The geographic features are graphically represented by symbols. Symbols have characteristics that can be varied in order to emphasize the differences, hierarchy, or importance of the features on a map.
The graphic characteristics or visual variables are referring to symbol size, color value (gray tone), hue (color), texture (pattern), orientation, and shape. These variables are applied individually or in combination to point, line, and area symbols depending on the type of data to be represented on a map.
For qualitative data, you can vary the following symbol characteristics: hue (color), texture, orientation, and shape.
For quantitative data, you can vary the following two symbol characteristics: size and color value (gray tone).