Geodetic Surveying

The art of surveying the earth surface taking into consideration its shape and size is called geodetic surveying. To find 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 normally geodetic surveying is used. The survey is suited for large areas and long lines and is used to find the precise location of basic points and it helps to set up control for other surveys. Long distance stations are used in this survey and more accurate and specific tools and surveying methods are required for this type of surveying. The shape of the earth is considered as spheroid.  In  the  calculation  of  distances  in  geodetic surveys,  allowance  are  made  for  the  earth’s minor and major diameters from which a spheroid of  reference  is  developed.  The position of each geodetic station is related to this spheroid. The methods involved in geodetic surveying are Triangulation & Precise Traverse.

Precise Traverse

Precise Traverse is a method of shaping the relative positions of points on the earth’s surface in order to construct a geodetic control network for purposes like topographic surveys, the planning and building of cities, and the planning of engineering structures. In this method the spots of the points in a given coordinate system are resolute using dimension of the lengths of the lines that successively connect the points and by measurement of horizontal angles between the lines ; and these particular series of lines is called a traverse. Theodolite and transits are used to measure traverse angles; the objects of observation are usually special marks set up and they are mounted at the stations being sighted. Steel or invar tapes or wires are used to measure the length of traverse legs and nets. Suitable corrections are made in the length and angle measurements so that accurate measurement can be obtained in coordinate system  and it is required that the locations of the traverse stations  should be stanched.

Triangulation

Triangulation is based on the trigonometry proposition that one side and three angles can be computed by applying particular rules. In this method suitable points called triangulation stations are selected and established throughout the area to be surveyed. The geometric figures used in triangulation are Triangles, Quadrilaterals, Pentagons and hexagons with centre angle. This arrangement is simple and economical. Triangulation system can be classified according to degree of accuracy required and magnitude of work.

Questions:

• What is meant by Geodetic Surveying?
• What are the different methods involved in Geodetic Surveying?