Categorical Coefficients of Agreement for Assessing Soft-Classified Maps at Multiple Resolutions

Kristopher Kuzera and R. Gil Pontius, Jr.
Department of International Development, Community and Environment
Department of Geography
Clark University
950 Main Street, Worcester, MA 01610 USA

An important issue regarding  map comparison involves examining agreement of pixels between two categorical maps.   Information in the maps can become less precise spatially as resolutions of the maps change from fine to coarse. This paper consists of two major components addressing this issue.  First, cross-tabulation matrices are produced  for multiple resolutions  using hard classification and  three different soft pixel classification operators: Multiplication, Minimum, and Composite. Second, the cross- tabulation matrices are analyzed through various statistical measures to produce the following categorical coefficients of agreement: user’s accuracy, producer’s accuracy, conditional kappa by row,  and conditional kappa by column.  These statistical measures are  graphed to demonstrate their behavior over multiple resolutions.  Land-cover maps of the same subject area for two different years are compared to illustrate the analysis.  The area examined is a  part of Worcester County, Massachusetts which has experienced about 10% change in land cover between 1971 and 1999.  The results from the analysis show that over multiple resolutions, the  Hard operator behaves chaotically, the Multiplication operator decreases agreement, the Minimum operator  is difficult to interpret, while the Composite operator offers increasing agreement, is interpretable, and is recommended for a multiple resolution analysis.  

Keywords: categorical coefficients of agreement, multiple resolutions, soft-classified maps

In: McRoberts, R. et al. (eds).  Proceedings of the joint meeting of The 6th International Symposium On Spatial Accuracy Assessment In Natural Resources and Environmental Sciences and The 15th Annual Conference of The International Environmetrics Society, June 28 – July 1 2004, Portland, Maine, USA.

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