Improvements in and relating to apparatus for use in solving nautical problems or plane and spherical trigonometry

摘要

146,614. Arimitsu, T. April 10, 1919. Spherical and plane trigonometry calculators for use, for example, in nautical astronomy, comprise a member having arms a, b and a graduated arc c with its centre at the point of intersection of the arms. The arc is graduated in degrees, and the arm a is provided with a uniformly divided scale of such dimensions that the radius OS of the arc is the unit of length. The parts may be made of transparent substances, upon the lower surfaces of which the scales are formed, or they may be made of metallic substances, the reading edges being bevelled. The device is used in conjunction with a Mercator's chart, of which L, Fig. 5, is a " parallel of latitude " and M a meridian. The methods are described in the Specification; in them the device is moved over the lines L and M in several ways with the centre of the are O always on the line M. and either the length of the tangent of the angle with the meridian as shown in Fig. 5, or the length of the sine as shown in Fig. 6, or the length O m as shown in Fig. 8, is maintained constant. The examples given are :-(1) Error in longitude due to 1' error in latitude, latitude and hour angle being known; (2) azimuth from hour angle, altitude, and declination.