In general, the minimum mapping unit for polygon features is from 1 to 3 acres depending on the wetland type and the scale and emulsion of the source aerial photography. In regions of the country where evergreen forested wetlands predominate, wetlands smaller than 3 acres may not be mapped. 7.5 minute quadrangles along the Minnesota border with the exception of Wisconsin contain data from adjacent states. Horizontal Positional Accuracy Horizontal positional accuracy for the digital data is tested by visual comparison of the source with hard copy plots. Enhanced digital data is also snapped to existing quadrangle boundaries and is compared to adjacent files.
Files contain ground planimetric coordinates and wetland attributes.
The determination of scanning versus manual digitizing production method was based on feature density, source map quality, feature symbology, and availability of production systems. The data were checked for position by comparing plots of the digital data to the source material. DLG data was downloaded from NWI ftp server for all of Minnesota. Wetland codes for each 7.5 minute quadrangle were loaded into a statewide NWI code list from which a unique code number was assigned for each wetland type. These data were changed into the correct upper and lower case codes.