Thematic Accuracy of Agriculture in Land Cover Layers of Select Virginia Counties

Abstract

<small>NLCD</small> and <small>NASS CDL</small> are freely available moderate resolution land cover datasets, but their accuracies vary widely and are untested for agricultural land in Virginia. We performed validation through aerial photointerpretation of agriculture at the field level, using cadastral parcels as proxies for fields, over Albemarle, Charles City, Chesterfield, and Henrico Counties for <small>NLCD</small> 1992, 2001, 2006 and <small>CDL</small> 2002, 2008, 2009, 2010, and 2011. The extent of agricultural land remained generally stable over 19 years but is generally overestimated by the datasets in all four counties, ranging from 70.06 percent to 697.48 percent of validation layer extent. Extent of agricultural land in our validation layer also differed from the Census of Agriculture, likely due to differing definition. Comparison of layer pairs on extent of agricultural land mostly reveals classification artifacts rather than change. The limited extent of agriculture and mixed land cover characteristics of the region suggest the use of multitemporal data to extract agricultural land cover.