Polyconic projection class
{{Short description|Class of map projections}}
{{about|the class of projections called "polyconic"|the specific projection called "polyconic"|American polyconic projection}}
File:American Polyconic projection.jpg
File:Van der Grinten projection SW.jpg
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.An Album of Map Projections (US Geological Survey Professional Paper 1453), John P. Snyder & Philip M. Voxland, 1989, p. 4.
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.
A series of polyconic projections, each in a circle, was also presented by Hans Mauer in 1922,{{Cite web| title=An Album of Map Projections - U.S. Geological Survey Professional Paper 1453 | url=https://pubs.usgs.gov/pp/1453/report.pdf | archive-url=https://web.archive.org/web/20121019082015/http://pubs.usgs.gov/pp/1453/report.pdf | archive-date=2012-10-19}} who also presented an equal-area polyconic in 1935.
{{ cite book
| title = Flattening the Earth: Two Thousand Years of Map Projections
| author = John P. Snyder
| year = 1993
| isbn = 0-226-76747-7
}}{{rp|248}} Another series by Georgiy Aleksandrovich Ginzburg appeared starting in 1949.{{rp|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.
John J. G. Savard.
[http://www.quadibloc.com/maps/meq0802.htm "The Dietrich-Kitada Projection"].
See also
References
{{reflist}}
External links
- [http://www.radicalcartography.net/?projectionref Table of examples and properties of all common projections], from radicalcartography.net
{{Map projections}}
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