughly that one party could secure primary and secondary 
 control for an area of about 10 miles square in one month. 
 Assuming each engineer survey company furnishes 10 con- 
 trol parties, it should be able to get 10 points per day, or 
 100 points in 10 days. Allowing for errors and other delays, 
 and assuming these control points 8 to 11 miles apart, this 
 engineer survey company should easily secure control on 
 an area 100 miles square at the rate of one area per month, 
 after the work had well started. 
 
 38. Transit Traverses and Sketching: — One would 
 naturally expect that engineer troops would be used for 
 running the transit traverses and for rilling in by sketching, 
 but there are not enough engineers and never will be enough 
 to do all the map work of mapping a large area. Calculations 
 in the office of the Chief of Engineers show that a survey 
 company can map completely and alone about 5,400 square 
 miles per year. As a survey battalion would need 1 company 
 for reproduction, they could put only 2 companies in the 
 field. As a result, a survey engineer battalion could map 
 10,800 square miles per year. There were in the proposed 
 Army Reorganization Bill 2 topographical battalions listed, 
 each battalion having 2 companies for survey work and 1 
 company for printing and reproduction work. 
 
 39. For the bulk of this work, the army would have 
 to organize and train special transit and sketching parties. 
 It would use say a survey company and the mapping de- 
 tachments of the division engineer regiments and obtain 
 the remaining personnel by details from the infantry, cav- 
 alry, and artillery. Two months' training would be desir- 
 able before sending one of these parties into the field. The 
 
120 TOPOGRAPHY 
 
 division engineer regiments should be able to furnish a 
 limited number of trained topographers. The best use of 
 such men would in general be to give them pivotal positions 
 in newly formed parties. 
 
 40. In Cuba, they did not train any special parties ; and 
 results were not very satisfactory. In the Philippines, they 
 gave a two months' training to these special parties before 
 sending them out into the field and the results were quite 
 satisfactory. Incidentally, no time is lost by such training, 
 as the control parties should be given about 2 months' start 
 in order to secure control for field sheets for use of these 
 specially trained parties. 
 
 41. The size of the special parties would vary accord- 
 ing to the kind of country and the degree of friendliness of 
 the inhabitants. In Cuba, it was found that a sketcher 
 could do best if he were accompanied by three men. One 
 man would assist him by holding his horse, or counting, or 
 putting down data, and the other two were the cook and 
 packer. One of these parties would go out to a certain 
 section and map all of that section before returning. Occas- 
 ionally the packer would appear at his headquarters with 
 his pack mule and take back more rations. Several sketch- 
 ing parties could thus travel through a certain section of 
 the country, the central party moving along a road or trail, 
 and the others scattering out into their assigned areas, 
 remaining by themselves until the area had been mapped 
 and then returning to the central party. 
 
 42. Assume that each sketcher can sketch one square 
 mile each day, and that each transit man can traverse 5 
 miles each day. In a 100-mile square there are 10,000 square 
 miles to be sketched and 20,000 linear miles to be traversed. 
 This is equal to 4,000 traverse party days and 10,000 sketch 
 party days. This shows that 4 traverse parties and 10 
 sketching parties could finish the 180-mile square in 1,000 
 work days (about 40 months including delays, etc.). If the 
 work must be finished in 4 months, it would mean 40 trav- 
 erse parties and 100 sketching parties. 
 
 43. For different countries, the various parties will be 
 different. However, as a fair basis, assume that the coun- 
 try is about 20 per cent wooded, and that the inhabitants are 
 hostile but have no organized bands and act only as in- 
 
MAPPING LARGE AREAS 
 
 121 
 
 dividual enemies, 
 the following: 
 
 The various parties could then consist of 
 
 (a) Control party: 
 
 (c) Traverse party 
 
 1 officer or sergeant. 
 
 1 officer. 
 
 2 instrument men. 
 
 1 cook. 
 
 1 recorder and calculator. 
 
 1 packer. 
 
 2 medical men. 
 
 1 medical man. 
 
 1 draftsman. 
 
 3 guards. 
 
 4 woodsmen. 
 
 4 instrument men 
 
 1 cook. 
 
 •7 woodsmen. 
 
 1 assistant cook. 
 
 2 pack mules. 
 
 4 guards. 
 
 
 2 teamsters. 
 
 
 2 Signal Corps men. 
 
 
 8 mules. 
 
 
 2 wagons. 
 
 
 1 wireless receiving outfit. 
 
 
 Total, 3 officers and 28 men. 
 
 
 (c) Central party: 
 
 (d) Sketching 
 
 2 officers. 
 
 1 cook. 
 
 1 medical officer. 
 
 1 packer. 
 
 2 draftsmen. 
 
 1 medical man. 
 
 1 cook. 
 
 3 guards. 
 
 6 guards. 
 
 2 sketchers. 
 
 2 extra medical men. 
 
 2 pack mules. 
 
 15 extras. 
 2 wagons. 
 8 mules. 
 Total, 3 officers and 28 men. 
 
 The above estimates of personnel are reasonable. They 
 are not exactly the same as were used in the Philippines, 
 but that country was not hostile and natives were used as 
 cooks and cargadores. 
 
 44. The engineer topographical battalion would prob- 
 ably be a basis for any complete map organization. , By 
 using the preceding figures, and assuming that the con- 
 trol parties are about two months ahead and everything is 
 working smoothly, the following appears to be a well bal- 
 anced organization: 
 
 1 topographical battalion headquarters. 
 1 printing and reproducing company. 
 1 survey company (10 control parties). 
 40 mapping parties as follows (including 1 survey company 
 
 and all division engineers available). 
 40 central headquarters parties. 
 160 traverse parties. 
 400 sketching parties. 
 
