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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.

The projection is defined by:

- $x\; =\; cot(phi)\; sin(lambda\; sin(phi)),$

- $y\; =\; phi\; +\; cot(phi)\; (1\; -\; cos(lambda\; sin(phi))),$

where $lambda$ is the longitude from the central meridian, and $phi$ is the latitude. To avoid division by zero, the formulas above are extended so that if $phi\; =\; 0$ then $x\; =\; lambda$ and $y\; =\; 0$.

- Mathworld's page on polyconic projections
- Table of examples and properties of all common projections, from radicalcartography.net
- An interactive Java Applet to study the metric deformations of the Polyconic Projection

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Last updated on Wednesday September 05, 2007 at 15:57:12 PDT (GMT -0700)

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This article is licensed under the GNU Free Documentation License.

Last updated on Wednesday September 05, 2007 at 15:57:12 PDT (GMT -0700)

View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation

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