polyconic projection


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polyconic projection

[¦päl·i¦kän·ik prə′jek·shən]
(mapping)
A conic map projection in which the surface of a sphere or spheroid, such as the earth, is conceived as developed on a series of tangent cones, which are then spread out to form a plane; a separate cone is used for each small zone.

polyconic projection

A map projection that is a combination of separate conic projections drawn for each parallel or latitude. In this projection, the central meridian is a straight line and other meridians are curves concave to the central meridians. Parallels are arcs of circles concave to the pole of the hemisphere. The scale is correct along all parallels. However, it is correct only along the central meridian and expands along other meridians away from the central meridian. Areas expand and shapes become distorted away from the central meridian. A great circle is a curve convex, whereas a rhumb line is a curve concave to the pole of the hemisphere. Map sheets fit North-South but not East-West. A polyconic projection has a worldwide coverage. See international modified polyconic projection.