Surveying is the art of determining the relative positions of points on, below or above the surface of the earth by means of direct or indirect measurements of distance, direction and elevation. It is the art of locating points by angular and linear measurements.

The application of surveying requires skill and knowledge of mathematics, physics and some basics of astronomy.

Levelling is the branch of surveying in which the objective is

The application of surveying requires skill and knowledge of mathematics, physics and some basics of astronomy.

Levelling is the branch of surveying in which the objective is

- To find the elevations of points with respect to a assumed datum

- To establish points at a given elevation or at different elevations with respect to a given or assumed datum.

The knowledge of surveying is useful in many fields of civil engineering. Earlier surveys were made in connection with land surveying. Every engineering project such as water supply, bridges and buildings etc. require surveys. Before plans and estimates are prepared, boundaries should be determined and the topography of the site should be created. After the plans are made, the structures must be built on the ground.

The objective of surveying is to prepare a horizontal map of site.

SURVEYING IS DIVIDED INTO 2 PARTS:

The objective of surveying is to prepare a horizontal map of site.

SURVEYING IS DIVIDED INTO 2 PARTS:

__In plane surveying the mean surface of the earth is considered as a plane and the spheroidal shape is neglected. Triangles formed by survey lines are considered as plane triangles. Level line is considered as straight and plumb lines are considered as parallel. Basically, when small area or small piece of land is to be surveyed, curvature of the earth’s surface is neglected. When curvature of earth is neglected and field is surveyed, it is called Plane surveying.__

**PLANE SURVEYING:****In geodetic surveying the curved shape of the earth is taken in to consideration. All lines lying in the surface are curved lines and the triangles are spherical triangles. Spherical trigonometry is used in geodetic surveying. Geodetic surveying requires highly skilled labour and complete knowledge of surveying as it includes work with larger magnitude and high degree of accuracy and precision. The main purpose of geodetic survey is to determine the precise and accurate position on the surface of the earth, of a system of widely distant points which form control stations in which surveys of less precision may be referred.**

__GEODETIC SURVEYING:__PRINCIPLES OF SURVEYING.

LINEAR MEASUREMENTS IN SURVEYING.