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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | GISList: Compressed Terrain Data |
| Date: |
01/07/2003 11:20:55 AM |
| From: |
Cameron Crum |
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This is a little off topic, but I'm trying to see if there would be an
interest in a very compressed (not zipped) form of elevation data. We
have come up with a technique for compressing DEM's that brings file
sizes down to about 127 KB per 1:24000 scale quad. To let you know, the
native USGS DEM's are over 1 MB each and the STDS archiving method in my
opinion is cumbersome to extract data from. We have also developed a DLL
and API that would allow programmers to access the data in these quads
programatically without having to decompress them, and we would offer a
free translator to convert the quads into an ascii grid, x,y,z, tab,
mif, mig or some other common format (but not back to native DEM) for
those who just want the raw data and do not need it in a program.
Additionally, the compression process detects and corrects the errors
inherent in many of the native USGS quads. So the end product is a
corrected quad at 1 tenth the original file size that doesn't require
3-4 steps to make it usable. Obviously, this is for the US only at the
moment, but the compression technique could be used on any data in the
world...we just don't happen to have access to that data. I'd be
interested to hear any questions or comments about this. Please Reply to
me directly so as not to clutter the list.
Thanks,
Cameron Crum
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