How does a gnomonic projection help navigators plan great-circle routes?

A gnomonic projection is a specialized cartographic tool that helps navigators by representing all great-circle routes as straight lines. Because a great circle represents the shortest distance between two points on a sphere, this projection allows a navigator to easily visualize and plot the most direct path across large distances, such as across an entire ocean.123

In practice, navigators use these charts to lay out a track between two distant ports. However, because a gnomonic projection does not maintain constant compass bearings, the navigator typically transfers points from the great-circle track onto a Mercator projection. By connecting these points, the navigator creates a series of short rhumb-line segments that closely approximate the ideal great-circle route while remaining practical for steering a ship.314