NCERT Class 11 Geography Chapter 27 Map Projections

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NCERT Class 11 Geography Chapter 27 Map Projections

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Map Projections

Chapter: 27

GEOGRAPY [ PART – III ]

VERY SHORT ANSWER TYPE QUESTIONS

Q.1. What is a map projection?

Ans. A map projection is a means of representing the lines of latitude and longitude of the globe on a flat sheet of paper by using geometrical and mathematical methods.

Q.2. What is graticule?

Ans. The network of parallels and meridians is known as graticule.

Q.3. What is meant by a standard parallel?

Ans. Standard parallel is that parallel along which the cone touches the globe.

Q.4. Why is a map projection needed?

Ans. A map projection is used to prepare maps from the globe.

Q.5. Classify the projection on the basis of construction.

Ans. Four types of map projections on the basis of their construction are:

(a) Cylindrical projection.

(b) Conical projection.

(c) Zenithal projection.

(d) Conventional projection.

Q.6. What do you understand by developable surface? 

Ans. The developable surface is that which can be cut or unfold into flat sheet of paper e.g. cylinder or cone.

Q.7. How do you find the radius of the globe according to a given scale?

Ans. Radius of the globe according to a given scale is calculated on the basis of the following formula:

Radius of the globe = Given R.F. actual radius of the earth.

Q.8. State the rule for finding out the length of equator.

Ans. L= 2πR.

Q.9. What is the demerit of cylindrical projection?

Ans. Scale along parallels is increased.

SHORT ANSWER TYPE QUESTIONS

Q. 1. Describe the elements of map projection.

Ans. The elements of map projection are as under:

1. Reduced earth: The model of the earth is represented by the help of a reduced scale on a flat sheet of paper. On this model the network of graticule can be transferred.

2. Parallels of Latitude: These are the circles round the globe parallel to the equator and maintaining uniform distance from the poles. They are demarcated as 0° to 90° North and South.

3. Meridians of Longitude: Longitudes are also the elements of map projection. These are drawn north to south direction from one pole to the other and two opposite meridians make a complete circle i.e. circumference of the globe.

4. Global Property: These are:

(i) distance between any given points of a region.

(ii) shape of the region.

(iii) size or area of the region in accuracy.

(iv) direction of any one point of the region bearing to another point.

Q.2. What do you mean by global property?

Ans. The global property means the:

1. Correctness of the area.

2. Direction.

3. Distance.

4. Shape of the area.

Q.3. How does a map differ from a globe?

Ans. Globe: Globe is a true representation of the earth. On the globe the meridians and parallels are circles. It is a model of the earth.

Map: Map is drawn on the sheet of paper. The meridians and parallels intersects straight or curved lines. Maps are drawn to show the physical and cultural features of area.

Q.4. Why is it necessary to know about map projection?

Ans. The need for map projection mainly arise from the fact that it is difficult to see a small place in details on a globe. Therefore drawing accurate large scale map on a flat paper is required. However it is impossible to transfer accurately the features from a sphere on to flat surface. Certain methods have been devised to retain with precision at least one or a few of these relationship. While drawing maps various kinds of projections have been evolved for drawing different kinds of maps.

Q.5. What facts need to be kept in view while transferring the globe on a plain surface?

Ans. The following facts are needed to be kept in view while transferring the globe on a plain surface which include preservation of area, shape, direction and distances.

(i) Source of light.

(ii) Developable surface.

(iii) Global properties.

Q.6. Which are important geographical relationships that one looks for in a map?

Ans. Following are the important geographical relations with reference to map projection:

(i) Shape of landmasses, waterbodies or political units.

(ii) Distance between places.

(iii) Areas of landmasses, waterbodies or political units.

(iv) Directions of any given place in relation to any other place.

(v) Locations of places or areas in relation to the entire earth.

Q.7. Explain the differences between Parallels and Meridians.

Ans. Parallels: The north or south angular distance of a place from the equator is called latitude. Lines drawn east-west parallel to the equator are called latitudes. There are 90° latitude north of equator and 90° latitude south of the equator. These distance of 90° latitude is points only called north pole and south pole.

The links joining north pole and south pole are called meridians of longitude. The meridian passing through Greenwich is known as Prime Meridian. There are 180 meridians towards the east and west of the prime meridian. Thus, there are 360 meridians in all.

