Surveying is the art of determining relative positions of objects on the surface of earth or above or beneath the surface earth by means of measurement in the horizontal and vertical plane.

The primary object of any survey is the preparation of plan or map.A plan may be defined as the projection of a ground and the features in it on a horizontal plane,Thus plan is the representation of an area and objects in it to some scale.If the selected area is very large and the scale adopted is very small then it is known as map.

Primary divisions of surveying:Surveying may be divided into two general classes (1) plane surveying and (2) geodetis surveying.

Plane surveying: Plane surveying is the type of surveying in which mean surface of earth is considered as plane and curvature of the earth is neglected,as the survey extend over small area.Surveys covering an area of 20KM^2 may be considered any two points on the earth surface are considered as straight line and angles between this lines as plane angle. Plane survey is used for layout of canals,highways,railways,construction of bridges,dams.buildings,etc

Geodetic surveying: Geodetic surveying is also called trigonometric surveying. In this survey it is necessary to take into account curvature of the earth. Geodetis survey used when survey extend over large area or accuracy of work required is great. I nthis survey,line connecting any two points on the earth surface is curved or considered as an arc of a great circle.