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A map projection is a method of transferring geometric shapes from one surface to another. For maps of the earth, this means transforming the locations of the boundary polygons of land masses and political entities, the lines of longitude, latitude, roads and rivers, and the points of populated places and mountain peaks from a spherical or ellipsoidal earth to a flat piece of paper. Appropriate map projection definitions, selections, and transformations may be required at various stages in a GIS process.

Map Projection Distortions

A globe is a useful way of representing the earth, but globes are difficult to make, awkward to carry, and hard to use for measuring areas, distances, and directions. Since there is no method of flattening a globe without distorting distance, direction, area, ...

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