The land is always bought and sold on the basis of cost per unit area. For road and railways land is to be acquired on the basis of area. In the design of bridges and bunds catchment area of river and nalla are required. Thus finding areas is the essential part of surveying. It may be noted that area to be found is the projected area. Units used for finding areas are square metres, hectare and square kilometre. Relation among them are
Hectare = 100 m Ã— 100 m = 1 Ã— 104 m2
Square kilometer = 1000 m Ã— 1000 m = 1 Ã— 106 m2
= 100 hectare
Similarly volume of earth work involved in projects like road, rail and canal are to be found by surveying. Capacity of reservoir also need volume calculations. In this chapter calculation of areas and volumes based on surveying are explained.