GRASS-Wiki - User contributions [en]

HOWTO import USGS elevation data

2007-09-26T17:51:21Z

⚠️Hajhouse: 1/3 arc second = about 10 meters

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 (= about 10 meters) with coverage of 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.'''
<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>r.in.gdal location=''name_of_your_new_location'' in=w001001.adf out=dem</code>

3. '''Start GRASS''' (or restart) in the new location.
: <code>grass name_of_your_new_location/PERMANENT</code>

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>
: ''.. 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.

[[Category:FAQ]]

Cropping maps

2007-07-18T22:15:47Z

⚠️Hajhouse: new page

Cropping maps means taking the contents of one map (the ''source'') and eliminating all data outside of the area you are studying (the ''boundary'') to yield a smaller new map (the ''cropped map''). Techniques differ depending on whether your source is raster or vector and whether your boundary is defined by another map or by coordinates. You especially might want to do this with vectors because GRASS operations always operate on the whole vector map, even features outside of the current region.

'''Vector source map''' and '''vector map as boundary'''. Use <code>v.overlay operator=and</code>. Example: you have a map of roads of the USA and you want a map of only roads in California. Formerly the module <code>v.cutter</code> did this task; it has however been replaced by <code>v.overlay</code> in GRASS release 6.

'''Vector source map''' and '''coordinates as boundary'''. Set region to desired coordinates (<code>g.region</code>), create new vector from region extent to use as boundary using <code>v.in.region</code>, then <code>v.overlay</code> as above.

'''Raster source map''' and '''raster map as boundary'''. Make boundary into mask using <code>r.mask</code> then copy raster source to new map (<code>g.copy</code>). All cells outside of the mask will be omitted from the new copy. Alternately, use <code>r.mapcalc</code>:

:r.mapcalc "cropped = if(boundary,raster_source)"
:r.colors map=cropped rast=source # may be required to transfer the color table

'''Raster source map''' and '''vector boundary'''. Convert the vector to a raster mask (1 where inside, null elsewhere):

:v.to.rast in=vector_boundary out=raster_boundary use=val value=1

Then proceed as above for two rasters.

[[Category:FAQ]]

HOWTO import USGS elevation data

2007-07-16T16:14:46Z

⚠️Hajhouse: copyediting

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 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.'''
<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>r.in.gdal location=''name_of_your_new_location'' in=w001001.adf out=dem</code>

3. '''Start GRASS''' (or restart) in the new location.
: <code>grass name_of_your_new_location/PERMANENT</code>

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>
: ''.. 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.

[[Category:FAQ]]

GRASS Metadata Management

2007-05-26T20:06:33Z

⚠️Hajhouse: /* Vector */ how to edit comments on vect map

== Metadata support ==

=== Raster ===
* [http://grass.itc.it/grass63/manuals/html63_user/r.support.html r.support] (r.support history="long text" now functional, it does line wrapping)
* [[Replacement_raster_format#Meta-data_support|Metadata support in GRASS raster library notes]]

=== Vector ===
* [http://mpa.itc.it/markus/grass63progman/Vector_Library.html#head_file_format 'head' file format]
* TODO: tool to edit this head file needed. In the future this may be provided by <code>v.support</code> (which has not yet been written). (Reference: http://grass.itc.it/pipermail/grassuser/2007-February/038323.html)

Comments on a vector map can be added manually by editing <code>$MAPSET/vector/$MAPNAME/hist</code>.

== Metadata management ideas for future versions of GRASS ==

== Links ==
* [http://www.eurogeographics.org/eng/documents/draftINSPIREMetadataIRv2_20070202.pdf DT Metadata – Draft Implementing Rules for Metadata]

[[Category:Development]]

Sharing a GRASS database

2007-05-22T18:31:59Z

⚠️Hajhouse: new article

== Sharing a GRASS database ==

Here are some suggestions on how multiple people at a site can collaborate on one GRASS database, sharing data.

===Using the same mapset, sequentially===
GRASS does not allow two users to run in the same mapset at the same time. It is possible for two different users to take turns using a mapset at different times. This is complicated by the fact that GRASS will not allow itself to be run in a mapset owned by a different operating-system user. If you try to do this, you will get a "permission denied" error, which is entirely independent of the permission checking of your operating system. The solution is either to change the ownership of the mapset (the directory and all files and subdirectories contained therein) prior to a different user running GRASS in that mapset, or to have a separate mapset for each username.

Limitations: possibly inefficient use of users' time because people must take turns.

===Using per-user mapsets===
If you use a separate mapset for each operating-system username, you can use <code>g.mapsets</code> to add additional mapsets to the search path,
which will allow you to access files from either mapset by name without having to use the map@mapset syntax.

Limitations: you still can only use <code>g.remove</code>, <code>g.rename</code>, and <code>g.copy</code> on maps in your current mapset.
If you try to replace a map that exists under the the same name in one of the other mapsets, the old map will continue to exist but will be masked for you (but not for other users) by your new map. This behavior may not be what you expect.

===References===

[http://grass.itc.it/pipermail/grassuser/2007-January/037971.html Thread on GRASS-user mailing list on "shared access to mapsets"] (source of the information in this article)

[[Category:FAQ]]

HOWTO import USGS elevation data

2007-05-22T18:08:03Z

⚠️Hajhouse: copyediting

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.

== 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.'''
<BR>From a GRASS shell:
: <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>

3. '''Start GRASS''' (or restart) in the new location.
: <code>grass name_of_your_new_location/PERMANENT</code>

4. 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>
: ''.. etc.''

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

[[Category:FAQ]]

HOWTO import USGS elevation data

2007-05-10T05:27:45Z

⚠️Hajhouse: r.in.gdal -e flag recommended

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.

== 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.'''
<BR>From a GRASS shell:
: <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>

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

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

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

[[Category:FAQ]]

HOWTO import USGS elevation data

2007-05-09T23:40:13Z

⚠️Hajhouse:

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.

== 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.

[[Category:FAQ]]

HOWTO import USGS elevation data

2007-05-09T23:38:41Z

⚠️Hajhouse: /* Importing USGS 1/3" NED datasets into GRASS */

HOWTO import USGS elevation data

2007-05-09T23:37:53Z

⚠️Hajhouse:

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.

== Importing USGS 1/3" NED datasets into GRASS ==

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