PLANE SURVEYING

We know that the shape of the earth is spheroidal Thus, the surface is obviously curved . But in plane surveying, the curvature of the earth is not taken into consideration. This is because Plane Surveying is carried out over a small area. So the surface of the earth is considered as plane. Basically a triangle is formed by assuming three points and the angles are assumed to be plane angles.

In America, the limit for treating a surface is as a plane is about to 250 km2 .
NOTE : The difference between the earth and the subtended chord on the surface of the earth is only 0.1 M in 18.2 KM, 0.3 M in 54.3 KM. respectively.