National Land Cover Dataset 1992 - ; Albers Grid [Pennsylvania] {1999}
Description
These data can be used in a geographic information system (GIS) for any
number of purposes such as assessing wildlife habitat, water quality,
pesticide runoff, land use change, etc. The State data sets are provided
with a 300 meter buffer beyond the State border to facilitate combining
the State files into larger regions.
The user must have a firm understanding of how the datasets were compiled
and the resulting limitations of these data. The National Land Cover Dataset
was compiled from Landsat satellite TM imagery (circa 1992) with a spatial
resolution of 30 meters and supplemented by various ancillary data (where
available). The analysis and interpretation of the satellite imagery was
conducted using very large, sometimes multi-state image mosaics (i.e. up to 18
Landsat scenes). Using a relatively small number of aerial photographs for
'ground truth', the thematic interpretations were necessarily conducted from a
spatially-broad perspective. Furthermore, the accuracy assessments (see below)
correspond to 'federal regions' which are groupings of contiguous states. Thus,
the reliability of the data is greatest at the state or multi-state level. The
statistical accuracy of the data is known only for the region.
Important Caution Advisory
With this in mind, users are cautioned to carefully scrutinize the data to
see if they are of sufficient reliability before attempting to use the
dataset for larger-scale or local analyses. This evaluation must be made
remembering that the NLCD represents conditions in the early 1990s.
The Pennsylvania portion of the NLCD was created as part of land cover
mapping activities for Federal Region III that includes the States of
Maryland, Delaware, Pennsylvania, Virginia, West Virginia, and the
District of Columbia. The NLCD classification contains 21 different
land cover categories with a spatial resolution of 30 meters. The NLCD
was produced as a cooperative effort between the U.S. Geological Survey
(USGS) and the U.S. Environmental Protection Agency (US EPA) to produce
a consistent, land cover data layer for the conterminous U.S. using
early 1990s Landsat thematic mapper (TM) data purchased by the
Multi-resolution Land Characterization (MRLC) Consortium. The MRLC
Consortium is a partnership of federal agencies that produce or use land
cover data. Partners include the USGS (National Mapping, Biological
Resources, and Water Resources Divisions), US EPA, the U.S. Forest Service,
and the National Oceanic and Atmospheric Administration.