The spatial resolution of the data is 30 meters and mapped in the Albers Conic Equal Area projection, NAD 83. The TM multi-band mosaics were processed using an unsupervised clustering algorithm. The resulting clusters were then labeled using aerial photography and ground observations. Clusters that represented more than one land cover category were also identified and, using various ancillary data sets, models developed to split the confused clusters into the correct land cover categories. A hierarchical land cover classification scheme of 21 classes was developed and applied in a consistent manner across the entire United States.
More information is available at the site.
There is some overlap between the content of the data being served through the National Atlas and the Water Resources Division. This coverage contains Hydrologic Unit Boundaries and Codes for the conterminous United States. This is a polygon coverage of major land uses in the United States.