The importance of line-of-position work in ocean navigation has resulted in the appearance of numerous tables for facilitating the computation and the laying down of the line of position from one or more measured altitudes of the sun or other celestial objects. Whatever method may be employed, whether that of St. Hilaire, Aquino, H.O.203 tables, or that recently advanced by Lieutenant Commander Weems, a point on the line must first be plotted on a Mercator chart and a line then drawn through this point at right angles to the sun’s true bearing. The large charts usually provided for this purpose are cumbersome, and though, of course, universal in their longitude scale, are necessarily limited in their latitude scales. This necessitates carrying a whole series to cover the range in latitudes which may be required, although only a small part of each chart may actually be utilized. The problem of handling and stowing the used and unused charts presents no small difficulty, especially in cramped quarters such as submarines, subchasers, or aircraft.
A New Line-of-Position Plotter
By Harlan T. Stetson, Assistant Professor of Astronomy, Harvard University