[GRASS-user] Import conditioned DEM from HydroSheds

[Markus Metz]

On Sat, May 18, 2013 at 1:55 PM, Johannes Radinger
<johannesradinger at gmail.com> wrote:
> Hi,
>
> I'd like to use the conditioned DEM from HydroSheds (15sec resolution)
> in GRASS to extract rivers etc. using r.watershed.

Various artifacts were introduced in the conditioned DEMs of
HydroSheds. Rather use the filled, but not conditioned DEMs,
particularly when you want to use r.watershed or r.stream.extract. The
results will be more realistic. Or to be 100% sure, use SRTM v2.1 and
fill nodata with GRASS.

> On the HydroSheds-
> Website (http://hydrosheds.cr.usgs.gov/dataavail.php) there are two possible
> file formats: bil and esri grid.
>
> The esri grid folder for Europe (eu_dem_15s) contains several files all with
> .adf ending and metadata (htm, xml).
> The bil folder contains the eu_dem_15s.bil and a *.hdr and *.prj and some
> more.

You should download both and investigate the output of gdalinfo for
both. One of them might have wrong extents and resolution. For
example, worldclim also provides the same two file formats: bil and
esri grid. In this case, the esri grid is wrong and the bil format
should be used (ESRI has problems with coordinate precision).

Markus M

>
> Which format is prefered for importing into GRASS? I guess its the .bil as
> there is only
> one bil-file with the different addtional info (header, projection etc.).
> Which format type
> is the .bil in r.in.gdal?
>
> /Johannes
>
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