122 TOPOGRAPHY 
 
 This organization could map one 100-mile square or 
 10,000 square miles in one month. 
 
 45. The following tables show more clearly the com- 
 plete and balanced mapping organizations which can map 
 10,000 square miles per month. Such an organization would 
 be assigned a district. An examination of this table shows 
 the very large force required to produce good maps of en- 
 tirely unmapped country in a short space of time. The con- 
 ditions would be very exceptional which would permit the 
 use of so much force for the purpose either in campaign or 
 at any other time. 
 
 46. Cost: — At present the cost of topographical map- 
 ping to the field scale 1:48,000 or 1:62,500 ranges from $25 
 to $50 per square mile, the average countries costing about 
 $33 per square mile. These figures increase rapidly with in- 
 crease of scale, and 1:10,000 scales run into hundreds of 
 dollars per square mile. A survey of the Island of Guam in 
 1915 at 3" to the mile for 210 square miles and 6" to the 
 mile for 30 square miles cost close to $40,000, which is $167 
 per square mile. 
 
 Assistance by Aeroplanes 
 
 47. The development of aero-photography indicates 
 that it will have a marked influence on topographic mapping 
 in the speed of work and in the accuracy and amount of the 
 detail shown. 
 
 (a) The average work to date by one aeroplane 
 is about 35 square miles in 2h hours, which would probably 
 constitute an average day's work if we count in the break- 
 downs and flying to and from the flying field. In other 
 words, an aeroplane with a well trained mapper can probably 
 do thirty times as rapid work as one sketching party. 
 
 (b) An aeroplane party should consist of the following l 
 
 1 Officer to lay out the photograph work and supervise. 
 
 1 pilot. 
 
 1 mapper (photographer). 
 
 3 mechanics. 
 
 5 field men. 
 
 3 control men. 
 
 There should be an office party of not less than — 
 
 1 man in charge. 
 
 3 men on transformer. 
 
 3 men preparing transformer photographs. 
 
 6 draftsmen. 
 
MAPPING LARGE AREAS 
 
 123 
 
124 TOPOGRAPHY 
 
 (c) Aeroplane photographs are of no real value in 
 determining elevations. By taking photographs at an angle, 
 this is possible ; but to date no very practicable method has 
 been devised. 
 
 (d) Thus, although it is known that aeroplane photo- 
 graphy has a great many possibilities, and although it is cer- 
 tain that it will be used to assist in any mapping of large 
 areas by the United States Army, it appears that it has also 
 very many difficulties. It can surely be used to assist in 
 sections where contours are not required; it can be most 
 profitably used for filling in details and for correcting de- 
 tails where the country has been poorly or incompletely 
 mapped; it can be used for rapid work in correcting maps 
 already in existence; it cannot be used for accurate work 
 unless primary and secondary control have been obtained, 
 but it can be used to obtain an inaccurate but effective map 
 covering a large area, even without control. The great ad- 
 vantage of the aeroplane is its speed; and the determining 
 factors of the speed of making the map is probably not the 
 actual time of photographing the area, but the kind of 
 camera, the distance from the ground, the number of ex- 
 perts available for reading and transferring the aeroplane 
 data to a real map, and the number of experts available 
 for reproducing the map. 
 
 48. Engineer troops will generally assist in mapping 
 large areas. Contrary to the general belief, not many of 
 the division engineer troops are experts in making maps. 
 Each division regiment has a topographical section, but its 
 number is very limited. All of the officers of the regiment 
 should be excellent map makers; but very few of the sol- 
 diers have the necessary experience. In addition, it must 
 be remembered that the engineer troops have other duties 
 to perform; and in some cases even the topographical sec- 
 tions are not available for mapping the area, as they are 
 needed for sketching and survey work connected with the 
 work of their regiments, such as roads, buildings, etc. The 
 main reliance for mapping large areas will be the topograph- 
 ical engineers, assisted by specially trained parties from 
 other sources. 
 
CHAPTER VII 
 
 Map Reproduction 
 
 1. General Classification of Methods of Repro- 
 duction: — The various methods of reproduction are di- 
 vided into four classes, according to the principle underly- 
 ing the method, viz.: 
 
 (a) Where the copy to be reproduced is obtained on a 
 transparent sheet, with the drawing in opaque lines, and the 
 reproduction is done by printing from this transparent sheet 
 on sensitized paper by means of light. The methods of repro- 
 duction using this principle are blue printing, brown printing 
 and photography. 
 
 (b) Where the copy is reproduced with special ink on paper 
 and this ink is transferred to another substance from which 
 copies can be made by pressing blank pieces of paper on it. This 
 is the principle upon which the hectograph is based as well 
 as the forms of hectograph called by other names, such as the 
 jelly roll and duplicator. 
 
 (c) Where paper or cloth is so cut or treated that ink can be 
 rubbed or forced through it onto blank sheets below. This is the 
 principle upon which the mimeograph, neo-cyclostyle (used in 
 France), and the Ellam duplicator (used by the British army) 
 are based. 
 
 (d) Where copy is transferred, generally by a rather com- 
 plicated process involving several transfers, to another substance 
 which is so fixed that the impression of the copy can be inked 
 and so that when paper is pressed in contact with the substance 
 a reproduction of the original will be made. This principle is 
 the one used in the Dorel and lithographic methods of repro- 
 duction. 
 
