Changes between Version 9 and Version 10 of Help/DEM_scripts

Feb 11, 2012 1:49:35 PM (7 years ago)



  • Help/DEM_scripts

    v9 v10  
    5555    *  Select the purpose of the tile usage
    5656    *  Then download the tiles.
     58==== Choosing Tiles ====
     59When creating an ASTER DEM it is important to choose the correct tiles to use, as this could impact on the speed at which the script runs, as if tiles with large gaps between them are chosen when grass fills the nulls it has a lot of nulls to fill, so will take a very long time.
     60I suggest that a square region of tiles should be chosen, as this means that the script should not need to fill a large number of nulls.
     61If you require tiles in the region (50.23 - 52.56, -2.34 - 1.23) lat/lon:
     62  To calculate the tiles round the numbers down to get (50 - 52, -3 - 1), so you need:
     63     ASTGTM2_N50W003_dem.tif
     64     ASTGTM2_N50W002_dem.tif
     65     ASTGTM2_N50W001_dem.tif
     66     ASTGTM2_N50E000_dem.tif
     67     ASTGTM2_N50E001_dem.tif
     68     ASTGTM2_N51W003_dem.tif
     69     ASTGTM2_N51W002_dem.tif
     70     ASTGTM2_N51W001_dem.tif
     71     ASTGTM2_N51E000_dem.tif
     72     ASTGTM2_N51E001_dem.tif
     73     ASTGTM2_N52W003_dem.tif
     74     ASTGTM2_N52W002_dem.tif
     75     ASTGTM2_N52W001_dem.tif
     76     ASTGTM2_N52E000_dem.tif
     77     ASTGTM2_N52E001_dem.tif
     78  The name of the tiles relates to the bottom left corner of the region so ASTGTM2_N50W003_dem.tif covers (50-50.9999, 3-3.0001).
    5880==== Geoid Height Grid ====
    131153I would advise that the grass version be 6.3 as the script was written to work with this grass version.
     155==== Using ====
     156The script is partly configured to be used in-house and so some options that are available are not applicable, as for example the navigation file is used to calculate the tiles to use by default. So here is a usage for out of house usage:
     160Generates a binary lat-long ASTER DEM from downloaded raw ASTER data[[BR]]
     163   (Optional)[[BR]]
     164      -h:   Display usage and exit[[BR]]
     165      -o:   Final output filename for DEM, defaults to leaving in grass database[[BR]]
     166      -j:   Filename to output a jpeg image of the DEM[[BR]]
     167      -a:   Directory containing ASTER tiles only. If not given then script needs to be run within a project[[BR]]
     168      -g:   Grass database to use, defaults to creating one[[BR]]
     169      -p:   Projection of output tiles:proj4 string or UTM[utm_num(zero padded)](N|S) or UKBNG or ll[[BR]]
     170      -r:   Resolution of output DEM, defaults to using resolution of ASTER tile[[BR]]
     171      -s:   binary geoid-spheroid seperation file[[BR]]
     172      -m:   Maximum size of output DEM in GB, will be overridden by specified resolution. Note this does change the output resolution[[BR]]
     173      -f:   Do not fill nulls or smooth, i.e. do not run the command r.fillnulls and r.neighbours on the DEM before outputting[[BR]]