Improvements in or relating to the solution of parallax triangles

摘要

532,234. Calculating-apparatus. LUTZ, J. Aug. 23, 1939, No. 24271. [Class 106 (i)] A method of determining the parallax angle for the indirect laying of ordnance based upon the geometrical relations given in Fig. 1 consists in laying off a base AF of given length b at right angles to the base line AB representing the gun and observation position so that from the known angles α, αSP1/SP and # and the range e the angle # can be determined from the equation A slide rule for carrying out the method is shown in Fig. 2 and is provided with scales k, m, n, p and q. The upper scale k represents values of log Cos αSP1/SP + b ; the scale m represents values of log tan # ; the scale n represents values 1 of log - and scale p represents values of log e Sin #. The additional scale q represents the value of e, Sin #. The scales on the stock and on the slide may be marked in distinctive colours and the back of the rule may be provided with a graduated dial consisting of two sets of subdivisions up to 6400 for the outer scale over 360 degrees and two sets of reversed numbers from 0-1600, 1600-0 for angle measurements.