Upper Midwest Environmental Sciences Center
Grayscale Scanned 100K USGS Quadrangles
PC Format Files : The PC format files contain a .TIF raster image and a .TFW world file. The data were compressed with a self extracting pkzip utility. To restore the data:
- Download and store the compressed file(s) on a personal computer (PC).
- Uncompress the data.
If uncompressing a file at the DOS prompt, enter the file's name as a command (filename without the .exe extension).
If uncompressing a file using Windows 3.1, File Manager or Windows 95, Windows Explorer, use the computer's mouse to double click on the file's name (e.g., o38090e1.exe).
UNIX Format Files: The UNIX format files contain a .TIF raster image and a .TFW world file. A Tar command was used to store the two files in a single file, then GNU compression utility "gzip" was used to compress the data. To restore the data:
- Download and store the compressed file(s) on a UNIX computer.
- Uncompress the file(s) using "gunzip." If you do not have a copy of the gzip utilities, they're available via anonymous ftp from prep.ai.mit.edu:/pub/gnu.
- Restore the image and world files by performing a tar xvf <filename.tar> on the .tar file.
Note: Once the data are uncompressed, the only difference between the PC and UNIX format files is the format of the .TFW world file. The PC .TFW file is a DOS ASCII file, the UNIX .TFW file is a UNIX ASCII file.
Metadata: Metadata for the georeferenced greyscale images is stored as an ASCII text file. The files are viewable by clicking on the metadata graphic. To download the metadata file, either hold the computer's mouse over the metadata graphic and press the mouse's right-hand mouse button or use whatever option your web browser contains for saving files.