 2. Drafting is generally the slowest part of any work 
 of reproduction. The classification below is based on the 
 drafting required. 
 
 First: Methods which require the redrafting of the 
 map or sketch on transparent paper or cloth : 
 
 (a) Blue and brown prints. 
 
 (b) Dorel. 
 
 (c) Certain processes in lithography. 
 
 Second : Methods which require a redrafting of the 
 map or sketch on special poper or with special inks : 
 
 (a) Hectograph, jelly roll, duplicator. 
 
 (b) Ellam duplicator. 
 
 125 
 
126 TOPOGRAPHY 
 
 (c) Neo-cyclostyle. 
 
 (d) Mimeograph. 
 
 (e) Autographic process in lithography. 
 
 Third: Methods which do not require redrafting: 
 
 (a) Special cases in blue printing. 
 
 (b) Photography. 
 
 (c) Photographic process in lithography. 
 
 Of the above named methods the hectograph is the 
 only one which will reproduce a number of colors at once. 
 The others all require a special reproduction for each color. 
 
 3. Description of Methods of Reproduction: — A 
 short general description is given below of the most common 
 methods of reproduction. 
 
 Hue Prints 
 
 4. The procedure followed consists in placing a piece 
 of prepared paper, and the tracing it is desired to repro- 
 duce, in a frame with one glass side. The glass holds the 
 transparent paper in contact with sensitized paper. Then 
 the frame is placed in sunlight or in strong artificial light 
 for a certain period of time, depending upon the intensity 
 of the light, the transparency of the paper, and the. sen- 
 sitiveness of the prepared paper. After this exposure the 
 print paper is washed out in water and when dried, the print 
 is ready for use. 
 
 5. The equipment for blue printing is simple, con- 
 sisting of the proper kinds of paper, a frame, a dark room, 
 and facilities for washing and drying paper. For relia- 
 bility, artificial light is also necessary. Two men should 
 be available for this work. To make and dry one blue print 
 requires from 30 minutes to 3 hours, depending upon con- 
 ditions. The speed is limited by the capacity of the frame. 
 As a general rule if more than 20 copies are desired it is 
 better to use some' other method. 
 
 The result obtained consists of white lines on a blue 
 background. A blue print can be corrected or changed as 
 desired by drawing on it with a solution which fades out 
 the blue and makes white. 
 
 This brings up another point of interest. Ink lines can 
 be drawn on a blue print and then the color faded out leav- 
 
MAP REPRODUCTION 127 
 
 ing the black lines on a white background. This resulting 
 drawing can be photographed and reproduced. The applica- 
 tion of this scheme is quite varied. For instance, many of the 
 plates in the Engineer Field Manual were made by photo- 
 graphing the object, say a pack mule, making a blue print 
 from the negative, inking the important features of the blue 
 print, fading out the blue, and then reproducing the result- 
 ing drawing. It gives a very clear plate with nothing on 
 it except essential details. 
 
 6. Ordinary paper is sufficiently translucent to permit 
 a blue print to be made through it. It is a very slow process, 
 however, as the time of exposure depends upon the trans- 
 parency of the paper. A map can be reproduced in this 
 way. The result is readable and in case a few copies only 
 are desired it is a very quick way of getting them. The 
 result is, of course, in one color. If the original map can 
 be oiled it will increase its translucency and copies can be 
 made much more quickly as the time of exposure is reduced. 
 
 As an example of this, before the St. Mihiel operation, 
 G3, G.H.Q., got out a number of maps showing the visible 
 areas from various observation posts within the German 
 lines. The data for these maps were obtained by the use 
 of relief maps and the shadow effect from small electric 
 lights. The reproduction facilities at this time were too 
 busy to do the work, and it was not possible to have these 
 maps reproduced in ordinary ways. It was necessary to 
 devise some scheme, so an original map was made and oiled 
 to make it transparent. With it about fifty copies were re- 
 produced rather quickly by ordinary blue printing methods. 
 
 Road sketches are often reproduced in this same way. 
 If the sketches are good, they are taken in the evening after 
 the day's work, joined up and finished in ink. The whole 
 map is oiled and reproduced by blue printing. This permits 
 a readable map to be obtained in a very brief time. 
 
 Brown Prints 
 
 7. The process of making brown prints is very similar 
 to that of making blue prints. The equipment is almost the 
 same. In the case of the brown print, the exposure is a little 
 shortened, and after exposure it is necessary to wash the 
 
128 TOPOGRAPHY 
 
 print, put it in a fixing solution, and then wash it again for 
 about half an hour. It, therefore, takes a little longer to 
 make a brown print than it does to make a blue print. 
 
 A brown print gives a result of white lines on a brown 
 background. This brown color is impervious to light, so 
 brown prints are largely used as negatives. Printing 
 from a brown print onto brown print or blue print paper 
 gives a result of brown or blue print lines on a white back- 
 ground. These last named prints are valuable in case it is 
 desired to have a result which can be written on with black 
 lines. A number of negatives can be made and then the print- 
 ing will proceed more rapidly, using several negatives so 
 as to make several prints at once. If more than 20 copies 
 are desired other methods are generally faster. 
 
