WHISTLER-HEARN PLOTTING-BOARD. (Perspective Drawing. Secondary and auxiliary arms should be parallel.)
Fig. 62.
Q. How are the range and azimuth for the directing-gun obtained for the same target?
A. Move the gun-arm up to the intersecting edge of the targ, and read the range from the scale on the gun-arm. The degrees of azimuth are read through the reading-opening, and the hundredths are read on the index-disc for the gun-arm.
Q. Suppose the range must be corrected for, say, 150 yards more, and the azimuth for 1·78 degrees less, how can the corrected range and corrected azimuth be automatically read on the gun-arm?