ABSTRACT
This chapter introduces the universally accepted measure for representing thematic map accuracy: the error matrix. It explores the evolution of thematic map accuracy assessment, beginning with a discussion of early quantitative, non-site-specific assessments. The chapter presents quantitative site-specific assessment techniques employing the error matrix, followed by the mathematical representation of the error matrix. In a quantitative non-site-specific accuracy assessment, only the total areas for each class mapped are computed without regard to the location of these areas. The significant issue with a non-site-specific assessment is that nothing is known about any specific locations on the map or how it agrees or disagrees spatially with the reference data. Given the obvious limitations of a non-site-specific accuracy assessment, there is a need to know how the map generated from the remotely sensed data compares with the reference data spatially. The use of site-specific assessments was instituted. Initially, a single value representing the accuracy of the entire classification was employed.