 Neo-Cyclostyle 
 
 8. This method of reproduction was in general use 
 throughout the French army during the war. 
 
 The drawing to be reproduced is pasted lightly on the 
 base plate. The wax paper fitted in the frame is then 
 placed over the drawing. The drawing is traced on the wax 
 paper with an instrument which has a very fine tooth wheel, 
 making a fine perforated line on the wax paper. The wax 
 tracing is then removed, a plain sheet of white paper sub- 
 stituted for the original drawing, and the wax tracing 
 placed over it. Ink of the desired color is then rolled over 
 the wax paper and printed on the plain sheet through the 
 perforated line. 
 
 About sixty reproductions can be made per hour and 
 from one to two hundred copies can be made before 
 the wax paper tears and a new tracing is necessary. More 
 than two hundred copies can be made by the use of silk 
 gauze stretched on a frame which is placed over the wax 
 paper. The inking is done over the silk gauze and this 
 keeps the wax paper from tearing. 
 
 With the exception of the paper used, the entire equip- 
 ment can be carried in a box 2' x 2' x 9". For small jobs, 
 two men can make the best speed. On special jobs, three 
 men can often be advantageously used. 
 
MAP REPRODUCTION 129 
 
 One advantage of the method is that registering can 
 be accurately done. When matter is printed on a map it is 
 essential that it be put in the proper place with respect to 
 the topographic features on the map, that is, that it reg- 
 isters properly. To accomplish this, the tracing is so ar- 
 ranged that two points marked on it near the edge corres- 
 pond to two points which appear on the map upon which 
 the printing is being done. When the over-print is made, 
 the points on the tracing are placed exactly over the points 
 on the map and this insures that the over-print has the 
 proper position to be correct for all features on the map. 
 The neo-cyclostyle was largely used by the French corps 
 to make minor changes in their Plans Directeurs, changes 
 such as those as resulting from aeroplane photographs, 
 raids, etc. 
 
 The advantages of this method are simplicity, speed 
 and reliability. The disadvantages are that the size of the 
 reproduction is limited and but one color at a time can be 
 printed. 
 
 Ellam Duplicator 
 
 9. This reproduction equipment was largely used by 
 the British. In using this equipment, the drawing to be 
 reproduced is placed on the base and a frame containing 
 fine silk gauze is stretched over the drawing, and on top of 
 this another frame containing wax paper. The drawing is 
 then traced on the wax paper with an ordinary stylus and 
 the silk screen produces a corrugated line. The method of 
 printing is the same as that for the neo-cyclostyle. The 
 number of copies which can be made and the advantages 
 and disadvantages of this method also correspond to those 
 of the neo-cyclostyle. 
 
 Hectograph 
 
 10. In this method of reproduction, a drawing or trac- 
 ing is made with special inks and is pressed on the hecto- 
 graph tray, which is filled with a base composed of gelatin, 
 clay, and glycerine. When the paper is pulled off the draw- 
 ing appears reversed on the gelatin surface. A piece of 
 blank paper pressed on the surface and then withdrawn 
 shows the drawing printed on it. When through, the draw- 
 
130 TOPOGRAPHY 
 
 ing can be erased off the base and another drawing repro- 
 duced. 
 
 From twenty to forty copies can be made in one hour* 
 It takes about fifty per cent more time to make a tracing 
 with the special inks necessary than it does to make a 
 tracing with ordinary inks. For best results, two or more 
 hours are necessary for the ink to dry on the drawing be- 
 fore it is transferred to the gelatin surface. From twenty 
 to forty copies can be made from one impression. 
 
 The equipment is fairly heavy and weighs more than a 
 hundred pounds. Several trays of the composition are gen- 
 erally necessary and from two to three men are required for 
 the reproduction work. 
 
 The main advantages of this method are simplicity, 
 rapidity, and reproduction of colors. The disadvantages 
 are that the 'number of copies is limited, the equipment is 
 quite heavy; the result is not a finished reproduction and 
 the paper after being in contact with the gelatin surface 
 retains a film of the compound on it and is sometimes sticky. 
 
 There are several other forms of hectograph. The 
 French used a gelatin coated paper roll- instead of the clay 
 composition base. This was generally known in our army 
 as a jelly roll. The method of using this roll was the same 
 as that of using the hectograph. As many as twenty-five 
 fair prints could be made. The ink could not be washed 
 off the roll, but after several days it would diffuse into 
 the mixture and the roll would be ready for use again. 
 There are many kinds of commercial hectographs on the 
 market. 
 
 Dorel Process 
 
 11. This method of reproduction was largely used by 
 all allied armies in Europe. A melted gelatin mixture is 
 poured on a zinc plate and allowed to cool for a brief per- 
 iod. A blue print of the tracing to be reproduced is made, 
 but not developed, and is placed face down on the gelatin 
 coated plate and smoothed out in contact with the gelatin. 
 Upon removing the blue print the lines will be found faintly 
 transferred to the gelatin. These lines will take ink from 
 the ink roller and the gelatin surface will not. After roll- 
 
MAP REPRODUCTION 131 
 
 ing the gelatin with the desired color of ink, a print can 
 be made by smoothing a sheet of paper over it. 
 
 Using this method, it takes at least one hour to get 
 twenty prints. From twenty to forty prints can be made 
 for each blue print. After twenty to forty prints are made 
 a new blue print and gelatin plate must be used. 
 
 The equipment necessary is fairly complicated, as blue 
 print facilities must be available as well as arrangements 
 for heating and drying the gelatin. Zinc plates, ink, ink 
 rolls, etc., are also necessary. Three men are required to 
 operate the equipment efficiently. 
 
