Maps are flat, but the surfaces they represent are curved. Transforming, three-dimensional space onto a two dimensional map is called “projection”. This process inevitably distorts at least one of the following properties:
- Direction, and often more.
It is known that a globe is a true representation of the earth, which is divided into various sectors by the lines of latitudes and longitudes. This network is called ‘graticule’. A map projection denotes the preparation of the graticule on a flat surface.
Theoretically map projection might be defined as “a systematic drawing of parallels of latitude and meridians of longitudes on a plane surface for the whole earth or a part of it on a certain scale so that any point on the earth surface may correspond to that on the drawing.”
Necessity of Map Projection
An ordinary globe is rendered useless for reference to a small country. It is not possible to make a globe on a very large scale. Say, if anyone wants to make a globe on a scale of one inch to a mile, the radius will be 330 ft. It is difficult to make and handle such a globe and uncomfortable to carry it in the field for reference. Not only topographical maps of different scales but also atlas and wall maps would not have been possibly made without the use of certain projections. So a globe is least useful or helpful in the field of practical purposes. Moreover it is neither easy to compare different regions over the globe in detail, nor convenient to measure distances over it. Therefore for different types of maps different projections have been evolved in accordance with the scale and purpose of the map.
Selection of Map Projection
There is no ideal map projection, but representation for a given purpose can be achieved. The selection of projection is made on the basis of the following:
The location and the extension of the feature of the globe.
- The shape of the boundary to be projected.
- The deformations or distortions of a map to be minimized.
- The mathematical model to be applied to preserve some identity of graphical features.
Based on these characteristics the utility of the projection is ascertained