Map Complexity: Comparison and Measurement

Abstract

Visual complexity is defined in this paper as the degree to which the combination of map elements results in a pattern that appears to be intricate or involved. A test involving judgments of choropleth and isopleth map complexity yields three conclusions: (1) choropleth maps are consistently perceived as more complex than isopleth maps made from the same data; (2) the relationship between choropleth and isopleth maps can be closely described with a power function; and (3) the number of class intervals has a greater effect on complexity than does the pattern of the distribution mapped. A measure of complexity applicable to the isopleth map as well as choropleth can be derived, then, using the power function. Three graph theoretic measures are considered as objective measures of choropleth map complexity, with correlations of 0.92 to 0.95 obtained between these measures and subjective complexity of choropleth maps. The graph theoretic measures for choropleth maps are then adjusted according to the power relationship observed between choropleth and isopleth subjective map complexity to yield a complexity measure for the latter map type. Similar procedures might be used to derive complexity measures for other map types.