Correct Answer - Option 1 : Triangulation

__Concepts:__

A geodetic survey determines the precise position of permanent points on the earth's surface, taking into account the **shape, size and curvature of the earth**. .

It is done by **Triangulation.**

**Triangulation** is a surveying method that measures the angles in a triangle formed by three survey control points. Using trigonometry and the measured length of just one side, the other distances in the triangle are calculated.

**Trilateration,** method of surveying in which the lengths of the sides of a triangle are measured, usually by electronic means, and, from this information, angles are computed.

__Note:__

The triangulation and Trilateration are similar to each other but only difference is that in Trilateration all **three side of triangle are measured** and using trigonometry angles are computed but in triangulation **angles are measured** and using trigonometry side lengths are calculated.