Polyconic projection class

American polyconic projection of the world
Van der Grinten projection of the world.

Polyconic can refer either to a class of map projections or to a specific projection known less ambiguously as the American polyconic projection. Polyconic as a class refers to those projections whose parallels are all non-concentric circular arcs, except for a straight equator, and the centers of these circles lie along a central axis. This description applies to projections in equatorial aspect.[1]

Polyconic projections

Some of the projections that fall into the polyconic class are:

A series of polyconic projections, each in a circle, was also presented by Hans Mauer in 1922,[3] who also presented an equal-area polyconic in 1935.[4]:248 Another series by Georgiy Aleksandrovich Ginzburg appeared starting in 1949.[4]:258–262

Most polyconic projections, when used to map the entire sphere, produce an "apple-shaped" map of the world. There are many "apple-shaped" projections, almost all of them obscure.[2]