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Copy file name to clipboardExpand all lines: book/03-Preliminary-Steps/sections/data-sources.asc
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@@ -40,7 +40,7 @@ and because it retains georeferencing information.
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.Why don't we use GeoTiff?
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****
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https://trac.osgeo.org/geotiff/[GeoTIFF] is a widely used raster format that has the advantage of containing georeferencing and the raster data in a single file.
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The disadvantage is that for pass:[c++] code you need to have two libraries (`libtiff` and `libgeotiff`) installed before you can read GeoTIFF files.
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The disadvantage is that for pass:[C++] code you need to have two libraries (`libtiff` and `libgeotiff`) installed before you can read GeoTIFF files.
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Because there are many open source, easily installed tools for converting GeoTIFF files
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(for example, the http://www.gdal.org/gdal_utilities.html[GDAL utilities] and the https://pypi.python.org/pypi/GDAL/[python GDAL bindings])
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we have opted for portability and not included the GeoTIFF libraries in our software. If you have GeoTIFF files, you
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which was completed in 1996 and contains ~1 km resolution global data.
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This was followed by the https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission[Shuttle Radar Topography Mission (SRTM)]
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that produced a 90 meter resolution DEM in 2003; followed by the
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https://asterweb.jpl.nasa.gov/gdem.asp[Advanced Spaceborne Thermal Emission and Rerflection Radiometer (ASTER)]
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https://asterweb.jpl.nasa.gov/gdem.asp[Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)]
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30 meter resolution global DEM in 2009. In 2014
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http://www.cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-1[SRTM released a global 30 meter dataset].
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2015 has seen the release of the http://www.geo-airbusds.com/worlddem/[WorldDEM], a 12 meter resolution topographic dataset.
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GTOPO30, SRTM and ASTER data are all freely available for download. The WorldDEM is a commercial product.
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If you are looking for a global dataset at reasonable resolution that is not commercial, you will most likeley choose between ASTER and SRTM.
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If you are looking for a global dataset at reasonable resolution that is not commercial, you will most likely choose between ASTER and SRTM.
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You can download ASTER and SRTM data at the same site and make your own comparisons,
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but ASTER has widely publicised http://www.digital-geography.com/dem-comparison-srtm-3-vs-aster-gdem-v2/#.ViS2wX6rRaQ[data quality issues]
The first line is the name of the DEM without the extension.
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In this example the name is `mandakini`. The next line is a minimum slope for the fill function.
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In this example the name is `Mandakini`. The next line is a minimum slope for the fill function.
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The default is 0.0001.
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The third line is the threshold number of pixels that contribute to another pixel before that pixel is considered a channel.
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You can play with these numbers a bit, in this example, I have set the threshold to 300
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300
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----
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. Once you have done this, you need to run the driver program.
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The driver program is called `chi1_write_junctions.exe`.
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You can check this in Linux with the `less` command. Just type `less Mandakini.drver` to see the file and `q` to quit.
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. Okay, if you have been following along, you should have two terminal windows open. One should be open in the folder containing your data, and the other should be open in the folder with the source code driver functions.
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