NCERT Solutions for Class 11 Geography Practical Work in Geography I Chapter 4: Map Projections

Chapter at a glance

Exercise Questions

Question 1 (i)

A map projection least suitable for the world map:
(a) Mercator (b) Simple Cylindrical (c) Conical (d) All the above

Answer

A conical projection cannot show the whole world; it is suited only to mid-latitude regions.

3. Conical

Question 1 (ii)

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

Answer

1. Simple Conical

Question 1 (iii)

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

Answer

2. Mercator

Question 1 (iv)

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

Answer

3. Gnomonic

Question 2 (i)

Describe the elements of map projection.

Answer

1. Reduced earth: a model of the earth reduced to the required scale on a flat surface (the globe).
2. Parallels of latitude: circles running east–west round the globe, parallel to the equator.
3. Meridians of longitude: semi-circles running north–south from pole to pole.
4. Global properties: the correct distance, shape, area and direction between places, which a projection tries to preserve.

Reduced earth (globe), parallels of latitude, meridians of longitude and global properties (distance, shape, area, direction).

Question 2 (ii)

What do you mean by global property?

Answer

Global properties are the characteristics of the globe that a map should ideally preserve: correct distance between places, correct shape, correct area (size) and correct direction. No single projection can maintain all of them; each preserves one or two at the cost of others.

Correct distance, shape, area and direction between places as they are on the globe.

Question 2 (iii)

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

Answer

The globe is a spherical (non-developable) surface; it cannot be flattened onto a plane without stretching or tearing. When the graticule is transferred to a flat surface, some distortion in distance, shape, area or direction is unavoidable. A projection can preserve only some properties at the cost of others, so no projection represents the globe truly.

Because a sphere cannot be flattened without stretching or tearing, so every projection distorts some of distance, shape, area or direction.

Question 2 (iv)

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

Answer

In the cylindrical equal area projection, parallels are drawn as straight lines whose spacing decreases towards the poles (distance from the equator = R sin φ), while the east–west length of each parallel is kept equal to the equator (stretched). The decrease in north–south spacing compensates exactly for the east–west stretching, so the area between parallels equals the corresponding area on the globe.

By reducing the spacing between parallels towards the poles (R sin φ) in proportion to the east-west stretching, so areas match the globe.

Question 3 (i)

Differentiate between developable and non-developable surfaces.

Answer

Developable surfaces (cylinder, cone, plane) can be flattened without distortion; non-developable surfaces (sphere) cannot.

Question 3 (ii)

Differentiate between homolographic and orthographic projections.

Answer

Homolographic projections preserve area (based on global property); orthographic projections place the light source at infinity (based on light position).

Question 3 (iii)

Differentiate between normal and oblique projections.

Answer

In a normal projection the surface touches the globe at the equator or pole; in an oblique projection it touches at a point between them.

Question 3 (iv)

Differentiate between parallels of latitude and meridians of longitude.

Answer

Parallels are east–west circles shrinking poleward (0°–90° N/S); meridians are equal north–south semi-circles (0°–180° E/W).

Question 4 (i)

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

Answer

1. Method of construction (drawing technique)

• Perspective projections: drawn with the help of a light source, projecting the graticule onto a surface.
  • Non-perspective: developed without a light source, by calculation or construction.
  • Mathematical: derived by mathematical computation and formulae; little relation to the projected image.

2. Developable surface used

• Cylindrical: surface wraps round the globe touching the equator; useful for world maps.
  • Conical: cone touches the globe along a parallel (standard parallel); useful for mid-latitudes.
  • Zenithal: a plane touches the globe at a point (often a pole); useful for polar areas.

3. Global property preserved

• Equal-area (homolographic): areas correct.
  • Orthomorphic: shapes correct (for small areas).
  • Azimuthal: directions correct from the centre.
  • Equidistant: distances correct along certain lines.

4. Position of light source

• Gnomonic: light at the centre of the globe.
  • Stereographic: light at the opposite end of the diameter from the point of contact.
  • Orthographic: light at infinity.

Projections are classified by drawing technique (perspective, non-perspective, mathematical), developable surface (cylindrical, conical, zenithal), global property (equal-area, orthomorphic, azimuthal, equidistant) and light position (gnomonic, stereographic, orthographic).

Question 4 (ii)

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

Answer

The Mercator projection (Gerardus Mercator, 1569) is most useful for navigation.

Properties

1. Parallels and meridians are straight lines intersecting at right angles.
2. All parallels are equal in length to the equator.
3. Spacing between parallels increases towards the poles in proportion to the stretching, so it is orthomorphic — shapes of small areas are correct.
4. Direction is correct: a line of constant compass bearing (rhumb line / loxodrome) is a straight line. Hence navigators can plot a straight course.
5. Useful for world maps showing ocean currents, winds, drainage, and for navigation and atlases.

Limitations

1. Areas are greatly exaggerated in high latitudes; e.g. Greenland appears as large as the USA, though it is much smaller.
2. The poles cannot be shown, as the 90° parallel and meridians become infinite.
3. Distances are not correct away from the equator.

The Mercator projection: straight, perpendicular graticule, correct shapes and directions (rhumb lines are straight) — ideal for navigation; but areas are hugely exaggerated poleward and the poles cannot be shown.

Question 4 (iii)

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

Answer

Properties

1. A cone is placed over the globe so that it touches it along one parallel — the standard parallel.
2. All parallels are arcs of concentric circles, and they are equally spaced.
3. All meridians are straight lines that converge at a common point (the apex) and are equally spaced.
4. Scale along the standard parallel and along meridians is correct.
5. The pole is shown as an arc.
6. Suitable for mid-latitude areas with small east–west extent and larger north–south extent, e.g. maps of countries like the Baltic states or India’s states.

Limitations

1. Not suitable for the world map or for areas of large latitudinal or longitudinal extent.
2. Scale is exaggerated away from the standard parallel (parallels other than the standard are too long).
3. In the hemisphere opposite to the standard parallel, distortion is extreme; the projection cannot show it properly.
4. It is neither equal-area nor orthomorphic.

Parallels are equally spaced concentric arcs and meridians straight converging lines; scale is true along the standard parallel and meridians, suiting small mid-latitude areas. Limitations: unfit for world maps, distortion grows away from the standard parallel, and it is neither equal-area nor orthomorphic.

Topic checklist

• Meaning and elements of map projection
• Classification of projections
• Conical projection with one standard parallel
• Cylindrical equal area projection
• Mercator projection

Total questions answered: 15 of 15