All map projections show some kind of distortion in the
areas that are far from the projection center. Depending on the kind
of projection used, the distortion may be of angle, area, shape, size,
distance, or scale. In this respect, projections fall into two main
categories, Equal Area and Conformal.
Equal area projections maintain a true
ratio between the various areas represented on the map.
Conformal projections preserve angles,
and locally also preserve shapes.
Other projections have properties that are worth noting,
such as maintaining the distances measured from the center of the
projection (azimuthal equidistant projection). Others offer a good
compromise between angular distortion and distortion of the area.
Projections should therefore be configured and selected
according to the areas to be represented (for example, it is impossible
to represent the polar regions with the Mercator projection) and the
domains they apply to (navigational or air-route applications, small-scale
or large-scale maps, and so on). Navigational applications, for example,
generally use conformal projections.
For more information on map projections, refer to these
books:
Map
Projections - A Working Manual (Snyder, 1987)
An Album
of Map Projections (Snyder and Voxland, 1989)