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Syntax
Graticule
The graticule described is for the polar aspect.
Meridians: Equally spaced straight lines intersecting at a central pole. The angles between them are the true angles.
Parallels: Equally spaced circles, centered on the central pole. The entire Earth may be shown.
Poles: Central pole is a point. The opposite pole is a bounding circle with a radius twice that of the Equator.
Features
This is an equidistant projection. It is neither equal-area nor conformal. In the polar aspect, scale is true along any meridian. The projection is distortion free only at the center point. Distortion is moderate for the inner hemisphere, but it becomes extreme in the outer hemisphere.
Parallels
There are no standard parallels for azimuthal projections.
Remarks
This projection may have been first used by the ancient Egyptians for star charts. Several cartographers used it during the sixteenth century, including Guillaume Postel, who used it in 1581. Other names for this projection include Postel and Zenithal Equidistant.
Limitations
This projection is available for the spherical geoid only.
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