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Geodetic Surveying

by Aakash Singha

The art of Surveying the earth surface considering its shape and size is called Geodetic Surveying . Geodetic Surveying is suitable for finding out the area of any region on the earth surface, the length and directions of the border lines, contour lines and location of basic points.

 

It is assumed that the shape of earth is spheroid. The convention held by the International Geodetic and Geophysical Union in 1924 assumed 41, 852, 960 ft as the earth’s diameter at the equator and at the poles the diameter is 41, 711, 940 ft. Computation of the equatorial diameter was based on the fact that due to gravitational attraction the earth was flattened exactly by 1/297. Thus, measurement of distances are taken along curved surfaces and not along straight lines. Therefore for Geodetic Surveying , earth’s both the diameters are considered. The latitudes and longitudes are determined considering the spheroidical shape of the earth. The points which are used to find out the shape , size and coordinates of the earth surface is called Geodetic Datum in Geodetic Surveying . Hundreds of such points are marked for carrying out Geodetic Survey .

 

Geodetic Surveying : Finding exact location of an object

  • Triangulation: As the name indicates, a triangle is incorporated to find out the location of the point in respect of latitude and longitude. The measurements of the sides of the triangle and the angles in the triangle which is drawn with respect to the particular point is found out. With the help of these measurements, longitude and latitude of the triangulation point is calculated.
  • Bench mark: In Geodetic Surveying , benchmarks are also used for determining the height or elevation of a point. The surveyor gives a permanent mark in the area which shows the benchmark for ages.
  • GPS based control station: The GPS or Global Positioning System based control station capture the radio signal given by the satellite. This signal is then processed and analyzed to find out the latitudes and logitudes of the given point.

 

Main instrument for Geodetic Surveying :

Theodolite: It is the basic surveying unit used for Geodetic Surveying . Theodolite consists of a telescope which is placed on a swivel and it can be rotated both horizontally and vertically. Triangulation point are determined by the theodolite in Geodetic Surveying . Two circles-one vertical and another horizontal, are used to read out the readings. But in the modern theodolite the reading is done electronically. Geodetic Surveying can be done by geographers, engineers and surveyors specialised in related disciplines.

Use of Geodetic Surveying :

  • Engineering purposes: The engineers uses Geodetic Surveying for finding out the exact location of the concerned point or area. Latitudes and longitudes are needed for any engineering constructions.
  • Construction purposes: The builders used Geodetic Surveying for finding out the direction of the buildings or their exact location for vaastu shastra.
  • Land Surveying and assessment: The vertical elevation and the horzontal attributes , the latitude and longitudes of the area surveyed are found out through Geodetic Surveying .

Geodetic Surveying is thus considered as an important method of Surveying.

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