HOWTO import USGS elevation data

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)

r.in.gdal location=name_of_your_new_location in=w001001.adf out=dem

3. Start GRASS in the new location. 4. Import additional files as needed:

r.in.gdal in=w001001.adf out=dem2

.. etc.

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