National Land Cover Database 2001 (NLCD 2001)

The National Land Cover Characterization project was created in 1995 to support the original Multi-Resolution Land Characterization (MRLC) initiative and develop a nationally consistent land cover data set from MRLC data called National Land Cover Data 1992 (NLCD 92). This culminated in the September 2000 completion of land-cover mapping using a modified Anderson level II classification for the conterminous United States. In addition to satellite data, scientists used a variety of supporting information including topography, census, agricultural statistics, soil characteristics, other land cover maps, and wetlands data to determine and label the land cover type at 30-meter resolution. Twenty-one classes of land cover were mapped, using consistent procedures for the entire U.S. and a subsequent accuracy assessment was performed. The resulting and cover data set is being used for a wide variety of national and regional applications, including watershed management, environmental inventories, transportation modeling, fire risk assessment, and land management.

The growing need for land-cover and other geospatial data within the federal government culminated in reforming the MRLC Consortium again in 2000 (MRLC 2001), with a second generation national land cover data set to be developed using Landsat 7 ETM+ data. Called the National Land Cover Database 2001 (NLCD 2001), this cooperative effort involves nine Federal agencies: USGS, EPA, USFS, NOAA, NASA, BLM, NPS, NRCS and USFWS. The land cover mapping effort has been developed using a database approach, which provides flexibility in developing a suite of independent data layers that provide more generic flexibility in applying the database to even more relevant applications.

The NLCD 2001 has been compiled across all 50 states and Puerto Rico. This land cover database uses mapping zones and contains standardized land cover components useful for a variety of applications.

The three products available for NLCD 2001 are Land Cover, Tree Canopy, and Imperviousness. Land Cover refers to the classification of the land using the land cover definitions mentioned previously. Imperviousness refers to impenetrable surfaces such as rooftops, roads, or parking lots. Tree canopy refers to a layer or multiple layers of branches and foliage at the top or crown of a forest's trees.

References:

Homer, C., C. Huang, L. Yang, B. Wylie and M. Coan. 2004. Development of a 2001 National Landcover Database for the United States. Photogrammetric Engineering and Remote Sensing, 70(7): 829-840.

Vogelmann, J. E., S. M. Howard, L. Yang, C. R. Larson, B. K. Wylie, and N. Van Driel. 2001. Completion of the 1990s National Land Cover Data Set for the Conterminous United States from Landsat Thematic Mapper Data and Ancillary Data Sources. Photogrammetric Engineering and Remote Sensing, 67: 650-652.