Introduction to Surveying

Levelling is the process of determining the height of points above or below a fixed reference point (benchmark).

Common instruments used include the dumpy level and levelling staff. 

Types of levelling include differential levelling and fly levelling.

It's used to create level surface, design roads or check slopes.

Contouring involves connecting points of equal elevation to form contour lines on map. These lines show the shape and height of landforms like hills and valleys.

Contour lines close together indicate steep slopes while widely spaced lines shows gentle slopes. 

Contour helps in planning drainage, roads and irrigation systems.

Purpose:

These methods are essential for planning, designing and constructing infrastructure accurately and safely.