USGS Frequently Asked Questions
Question:
I downloaded 1:100,000-scale Digital Line Graph (DLG) files from the USGS web site and can't read them into Arc.
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Answer: - To read DLG files accessed on the EDC site into ARC/INFO requires two steps:
- These files are gzip compressed. Before anything else can be done, they must be uncompressed.
- These files are unblocked (all line feeds have been removed). To be read into Arc, these DLGs must be blocked to 80
characters per line.
In the UNIX environment, the dd command can be used to block the DLGs. (dd if=old.dlg of=new.dlg ibs=1064 obs=80 cbs=80 conv=unblock)
In the PC environment (DOS, win3.1, win95), use the DOS program CHOP to break
the files into the appropriate length.
If a C compiler is available for NT, the source code for a program called
block.c can be
obtained at http://thor-f5.er.usgs.gov/dxf/. |
Source of this FAQ: http://mcmcweb.er.usgs.gov/mcgsc/
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