Directory of Map Projections

What is a projection?

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Meridians: Equally spaced straight lines converging at the north pole.
Parallels: Unequally spaced straight parallel lines, farthest apart near the north pole, closest near the south pole. Perpendicular to the central meridian.
Poles: North pole is a point; south pole is a line 1.41 times as long as the equator.
Symmetry: About the central meridian.


True along latitudes 15°51′N Constant along any given latitude; different for each latitude.


Severe in many regions. Free of distortion only at latitude 15°51′N at the central meridian.


Novelty showing straight-line equal-area graticule.

Similar projections

Eckert I and II also use straight lines for both meridians and parallels, but meridians are broken at the equator.
The Trapezoidal projection has equidistant straight parallel lines for parallels and converging straight meridians equally spaced along each parallel (top and bottom parallels and perpendicular central meridian true to scale). It was used for numerous maps from the 15th to the 18th centuries but is neither equal-area nor conformal.
Polyhedric projection, formerly used for large scale mapping in various parts of central Europe. There were various forms, all resembling the Trapezoidal projection but applied to the ellipsoid.


Presented by Edouard Collignon of France in 1865.

Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.