Equal Area or Conformal Projections

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 which 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 to 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.

The projections supplied in this package are derived from the proj program by Gerald I. Evenden.

For more information on map projections, refer to these books:

• Map Projections - A Working Manual (Snyder, 1987) and

• An Album of Map Projections (Snyder and Voxland, 1989)