CHAPTER 4 : Map Projections NCERT SOLUTION CLASS 11TH PRACTICAL WORK IN GEOGRAPHY | EDUGROWN NOTES

Short Answer Type Questions:

Q1.How are conical projections drawn?
Answer:
A Conical projection is drawn by wrapping a cone round the globe and the shadow of graticule network is projected
on it. When the cone is cut open, a projection is obtained on a flat sheet. 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 called the standard parallel. As the cone touches the globe located along AB, the position of this parallel on the globe coinciding with that on the cone is taken as the standard parallel. The length of other parallels on either side of this parallel are distorted.

Q2.What is map projection?
Answer:
It is the system of transformation of the spherical surface onto a plane | surface. It is carried out by an orderly
and systematic representation of the parallels of latitude and the meridians of longitude of the spherical earth or part of it on a plane surface on a conveniently chosen scale. 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.

Q3.What are the qualities and limitations of a globe?
Answer:
Qualities of globe can be expressed as follows:

• A globe is the best model of the earth. Due to this property of the globe, the shape and sizes of the continents and oceans are accurately shown on it.
• It shows the directions and distances very accurately.
• The globe is divided into various segments by the lines of latitude and longitude.

Limitations:

• It is expensive.
• It can neither be carried everywhere easily nor can a minor detail be shown on it.
• Besides, on the globe the meridians are semi-circles and the parallels are circles. When they are transferred on a plane surface, they become intersecting straight lines or curved lines.

Q4.Classify the projections on the basis of method of construction.
Answer:
On the basis of method of construction, projections are generally classified into perspective, non-perspective and conventional or mathematical.

• Perspective projections: These can be drawn taking the help of a source of light by projecting the image of a network of parallels and meridians of a globe on developable surface.
• Non-perspective projections: These are developed without the help of a source of light or casting shadow on surfaces, which can be flattened.
• Mathematical or conventional projections: These are those, which are derived by mathematical computation and formulae and have little relations with the projected image.

Q5.Classify projections on the basis of global properties.
Answer:
On the basis of global properties, projections are classified into:

• Equal Area Projection
• Orthomorphic Projection,
• Azimuthal Projection and
• Equidistant Projections.
  • Equal Area Projection: It is also called homolographic projection. It is that projection in which areas of various parts of the earth are represented correctly.
  • Orthomorphic or True-Shape projection: It is one in which shapes of various areas are portrayed correctly. The shape is generally maintained at the cost of the correctness of area.
  • Azimuthal or True-Bearing projection: It is one on which the direction of all points from the centre is correctly represented.
  • Equidistant or True Scale projection: It is that where the distance or scale is correctly maintained.
• However, there is no such projection, which maintains the scale correctly throughout. It can be maintained correctly only along some selected parallels and meridians as per the requirement.

Q6.Write a short note on developable surface and zenithal projections.
Answer:
A developable surface is one, which can be flattened, and on which, a network of latitude and longitude can be projected. A cylinder, a cone and a plane have the property of developable surface. On the basis of nature of developable surface, the projections are classified as cylindrical, conical and zenithal projections.

1. Cylindrical Projections: These are made through the use of cylindrical developable surface. A paper-made cylinder covers the globe, and the parallels and meridians are projected on it.

2. Zenithal projection: It is directly obtained on a plane surface when plane touches the globe at a point and the graticule is projected on it. Generally, the plane is so placed on the globe that it touches the globe at one of the poles. These projections are further subdivided into normal, oblique or polar as per the position of the plane touching the globe.

• Normal Projection: If the developable surface touches the globe at the equator, it is called equatorial or normal projection.
• Oblique Projection: If it is tangential to a point between the pole and the equator, it is called the oblique projection;
• Polar Projection: If it is tangential to the pole, it is called the polar projection.

Q7.What is the need of map projection?
Answer:
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. It gives birth to a problem. 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.

Map projection helps to solve this problem. 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.

Long Answer Type Questions:

Q1.Explain the qualities of Mercator 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:

• It is an orthomorphic projection in which the correct shape is maintained.
• The distance between parallels increases towards the pole.
• Like cylindrical projection, the parallels and meridians intersect each other at right angle. It has the characteristics of showing correct directions.
• A straight line joining any two points on this projection gives a constant bearing, which is called a Laxodrome or Rhumb line.
• 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; hence the scale is not correct along them.
• 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.

Q2.Explain properties, limitations and uses of cylindrical equal area projection.
Answer:
The cylindrical equal area projection is also known as the Lambert’s projection. It 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.

Properties

• All parallels and meridians are straight lines intersecting each other at right angle.
• Polar parallel is also equal to the equator.
• Scale is true only along the equator.

Limitations

• Distortion increases as we move towards the pole.
• The projection is non-orthomorphic.
• Equality of area is maintained at the cost of distortion in shape.

Uses

• The projection is most suitable for the area lying between 45° N and S latitudes.
• It is suitable to show the distribution of tropical crops like rice, tea, coffee, rubber and sugarcane.

Q3.Explain properties of Conical Projection with one Standard Parallel.
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 called the standard parallel. As the cone touches the globe located along AB, the position of this parallel on the globe coinciding with that on the cone is taken as the standard parallel.

Properties

• All the parallels are arcs of concentric circle and are equally spaced.
• All meridians are straight lines merging at the pole. The meridians intersect the parallels at right angles.
• The scale along all meridians is true.
• An arc of a circle represents the pole.
• The scale is true along the standard parallel but exaggerated away from the standard parallel.
• Meridians become closer to each other towards the pole.
• This projection is neither equal area nor orthomorphic.

Q4.Explain the limitations and uses of Conical Projection with one Standard Parallel.
Answer:
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.

Uses

• This projection is commonly used for showing areas of mid-latitudes with limited latitudinal and larger longitudinal extent.
• A long narrow strip of land running parallel to the standard parallel and having east-west stretch is correctly shown on this projection.
• Direction along standard parallel is used to show railways, roads, narrow river valleys and international boundaries.
• This projection is suitable for showing the Canadian Pacific Railways, Trans- Siberian Railways, international boundaries between USA and Canada and the Narmada Valley.

Q5.Prepare graticule for a Cylindrical Equal Area Projection for the world when R.F. is 1: 300,000,000 and the interval is 15° apart.
Answer:
Construction

• Draw a circle of 2.1 cm radius;
• Mark the angles of 15°, 30°, 45°, 60°, 75° and 90° for both, northern and southern hemispheres;
• Draw a line of 13.2 cm and divide it into 24 equal parts at a distance of 0.55cm apart.
• This line represents the equator;
• Draw a line perpendicular to the equator at the point where 0° is meeting the circumference of the circle;
• Extend all the parallels equal to the length of the equator from the perpendicular line; and Complete the projection as shown in figure given below:
  

Q6.Draw a Mercator Projection for the world map when the R.F. is 1:250,000,000 and the interval between the latitude and longitude is 15°.
Answer:
Calculation: Radius of the reduced earth R is “1 is 1: 250,000,000 Length of the equator 2πR or

1 × 227 × 2=6.28 inches

Construction

• Draw a line of 6.28″ inches representing the equator as Equation.
• Divide it into 24 equal parts. Determine the length of each division using the following formula: Length of the equator multiplied by interval divided by 360°.
• Calculate the distance for latitude with the help of the table given below:
  Latitude Distance 15° 0.25 x 1 = 0.25″ inch 30° and so on, Complete the projection as shown in Figure given below: