Map projection is the process of transforming earth’s spherical surface to a flat map while maintaining its spatial relationships. It is the transformation of all-side-curved-geoidal surface into a plane surface. There are changes in directions, distances, areas and shapes from the way they appear on a geoid after the projection.
Map projections are required to have a detailed study of a region and to compare the two natural regions.
Following aspects need to be kept in mind while projecting a map:
Parallels of latitude
Meridians of Longitude, and
Map projection can be based on
Source of Light
On this basis, map projection can be of various types.
On the basis of method of construction, projections are classified as perspective, non-perspective and mathematical or conventional projection.
On the basis of nature of developable surface, the projections are classified as cylindrical, conical and zenithal projections.
On the basis of global properties, projections are classified into equal area or homolographic projection, orthomorphic or true shape projection, azimuthal or true bearing projection and equi-distant or true scale projection.
On the basis of location of source of light, projections may be classified as gnomonic, stereographic and orthographic projection
Choice of map projection depends upon:
Purpose for which the data is to be used
Property in which distortion is minimised
Extent and location of area
Different map projections are useful for representing different aspects.