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
  1. Start GRASS in the new location.
  2. Import additional files as needed: in=w001001.adf out=dem2
.. etc.
  1. Use r.patch to combine the tiles into one continuous map, if desired.