Since, the Surveyed area is very large,it is never possible to make full size Drawing for make full size Drawing for convenience it is generally necessary to draw them to a reduced size, this operation is called "Drawing to Scale".
There are two types of scale used in surveying,
A. Numerical Scale
B. Graphical Scale
A. NUMERICAL SCALE:-
Numerical Scale is also further classified in to two general types,
i. Engineers Scale
ii. Fraction Scale
i. Engineers Scale:-
In an Engineers Scale of a map or drawing is the proportion which every distance on the map or drawing bears to the corresponding distance on the ground.
Ex. 1 cm = 10 m
This means, 1 cm on the drawing represents 10 m on the ground, the scale of the map is 10 m to 1 cm.
ii. Fraction Scale:-
The scale is also expressed by means of a vulgar fraction whose numerator is in variable unity. The fraction is called 'Representative Fraction' or R.F. it is therefore. the ratio of map distance to the corresponding ground distance in forming the representative fraction both numerator and denominator must be reduced to same denomination.
Ex. If the scale is 10 m to 1 cm
the R.F. of the scale is 1 cm / 10 X 100 cm
= 1/1000.
B. GRAPHICAL SCALE:-
On a Graphical Scale, the unit's of measurement should always be stated.
Characteristics of a good scale,
1. It should read to the greatest accuracy required.
2. It should be convenient to use.
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