map projection

A mathematical model that transforms the locations of features on the Earth's surface to locations on a two-dimensional surface. Because the Earth is three-dimensional, some method must be used to depict a map in two dimensions. Some projections preserve shape; others preserve accuracy of area, distance, or direction. See also coordinate system.

Map projections project the Earth's surface onto a flat plane. However, any such representation distorts some parameter of the Earth's surface be it distance, area, shape, or direction.

A systematic conversion of locations on the Earth's surface from spherical to planar coordinates. Several of the more popular projections are: State Plane Coordinates (SPC) which uses feet for units of measure; Universal Transverse Mercator (UTM) which uses meters for units of measure; and latitude and longitude which uses degrees, minutes, and seconds of arc for units of measure.