NCERT Book Class 11 Geography Map Projections

NEED FOR MAP PROJECTION

The need for a map projection mainly arises to have a detailed study of a region, which is not possible to do from a globe. Similarly, it is not easy to compare two natural regions on a globe. Therefore, drawing accurate large-scale maps on a flat paper is required. Now, the problem is how to transfer these lines of latitude and longitude on a flat sheet. If we stick a flat paper over the globe, it will not coincide with it over a large surface without being distorted. If we throw light from the centre of the globe, we get a distorted picture of the globe in those parts of paper away from the line or point over which it touches the globe. The distortion increases with increase in distance from the tangential point. So, tracing all the properties like shape, size and directions, etc. from a globe is nearly impossible because the globe is not a developable surface. In map projection we try to represent a good model of any part of the earth in its true shape and dimension. But distortion in some form or the other is inevitable. To avoid this distortion, various methods have been devised and many types of projections are drawn. Due to this reason, map projection is also defined as the study of different methods which have been tried for transferring the lines of graticule from the globe to a flat sheet of paper.

ELEMENTS OF MAP PROJECTION

a. Reduced Earth: A model of the earth is represented by the help of a reduced scale on a flat sheet of paper. This model is called the “reduced earth”. This model should be more or less spheroid having the length of polar diameter lesser than equatorial and on this model the network of graticule can be transferred.

b. Parallels of Latitude: These are the circles running round the globe parallel to the equator and maintaining uniform distance from the poles. Each parallel lies wholly in its plane which is at right angle to the axis of the earth. They are not of equal length. They range from a point at each pole to the circumference of the globe at the equator. They are demarcated as 0º to 90º North and South latitudes.

c. Meridians of Longitude: These are semi-circles drawn in northsouth direction from one pole to the other, and the two opposite meridians make a complete circle, i.e. circumference of the globe. Each meridian lies wholly in its plane, but all intersect at right angle along the axis of the globe. There is no obvious central meridian but for convenience, an arbitrary choice is made, namely the meridian of Greenwich, which is demarcated as 0° longitudes. It is used as reference longitudes to draw all other longitudes.

EXERCISE

1. Choose the right answer from the four alternatives given below:

A map projection least suitable for the world map:

(a) Mercator

(b) Simple Cylindrical

(c) Conical

(d) All the above

A map projection that is neither the equal area nor the correct shape and even the directions are also incorrect

(a) Simple Conical

(b) Polar zenithal

(c) Mercator

(d) Cylindrical

A map projection having correct direction and correct shape but area greatly exaggerated polewards is

(a) Cylindrical Equal Area

(b) Mercator

(c) Conical

(d) All the above

When the source of light is placed at the centre of the globe, the resultant projection is called

(a) Orthographic

(b) Stereographic

(c) Gnomonic

(d) All the above

2. Answer the following questions in about 30 words:

1.Describe the elements of map projection.

2.What do you mean by global property?

3.Not a single map projection represents the globe truly. Why?

4.How is the area kept equal in cylindrical equal area projection?

3. Differentiate between—

1.Developable and non-developable surfaces

2.Homolographic and orthographic projections

3.Normal and oblique projections

4.Parallels of latitude and meridians of longitude

4. Answer the following questions in not more than 125 words:

Discuss the criteria used for classifying map projection and state the major characteristics of each type of projection.

Which map projection is very useful for navigational purposes?

Explain the properties and limitations of this projection.

Discuss the main properties of conical projection with one standard

parallel and describe its major limitations.

Please refer to attached file for NCERT Class 11 Geography Map Projections