 The result obtained is very good; and most reproduc- 
 tion work in France, when less than two hundred copies 
 were desired, was done by the Dorel process. An example 
 of this work is the order of battle maps issued at G. H. Q. 
 It is a very quick method of reproduction, considering the 
 appearance of the results. The disadvantages of the method 
 are that the gelatin mixture is a secret preparation and is 
 sometimes unreliable, especially in very cold or very hot 
 weather. A separate tracing and blue print are necessary 
 for each color and fifteen to forty prints can be made with 
 one plate. 
 
 Assuming twenty prints for a blue print, it is more 
 economical to print from zinc plates when more than two 
 hundred copies are desired. 
 
 Lithography 
 
 12. The finest reproduction work is done by litho- 
 graphy. The word literally means "to write on or from 
 stone." The first lithographic work was done on stone, and 
 even yet some of the finest work is done in this way. Zinc 
 plates, however, are now generally used. There are a num- 
 ber of lithographic methods in use. 
 
 Practically all standard maps are made by lithography. 
 Examples of lithography can be seen in almost any book or 
 newspaper, as most reproduction work of pictures, charts, 
 drawings, etc., in quantity, is done by lithography. 
 
 The equipment varies from small hand presses, such 
 as those used in engineer regiments, capable of printing 
 
132 TOPOGRAPHY 
 
 forty copies per hour, to the large rotary offset presses 
 capable of running as many as five thousand copies per hour. 
 
 There are two general methods in use in commercial 
 work. In one, drawing is done direct upon the plate; and 
 in the other, the drawing is transferred to the plate by one 
 of a number of different processes. 
 
 The zinc plates used in this work have to be carefully 
 prepared. They are put through a process called "graining." 
 By graining is meant that the surface is made slightly 
 rougher so as to absorb or retain the lines. This graining 
 is done by the use of powdered pumice stone, water, and 
 spinning glass marbles on the surface of the plate. After a 
 plate is used once, regraining is necessary. 
 
 In army lithographic work, no drawing is ever done 
 directly upon the zinc plate. It is always transferred to the 
 plate and our methods of lithographic reproduction are 
 classified according to the way in which the zinc plates are 
 prepared. Using this classification, the methods most gen- 
 erally used in lithography are the Mowing : 
 
 (a) Autographic process. 
 
 (b) The direct process. 
 
 (c) The photographic process. 
 
 (d) The transfer process. 
 
 These methods will be briefly outlined. 
 
 (a) Autographic Process: — In this process the orig- 
 inal drawing or a tracing of it is made with special ink 
 upon certain prepared paper of a transparent nature. The 
 prepared paper is then placed between moist blotters until 
 it is damp. The moist tracing is then placed upon a pre- 
 pared plate. This plate is run through a press a number of 
 times and moistened until the transfer ink has been pressed 
 from the paper to the plate. The plate is then thoroughly 
 washed with water and covered with a solution. It is then 
 rubbed with another solution which prevents the ink from 
 adhering to any place on the plate with the exception of the 
 impression left by the transfer. After this the plate is 
 rubbed with ink, dried, the solution washed off and a fresh 
 one applied. The plate is then washed with turpentine 
 which removes the ink lines, leaving a white impression 
 on the plate where they have been. The plate is again 
 washed with another solution, dried and then washed with 
 
MAP REPRODUCTION 133 
 
 water. It is then gone over with a dampening cloth and 
 rolled up with printing ink. It is kept moist during this 
 rolling to prevent adherence of ink upon other parts of the 
 plate than the design. The theory of this last is that water 
 will not adhere to the lines, which are greasy, and the greasy 
 ink will not adhere to the water which is on the rest of the 
 plate. 
 
 If only twenty-five or thirty copies are desired, it will 
 not be necessary to etch the plate. When more than thirty 
 copies are desired, the plate is etched with chemicals. 
 
 The above outline has been given mainly to give an 
 idea concerning the large number of separate operations 
 and the complication involved in reproduction by litho- 
 graphy. 
 
 (b) The Direct Process: — A tracing on transparent 
 paper or cloth is made with opaque drawing ink, the zinc 
 plate is coated with a solution sensitive to light, and the 
 plate and tracing are then put in a frame as in blue printing 
 and exposed to sunlight or a strong artificial light. The 
 plate is then finished up in a manner similar to that de- 
 scribed in the process outlined above. 
 
 (c) Photographic Process: — In this process the 
 drawing is photographed on a glass plate, from which 
 plate a zinc plate is prepared by essentially the same meth- 
 ods as in the direct process just described. 
 
 (d) Transfer Process: — New plates may be made 
 from old ones by a transfer involving the use of special 
 transfer paper and ink. It is by this method that new plates 
 are made by combining portions of several plates. 
 
 The autographic and direct processes do not involve 
 the use of a camera or of complicated methods, hence they 
 are adapted to the field or small plants, such as that of the 
 corps topographic section. The photographic and trans- 
 fer process involve rather complicated methods and very 
 careful work. The photographic process also requires a 
 reproduction camera. Hence the last two processes are 
 only adapted to large plants such as a base printing plant 
 or that at army headquarters. 
 
