Map projections

Article By:

Robinson, Arthur H. Formerly, Department of Geography, University of Wisconsin, Madison, Wisconsin.

Wikle, Thomas A. Department of Geography, Oklahoma State University, Stillwater, Oklahoma.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.404400

Systematic methods of transforming the spherical representation of parallels, meridians and geographic features of the Earth's surface to a nonspherical surface, usually a plane. Map projections have been of concern to cartographers, mathematicians and geographers for centuries because globes and curved-surface reproductions of the Earth are cumbersome, expensive and difficult to use for making measurements. Although the term “projection” implies that transformation is accomplished by projecting surface features of a sphere to a flat piece of paper using a light source, most projections are devised mathematically and are drawn with computer assistance. The task can be complex because the sphere and plane are not applicable surfaces. As a result, each of the infinite number of possible projections deforms the geometric relationships among the points on a sphere in some way, with directions, distances, areas and angular relationships on the Earth never being completely recreated on a flat map.

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