Conic projection (technique)

Refers to a system of projection generally used in map-making and based on the principle of a hollow cone being placed over a sphere so that when the cone is unrolled the line of tangency becomes the central or standard parallel of the area being mapped. In this system, all parallels of latitude are arcs of concentric circles and the meridians of longitude are straight lines generated from the cone's vertex to the divisions of the standard parallel. It is typically derived from a projection of the globe on a cone drawn with a point above one of the poles and tangent to the Earth or other heavenly body at one selected parallel. It may also be derived from a projection where the cone is arranged to intersect the sphere at two closely spaced parallels.