Quantification error versus location error in comparison of categorical maps

Abstract

This paper analyzes quantification error versus location error in a comparison between two cellular maps that show a categorical variable. Quantification error occurs when the quantity of cells of a particular category in one map is different from the quantity of cells of that category in the other map. Location error occurs when the location of a category in one map is different from the location of that category in the other map. The standard Kappa index of agreement is usually not appropriate for map comparison. This paper offers alternative statistics: (1) proportion correct with perfect ability to specify location, (2) proportion correct with perfect ability to specify quantity, (3) Kappa for no ability, (4) Kappa for location, and (5) Kappa for quantity. These statistics can help scientists improve classification. This paper applies these theoretical concepts to the validation of a land-use change model for the Ipswich Watershed in Massachusetts.