Question

Discuss the criteria used for classifying map projection and state the major characteristics of each type of projection.

Answer 1

Types of Map Projection:

1. On the basis of drawing techniques, map Projections may be classified perspective, non-perspective, and conventional or mathematical. Perspective projections can be drawn taking the help of a source of light by projecting the image of a network of parallels and meridians of a globe on a developable surface. Non¬perspective projections are developed without the help of a source of light or casting shadows on surfaces, which can be flattened. Mathematical or conventional projections are those, which are derived by mathematical computation and formulae and have little relations with the projected image.
2. On the basis of developable surface, it can be developable surface and non-developable surface. A developable surface is one, which can be flattened, and on which, a network of latitude and longitude can be projected. A globe or spherical surface has the property of a non-developable surface whereas a cylinder, a cone, and a plane have the property of a developable surface. On the basis of the nature of the developable surface, the projections are classified as cylindrical, conical, and zenithal projections.
3. On the basis of global properties, projections are classified into equal area, orthomorphic, azimuthal, and equidistant projections.
4. On the basis of location of a source of light, projections may be classified as gnomonic, stereographic, and orthographic.
   The correctness of area, shape, direction, and distances are the four major global properties to be preserved in a map. But none of the projections can maintain all these properties simultaneously. Therefore, according to a specific need, a projection can be drawn so that the desired quality may be retained.