 It is to be noted that both the autographic and direct 
 processes require a tracing. The autographic is not as re- 
 
134 
 
 TOPOGRAPHY 
 
 liable as the others, because if something goes wrong with 
 the plate the whole drawing must be made over again. It 
 has the advantages that it is entirely independent of light, 
 it is more rapid than the direct process, and the results 
 with trained men are satisfactory. The photographic pro- 
 cess does not require a tracing and permits of enlargement 
 or reduction of the original drawing as may be desired. 
 The direct process was used in most large plants during 
 the war, especially those at Washington. Its main advan- 
 tages are great speed and certainty in its results. 
 
 13. The following table gives the approximate speed 
 and capacities of various reproduction methods described : 
 
 Apparatus 
 
 1 copy 
 5 min. 
 
 20 copies 
 
 200 copies 
 
 1000 copies 
 
 Blueprint* 
 
 1 hr., 40 min. 
 
 
 
 
 
 Duplicator** 
 
 2 hrs. 
 
 2 hrs., 30 min. 
 
 
 
 
 
 Cyclostyle 
 
 3 hrs. 
 
 4 hrs. 
 
 3 hrs., 10 min. 
 
 5 hrs., 10 min. 
 
 
 
 Hand lithograph 
 
 5 hrs. 
 
 14 hrs. 
 
 54 hrs. 
 
 Power Lithograph 
 
 4 hrs. 
 
 4 hrs., 5 min. 
 
 4 hrs., 20 min. 
 
 5 hrs., 20 min. 
 
 *Good sunlight. 
 
 **Same time for multi-colored job. 
 
 14. Facilities for Reproduction Available in the 
 Various Units. 
 
 It is reasonable to assume that in our future operations 
 the reproduction facilities available to each unit will be 
 the same or similar to those used in France during the late 
 war. There the authorized equipment was as follows : 
 
 Division — Neo-cyclostyle or Ellam duplicator, and hectograph. 
 
 Corps — A hand lithograph press capable of printing sheets 
 26"x36"; a Dorel equipment; and the equipment noted 
 for a division. 
 
 Army — In addition to the above equipment given for a corps, 
 a rotary lithographic press capable of printing sheets 
 35"x 45", and type presses. 
 
 Base plant — In addition to the above equipment given for 
 an army, rotary lithographic presses capable of print- 
 ing sheets 35"x 45", and type presses. 
 
 15. The above equipment belonged to G2. In each 
 sapper engineer regiment there were lithograph, Dorel and 
 blue print equipments. The lithographic equipment was 
 
MAP REPRODUCTION 135 
 
 a very small one. The maximum size of reproduction was 
 24"x30". 
 
 Mobile Train 
 
 16. With the American Forces in France, in 1918, there 
 was provided a printing train designed for the work required 
 by an army. The whole equipment was mounted on trucks 
 both for transportation and operation. Power for opera- 
 tion was furnished from a dynamo coupled to the motor of 
 one of the trucks. The equipment consisted of a complete 
 outfit for drafting, photography, map reproduction and 
 printing. 
 
 The idea of mobilizing a printing train in this manner 
 has not been finally adopted, nor has standard equipment 
 been provided. There are some serious objections to 
 mounting the heavy and delicate machines on trucks in 
 operating positions, and it appears feasible only where good 
 roads exist. 
 
 A. E. F. Results 
 
 17. 1st Army Plant. Nine officers and 90 men. In 10 
 weeks distributed over a million and a quarter maps and 
 documents — of these 550,000, involving 800,000 impressions, 
 were printed at the army plant. 
 
 2d Army Plant. Sixteen officers and 155 men. In 5 
 weeks distributed 540,000 maps and documents. Of these 
 over 500,000, involving 000,000 impressions, were made at 
 the army plant. 
 
 18. Map reproduction plants will give satisfaction in pro- 
 portion as the following points are appreciated by all con- 
 cerned : 
 
 (a) A realization o fthe importance of an adequate 
 supply of maps to the conduct of military operations. 
 
 (b) Advance information of the demands that are to 
 be made for maps. The authorities charged with map re- 
 production must at all times be kept properly informed as 
 to the prospective needs with respect to maps. No one 
 needs this advance information more than they do. Defi- 
 nite information is not essential, but they do need to be 
 told concerning what the future demands on them will be. 
 If they do not have this advance information the conduct 
 of the operation will be severely hampered by lack of maps. 
 
136 TOPOGRAPHY 
 
 (c) Keep the colors on the map and the drawing to 
 be reproduced down to a minimum. 
 
 (d) State the time the work is desired. 
 
 (e) If practicable state the method of reproduction that 
 will be satisfactory. 
 
 . (f ) If possible, state whether any future demands for 
 the same work will be necessary. 
 
 (g) Present work to be reproduced in the form of trac- 
 ings when practicable. If draftsmen are available the re- 
 production of any job can often be facilitated by having 
 them make the necessary tracings. 
 
 (h) Visits to the reproduction plant by the commander 
 and others high in authority are beneficial to the morale 
 of personnel, which by virtue of its isolation often needs 
 encouragement. 
 
MAP REPRODUCTION 
 
 137 
 
 19. A. E. F. Issue Schedule of Maps for Infantry Division 
 
 (Based on experience of A. E. F.) 
 
