Summary
Abstract:
Since the early 1980's the EROS Alaska Field Office (AFO) has been involved in
the acquisition, classification, and analysis of digital land cover data over
the State of Alaska, and to a limited extent, northwestern Canada and Wrangle
Island, Russia. The digital data currently covers approximately 77% of the land
and water within the boundaries of the State of Alaska. These data are
currently being made available via the AFO web site to land managers and
researchers who may be interested in land cover conditions over various
portions of Alaska. The land cover maps as a result of digital analysis of
Landsat multispectral scanner, Landsat thematic mapper, and SPOT multispectral
scanner satellite data. Some data however, are missing from the database due to
data degradation on storage media or loss of data tapes, although a limited
number of hard copy map products may be in existence, for example, U.S. Forest
Service land cover data for southeast Alaska. The land cover data are stored
online in a series of directories and are available via the web. Each directory
name is indicative of the area for which the land cover data exists. Some
directories connote a U.S. Geological Survey 1:250,000 quadrangle (for example,
anchorage_int), while others indicate a particular project area (for example,
anwr represents Arctic National Wildlife Refuge) or the agency responsible for
producing the data. For example, nowitna.fws indicates that the data were
produced for the U.S. Fish and Wildlife Service. Directories with an '_int'
suffix denote that the data correspond to the Interim Landcover Mapping
project. Each directory contains five files with the following extensions:
.bil, .blw, .hdr, .prj, and .stx. As a group, one or more of the files can be
read by most image analysis and GIS software packages. The .bil file contains
the binary raster land cover data and the others are ASCII files. The .bil file
does not contain any header or footer records, and can be easily imported into
image processing software by using the information contained in the .blw and
.hdr files. The .blw file provides pixel size information as well as the upper
left corner coordinate. The .hdr contains number of rows and columns of the
data set, as well as band format (band interleave). The .prj file gives
projection information, and the .stx file gives information on minimum/maximum/
mean values of the data. Projection parameters for the data sets are either in
Universal Transverse Projection (UTM) or Alaska Albers Equal Area Conic.
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