Gnomonic Projection

A type of map projection where the surface of the Earth is projected onto a plane from the centre of the globe, causing great circles to appear as straight lines.

A gnomonic projection is a method of map-making that projects the surface of a sphere, such as the Earth, onto a flat plane. The projection is created by imagining a light source at the centre of the Earth and projecting the surface features outward onto a tangent plane. This results in a map where all great circles, which represent the shortest path between two points on a sphere, appear as straight lines. This characteristic makes the gnomonic projection particularly useful for navigation, as sailors and navigators can plot the shortest route between two points by drawing a straight line on the map. However, the projection distorts other aspects of the map, such as angles, distances, and shapes, especially as one moves away from the point of tangency. The gnomonic projection is not typically used for general-purpose mapping due to these distortions, but it remains valuable in marine navigation for plotting long-distance, transoceanic routes. After plotting a course on a gnomonic chart, navigators often transfer the route to a Mercator projection for more practical use, as the Mercator projection preserves angles and is more suitable for day-to-day navigation.