Give an account of six basic types of graphic variables.

The following six basic types of graphic variables are popular:

(i) Size of Typology: Differences in size of the symbols and lines showing the spatial distribution pattern of a phenomenon without much clustering. The dots of different sizes represent different quality of an element.

(ii) Lightness or (grey) value: In this process the distribution of an element is shown by the variation in the intensity of grey colour. The lighter shades show lower densities and deeper or darker shades show higher densities.

(iii) Grain or Texture: The distribution of an element is shown by different shades to represent varying intensity or density. In this method black and white colours are mostly used.

(iv) Colour Hue: Hue refers to various colours we perceive: red, green, blue and combinations. This method makes use of different colours to make the distribution of various features distinct on map.

(v) Orientation: Difference in orientation refers to patterns and not to the line elements that form the base map.

(vi) Shape: Differences in shape can refer differences in the points, lines, and area patterns used as symbols. The various symbols are included for identifying shape differences.