|Summary:||The NLCD includes the source images, as well as classified land-cover data for specific acquisition dates. It is the first national land-cover data set produced since the early 1970s, effectively replacing the LUDA and GIRAS data sets. Data for the conterminous United States circa 1992 (NLCD 1992) , were derived from Landsat-5 TM images and are complete.|
"NLCD 92 (National Land Cover Dataset 1992) is a 21-category land cover classification scheme that has been applied consistently over the conterminous U.S. It is based primarily on the unsupervised classification of Landsat TM (Thematic Mapper) 1992 imagery. Ancillary data sources included topography, census, agricultural statistics, soil characteristics, other land cover maps, and wetlands data. The NLCD 92 classification is provided as raster data with a spatial resolution of 30 meters."
"NLCD 2001 is being compiled across all 50 states and Puerto Rico as a cooperative mapping effort of the MRLC 2001 Consortium. This land cover database is being created using mapping zones (download zones here) and contains standardized land cover components useful for a variety of applications."
"NLCD 2006 quantifies land cover and land cover change between the years 2001 to 2006 and provides an updated version of NLCD 2001. These products represent the first time this type of 30-meter cell land cover change has been produced for the conterminous United States. Products were generated by comparing spectral characteristics of Landsat imagery between 2001 and 2006, on an individual path/row basis, using protocols to identify and label change based on the trajectory from NLCD 2001 products."