The design of symbols requires attention to their visual dimensions. According to Jacques Bertin (1967), the ways in which we can vary a symbol's quality are:
- Hue (color)
Some of these are easier to interpret than others. The cartographic designer makes selections on the basis of visual dimensions, and the symbol's functionality is tied to the level (or scale) of measurement of the data.
Size, value, and texture can convey quantitative differences. Shape and orientation are exclusively qualitative, and color hue (not value) tends to be qualitative as well, unless used as part of a diverging scheme (as seen previously in Chapter 5, Picking Colors with Confidence). For example, we can ...