Which chart is used to represent great-circle routes for navigation?

• A. Gnomonic Chart
• B. Great circle chart
• C. Aeronautical Chart
• D. Bathymetric Map

Answer: (A)

Great-circle routes, the shortest paths between two points on the globe, become straight lines on a gnomonic chart. This projection maps the Earth from its center onto a tangent plane, and its key property is that any great circle plots as a straight line. That makes planning long-distance navigation intuitive: you can draw a straight line between two locations on the chart to represent the intended great-circle path. Keep in mind, distances and areas aren’t preserved away from the center of the projection, so it’s mainly a planning aid and is often used in conjunction with other charts for actual routing. The other chart types don’t provide this straight-line representation of great circles: bathymetric maps show ocean depths, aeronautical charts show airspace and procedures, and a nonstandard “great-circle chart” isn’t the conventional tool for plotting great-circle routes.