HOWTO import USGS elevation data

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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. Start GRASS (or restart) in the new location.

grass name_of_your_new_location/PERMANENT

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

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

Note that you can also download SRTM 90 data in tif format from These come in 5 degree by 5 degree tiles.