||The U.S. Environmental Protection Agency (EPA) has long employed data of spatial orientation in pursuit of its mission to understand and protect the environment. For years, these data were applied in standard cartographic presentation techniques, either via hand drawn or digital transposition from a source map. In either case, the map developer or analyst had the ability during this transposition to apply decision rules of logical consistency to make the map 'right,' shift, and offset map elements so that their relationships to each other did not violate inherent rules of consistency (e.g., streets did not cross buildings; city boundaries followed the delimiting streets). These adjustments and the inaccuracies introduced in the transposition process may or may not be considered viable, depending upon whether these adjustments and errors exceeded traditional map accuracy standards. Regardless of the acceptability of these errors, they are virtually undetectable to the decision maker or technical analyst, who is presented with a map product. The nature of these errors in hard copy maps is attributable to the medium itself, which is not amenable to overlay and comparison analysis. More often than not, mapped data are presented in its own singular context, with few other types of spatially-correlated data simultaneously presented. However, with the advent of Geographic Information Systems (GIS), digital spatial data sets are generated and stored independently and then combined in analysis, making differences in resolution and accuracy of spatial data visually detectable. Although each separate data set may not violate its own accuracy standard, the use of these differing maps may produce a composite map that is perceived to be flawed. Recognizable inconsistencies may or may not detract from the accuracy of the spatial analysis of interest, depending upon the nature of the analysis. At a minimum, they possibly detract from the credibility of the analysis product.