Table of Contents - The Atmospheric Studies Group at TRC

Section 2: Geophysical Data Processors
map names. In some regions, land use data are also available at the 1:100,000-scale. Land use and land
cover types are divided into 37 categories. A description of the USGS LULC data is provided in
Attachment 2-B.
The user must first identify the names of the quadrants encompassed by the domain. These names are
listed in a USGS map index as well as on the WWW home page of the USGS. A copy of the USGS
webpage is provided in Attachment 2-C. Select the “250K FTP via Graphics” in the LULC section to
view a map of the US and the names of the quadrants.
2.2.1.2 Composite Theme Grid (CTG)
Follow the links on www.src.com for the USGS CTG Land Use/Land Cover (LULC) data. The LULC
data consists of historical land use and land cover classification data that was based primarily on the
manual interpretation of 1970’s and 1980’s aerial photography. Secondary sources included land use
maps and surveys. A copy of the webpage is shown in Attachment 2-E and a copy of the readme file for
the 1:250,000 maps is shown in Attachment 2-F. Note that the CTG files (named ‘grid_cell’) do not
contain record delimiters; the latter must be added as described in Attachment 2-E for the GIRAS files.
CTG LULC data are available by anonymous ftp from: edcftp.cr.usgs.gov, or can be downloaded from
the WWW site: http://edcftp.cr.usgs.gov/pub/data/LULC. FTP File Access information is presented in
Attachment 2-E.
2.2.1.3 Generic Data set
CTGPROC supports two types of generic data formats where the Land Use data does not conform to
eitherNLCD, USGS CTG or global Land Use cover. The formats of these files are described in more
depth in Section 2.2.4. The first data set is of the form; row number, Land Use category, latitude
(negative for Southern Hemisphere) and, longitude (negative for Western Hemisphere). This data set uses
non-random Land Use categories which are mapped to the USGS categories. The second data set is of
the form; Land Use category, longitude (negative for Western Hemisphere) and, latitude (positive for
Northern Hemisphere). This data set uses random Land Use categories and the user can map the random
Land Use values to the appropriate default or user defined surface parameters independently of the
model’s default USGS categories.
2.2.1.4 National Land Cover Dataset (NLCD)
Follow the links on www.src.com for the 1992 National Land Cover Dataset (NLCD). Then click on the
link “Click here to link to the NLCD 92 data by state” which takes you to
(http://edcftp.cr.usgs.gov/pub/data/landcover/states/) . The data are distributed on a state by state basis.
The NLCD data have been compressed using gzip utility and are stored as generic binary ‘flat files’.
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