National Center for Geographic Information and Analysis

This report summarizes research into the nature and sources of errors that occur in medium to small scale vegetation maps such as those used for statewide forestry and conservation planning. The objective of this research was to develop a coherent approach and specific methods for quantifying such errors by jointly analyzing ground observations and multiscale map data using Geographic Information Systems (GIS) operations. Section I of the report provides an overview of statistical approaches to assessing cartographic errors, including uncertainty in points, lines, irregular polygons and classified digital imagery. Section 2 describes an error analysis of the CALVEG map of vegetation in California. The report concludes with a series of recommendations to CDF concerning changes in map accuracy assessment procedures. These recommendations pertain to data collection, sampling design, and methods for representing uncertainty in map products.