[GRASS-user] r.basin does not complete properly on one stream

Margherita Di Leo diregola at gmail.com
Fri Oct 26 00:53:57 PDT 2012

Hi Rich,

unfortunately I don't have enough information in order to help you, would
it be possible to provide a sample data?

thanks and regards,

On Fri, Oct 26, 2012 at 1:40 AM, Rich Shepard <rshepard at appl-ecosys.com>wrote:

>   For a reason I've not been able to determine in a long day today r.basin
> fails to properly complete when passed easting/northing coordinates of a
> cell generated by r.stream.extract. The last three ratios are shown as NAN
> and the area is shown as only 4km^2 when it's actually much larger. With
> other sub-basins this result was corrected by moving the outlet point
> further upstream from the confluence with a larger stream.
>   Following the r.basin wiki that madi wrote, I re-extracted the streams
> from the DEM. Ran r.watershed to generate an accumulation map, then
> r.stream.extract. Both modules take the same DEM map (named dem_proj). But,
> when I place the outlet point several cells above the confluence r.basin
> does not properly complete. I tried moving the outlet away from the
> confluence, but still no joy.
>   The attached PDF shows the outlet point sitting in the middle of a cell
> on
> the stream_network raster generated by r.stream.extract.
>   I'm at a loss to understand why this one sub-basin is fighting me, and I
> would like outside opinions on what might be the cause and suggestions of
> what to try to isolate the cause of this problem. If more information is
> desired, I'll try to provide it.
> Rich
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Margherita DI LEO
Postdoctoral Researcher
European Commission - DG JRC
Forest Resources and Climate
I-21020 Ispra (VA) - Italy - TP 261

Tel. +39 0332 78 3600
margherita.di-leo at jrc.ec.europa.eu
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