The school of the battery commander, 75 m|m gun and 155 m|m howitzer, from the pamphlet of the Saumur Artillery School

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 Excerpt: ...both the line gun aiming point and the base line are drawn. Restrictions. With a 1/20,000 battle map, the aiming point must be more than 2000 meters away With a 1/50,000 battle map, more than 5000 away. 185. 2. Reciprocal laying on a director. When the above conditions are not fulfilled, a declinated instrument must be used, and set up at more than 50 meters from the gun, so that its zero line is parallel to the base line. To do this: 187. (a) When using a compass goniometer. (1) Take the bearing of the magnetic north (declination of the instrument1) Bn. (2) Measure on the battle map the bearing Bt of the base line. (3) Subtract this bearing from the declination Bn of the instrument or from Bn+6400 if BtBn. (4) Set the angle thus obtained on the instrument and manipulate the two dials until the magnetic needle is opposite its index. Then execute reciprocal laying with the gun. 188. (b) Using the plane table. (1) Orient the plane table by means of the declinator. B. Using an orienting line. 189. When preliminary topographical operations have been performed on the ground they give the following results: 1st. The determination of the coordinates of the base piece. 2nd. The staking out of an orienting line. The Battle Map or the battery firing board on which these elements are marked off, will therefore show: 1st. the base line CT. 2nd. the orienting line CD. Base angle--It is the angle formed by CT and CD measured from C T in the same sense as the sight scale (clock j wise for the 155 and 75). Either I or i, can be measured (ii=i +3200), depending upon whether the point which will be later used for orienting the instrument (director) is in the direction ED or the direction EC. Reciprocal laying on a director 190. (1) With a goniometric instrument (graduated cl...