The USGS Land Cover Institute (LCI)
National Land Cover Data 1992
Derived from the early to mid-1990s Landsat Thematic Mapper satellite data, the National Land Cover Data (NLCD) is a 21-class land cover classification scheme applied consistently over the United States. The spatial resolution of the data is 30 meters and mapped in the Albers Conic Equal Area projection, NAD 83. The NLCD are provided on a state-by-state basis. The state data sets were cut out from larger "regional" data sets that are mosaics of Landsat TM scenes. At this time, all of the NLCD state files are available for free download as 8-bit binary files and some states are also available on CD-ROM as a Geo-TIFF.
The TM multi-band mosaics were processed using an unsupervised clustering algorithm. Both leaves-off and leaves-on data sets were analyzed. 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. Click here for a more detailed discussion of the mapping and classification procedures.
A hierarchical land cover classification scheme of 21 classes (a modified Anderson Land Cover Classification) was developed and applied in a consistent manner across the entire United States. The classification scheme follows:
NOTE - All Classes May NOT Be Represented in a specific state data set. The class number represents the digital value of the class in the data set (for a detailed description of each class, see any state "readme" file).