(i) Map Projections may be classified on the following bases:
a. Drawing Techniques: On the basis of method of construction, projections are classified as follows:
(ii) Mercator’s Projection is an orthomorphic projection in which the correct shape is maintained. It has the characteristics of showing correct directions. Therefore, it is very useful for navigation purposes showing sea routes and air routes.
Properties
Limitations
(iii) A conical projection with one standard parallel 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.
Properties
Limitations
(i)
Homolographic projection |
Orthographic projection |
It is an Equal Area Projection. |
It is True-Shape projection. |
Areas of various parts of the earth are represented correctly. |
Shapes of various areas are portrayed correctly and maintained at the cost of the correctness of area. |
(ii)
Homolographic projection |
Orthographic projection |
It is an Equal Area Projection. |
It is True-Shape projection. |
Areas of various parts of the earth are represented correctly. |
Shapes of various areas are portrayed correctly and maintained at the cost of the correctness of area. |
(iii)
Normal projections |
Oblique projections |
In the normal projection, the developable surface touches the globe at the equator. |
In the oblique projection, the developable surface touches tangential to a point between the pole and the equator. |
(iv)
Parallels of Latitude |
Meridians of Longitude |
They are demarcated as 0º to 90º North and South latitudes. |
There is no central meridian |
Each parallel lies wholly in its plane which is at right angle to the axis of the earth. |
Each meridian lies wholly in its plane, but all intersect at right angle along the axis of the globe. |
These are the circles running round the globe parallel to the equator. |
These are semi-circles drawn in northsouth direction from one pole to the other. |
They are not of equal length. |
They are of equal length. |
(i) Reduced earth, parallels of latitude, meridians of latitude and gross property are four elements of map projections.
(ii) The correctness of area, shape, direction and distances are the four major global properties.
(iii) In preparing a map projection the distance between any given points of a region; shape of the region; size or area of the region in accuracy; and direction of any one point of the region bearing to another point are to be preserved by using one or the other methods of projections. But none of the projections can maintain all these properties simultaneously. Therefore, not a single map projection represents the globe truly.
(iv) The cylindrical equal area projection 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.
(i) (c) Conical
(ii) (c) Mercator
(iii) (b) Mercator
(iv) (c) Gnomonic
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