A simple geometric map projection in which the surface of the Earth is transformed to one of three developable surfaces; the plane, cylinder, or cone. Most map projections can be described and categorized according to from which geometric surface they are derived. The point of perspective of most projections is at the centre of the Earth. However, with the planar family of map projections the point of perspective may also be a location opposite to the point of tangency or from an external point, as if the Earth were viewed from outer space.