4 GRAPHICAL : MPASS CONVERSION © OHART AND TABLES COMPILED BY. | Masor JOHN F. FAIRCHILD 56TH Pioneer Inrantry, U. 8. Army D. VAN NOSTRAND COMPANY _ MILITARY AND NAVAL BOOKS : Park PLAcE NEW YORK oe Hq., Prov. Depot for Corps and Army Troops, : Camp Wadsworth, 6/13/18. \ To the Adjutant General of the Army, Washington, D. cu J Recommending approval. 2. This chart appeals to me as an excellent piece of work for which Major Fairchild should receive “commenda tion. Its utility in visualizing, and comparing angles; according to the several systems is obvious, and I think of sufficient value to warrant approval. Major Fairchild) was an engineer before entry into Federal Service and ; has performed some engineering work for me with marked ability. : . GUY CARLETON, Brigadier General, Commanding. { .061 (Pub. Div.) 4 A-G..0., hnly 29 1918. é ; To Major John F. Fairchild, Hq. 1st Corps Troops, re) Camp Wadsworth, 8S. C. : Your letter reference ‘‘ Publication of, Graphical Compass Conversion Chart”’ is approved. By order of the Secretary of War, iy F. W. LEWIS, Adjutant General. GRAPHICAL “COMPASS CONVERSION CHART AND TABLES ~ Compiled by < Major John F. Fairchild 56th Pioneer Infantry U.S. Army |.. D. VAN NOSTRAND COMPANY te MILITARY AND NAVAL BOOKS | 25 Park Place NEW YORK | iL CAO TIO GRAPHICAL COMPASS CONVERSION CHARTS TABLES COMPILED BY MAJOR JOHN F. FAIRCHILD 56TH. PIONEER INFANTRY U.S.ARMY. SERG'T CLARENCE R.HAYWARD. ORAFTING ASSISTANTS. SERG'T ROBERT C.SCHOPP 54TH PIONEER INF, U.S.A. 5IST. PIONEER INF. U.S.A. 10° 60-0" yun ° \ \ \ ee —— ce cee COMPASS TABLES FRENCH COMPASS SYNONYMS ROM ARIOUS AUTHORITIES For the SEXAGESIMAL (English); CENTESIMAL (French) and MILS(Military) SYSTEMS. | Grade; Grad; Degree; 6;%3;%. [Degrees [Minutes [Seconds] | Grades [Centigrades[pectwiigraded | Mils |wincte Contectrule a ac = 1r Seay ee + Minute Centesimal; Minute *;°¢. = 60” * | Deci-Miligrade; Seconde; Seconde —Centesimal; “;¢, VARIOUS MILS SYSTEMS True’ Tan='/,000=6,283,18 to Circle. =3726.265'— 636.624 Common= 1600 System-6400 to Circle.=3’22.57=6*°25> Quadrant = 90 Degrees = 100 Grades = 1,600 Mils Rimailho”System,=6,000 to Circle.=3’367=6°6.667" Circle =360 » =400 » =6400 » German Heavy Artillery=5760 to Circle=345"=6'94.44.4" Copyright, 1918, by D. VAN Nostrand Company GRAPHICAL COMPASS CONVERSION CHART AND _ TABLES et The graphical chart is designed, primarily, to afford a ready method of comparison between the American (English) and French method of denot- ing circle and magnetic compass angles and also of comparison with the | mils system used in military practice, accompanied by a clock face fdr | assistance in visualizing angles. . It consists of a Mariner’s Compass (la ma‘ine boussouie), showing the | twelve principal compass points, and the mariner’s designation of each | point with their abbreviation and quadrant direction in both English and | French. : Outside of the Mariner’s Compass is given a, circle divided for the 6400 | divisions of the “common” mils system. Outside of the mils circle is given a clock face for assistance in visual- | izing angles. | outside give the minutes. The inside divisions and numbers give the hours and those A clock hand in passing from 12 o’clock to. 1 o’clock passes through an angle of 30 degrees or 333 grades; from 12 to. | 2 o'clock of 60 degrees or 663 grades; from 12 to 8 o’clock of 90 degrees or } 100 grades and 30 on around the clock face. | Tepresents an angle of 6 degrees or 63 grades. Each minute on she clock | 4 Next to the clock face is given a circle divided according to the French | Centesimal or “grade” system. The inside figures state the divisions trom 0-400 grades around he circle, clockwise, while the outside figures | | state the divisions by quadrants from the north and south. (English) used in America. The inside figures state the divisions from | | 0-360 degrees around the circle, clockwise, while the outside figures state | the divisions by quadrants from the north and south. 