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| [[File:Polyconic projection SW.jpg|300px|thumb|American polyconic projection of the world]]
| | The name of the author is Numbers. My working day occupation is a librarian. Years in the past we moved to North Dakota and I love every day residing here. One of the issues she enjoys most is to do aerobics and now she is attempting to earn money with it.<br><br>Visit my web page ... std testing at home, [http://facehack.ir/index.php?do=/blog/20/what-you-have-to-do-facing-candida/ Going at facehack.ir], |
| '''Polyconic''' can refer either to a class of [[map projection]]s or to a specific projection known less ambiguously as the American Polyconic. 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.<ref>''An Album of Map Projections'' (US Geological Survey Professional Paper 1453), John P. Snyder & Philip M. Voxland, 1989, p. 4.</ref>
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| As a specific projection, the American Polyconic is conceptualized as "rolling" a cone tangent to the Earth at all parallels of latitude, instead of a single cone as 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 the time of its proposal by [[Ferdinand Rudolph Hassler]] in 1825 until the middle of the 20th century.<ref>''Flattening the Earth: Two Thousand Years of Map Projections'', John P. Snyder, 1993, pp. 117-122, ISBN 0-226-76747-7.</ref>
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| The projection is defined by:
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| :<math>x = \cot(\varphi) \sin((\lambda - \lambda_0)\sin(\varphi))\,</math>
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| :<math>y = \varphi-\varphi_0 + \cot(\varphi) (1 - \cos((\lambda - \lambda_0)\sin(\varphi)))\,</math>
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| where <math>\lambda</math> is the longitude of the point to be projected; <math>\varphi</math> is the latitude of the point to be projected; <math>\lambda_0</math> is the longitude of the central meridian, and <math>\varphi_0</math> is the latitude chosen to be the origin at <math>\lambda_0</math>. To avoid division by zero, the formulas above are extended so that if <math>\varphi = 0</math> then <math>x = \lambda</math> and <math>y = 0</math>.
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| ==See also==
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| {{Portal|Atlas}}
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| * [[List of map projections]]
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| ==References==
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| {{reflist}}
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| ==External links==
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| *{{Mathworld|PolyconicProjection}}
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| * [http://www.radicalcartography.net/?projectionref Table of examples and properties of all common projections], from radicalcartography.net
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| * [http://www.uff.br/mapprojections/Polyconic_en.html An interactive Java Applet to study the metric deformations of the Polyconic Projection].
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| {{Map Projections}}
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| [[Category:Cartographic projections]]
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| {{cartography-stub}}
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The name of the author is Numbers. My working day occupation is a librarian. Years in the past we moved to North Dakota and I love every day residing here. One of the issues she enjoys most is to do aerobics and now she is attempting to earn money with it.
Visit my web page ... std testing at home, Going at facehack.ir,