ACCESSING LAND USE/LAND COVER (LULC) DATA FROM INTERNET
THIS IS NOT AN AML
Land Use/Land Cover (LULC) files are developed by the USGS and are available via internet from either USGS or the EPA. In both cases, the user must specify the 1:250,000-scale mapsheet name(s) corresponding to the region(s) of interest, and then download the coverage(s). Accessing the actual LULC files from the USGS has proven problematic to date, as the files exist in a "modified" UTM projection that is not clearly defined in the users guide. Given these difficulties and the relative ease with which the same files are obtained from EPA, the EPA Home Page is currently the preferred source of this data. However, the 1:250,000-scale mapsheet names for the United States are still accessible at the USGS Home Page.
The following procedure is a THREE step process and may not sound very efficient. However, it is the only way we have found, so far, to successfully obtain the LULC files. Please be patient when following these directions, they seem long and redundant, but this is the method that has worked for our research group.
STEP 1 Accessing the 1:250,000-scale mapsheet names:
- Once at the initial Home Page of a particular data browser (Mosaic, Netscape, etc.), enter the address of the USGS EROS Data Center Home Page - http://sun1.cr.usgs.gov/eros-home.html.
- At the Home Page, scroll down to the 1:250,000-Scale and 1:100,000-Scale LULC section of the page and select 250K FTP via Graphics. A map of the continental United States will appear.
- Using the cursor, click in the general area of the particular region of interest, and a finer resolution map will appear with the 1:250,000-scale maps and mapnames superimposed.
- Note the mapnames that correspond to the hydrologic or political region of interest.
STEP 2 Obtaining the Filenames from EPA:
- An alternate source for LULC data is the EPA Home Page - http://www.epa.gov.
Retrieval of LULC files from this location still requires mapsheet names to be known ahead of time (see step 1 above).
- Once at this Home Page, select the Search the EPA Server hypertext. When you execute this like, a query box will appear, within the query box, type land use and then press 'start query'. The result of the query should appear after a minute or two.
- Scroll down to and select the EPA EPAGIRAS hypertext and then enter a mapsheet name of a LULC coverage to be downloaded. This will lead to a page where an export file (.e00.gz) should be available for selection.
- write down the actual name of the e00 file -- it should be a series of three letters and 5 numbers, followed by .e00.gz.
STEP 3 Obtaining the file from the EPA ftp site
Since downloading the file through Netscape or Mosaic is not aloways succesful (especially in the middle of the day). It is best to go to the EPA ftp site. Now that you know the actual filename of what you are looking for, this process is pretty straightforward.
- At a command prompt, type ftp earth1.epa.gov
- Logon anonymously by typing anonymous at the user name prompt and your e mail address for the password
- Change directories to /pub/EPAGIRAS/mgiras (note that ftp is case sensitive!)
- Once in this directory, you can type get filename. The download process will take some time. Typically, these files are between 1.5 and 2 megs. When you are done getting the files you need, exit out of the ftp prompt by typing bye. - At the Unix prompt of the host workstation, unzip the compressed file:
$: gunzip filename.e00.gz
Invoke Arc/Info and import the file as an Arc/Info coverage:
Arc: import cover filename.e00 filename
The process is now complete as the LULC coverage exists in an Albers projection that can easily be manipulated with other coverages and LULC files.
Quick Connect to EPA LULC Web Site
Go to AML Listing