Principles of Surveying

Surveying


Definition of Surveying:

Surveying is the art of determining the relative positions of points on, above or beneath the surface of the earth by means of direct or indirect measurement of distance, direction and elevation.

  • Surveying also includes the art of establishing points by predetermined angular and linear measurements.
  • The object of surveying is to prepare plan or map so that it represent the area on a horizontal plane.
  • Surveying differs from leveling in following ways:
Leveling is a branch of surveying the object of which is:

1. To find the the elevation of points with respect to a given or assumed datum.
2. To establish points at a given or different elevations with respect to the datum.
  • Leveling deals with measurement in vertical plane.

  • In surveying, all measurement of lengths are horizontal or reduced to horizontal distances.


Division of Surveying:

Broadly, Surveying can be divided into two classes:

1. Plane surveying:

Plane surveying is that type of surveying in which the mean surface of the earth is considered as a plane and the spheroidal shape is neglected.

2. Geodetic Surveying: 

The type of surveying in which the spheroid shape of the earth is taken into consideration.

Principles of surveying:

The fundamental principles upon which the various method of surveying are based can be stated under following two aspects-

1. Location of a Point by measurement from two points of reference:

The relative position of the points to be surveyed should be located by measurement of at least two points of reference, the position of which have already been fixed.

2.  Working from whole to part:


The second ruling principle of surveying is to work from whole to part. It is very essential to establish first a system of control points and to fix them with higher precision. Minor control points can be established by less precise methods and details can be located using these minor control points.


The idea of working in this way is to prevent the accumulation of errors and to control and localise minor errors which, otherwise, expand to greater magnitude if the reverse process is followed.