<P> A map projection is a systematic transformation of the latitudes and longitudes of locations from the surface of a sphere or an ellipsoid into locations on a plane . Maps cannot be created without map projections . All map projections necessarily distort the surface in some fashion . Depending on the purpose of the map, some distortions are acceptable and others are not; therefore, different map projections exist in order to preserve some properties of the sphere - like body at the expense of other properties . There is no limit to the number of possible map projections . </P> <P> More generally, the surfaces of planetary bodies can be mapped even if they are too irregular to be modeled well with a sphere or ellipsoid; see below . Even more generally, projections are a subject of several pure mathematical fields, including differential geometry, projective geometry, and manifolds . However, "map projection" refers specifically to a cartographic projection . </P>

What is a two dimensional representation of the earth