Q.8. Explain the differences between Map and Map Projection.

Ans. Map: A map is the conventional picture of the earth surface or a part of it. Maps are drawn to show the physical and cultural features of an area.

Map Projection: A map projection is a means of representing the lines of latitude and longitude of the globe on a flat sheet of paper.

Q.9. Distinguish between developable and non-developable surface.

Ans. Developable Surface: A developable surface is that which can be cut or unfold into a flat sheet of paper, e.g., cylinder or cone.

Non-developable Surface: A non-developable surface is that which cannot be cut of any folded into flat sheet paper, e.g. globe.

Q.10. Not a single map projection represents the globe truly. Why?

Ans. Map projection project the network of latitudes and longitudes on a plain surface by using the geometrical and mathematical methods. It is transformation of the spherical network of latitudes and longitudes on a plain surface. The globe is true representation of earth. The projections give a shadowed picture of the globe which is distorted in those parts which are further away from the point where the paper touches the globe.

Q.11. How is the area kept equal in cylindrical equal area projection?

Ans. The area is kept equal in cylindrical equal area projection because the parallels and meridians are projected as straight lines intersecting one another at right angles.

Q.12. Differentiate between:

(i) Developable and non-developable surfaces.

Ans. Developable Surface: A developable surface is that which can be cut or unfold into a flat sheet or paper e.g., cylinder or cone.

Non-developable Surface: A non- developable surface is that which cannot be cut or folded into flat sheet paper, e.g. globe.

(ii) Homolographic and orthographic projections.

Ans. Homolographic Projection: In these projection the graticule of latitudes and longitude on the map its equal in area. It is also known equal area projection.

Orthographic Projection: On these projection the correct shape of the area of a country is shown.

(iii) Normal and oblique projections.

Ans. Normal Projection: In these projection the longitudes are drawn perpendicular on latitudes on right angles. They are cylindrical projection.

Oblique Projection: These projects are known as conical projection. In these projection in inner surface of the cone touches some parallel known as standard parallel.

(iv) Parallels of latitude and meridians of longitude.

Ans. Parallels of Latitude: The parallels of latitude refer to the angular distance in degrees, minutes and seconds of a point north or south of the Equator. Lines of latitude are often referred to as parallels.

Meridians of Longitude: The meridians of longitude refer to the angular distance, in degrees, minutes and seconds of a point east or west of the Prime (Greenwich) Meridian. Lines of longitude are often referred to as meridians.

LONG ANSWER TYPE QUESTIONS

Q.1. Discuss the criteria used for classifying map projection and state the major characteristics of each type of projection.

Ans. Map projections can be classified using the following criteria:

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.

Q.2. Which map projection is very useful for navigational purposes? Explain the properties and limitations of this projection.

Ans. The Mercators projection is very useful for the navigational purposes. The properties and limitations are as under:

Properties:

1. Parallels and meridians are straight lines. They intersect at right angles.

2. The distance between meridians remains equal whereas distance of parallels go on increasing towards the pole.

3. All parallels are of the same length.

4. The scale along the equator is correct as the length of equator is equal to the length.

5. The meridians are longer than the meridians on the globe.

6. The shape of country is represented truly at every point as parallels and meridians intersect each other.

7. The projection is orthomorphic.

Limitations:

1. The scale along the poles and meridians increases rapidly towards the poles.

2. Poles in this projection cannot be shown.

Q.3. Discuss the main properties of conical projection with one standard parallel and describe its major limitations.

Ans. Properties:

1. The parallels of latitudes are areas of concentric circles and are equally spaced.

2. The meridians are straight lines. The meridians intersect the parallels at right angles.

3. Distance at meridians are fairly accurate.

4. The distance between two parallels on this projection is true.

5. There is a convergence of meridians towards the poles and closer to each other towards the poles.

6. This projection is neither equal area nor orthomorphic.

7. The standard parallel is truly divided.

Limitations:

1. It is not used for world map due the extreme distortion.

2. The distortions along the poles and near the equator makes the projection disadvantageous for representing very large areas.

Uses:

1. It is most suited for mapping middle latitude areas.

2. A long narrow strip of land running along the standard parallel in the east-west direction is shown fairly correctly.