NLCD 92 (National Land Cover Data 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.
A consortium consisting of several federal
agencies was formalized to produce a consistent and
seamless National Land Cover Dataset (NLCD) for the
conterminous United States (Loveland and Shaw,
1998). Land cover mapping has been conducted for
each of ten geographic regions using early 1990s
Landsat Thematic Mapper (TM) imagery augmented by a
suite of other geospatial ancillary data sets.
Briefly, the NLCD was compiled through unsupervised
clustering (Kelly and White, 1993) of Landsat TM
data. The resulting spectral clusters were resolved
into one of 21 thematic classes using logical
modeling and ancillary data sources (e.g., census,
slope/aspect/elevation, etc.) as required. The
twenty-one thematic classes resemble the
well-established Anderson land use/cover
classification system (Anderson et al. 1976).
Details of the classification process are discussed
in Vogelmann et al. (1998a, 1998b).
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