what is contouring?

A contour is defined as an imaginary line of constant elevation on the ground surface. It can also be defined as the line of intersection of a level surface with the ground surface. For example, the line of intersection of the water surface of a still lake or pond with the surrounding ground represents a contour line.                                                                                                  
It facilitates depiction of the relief of terrain in a two dimensional plan or map.

The process of tracing contour lines on the surface of earth is called contouring. A contour map gives the idea of the altitudes of the surface features as well as their relative positions in a plan

CONTOURING BY INDIRECT METHOD:

The points surveyed are not necessarily on the contour lines but spot levels taken along with series of lines laid over the area. The position of spot levels is plotted on the plan and contours drawn by interpolation.

BY SQUARES:
In this method the whole area is divided into a number of squares. The size of the side depends upon the nature of the ground and contour interval.
The important points within the squares may be taken when needed. The squares are plotted and R.Ls of corners written on the plan. The contour lines are then plotted.