HOWTO import USGS elevation data

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Revision as of 05:27, 10 May 2007 by Hajhouse (talk | contribs) ( -e flag recommended)
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The US Geological Survey offers a variety of digital elevation models through the Seamless Distribution System. Here is an approach to working with them in GRASS.

Importing USGS 1/3" NED datasets into GRASS

1. Download the datasets you desire. They will arrive in a zip archive of a directory containing a subdirectory containing a file called w001001.adf, which is the main data file (tip: this is the biggest file).

2. Create a new GRASS location to work with the DEMs.
From a GRASS shell:

cd 18437824/18437824 (example directory names --- replace with your actual names) location=name_of_your_new_location in=w001001.adf out=dem

3. (re)Start GRASS in the new location.

4. Import additional files as needed (note the -e flag causing the location's bounds to be extended as needed): -e in=w001001.adf out=dem2
.. etc.

5. Use r.patch to combine the tiles into one continuous map, if desired.