HOWTO import USGS elevation data: Difference between revisions
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The US Geological Survey offers a variety of digital elevation models through the [http://seamless.usgs.gov/website/seamless/viewer.php Seamless Distribution System]. Here is an approach to working with them in GRASS. | The US Geological Survey offers a variety of digital elevation models through the [http://seamless.usgs.gov/website/seamless/viewer.php Seamless Distribution System]. The highest resolution offered is 1/3 second (coverage: much of the USA). Here is an approach to working with them in GRASS. | ||
== Importing USGS 1/3 | == Importing USGS 1/3 arc second NED datasets into GRASS == | ||
1. '''Download the datasets you desire | 1. '''Download the datasets you desire''' through the provided web interface. 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.''' | 2. '''Create a new GRASS location to work with the DEMs.''' | ||
<BR>From a GRASS shell: | <BR>Pick one DEM to start with. From a GRASS shell: | ||
: <code>cd 18437824/18437824</code> ''(example directory names --- replace with your actual names)'' | : <code>cd 18437824/18437824</code> ''(example directory names --- replace with your actual names)'' | ||
: <code>r.in.gdal location=''name_of_your_new_location'' in=w001001.adf out=dem</code> | : <code>r.in.gdal location=''name_of_your_new_location'' in=w001001.adf out=dem</code> | ||
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: <code>grass name_of_your_new_location/PERMANENT</code> | : <code>grass name_of_your_new_location/PERMANENT</code> | ||
4. | 4. If you have more than one DEM archive, import additional files as needed (note the <code>-e</code> flag, which causes the location's bounds to be extended to accomodate the new data): | ||
: <code>r.in.gdal -e in=w001001.adf out=dem2</code> | : <code>r.in.gdal -e in=w001001.adf out=dem2</code> | ||
: ''.. etc.'' | : ''.. etc.'' | ||
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5. Use r.patch to combine the tiles into one continuous map, if desired. | 5. Use r.patch to combine the tiles into one continuous map, if desired. | ||
==Alternatives to the USGS DEM data== | |||
Other sources of digital elevation models include: | |||
* SRTM 90 data in TIFF format from http://srtm.csi.cgiar.org/. These come in 5 degree by 5 degree tiles. Horizontal resolution: 3 arc second (90 m at equator). Coverage: world. | |||
[[Category:FAQ]] | [[Category:FAQ]] | ||
Revision as of 16:14, 16 July 2007
The US Geological Survey offers a variety of digital elevation models through the Seamless Distribution System. The highest resolution offered is 1/3 second (coverage: much of the USA). Here is an approach to working with them in GRASS.
Importing USGS 1/3 arc second NED datasets into GRASS
1. Download the datasets you desire through the provided web interface. 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.
Pick one DEM to start with. 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 (or restart) in the new location.
grass name_of_your_new_location/PERMANENT
4. If you have more than one DEM archive, import additional files as needed (note the -e flag, which causes the location's bounds to be extended to accomodate the new data):
r.in.gdal -e in=w001001.adf out=dem2- .. etc.
5. Use r.patch to combine the tiles into one continuous map, if desired.
Alternatives to the USGS DEM data
Other sources of digital elevation models include:
- SRTM 90 data in TIFF format from http://srtm.csi.cgiar.org/. These come in 5 degree by 5 degree tiles. Horizontal resolution: 3 arc second (90 m at equator). Coverage: world.