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NCERT Class 11 Practical Geography Chapter 4: Map Projections | CBSE | English
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Need for map projection
Detailed regions
Compare 2 natural regions
Transfer latitude and longitude on flat paper
Distortions increase with distance from tangential point (throwing light from center)
Tracing shape, size and directions, etc. from a globe is nearly impossible because the globe is not a developable surface
Lexodrome or Rhumb Line: It is a straight line drawn on Mercator’s projection joining any two points having a constant bearing. It is very useful in determining the directions during navigation.
The Great Circle: It represents the shortest route between two points, which is often used both in air and ocean navigation.
Homolographic 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 equal-area projection.
Orthomorphic Projection: A projection in which the correct shape of a given area of the earth’s surface is preserved
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 north south 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
d. Global Property: In preparing a map projection the following basic properties of the global surface are to be preserved by using one or the other methods:
(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.
Chapters:
0:00 NCERT Class 11 Chapter 4: Practical Geography- Map Projections
0:10 Need of Projection
3:19 Latitudes and Longitudes
6:41 Preserving Distortion
7:22 Elements of Map Projection
9:05 Classification of Map Projection
17:25 Examples of Cylindrical and Conical Projections
18:36 Mercator Projection
24:48 Cylindrical Projection
29:05 Conical Projection
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