The importance of visual contrast for graduated circles

Abstract

There is widespread acceptance in thematic cartography of the importance of visual contrast in establishing a strong figure-ground relationship. For maps employing graduated circles this visual contrast may be produced in two basic ways. Firstly, the circles may be separated from their background by eliminating all underlying detail, thus making them opaque. Secondly, this separation can be accentuated by adding a colour fill to the circles.

Two experiments were undertaken with monochromatic materials. In the first, the subjects exhibited a nearly unanimous preference for a contrasting colour fill, but were equally divided in their preference for opaque symbols (emphasising simplicity) and transparent symbols (providing more precise locational detail). In the second experiment, maximum variation in circle colour fill was shown to have no significant impact on relative size judgment.