A Methodological Study for Accuracy Assessment of GAP Land Cover Maps

Abstract

<p>Quantifying the accuracy of a GAP land cover map involves comparing the thematic content of the digital map with corresponding thematic reference data (i.e., some form of “truth”) obtained from the field. Typically, assessment locations are selected from the target area, and reference data are gathered from field visits or photo-interpretation (Congalton 1991). Methods of selecting assessment locations vary widely from purposive sampling, in which areas are intentionally selected for observation without applying a randomization mechanism, to selecting statistical samples from the entire target area or from some portion of the target area (e.g., roadsides). Sampling units may be areas (polygons) or points on the land. To analyze assessment data, a number of accuracy measures are available to compare the reference data and land cover maps (Stehman 1997). The choice of accuracy assessment methodologies is influenced by scientific, statistical, and operational concerns.</p>