 Div 
 
 Brig 
 
 Regt 
 
 Bn 
 
 Co 
 
 INFANTRY : 
 
 Hq Co 
 
 Sup Co 
 
 Regt (Med Dept and Chap) 
 
 MG Bn (Brig) 
 
 MG Bn (Div) 
 
 MG Co 
 
 Headquarters : 
 
 Div 
 
 Brig 
 
 Regt 
 
 Bn 
 
 MG Bn 
 
 ARTILLERY : 
 
 Brig 
 
 Regt* 
 
 Bn (LA) 
 
 Bn (HvA) 
 
 Btry 
 
 Regt (Med Dept and Chap) 
 
 TM Btry 
 
 Hq Co 
 
 Sup Co 
 
 Headquarters : 
 
 Brig 
 
 Rest 
 
 Bn 
 
 ENGINEERS : 
 
 Regt 
 
 Bn 
 
 Co 
 
 Regt (Med Dept and Chap) 
 Headquarters : 
 
 R«gt 
 
 Bn 
 
 SIGNAL CORPS: 
 
 F Sig Bn 
 
 Sup Sec 
 
 Wire Co 
 
 Rad Co , 
 
 Outpost Co 
 
 Hq Bn 
 
 Med Dept and Chap 
 DIVISIONAL TRAINS: 
 
 Tn Hq and MP 
 
 Am Tn 
 
 Sup Tn 
 
 Engr Tn 
 
 San Tn 
 
 Mob Ord Rep Sh 
 
 200.000 
 
 251 
 55 
 24 
 5 
 1 
 2 
 1 
 3 
 5 
 8 
 1 
 
 24 
 
 2 
 1 
 1 
 
 61 
 18 
 5 
 4 
 1 
 8 
 1 
 1 
 1 
 
 4 
 8 
 2 
 
 17 
 5 
 1 
 2 
 
 5 
 2 
 
 7 
 1 
 1 
 1 
 1 
 2 
 1 
 
 6 
 
 11 
 
 4 
 
 2 
 6 
 
 80,000 
 
 1,048 
 
 297 
 
 ISO 
 
 35 
 
 8 
 
 7 
 
 7 
 
 2 
 
 81 
 
 17 
 
 7 
 
 S« 
 6 
 2 
 8 
 8 
 
 211 
 
 65 
 
 28 
 
 16 
 
 7 
 
 2 
 
 7 
 
 7 
 
 7 
 
 7 
 8 
 2 
 
 84 
 81 
 10 
 
 2 
 
 20 
 
 1 
 
 81 
 1 
 8 
 8 
 8 
 5 
 1 
 
 32 
 
 11 
 
 8 
 
 6 
 
 12 
 
 1 
 
 1 
 
 i 
 
 50,000 
 
 20,000 
 
 147 
 
 171 
 
 3 
 
 28 
 
 1 
 
 10 
 1 
 
 "~i 
 
 e 
 
 4 
 1 
 
 20 
 
 80 
 
 1 
 
 2 
 
 1 
 
 6 
 1 
 2 
 
 66 
 
 96 
 
 29 
 
 19 
 
 5 
 
 5 
 
 4 
 
 4 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 6 
 
 
 
 16 
 
 e 
 
 2 
 
 2 
 
 10 
 
 n 
 
 4 
 
 4 
 
 1 
 
 1 
 1 
 
 2 
 
 2 
 
 1 
 
 1 
 
 5 
 
 6 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 1 
 
 2 
 
 2 
 2 
 
 :::: 
 
 1 
 1 
 1 
 
 10,000 
 
 262 
 
 69 
 
 28 
 
 5 
 
 1 
 
 2 
 
 1 
 
 2 
 
 21 
 
 11 
 
 5 
 
 24 
 
 2 
 2 
 1 
 
 1 
 
 61 
 18 
 5 
 4 
 1 
 8 
 1 
 1 
 1 
 
 4 
 8 
 2 
 
 17 
 5 
 1 
 2 
 
 5 
 2 
 
 7 
 1 
 1 
 1 
 1 
 2 
 1 
 
 1 
 1 
 1 
 1 
 
 258 
 69 
 23 
 5 
 1 
 2 
 1 
 2 
 
 21 
 
 11 
 
 5. 
 
 24 
 2 
 2 
 
 61 
 
 18 
 
 5 
 
 4 
 
 1 
 8 
 
 1 
 1 
 1 
 
 17 
 8 
 1 
 2 
 
 8 
 8 
 
 7 
 
 1 
 1 
 1 
 1 
 2 
 1 
 
 •For heavy artillery regiment add one battalion headquarters. 
 
 20. The following is copied from the report of the 
 base printing plant at Langres, France, in order to show 
 the character and extent of the operations necessary for 
 map reproduction on a large scale. 
 
138 TOPOGRAPHY 
 
 The construction of the base printing plant at Lan- 
 gres was started on the arrival of A Company, 29th En- 
 gineers, on December 3, 1917. The original construction 
 with the expansion, which continued up to the time of the 
 armistice as the needs increased and as additional machinery 
 was received, was all executed by the 29th Engineers. 
 
 During the construction period a small lithographic 
 and type printing plant was established at G. H. Q., for doing 
 urgent special work for the General Staff sections. The 
 original construction of the base printing plant was com- 
 pleted and the plant put in operation June 15, 1918, with a 
 drafting room, power plant, one wet plate camera, three 
 lithographic presses and a job type printing plant. These 
 departments were all planned for an expansion which con- 
 tinued up to the tim3 of the armistice. The following ad- 
 ditional departments were added: 
 
 Automatic type setting machinery. 
 Automatic type printing - machinery. 
 Stereotyping plant. 
 
 Photo-engraving and zinc etching plant. 
 Book bindery. 
 
 Map, storage and distributing department. 
 Graining plant. 
 
 Rapid photographic reproduction plant. 
 Machine shop. 
 
 Gas generating plant for relief maps. 
 
