Geographers are constantly relying on maps to communicate their concepts and search for solutions to problems. A map is a two dimensional or flat scale-model of the earth s surface. Because the earth is spherical in shape, it is impossible to draw a map that is totally accurate on a flat piece of paper. In order to show the 3D surface of the earth on a flat map, geographers make use of projections. To understand projections, one can imagine a globe with a light inside of it.
Cartographers make two very important decisions when they create maps.
First is determining which projection they will use, and is the scale or level generalization. It is easy to understand why scale or level of generalization is a key decision. The size of the area under consideration and the level of detail under analysis determine the appropriate scale. Projection decisions are more difficult because the influences of the projection are subtle. There are four types of distortions that result from the surface of the earth being put down as a flat map.