Map Projections and Coordinate Systems

Abstract

Map projections are the means by which data about the 3‐D surface of the Earth and its features are transformed onto a flat plane for the purpose of mapping. All map projections introduce distortion: of scale, distance, shape, and direction, and it is impossible to simultaneously satisfy the goals of conformality (shape preservation) and equivalence (area preservation), although recent new projections have attempted distortion minimization. Many classifications of projections have been proposed; these are discussed with respect to the trend from mechanical construction via the graticule, to mathematical derivation as used in computer programs. Once the map has been projected, the Euclidean space can be mapped onto standard coordinate systems such that positions can be described by coordinates consisting of eastings and northings. Many standard coordinate systems use conformal projections, in particular the Transverse Mercator, which serves as the basis for the Universal Transverse Mercator coordinate system, and the several grid systems based upon it. The Military Grid Reference System, in use by NATO, is given as an example.