Polyconic can refer either to a class of

map projection In cartography, map projection is the term used to describe a broad set of transformations employed to represent the two-dimensional curved surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longitud ...

s or to a specific projection known less ambiguously as the

American polyconic projection The American polyconic map projection is a map projection used for maps of the United States and regions of the United States beginning early in the 19th century. It belongs to the polyconic projection class, which consists of map projections who ...

. 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.

Polyconic projections

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

—each parallel becomes a circular arc having true scale, the same scale as the central meridian *

Latitudinally equal-differential polyconic projection The latitudinally equal-differential polyconic projection ( 等差分纬线多圆锥投影) is a polyconic map projection in use since 1963 in mainland China. Maps on this projection are produced by China's State Bureau of Surveying and Mapping a ...

Rectangular polyconic projection The rectangular polyconic projection is a map projection was first mentioned in 1853 by the United States Coast Survey, where it was developed and used for portions of the U.S. exceeding about one square degree. It belongs to the polyconic project ...

Van der Grinten projection The van der Grinten projection is a compromise map projection, which means that it is neither equal-area nor conformal. Unlike perspective projections, the van der Grinten projection is an arbitrary geometric construction on the plane. Van der ...

—projects entire earth into one circle; all meridians and parallels are arcs of circles. *

Nicolosi globular projection The Nicolosi globular projection is a polyconic map projection invented about the year 1,000 by the Iranian polymath al-Biruni. As a circular representation of a hemisphere, it is called ''globular'' because it evokes a globe. It can only display ...

—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,https://pubs.usgs.gov/pp/1453/report.pdf who also presented an equal-area polyconic in 1935. Another series by

Georgiy Aleksandrovich Ginzburg Georgy (; russian: Георгий, Georgiy; bg, Георги, Georgi) is a Slavic masculine given name, derived from the Greek name Georgios. It corresponds to the English name George. The name Georgi is the most used masculine name in Bulgaria an ...

appeared starting in 1949. 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
"The Dietrich-Kitada Projection"

References

External links

Table of examples and properties of all common projections
from radicalcartography.net Map projections {{cartography-stub

Polyconic projections

See also

References

External links