Changes between Version 21 and Version 22 of Processing/SRTMDEMs


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Timestamp:
Feb 22, 2011, 1:51:33 PM (14 years ago)
Author:
benj
Comment:

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  • Processing/SRTMDEMs

    v21 v22  
    1212 * SRTM from http://earthexplorer.usgs.gov. Expand the "Digital Elevation" link on the left and tick the box labelled "SRTM". Enter bounding co-ordinates for the area you want data for, clicking the green "+" icon after each one. Note that this currently seems not to always work correctly for locations in DMS format (at least in Firefox), you may need to switch to decimal degrees (which work fine). Click on the "Search" button in the bottom-right, and you should be presented with a list of items matching your search (there should be only one thing in it). Click on the "SRTM" link (you may need to enable pop-ups if you've got them blocked), and you will be presented with a list of matching SRTM tiles and download links - download the data you want to use. Note that only SRTM 3-arc-second resolution data is available for sites outside North America. For sites in North America higher resolution data can be obtained via the USGS [http://seamless.usgs.gov/ Seamless Server]
    1313
    14 '''The raw ASTER and SRTM data should be placed in ~arsf/ASTER and ~arsf/SRTM respectively.'''
     142. The raw ASTER and SRTM data should be placed in ~arsf/ASTER and ~arsf/SRTM respectively (ARSF-DAN internal only - this isn't a requirement for use of azgcorr).
    1515
    16 2. Unzip the downloaded zip file. ASTER data will contain two GeoTIFFs (you want the "_dem" one) - the file name refers to the lat/lon of the bottom-left corner of the tile. For SRTM data, descend into the directory structure to find the file w001001.adf - this holds the actual data, though you can't move it without the rest of the directory structure.
     163. Unzip the downloaded zip file. ASTER data will contain two GeoTIFFs (you want the "_dem" one) - the file name refers to the lat/lon of the bottom-left corner of the tile. For SRTM data, descend into the directory structure to find the file w001001.adf - this holds the actual data, though you can't move it without the rest of the directory structure.
    1717
    1818If the ASTER data covers more than one tile, you will need to unzip lots of files - for convenience:
    … …  
    2222Each zipfile contains a file called Readme.pdf and piping yes into unzip lets us overwrite it each loop.
    2323
    24 3. Fire up Grass. Select a location in lat/long projection using WGS84 datum (create one if none available), make a note of the selected location and mapset names.
     244. Fire up Grass. Select a location in lat/long projection using WGS84 datum (create one if none available), make a note of the selected location and mapset names.
    2525
    26 4. Import the data file.
     265. Import the data file.
    2727
    2828For ASTER data:
    … …  
    8181Write down <MAP_NAME> somewhere - you will need it in a minute.
    8282
    83 5. Quit Grass and then start it up again. Select a location using UTM projection for the target area or create one if none is available - make sure you've got the right UTM zone. Note you can also use whatever other projection you want, but this guide assumes you want UTM.
     836. Quit Grass and then start it up again. Select a location using UTM projection for the target area or create one if none is available - make sure you've got the right UTM zone. Note you can also use whatever other projection you want, but this guide assumes you want UTM.
    8484
    8585Check [http://www.gpsinformation.org/utm-zones.gif] For the UTM zone
    8686
    87 6. Here we can use the manual method of calculating the eastings/northings or simply grab them from the tile(s) we have input.
     877. Here we can use the manual method of calculating the eastings/northings or simply grab them from the tile(s) we have input.
    8888
    8989'''Manual:'''
    … …  
    129129}}}
    130130
    131 7. To output an ASCII DEM from the converted map, the instructions are the same as [wiki:Processing/NextMapDEMs those on the NextMap page]. Follow the instructions from about half-way down. Make sure to covert your DEM to an az-style header.
     1318. To output an ASCII DEM from the converted map, the instructions are the same as [wiki:Processing/NextMapDEMs those on the NextMap page]. Follow the instructions from about half-way down. Make sure to covert your DEM to an az-style header.
    132132
    133 8. To elevate the SRTM/ASTER DEM to the WGS84 spheroid (as is required for LiDAR deliveries and LiDAR DEM patching) see [wiki:Processing/DEM2WGS84 Elevate an SRTM/ASTER DEM to the WGS84 spheroid].
     1339. To elevate the SRTM/ASTER DEM to the WGS84 spheroid (as is required for LiDAR deliveries and LiDAR DEM patching) see [wiki:Processing/DEM2WGS84 Elevate an SRTM/ASTER DEM to the WGS84 spheroid].
    134134
    135 9. When your DEM is finished, place it in ~arsf/dems and link it from within the individual projects. Make sure it's origin is contained in the file name e.g. <PROJECT_NAME>-ASTER.dem.
     13510. When your DEM is finished, place it in ~arsf/dems and link it from within the individual projects. Make sure it's origin is contained in the file name e.g. <PROJECT_NAME>-ASTER.dem.