text file that describes the spatial digital database for the U. S. Geological Survey Open-File Report 01-275.

  This report describes the contents of a spatial digital database which consists of ArcInfo exchange-format files and associated files. A page-sized, color version of the digital geologic map is included in the report. The data sets are available on the World Wide Web at:
           http://geopubs.wr.usgs.gov/open-file/of01-275/

  They are also available via anonymous FTP from: geopubs.wr.usgs.gov,
in the directory: pub/open-file/of01-275

  Requirements: A networked computer system is required to copy the database files from the host computer across the Internet. A geographic information system (GIS) capable of importing ArcInfo exchange-format files is required for access to the digital files. The plot file is stored in Adobe portable document format (tn-map.pdf).
 
  The digital spatial database for the geologic map of of Tucson and Nogales 1:250,000-scale quadrangles is available as one UNIX compressed TAR file, tn250k.tar.Z, which includes the report text (tn250k.pdf) in an Adobe portable document file (PDF) format.

  To download the spatial digital database data files, create a new workspace on your system and copy the tn250k.tar.Z file to your new workspace. Use the command 'uncompress -v tn250k.tar.Z' to uncompress the file. Then use the command 'tar -xvf tn250k.tar' to extract the files from the TAR file. Use the ArcInfo import command or other utility to import the ArcInfo interchange (*.e00) file.

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Explanation of digital data files:

Your working directory should contain the following files:
  tn250k.pdf - Open-File Report text in Adobe portable document file (PDF) format. 
  readme.txt - this file in DOS ASCII format

Primary ArcInfo exchange-format files (*.e00) and metadata (*.met) include:
  tn250k.e00 - principal line and polygon contacts, structures, and map units data set
  tn250k.met - metadata file

Geologic map plot files derived from the spatial digital database:
  tn-map.eps - postscript level 2 version
  tn-map.pdf - Adobe portable document format