Defination- The art of determining the relative positions of objects on the surface of the earth by taking measurements in the horizontal and vertical plane is called surveying.
Types of surveying:-
1) Plane surveying- The surveys in which the curvature of earth is not taken into consideration are known as plane surveys. These surveys extend over small areas. The degree of accuracy obtained in this type of surveying is comparatively low. Generally areas less than 250 km square are treated as plane.
2) Geodetic surveying- the surveys in which the curvature of earth is taken into consideration are known as Geodetic surveying ( also called trigonometrical surveying). These surveys extend over large areas ( more than 250 km square) and where the degree of accuracy required is great.
Classification of surveys:-
1) According to the instrument used- a) chain survey b) compass survey c) plane table survey d) theodolite Survey.
2) According to the purpose of survey- a) mine survey b) geological survey c) archaeological survey d) military survey
3) According to the method employed- a) triangulation survey b) traverse survey
4) According to the place of work- a) land survey b) hydrographical or marine survey c) aerial survey.
Land survey further subdivided into the following classes:-
A) Topographical survey – it is carried out for determining the natural features of the country such as hills, valleys, rivers, lakes and nallahs etc.
B) cadastral survey- this survey is performed to determine the additional details such as boundaries of fields, houses and other property.
C) city survey- this survey is performed in connection with town planning schemes such as drainage, water supply and for laying out plots ,roads ,streets etc.
D) engineering survey- this survey is performed for determining and for collecting data for the design of engineering works such as roads ,railways , reservoirs or works in connection with water supply sewerage etc.
Engineering survey further subdivided into the following classes:-
1) Reconnaissance survey-determining the feasibility and rough cost of scheme.
2) preliminary survey- collecting more precise data to choose the best location for the work.
3) location survey-setting out the work on the ground.
Principles of surveying:-
1) to work from whole to the part-the working from whole to the part is done in surveying in order to ensure that errors and mistakes of one portion do not effect the remaining portion.
2) to fix the positions of new stations by at least two independent processes- the new stations are fixed from points already fixed by linear measurements, angular measurements or by both linear and angular measurements.