 Modeling department for relief maps and 3 large supply 
 warehouses. 
 
 At the time of the armistice over fifty machines of 
 different types were in operation, occupying 60,000 square 
 feet of floor space. The operating force on a 3-shift basis 
 totalled 650 ; and about 2i tons of supplies were consumed 
 daily. 
 
 The starting of the plant on June 15th was practically 
 coincident with the commencement of independent opera- 
 tions of American units and consequent demands. It had 
 been in operation only two months when it was subjected to 
 the severe strain of the St. Mihiel offensive. The original 
 order for 140,000 maps was received on August 20th and it 
 was apparent that French sources, already overburdened, 
 could not be relied on. The operating force at the plant 
 was accordingly divided into two 12-hour shifts and operated 
 continuously night and day from that time on until the con- 
 
MAP REPRODUCTION 139 
 
 elusion of the armistice. In addition to a very large num- 
 ber of information documents and pamphlets, the total num- 
 ber of maps actually printed for the St. Mihiel offensive 
 between August 20th and September 9th was 456,000. 
 
 Before this work was completed, it became necessary 
 to undertake the printing of maps and documents for the 
 Meuse-Argonne operation. The St. Mihiel sector had long 
 been indicated as a probable field of operations for Ameri- 
 can forces, and the greater part of the necessary plates, 
 tracings, and other data for the production of maps had 
 been accumulated prior to the announcement of the opera- 
 tion ; but the Argonne-Meuse operation was a complete sur- 
 prise and great speed was necessary. The system of the 
 French Service Geographique required that tracings brought 
 up to date should be sent to Paris to be printed, which oc- 
 casioned a delay of 4 days. This delay would have been 
 fatal to the production in sufficient time for the U.S. Army, 
 and in many cases tracings were taken first from the 2d 
 French Army Headquarters at Laheycourt to Langres, a 
 distance of 168 kilometers, the necessary plates made, and. 
 the tracings returned in from 24 to 36 hours' elapsed time.. 
 The total number of maps printed for the Meuse-Argonne 
 offensive was 747,000. 
 
 At the time of the armistice, the period of trial and 
 strain was over. The American Expeditionary Forces were 
 independent in map printing and supply, with not only 
 a comfortable margin over present needs but with adequate 
 provision for future expansion to meet all needs of our 
 growing forces. The organization was complete and the 
 equipment was the most modern and efficient in France, 
 and in the technical processes and plant for reproduction 
 of photographic data we were far in advance of French 
 plants. 
 
 The total work completed up to November 11th was 
 as follows : 
 
 Total number of maps printed 3,134,000 
 
 Total number of documents and pamphlets printed 352,000 
 
 Total number of lithograph impressions 7,000,000 
 
 Total number of type impressions 2,700,000 
 
 After the armistice the plant operated with full force 
 on the supply of maps for the 3 armies in the field, reproduc- 
 
140 TOPOGRAPHY 
 
 ing historical maps and documents in great quantity for 
 the records and reports of divisions, corps, armies and G. 
 H. Q. Work was carried on during this period on the pre- 
 paration of German maps as far east as Berlin, in prepara- 
 tion for the possible resumption of hostilities. The equip- 
 ment for the printing plant of the 3d Army was collected 
 and transferred to Coblenz, and the printing plants of the 
 1st and 2d Armies were dismantled and returned to Langres. 
 The following is a summary of the work done up to 
 May 1, 1919: 
 
 Total number of maps or charts printed 4,357,000 
 
 Total number of documents or pamphlets printed 1,383,000 
 
 Total number of lithographic impressions 11,500,000 
 
 Total number of type impressions 11,000,000 
 
 14,000 reams of paper and 12 tons of ink were used. 
 
MAP REPRODUCTION 
 
 141 
 
 Figure Tl 
 
 Figure T2 
 
142 
 
 TOPOGRAPHY 
 
 665 
 
 Figure T3 
 
 Figure T4 
 
MAP REPRODUCTION 
 
 143 
 
 Figure T5 
 
144 
 
 TOPOGRAPHY 
 
 Figure T6 
 Put in 10-foot contours. 
 
MAP REPRODUCTION 
 
 670 
 
 860 
 
 6/0 > 
 
 797 
 
 785 
 
 Figure T7 
 
 Scale 1:20,000 
 
 Put in proper contours. 
 
146 
 
 TOPOGRAPHY 
 
 917 
 
 060 
 
 96Z 
 
 S30 
 
 878 
 
 Put in 20' Contours. 
 
 Figure T8 
 
MAP REPRODUCTION 
 
 147 
 
 .617 
 
 960 
 
 962 
 
 930 
 
 880 
 
 678 
 
 780 
 
 870 
 
 Figure T9 
 
 Scale: 6" = 1 mile. 
 Put in proDer contours. 
 
148 
 
 TOPOGRAPHY 
 
 930 
 
 640 
 
 Figure T10 
 
 Scale: 1:10,000 
 
 Put in proper contours. 
 
MAP REPRODUCTION 
 
 149 
 
 -^. soo 
 
 ?~> 
 
 Put in 20' Contours. 
 Figure Til 
 
150 
 
 TOPOGRAPHY 
 
 (ogojl 2 
 
 Put in 20-foot contours. 
 Figure T12 
 
760 
 
 Figure T13 
 
300 
 764 
 
 760 
 
 Figure T14 
 
Figur* T15 
 

LIBRARY OF CONGRESS 
 
 011 392 990 A 
 
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