NCERT Solution for Class 1 1 Geography Chapter 4 Map Projections
Question.1. Choose the right answer from the four alternatives given below:
(i) A map projection least suitable for the world map:
(a) Mercator
(b) Simple Cylindrical
(c) Conical
(d) All the above
Answer
(c) Conical
(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
(a) Simple Conical
(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
(b) Mercator
(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
(c) Gnomonic
Question.2. Answer the following questions in about 30 words:
(i) Describe the elements of map projection.
Answer.
- 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.”
- Parallels of Latitude: These circles run around the globe parallel to the equator and maintain a uniform distance from the poles.
- Meridians of Longitude: These are semicircles drawn in a north-south direction from one pole to the other, and the two opposite meridians make a complete circle, i.e., circumference of the globe.
- Global property: the correctness of area, shape, direction and distance are the four major global properties to be preserved in a map.
(ii) What do you mean by global property?
Answer. In preparing a map projection the following basic properties of the global surface are to be preserved by using one or the other methods:
- Distance between any given points of a region,
- Shape of the region,
- Size or area of the region in accuracy,
- Direction of any one point of the region bearing to another point.
(iii) Not a single map projection represents the globe truly. Why?
Answer. However, there isn’t such a projection, which maintains, the scale remains accurate throughout. Depending on the situation, it can be successfully maintained only along a few carefully chosen parallels and meridians. Projection is a shadow of globe which has to be presented on a map. When the shape of the globe changes, certainly inaccuracy comes in. Therefore, it is rightly said that not a single map projection represents the globe truly.
(iv) How is the area kept equal in cylindrical equal area projection?
Answer. The area is kept equal in cylindrical equal-area projection because latitudes and longitudes intersect each other at right angles in the straight line form.
Question.3. Differentiate between:
(i) Developable and non-developable surfaces.
Answer.
| Developable Surface | Non-Developable Surface |
|---|---|
| A developable surface is one, which can be flattened, and on which, a network of latitude and longitude can be projected. | A non-developable surface is one, which cannot be flattened without shrinking, breaking or creasing. |
| Example: A cylinder, a cone and a plane have the property of developable surface. | Example: A globe or spherical surface has the property of non-developable surface. |
(ii) Homolographic and orthographic projections.
Answer.
| Homolographic Projection | Orthographic Projection |
|---|---|
| A projection in which the network of latitudes and longitudes is developed in such a way that every graticule on the map is equal in area to the corresponding graticule on the globe. It is also known as the equalarea projection. | A projection in which the correct shape of a given area of the earth’s surface is preserved. |
(iii) Normal and oblique projections.
Answer.
- Normal Projection: If the developable surface touches the globe at the equator, it is called equatorial or normal projection.
- Oblique Projection: If a projection is tangential to a point between the pole and the equator, it is called oblique projection.
(iv) Parallels of patitude and meridians of longitude.
Answer.
| Meridians of Longitude | Parallels of Latitude |
|---|---|
| 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. | The parallels of latitude refer to the angular distance, in degrees, minutes and seconds, of a point north or south of the equator. |
| It helps to determine the time of a place. | It helps to determine the temperature of a place. |
| Reference point: 0° longitude is called the prime meridian. | Reference point: 0° latitude is called the equator. |
| It divides the earth into the eastern hemisphere and western hemisphere. | It divides the earth into the northern hemisphere and southern hemisphere. |
Question.3. Answer the following questions in not more than 125 words:
(i) Discuss the criteria used for classifying map projection and state the major characteristics of each type of projection.
Answer. Map projection can be classified as drawing technique, Developable surface, Global properties, Source of light.
The classification is given below:
- On the basis of drawing techniques, map Projections are classified as perspective, non-perspective and conventional or mathematical. Drawing perspective projections with the help of a light source involves projecting an image of a globe’s network of parallels and meridian lines onto a surface that may be developed. Nonperspective projections are created without the aid of a light source or the ability to cast shadows on easily flattened objects. Conventional projections are ones that are created using formulas and calculations that have little connection to the projected picture.
- Depending on the surface that can be developed, it might be either a developable surface or a non-developable surface. A surface that can be flattened and onto which a network of latitude and longitude are projected is referred to as a developable surface. On the basis of the nature of the developable surface, the projections are classified as cylindrical, conical and zenithal projections.
- Based on their global features, projections are divided into equal area, orthomorphic, azimuthal, and equidistant categories.
- Depending on where the light source is located, projections can be categorised as gnomonic, stereographic, or orthographic.
The four main general features that must be retained in a map are area, form, direction, and distance accuracy. However, none of the projections can hold onto all three characteristics at once. Therefore, a projection can be drawn according to a specific need to retain the desired quality.
(ii) Which map projection is very useful for navigational purposes? Explain the properties and limitations of this projection.
Answer. Mercator’s Projection is very useful for navigational purposes. A Dutch cartographer Mercator Gerardus Karmer developed this projection in 1569. The projection is based on mathematical formulae.
Properties are as follow:
- All parallels and meridians are straight lines and they intersect each other at right angles.
- All parallels have the same length which is equal to the length of equator.
- All meridians have the same length and equal spacing. But they are longer than the corresponding meridian on the globe.
- Spacing between parallels increases towards the pole.
- Scale along the equator is correct as it is equal to the length of the equator on the globe; but other parallels are longer than the corresponding parallel on the globe.
- Shape of the area is maintained, but at the higher latitudes distortion takes place.
- The shape of small countries near the equator is truly preserved while it increases towards poles.
- It is an azimuthal projection.
- This is an orthomorphic projection as scale along the meridian is equal to the scale along the parallel.
Limitations:
- There is greater scale exaggeration along the parallels and meridians in high latitudes. As a result, the size of the countries near the pole is highly exaggerated.
- Poles in this projection cannot be shown as 90° parallel, and the meridian touching them are infinite.
(iii) Discuss the main properties of conical projection with one standard parallel and describe its major limitations.
Answer. A conical projection is one, which 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 i.e., standard parallel.
Properties:
- All the parallels are arcs of concentric circle and are equally spaced.
- All meridian lines are parallel and converge at the pole. The parallels and meridians intersect the parallel at right angle.
- The scale is accurate along all meridians i.e., distance along the meridians are accurate.
- The pole is represented as an arc of a circle.
- The scale is accurate along the normal parallel but distorted away from it.
- Meridians become closer to each other towards the pole.
- This projection is neither orthomorphic nor has an equal area.
Limitations:
- It is not suitable for a world map due to extreme distortions in the hemisphere opposite the one in which the standard parallel is selected.
- Even within the hemisphere, it is not suitable for representing larger areas as the distortion along the pole and near the equator is larger.
