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Essentials of Geography

Map projections

A map projection is a method of portraying the curved surface of the Earth on a flat planar surface of a map. Projections are created to preserve one or several measurements of the following qualities:

Each projection handles the conversion of these metric properties from the curved surface of a globe to the flat surface of map projection

Figure 1.19 Visualizing a map projection (Courtesy USGS. Source)

The purpose of the map is of primary importance in choosing a projection to illustrate spatial patterns of Earth phenomena. For instance, the Mercator projection was long used for navigation or maps of equatorial regions. The cylindrical Mercator projection mathematically projects the globe onto a cylinder tangent to the Equator. Large areas become distorted which increases toward away from the Equator. Distances are true only along the Equator, special scales are provided for other latitudes for measurement.

A diagram of Mercator projection on a  flat map in relation to the globe.

Figure 1.20 Cylindrical Mercator projection
(Courtesy USGS - Source)

The Robinson projection uses tabular coordinates rather than mathematical formulas to make earth features look the "right" size and shape. A better balance of size and shape result is a more accurate picture of high-latitude lands like Russia, Soviet and Canada. Greenland is truer to size but compressed.

A diagram and explanation of Robinson projection.

Figure 1.21 Robinson projection
(Courtesy USGS - Source)

For more on projections see: Map Projections from the United States Geological Survey.

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For Citation: Ritter, Michael E. The Physical Environment: an Introduction to Physical Geography.
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