2 Outside of the circles are given the English and French Gesznat ony of | | the four quadrants. The “‘ Compass Tables ”’ ~ on the face of the chart give on the left of the upper space the English system complete in itself and in the center of the | | second space the French system complete in itself. Opposite each of these ‘ | is given the value of the subdivision in terms of the other system and also | Q Qa S| con! oma] woe 2 0 S1|SSd0/] S500] S500] CON] Orb] WHe e y = ee @ oGl|ono!]opwl] ve 08 Sl ewol Ba] Tao |] os | bw] MRO] .F . B/E ts] = |6 Ore | www] Reo = a Clooo|] coo] ooo] SGNO] FSG] Naor g p ® 8 si a > Q 2 > phe Ooodm |] PWR] eRe 25 "3 wD] ook! ONO! BNK |] COM] RwWH] EF S|/528|SS8S5| SSS) REN) SSK] Na] @E 5 5 7) STI GNV “OLE ‘STLONIP, OL SUAVUDIINAD 8Q = crs |] COO 30 fe) — 5 = ee S35 Boo poms my Gs: wn] PRO] WNHN] Ee Ex — own nN oon He H= Co QQ bo bo ree © &5 : 0 ; ; spuo0eg . Q Send ell aes & a PN | COM] POR] err es on lone! ENB] COD] PWeE|] ZB S SES SS51|SSS/ Ow] SSK| ONG ° 00 sopvis -T[tu109q | ! STI ANV SGNOOEQ OL SXaVUDITINIDAGC : | ; spuoseg STA wouuIOD SINDLLSAS STIW NOWINOO GNV 'IVWISHOVXES OL WHLSAS AAVUDILNAD WFAVL NOFSUAANOO f The outside circle is divided according to the Sexagesimal system | i 1 on the face of the chart. of the “ common ”? mils system. Below is given the value of a mil in each | of the other systems and the division of the quadrant and si ii ee each of the three systems. "The research necessary to obtain accurate information in the prepara- tion of the chart developed the fact that various French and English tech- nical and military dictionaries and works use different terms in referring to%he French circle divisions. A table of all such synonyms found is given In the chart and tables those terms are used which seemed the most harmonious and euphonious and which afforded no chance for confusion with those used in the other tables. - The research also developed four “ mils” systems in use. The original or “ true ” mils system was devised for military use, so as to give an angle based on a direct relation between the tangent of the angle and the radius of the circle (the range of the artillery) this relation being 1 =tangent 1000 = radius of circle. > This scheme divided the circle into 6283.18 parts, each part being called a “mil.” This odd division was found cumbersome and about 1880 Colonel Rimailho, a French officer, devised the system (“‘Rimailho”’) of using an even 6000 parts to the circle instead of 6283.18, making an error of 283.18 parts from the “true” system. This amount of error was found unsatisfactory and the “common” mils system of 6400 divisions to the circle was adopted, this number being the nearest even hundred to the “true” system, making an error of only 116.82 points instead of 283.18 as in the ‘‘Rimailho” system. A table of these four m il systems is given on the face of the chart. a The chart can be used as a protractor by cutting out a small triangle at the 180 degrees—O degrees or 90 degrees—90 degrees points and half of the small circle in the center of the mariner’s compass and using a ruler to | carry the angle over the chart paper. s The general Conversion Tables accompanying the chart will enable the | use in computation of any table of logarithms or natural functions by con- verting the given angle into the angular designation on which is based the available table of logarithms or natural functions. ; g Oak | wor 0 S351 SS5/1 SSS] cmn| one} owner]! 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CONVERSION TABLE COMMON MILS SYSTEM TO SEXA - GESIMAL AND CENTESIMAL SYSTEMS Mits TO DEGREES, ETC., AND GRADES, ETC. _ SMe Deniees Minutes Seconds Grades ares Rete : 1 0 3 22.5 0 6 25 2 0 6 45 0 12 Be 8 3 0 10 07.5 0 18 ee 4 0 13 30 0 25 0. a 5 0 16 52.5 0 31 25 = 6 0 20 15 0 37 50° 4 7 0 23 87.5 0 43 75 4a 8 0 27 0 0 50 oO. § 9 0 30 22.5 0 56 25 . 10 0 33 45 0 62 50 20 1 07 30 1 25 0s 30 it 41 15 1 87 50 4 40 2 15 0 2 50 Oia 50 2 48 45 3 12 50 60 3 22 30 3 75 Ogg 70 3 56 15 4 37 50 80 4 30 0 5 0 On 90 5 03 45 5 62 50x 100 5 37 30 25 0 a 200 11 15 0 50 oy 300 | 16 52 30 75 0 4 400 | 22 30 0 0 0: 500 | 28 07 30 25 0-4 600 | 33 45 0 | 50 0 j 700 39 22 30 75 0 800 45 0 0 0 0. 900 | 50 37 30 25 0-4 1000 | 56 15 0 50 b.% 4 1100 | 61 52 30 75 0°. 1200 | 67 30 0 0 O% 1300 | 73 07 30 25 0-2 | 1400 | 78 45 0 50 ox 7 1500 84 22 30 75 0 1600 | 90 0 0 0 08g To reduce other mils systems to ‘‘Common”’ mils, multiply ‘‘ True’’ mils by 1. 018592; 1 multiply ‘‘Rimailho” mils by 1.066667; multiply German H. 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