GB191215349A - Instrument for use in Navigation. - Google Patents

Abstract

15,349. Vaughan, M. July 1. Spherical-trigonometry calculators, arranged for computing by plotting.-A device to be used in obtaining the correction to be applied to a ship's dead-reckoning position to give the position as deduced from a single observed altitude according to the position-line method comprises a board A within which is rotatably mounted a disk B divided into quadrants. Each of the two upper quadrants is graduated in degrees, and each of the two lower ones is provided with a scale l so constructed that from it the meridional difference corresponding to any given latitude difference may be obtained, in order that the latitude difference may be set off correctlv on a Mercator's chart. If # be the angle between the horizontal line and the radius to the graduation n on the scale l, then Sin # = ¢ Cos n. Each of the radii O N, O S is divided into thirty equal parts: the radii O E, O Ware also graduated from 0 to 30, but the divisions are only half the length of those on the N S diameter. A ruler C can move parallel to itself across the board, and index marks e, ware provided, against which the graduations on the disk B are read. From the difference between the observed and calculated altitudes of a star, its calculated bearing, and the latitude in which the observation is made, the latitude and longitude corrections to be applied to the deadreckoning position can be obtained, the calculated quantities being determined according to the dead-reckoning position. In a modification, the scales b, l are arranged in a reversed position on the board, and the index marks are on the disk.