A map projection is a coordinate conversion calculation that converts geodetic coordinates—latitude and longitude—to plane (map) coordinates. Plane coordinates are used to portray the world’s surface, an irregularly shaped spheroid, on a flat surface, such as a computer screen or a piece of paper.

Map projections are created to preserve the accuracy of one or more of four main characteristics: distance, area, shape or direction. Depending on the size of the coverage area on a map, and its location on the Earth, the map projection best suited to portray that area most accurately will change.