1-3 Map Projection

A map projection is a process of transforming location on the curved surface of the Earth with the geodetic coordinates (j , l) to planar map coordinates (x, y).

More than 400 difference map projections have been proposed. The map projections are classified by the following parameters.

- projection plane: perspective, conical, cylindrical
- aspect: normal, transverse, oblique
- property: conformality, equivalence, equidistance

Perspective Projection
Perspective projections are classified based on the projection center or viewpoint as shown in Figure 1.5. One of the most popular perspective projections is polar stereo projection with the projection plane tangent to the north or South Pole and the viewpoint at the opposite pole. This polar stereo projection is used in NOAA GVI (Global Vegetation Index) data for global study.

Conical Projection
Conical projections are classified by the aspect as well as the cone size as shown in Figure 1.6 and Figure 1.7 respectively.

One of the popular conical projection is Lambert’s conformal conical in which the angle is conformal with an equal angle and distance in an area of 300 km in East-West and 500 km in North-South.

The shortest distance is given as a straight line. The projection is used in the world aeronautical chart of 1:1,000,000 scale.

Cylindrical Projections
Cylindrical projections are classified as in case of conical projections as shown in Figure 1.8 and Figure 1.9 respectively.

One of the most popular cylindrical projections is the Universal Transverse Mercator (UTM) with a transverse axis, secant cylinder and conformality (equal angle). UTM is commonly used for topographic maps of the world, devided into 60 zones with a width of 6 degree longitude.

Figure 1.10, Figure 1.11 and Figure 1.12 show polar stereo projection, Lambert’s conformal conical projection and UTM respectively.