NCERT Solutions For Class 11 Geography Chapter 12 Map Projections

(i) Map Projections may be classified on the following bases:

      a.  Drawing Techniques: On the basis of method of construction, projections are classified as follows:

1. Perspective projections are developed with the help of a source of light.
2. Non–perspective projections are developed without the help of a source of light.
3. Mathematical projections are derived by mathematical computation, and formulae.

2. Developable Surface: A developable surface is a geometric shape that can be laid out into a flat surface without stretching or tearing. The three types of developable surfaces are cylinder, cone and plane, and their corresponding projections are called cylindrical, conical and planar.
3. Global Properties: The correctness of area, shape, direction and distances are the four major global properties to be preserved in a map. On the basis of global properties, projections are classified into equal area, orthomorphic, azimuthal and equi-distant projections.
4. Source of Light: On the basis of location of source of light, projections may be classified as gnomonic, stereographic and orthographic. These projections are obtained by putting the light at the centre of the globe or at the periphery of the globe or at infinity from the globe.

(ii) Mercator’s Projection is an orthomorphic projection in which the correct shape is maintained. It has the characteristics of showing correct directions. Therefore, it is very useful for navigation purposes showing sea routes and air routes. 

Properties

1. All parallels and meridians are straight lines.
2. All parallels are equal to the length of equator.
3. All meridians have the same length and equal spacing.
4. Scale along the equator is correct.
5. The shape of small countries increases towards poles.

Limitations

1. There is greater exaggeration of scale along the high latitudes. For example, the size of Greenland equals to the size of USA.
2. Poles in this projection cannot be shown as the poles lie at infinity.

(iii) A conical projection with one standard parallel is drawn by projecting the image of the graticule of a globe on a developable cone, which touches the globe along a parallel of latitude called the standard parallel.  

Properties

1. All the parallels are arcs of concentric circle and are equally spaced.

1. All meridians are straight lines merging at the pole and intersect the parallels at right angles.
2. The scale along all meridians is true.
3. The scale is true along the standard parallel but exaggerated away from the standard parallel.
4. Meridians become closer to each other towards the pole.

Limitations

1. A conical projection with one standard parallel is not suitable for a world map as distortion is moderate for one hemisphere, but becomes extreme in the hemisphere opposite one in which the standard parallel is selected.
2. It is not suitable for representing larger areas within the hemisphere as the distortion along the pole and near the equator is larger.

(i) Reduced earth, parallels of latitude, meridians of latitude and gross property are four elements of map projections.

(ii) The correctness of area, shape, direction and distances are the four major global properties.

(iii) In preparing a map projection the distance between any given points of a region; shape of the region; size or area of the region in accuracy; and direction of any one point of the region bearing to another point are to be preserved by using one or the other methods of projections. But none of the projections can maintain all these properties simultaneously. Therefore, not a single map projection represents the globe truly.

(iv) The cylindrical equal area projection has been derived by projecting the surface of the globe with parallel rays on a cylinder touching it at the equator. Both the parallels and meridians are projected as straight lines intersecting one another at right angles. The pole is shown with a parallel equal to the equator; hence, the shape of the area gets highly distorted at the higher latitude.

(i) (c) Conical

(ii) (c) Mercator

(iii) (b) Mercator

(iv) (c) Gnomonic