SURVEYING

Surveying

Surveying is the art of making suitable measurements in horizontal or vertical planes. This is one of the important subjects of civil engineering. Without taking a survey of the plot where the construction is to be carried out, the work cannot begin.

Surveying Chart

Levelling

Levelling is the art of representing relative positions in the vertical plane of different points on the earth’s surface.

It helps in determining the areas that are to be levelled to achieve a certain slope.

Principles of Surveying

All the surveys that are conducted are based on two fundamental principles. They are as follows:

1. Working from whole to part
2. Fixing a point with reference to two fixed points

Working from whole to part

In order to localize errors and prevent their accumulation, a set of control points is always established with great precision first for the whole area to be surveyed.

Later on, details or filled in between these control points to a relatively smaller precision.

This fundamental work principle is known as “Working from whole to part”.

Fixing a point with reference to two fixed points

Survey stations are fixed by atleast two measurements, either both linear or angular measurements or linear and angular measurements from two control points.

Let A and B be two control points. Another point C can be located by any of the following methods:

By two distances AC and BC

The point C is plotted by intersection of arc taking AC and BC as radius and with centres A and B.

Two Distances Method

By perpendicular distance CD and distance AD

Perpendicular distances Method

By angle <CAB and distance AC

Angle Method

By the angles BAC and ABC

Two Angles Method

By the <ABC and distance AC

Arc and Angle Method