Enhanced National Land Cover Data 1992 (NLCDe 92)

The enhanced National Land Cover Data 1992 ("NLCDe 92") served as the
primary source for nationally consistent mapped land cover during the
first decade of sampling for the National Water-Quality Assessment
(NAWQA) Program of the U.S. Geological Survey (USGS). This 30-meter
(30-m) resolution digital map was developed by overlaying USGS's original
satellite imagery-based 1992 National Land Cover Data ("NLCD 92")
with selected classifications from USGS's aerial-photograph-based
Land Use and Land Cover (LULC) data of the 1970s to mid-1980s.
The LULC data set were combined with NLCD 92 because 1) some land
land cover types important to NAWQA were not fully represented in the
NLCD 92 and 2) the LULC data set is accepted as a better source of
information for certain land cover types that are difficult to interpret
from satellite imagery alone. Decision rules were used to modify the
NLCD 92 data set based on the co-located LULC data on a cell-by-cell
basis. The LULC classifications that were used to develop NLCDe 92
were "Residential," "Orchards, Groves, Vineyards, Nurseries, and
Ornamental Horticultural Areas," and all 5 classifications of
Tundra. Although NLCDe 92 is nominally referenced to 1992, it
generally represents conditions in the early 1990s, the time period
when the majority of the imagery for NLCD 92 was captured.