map proj lesson-2 - DISTORTIONS IN MAPS DUE TO PROJECTIONS...

DISTORTIONS IN MAPS DUE TO
PROJECTIONS
Projecting Earth’s surface always involves
distortion:
shape
area
distance
direction

AVOIDING DISTORTIONS IN PROJECTIONS
1. PRESERVATION OF AREA
For some purposes it is important that areas should be represented in
correct proportions . A map which possesses this property is called Equal
Area or Equivalent.
This can be achieved if the product of the scale factors in the two
perpendicular directions at right angles remains unity.
SF ( X ) X SF ( Y ) = 1
2. PRESERVATION OF SHAPE (CONFORMALITY)
It is not possible to represent the shape of a large area of earth’s surface
correctly upon a flat map, but on a topographical map it is important to
obtain a best possible representation of shape because distances and
bearings must be measured in any direction to a reliable standard.
This can be achieved if:-
a. The scale factor along the meridians and along the parallels are
equal.
b. The meridians and parallels intersect at right angles on the
projection.
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AVOIDING DISTORTIONS IN PROJECTIONS
3. ACCURACY OF BEARING
Projections selected for the construction of charts for long range
navigation by sea or air must permit rapid and accurate plotting of
bearings . Hence the projection should be :-