Directory of Map Projections

What is a projection?

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Mercator equal-area




Meridians: Central meridian is a straight line half as long as the equator. Other meridians are equally spaced sinusoidal curves intersecting at the poles and concave toward the central meridian.
Parallels: Equally spaced straight parallel lines perpendicular to the central meridian.
Poles: Points.
Symmetry: About the central meridian or the equator.


For educational purposes, it has been shown in various aspects as examples of normal, transverse, and oblique aspects of almost any pseudocylindric projection.


True along every parallel and along the central meridian.


Severe near outer meridians at high latitudes but can be substantially reduced by interruption with several central meridians. Free of distortion along the equator and along the central meridian.


Atlas maps of South America and Africa. Occasionally used for world maps. Formerly used for other continental maps and star maps. Combined with Mollweide projection to develop other projections such as the Homolosine and the Boggs.

Similar projections

Several other pseudocylindric projections, such as Craster parabolic and Boggs eumorphic, are very similar, but parallels are not equally spaced, and meridians are curved differently. Eckert V and VI have sinusoidal meridians but have lines for poles.


Developed in the 16th century. Used by J. Cossin in 1570 and by J. Hondius in Mercator atlases of the early 17th century. Often called Sanson-Flamsteed projection after later users. Oldest current pseudocylindric projection.

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.