What is SURVEYING and LEVELLING ?

SURVEYING and LEVELLING

Surveying is a science and also the art of determining the relative positions of points on, above or beneath the surface of the earth, it means the measurement of distance, direction and elevation either directly or indirectly. It is essentially a process of determining the positions of points in a horizontal plane.

Surveying includes levelling, in which it is possible to find the elevations or levels or height of the points with respect to a given or assumed datum(information).

Levelling is essentially a process of determining the positions of points in a vertical plane.

 The scope of surveying and levelling are:

1) To determine the dimensions and outline of any part of the earth's surface.

2) To prepare the plan or map. The results of the surveys when plotted and drawn on paper will constitute a plan.

3) To measure the area and volume of land.

4) To select a suitable site for an engineering project.

5) To establish boundaries of land.

6) To provide a modern method of surveying for building and construction, transportation, communication, mapping and decide the boundary for land ownership.

7) conduct engineering survey, topographic survey, military survey, mine survey, geological survey, archaeological survey, photogrammetric survey, hydrographic survey, aerials survey, astronomical survey, environmental survey, global positioning survey (GPS) geodetic survey etc.

9) The advent of Electronic devices has made easier the method or surveying even of inaccessible.

The knowledge of surveying is essential in many phases.

For every engineering project such as buildings, roadways, railways, tramways, transmission line, dams, bridges, tunnels harbours, mines, water supply and sanitation, pipeline laying, airports, etc.

Surveying is of two types.

a) Geodetic survey: The survey in which the shape or curvature of the earth is taken into the account is called Geodetic Survey.

b) Plane Survey: The survey in which the shape or curvature of the earth is not taken into account is called Plane Survey.

Difference between Geodetic surveying and Plane Surveying

Geodetic Surveying

The surface of earth is considered spherical.

The line formed by joining two points is regarded as an arch, since the same angles are spherical angles

 Large area surveying is possible.

Survey accuracy is high.

Special instrument needed and long survey method.

Plane Surveying

 Earth surface is assumed as plain

  A line formed by any two points is considered as a straight line – as the same angles are plain angles.

Only small area surveying is possible.

Survey accuracy is low.

Economic and easy survey method.