Objective and Subjective Comparison in Choroplethic Mapping

Abstract

Visual map comparison can supplement statistical analysis by providing information as to where and how spatial correspondence occurs. The associations that may be discovered are influenced by the nature of the map features being compared and the criteria used for making the comparisons. In this paper the author has tried to identify the elements of visual recognition that map readers use to associate or differentiate geographical distributions represented by choropleth maps. The main components of the multivariate map reading process are pointed out, including the perceptual interactions between the actual locations of map tones and the overall similarity between map patterns.