(i) First of all mark heights of various points on the map. It is worth remembering that large the number of points, better will be the interpolation.

(ii) Note the points having maximum and minimum heights. The difference between maximum and minimum heights is known as range of elevation.

Kinds of Conventional Signs. These are two types :

(i) Natural signs

(ii) Cultural signs.

(i) Natural signs : These signs are used for depicting the physical features of the earth's surface such as relief, vegetation and drainage etc.

(ii) Cultural signs : These signs are meant for showing man-made things on the map, such as railways, roads and human settlement etc.

Use of Conventional Signs: It is essential for a geographer or a map reader to make himself familiar with the conventional signs. He can read almost every map easily. He can read even those maps which are in foreign languages since these symbols are universally accepted. Different colours are used for showing different objects in the conventional signs such as water is shown by blue colour, vegetation by green and man-made objects by black colour.