The
two fundamental principles of surveying are:
- Location of a point by measurement from two reference points
- Working from whole to part
Location of a point by measurement from two reference points
The
relative position of a point to be surveyed is located by measurement from at
least two reference points whose positions are already fixed.
Let
A and B are the reference points on the ground.
The
distance AB is measured and positions are plotted on a sheet to some scale.
Thus,
these reference points A and B are used for fixing the relative positions of
the other points.
Let the other point be C, which can be located
by different direct methods.
· Method
1: The distance AC and BC are measured and point C is plotted by swinging the
two arcs.
This
method is commonly employed in chain surveying.
Method
2: The perpendicular CD is fixed on the reference line AB and lengths AD and DC are measured.
The
point C is plotted using set square.
· Method
3: The distance BC and ABC can be measured and point C is plotted using a protractor or trigonometrically. This principle
is used in traversing.
· Method
4: The angle BAC and CBA are measured using angle measuring instrument.
Knowing
the distance AB, point C is plotted by protractor or by the trigonometric equation. This principle is used
in triangulation.
· Method
5: Angle CBA and AC are measured and point C is plotted using a protractor or swing an arc from A or trigonometric equation. This principle is
used in traversing.
Working from Whole to Part
According
to this principle, the required survey work is carried out from whole to part.
In
the required area to be surveyed, the first system of control points is established with high precision.
Minor
control points are then established with less precision.
With
the help of minor control points, the details of the area surveyed and
calculated.
This
principle helps in preventing accumulation of errors.
If
this principle is not followed will result in accumulation of errors of greater
magnitude.
Which
finally result in making work uncontrollable.
These
are principles of surveying.
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