1. Source of light : It includes perspective and non-perspective projections and mathematical projections. Perspective projections can be drawn by projecting the image of the network of the meridians and parallels of a globe on developable surface.
2. Developable surface : These are classified as conical-cylindrical and zenithal projections.
3. Global properties : The projections are also classified on the basis of global criteria they satisfy. The criteria include equal area, projections, correct shape projections and azimuthal projections.
Characteristics of conical projection with one standard parallel :
1. The parallel scale correct only along the standard parallel. It is exaggerated as to proceed to north and south of it.
2. The meridian scale is correct everywhere.
3. The pole is represented by an arc.
4. The meridians and parallels cut each other at right angle.
5. As the distortion of shape occurs both north and south of the standard parallels, the projection neither equal area of orthomorphic.
6. It is suitable to the area which covers more than 20° of latitude.
7. It is fairly accurate for narrow latitudinal zone lying in temperate latitudes.
Characteristics of Mercator’s Projection
1. All parallels of latitude are projected equal in the length to the equator of the reduced earth.
2. The parallel scale along the equator is always true, but away from it, it is exaggerated towards north and south. Hence the polar regions are not shown in this projection.
3. The meridians are placed evenly, so that their spacing is true to scale on the equator.
4. Since, the exaggeration of the scale along the parallels is accompanied by equal exaggeration of the scale along the meridians areas become grossly exaggerated in high latitudes. For this very reason, polar regions are not shown in this projection.
5. The projection is orthomorphic as each meridian intersects the parallel at right angles and the scale ratio remains constant throughout.
6. Although the area of a small square is enlarged considerably but the shape is preserved in this projection.
7. Since, it shows the correct directions, it is always valuable to the navigators and pilots.
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