Polyconic projection
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A polyconic projection is a conical map projection. The projection stems from "rolling" a cone tangent to the Earth at all parallels of latitude, instead of a single cone in a normal conic projection. Each parallel is a circular arc of true scale. The scale is also true on the central meridian of the projection. The projection was in common use by many map-making agencies of the United States from its proposal by Ferdinand Rudolph Hassler in 1825 until the middle of the 20th century.[1]
The projection is defined by:
![(\lambda,\phi)\mapsto\left(\cot \phi \sin(\lambda \sin \phi), \phi+\cot \phi[1-\cos(\lambda\sin\phi)]\right)](../../../math/b/0/5/b059d21bbb09fb6864ebf4dc34c5b98e.png)
where 
is the longitude from the central meridian, and 
is the latitude. When is zero, then
[edit] References
- ^ Flattening the Earth: Two Thousand Years of Map Projections, John P. Snyder, 1993, pp. 117-122, ISBN 0-226-76747-7.
[edit] External links
- Mathworld's page on polyconic projections
- Table of examples and properties of all common projections, from radicalcartography.net
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