Modified Polyconic Projection

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A pseudoconical projection that is neither conformal nor equal area. Based on the Polyconic, but differs from the ordinary Polyconic in two principal features: All meridians are straight, and there are two meridians that are made true to scale.

 

Scale

 

Meridians true to scale are 2 degrees east and west of the central meridian on sheets between latitudes 60 North and South, 4 degrees E / W between latitudes 60 and 76 N and S, and 8 degrees E / W between latitudes 76 and 84 N and S.

 

Distortion

 

Adjacent map sheets fit exactly together not only North to South but also East to West.

 

Usage

 

Used as the basis for the 1:1,000,000-scale International Map of the World (IMW) Series.

 

Limitations

 

Normally used only for a single hemisphere.

 

Origin

 

Devised by Lallemand of France and in 1909 adopted by the International Map Committee in London as the basis for the IMW. In 1962, a UN conference on the IMW adopted the Lambert Conformal Conic and Polar Stereographic projections to replace the Modified Polyconic.

 

Options

 

Specify the center longitude to center the map. The first standard latitude and second standard latitude should be approximately one fifth up from the bottom of the region covered and one fifth down from the top of the region covered. The true-scale longitude is usually the same as the center longitude.