Thursday, June 28, 2007

map projections 1

A map projection is any method used in cartography mapmaking) to represent the two-dimensional curved surface of the earth (or other body) on a plane.

There is a fairly detailed article at Wikipedia: Map Projection.
Flat maps could not exist without map projections, because a sphere cannot be laid flat over a plane without distortions. One can see this mathematically as a consequence of Gauss's Theorema Egregium. Flat maps can be more useful than globes in many situations: they are more compact and easier to store; they readily accommodate an enormous range of scales; they are viewed easily on computer displays; they can facilitate measuring properties of the terrain being mapped; they can show larger portions of the earth's surface at once; and they are cheaper to produce and transport. These useful traits of flat maps motivate the development of map projections.
Another excellent article is here.

South America in shown, to the left, in selected projections at identical scale. Which projection is best? Which is right? The short answer is none, at least not all the time. Even if a single projection is used, just switching the aspect can also radically reshape the continents.

If you have read this far, let me make the most important statement of this article - one I will explore in a later post: all maps are lies

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