Data layers for cost-distance analyses on the Virginia Coast Reserve, 2005

Cost-distance analysis is a means of incorporating the influence of landscape heterogeneity on potential animal movements. It requires that the landscape be characterized in a meaningful way with respect to movements, that appropriate landscape resistance values be assigned, and that sources be properly identified. A raster resistance surface contains the resistance value (i.e., cost of traversing) for each raster cell. Resistance may also be referred to as friction or impedance. Resistance may be estimated based on expert opinion or physiological energy expenditure, or it may be inferred from occurrence, observed movements, or genetic relatedness. To create a resistance surface, we started with the NOAA C-CAP land-cover data layers for the lower Delmarva Peninsula (Virginia and Maryland) for the year 2005. We simplified the classification from 23 cover classes to 3 classes: upland, salt marsh, and water, with resistance values of 1, 2 and 4 respectively. The layer had 30-m pixel resolution, and classification accuracies >90% for water and salt marshes (layer metadata).