Surveying is the art to determine the relative position of object on or below the surface of the earth by measuring horizontal distance between them and prepare a map to any suitable scale.

**Classification of surveying-**

1) Primary classification –primary surveying can be divided into two type.

a) Plane surveying

b) Geodetic surveying

a) Plane surveying –

• We know that the shape of earth is spheroidal, thus the surface is obviously curve, but in a plane surveying curvature of earth is not taken into consideration.

• This is because plane surveying is carried out over a small area so the surface of earth is considered as plane.

• In a plane surveying line joining two points is consider as a plane line.

• Triangle formed by joining three points is called as plane triangle and angle of this triangle is considered as plane angle. • Plane surveying is done in an area less than $250 \ km^2$

• Plane surveying is conducted by state agencies like the irrigation department, railway department etc.

b) Geodetic survey- • In a geodetic surveying curvature of earth is taken into consideration. This is because geodetic survey carried out over large area.

• In a geodetic survey line joining two points is consider as a curve line.

• The triangle formed by joining three points is considered as a spheroidal triangle and angle of this triangle is considered as a spheroidal angle.

• Geodetic survey carried out over and area exceeding $250 \ km^2$

• Geodetic survey is conducted by survey of India department

2) Secondary surveying-

a) Based on instrument- based on instruments surveying is classified as

• Chain surveying

• Compass surveying

• Plane table surveying

• Theodolite surveying

• Tachometry surveying

• Photographic surveying

b) Based on method- based on method surveying is classified as

• Triangulation surveying

• Traverse surveying

c) Based on object- based on object surveying is classified as

• Geological surveying

• Mine surveying

• Archaeological surveying

• Military surveying

d) Based on nature of fields- based on nature of fields surveying is classified as

• Land surveying

• Marine surveying

• Astronomical surveying