Polyconic projection class

This article is about the class of projections called "polyconic". For the specific projection called "polyconic", see American polyconic projection.

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:

• American polyconic projection—each parallel becomes a circular arc having true scale, the same scale as the central meridian
• Latitudinally equal-differential polyconic projection
• Rectangular polyconic projection
• Van der Grinten projection—projects entire earth into one circle; all meridians and parallels are arcs of circles.
• Nicolosi globular projection—typically used to project a hemisphere into a circle; all meridians and parallels are arcs of circles.[2]

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]

See also

• List of map projections

References

1. An Album of Map Projections (US Geological Survey Professional Paper 1453), John P. Snyder & Philip M. Voxland, 1989, p. 4.
2. John J. G. Savard. "The Dietrich-Kitada Projection".
3. https://pubs.usgs.gov/pp/1453/report.pdf ^[bare URL PDF]
4. John P. Snyder (1993). Flattening the Earth: Two Thousand Years of Map Projections. ISBN 0-226-76747-7.

External links

• Table of examples and properties of all common projections, from radicalcartography.net