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Map Projections

When you try to flatten a tennis ball, what happens? The sides split, and the shape is changed. The same thing happens when you try to take a world map and flatten it onto a piece of paper. It can't be done without stretching some places. This stretching is called distortion. A globe can show size, shape, distance, and direction accurately, but since paper is not three dimensional, we will have to use map projections. A map projection is a way to show a drawing of the earth on a flat surface. All flat maps have distortion, so we use different map projections to meet different needs.

Gerardus Mercator created a map where parallels and meridians crossed at right angles. The Mercator Projection is excellent for navigation because it shows direction clearly. The Mercator Projection, however, has a great deal of distortion. In order to get the parallels and meridians to cross at right angles, Mercator stretched the areas further away from the poles and squeezed the areas closer to the equator.

An equal area map displays the shapes and sizes of things more accurately than a Mercator Projection. Compare Greenland and Africa on the two projections. Africa is actually fourteen times larger than Greenland, but on a Mercator Projection, they seem to be about the same size.

Many modern mapmakers use complicated mathematical formulas that combine the advantages of the Mercator Projection and an equal area map. The border of the western United States and Canada is the longest straight border in the world. On some map projections the line will be straight, while on others you will notice a slight curve.

To cite this page:
Dowling, Mike, "Mr. Dowling's Map Projections Page," available from http://www.mrdowling.com/601-projections.html; Internet; updated Saturday, June 17, 2006 . ©2009, Mike Dowling. All rights reserved.