Plotting Detail: Offset Scale.
Scale: It is not always possible
to represent the actual length of an object on a drawing. So, it is required to
reduce the object in order to accommodate it on the drawing, in some portion.
The ratio by which the actual length of the object is reduced or increased is
known as the ‘scale’.
Full-Size Scale- If the
actual length of the objects is shown on the drawing, the scale used is said to
be a full-size scale.
Reducing Scale - If the
actual length of the objects is reduced in order to accommodate it in the
drawing sheet, the scale used is said to be a reducing scale.
Increasing or Enlarging
Scale - If the actual length of the objects is enlarged so as to bring out
its details more clearly on the drawing, the scale used is said to be an enlarging
scale.
Representative Fraction (RF): The ratio of the distance on the drawing to the corresponding actual
length of object is known as the representative fraction, i.e.
Distance on the
drawing of object
RF = ---------------------------------------Corresponding actual distance of object
RF = ---------------------------------------Corresponding actual distance of object
(Both distance in same unit.)
Conversional Symbols
In a map the objects are shown by symbols and not by name. so the surveyor
should know the following standard conventional for some common objects.
(Next post on “Procedure of plotting”)
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