The purpose of this article is to describe a graphical solution to the problems of great-circle sailing. The work is done directly upon a Mercator chart with the aid of a special diagram, part of which is shown in Fig. 1, constructed with the same scale as the chart. This diagram has three sets of lines, one each for tracks, courses, and distances, and may be superimposed over the chart. The portion shown in the figure is sufficient for all tracks in ordinary latitudes when the initial and final positions are both on the same side of the equator. In the examples which follow it is assumed that the base of the diagram is opaque, although speed and accuracy may be increased somewhat by the use of transparent material.
A Diagram for Great-Circle Sailing
By B. C. Getchell