[GRASS-user] Problem with r.basin in grass7

[Margherita Di Leo]

Dear Andrea,

On Sun, Nov 2, 2014 at 6:26 PM, Markus Neteler <neteler at osgeo.org> wrote:

> HI Andrea,
>
> On Fri, Oct 31, 2014 at 3:18 PM, Andrea Timmermann <timmermann at gmx.at>
> wrote:
>
>
> > Reading features...
> > Writing raster map...
> > Converted points/lines: 1 of 1
> > v.to.rast complete.
> > ERROR: Module built against version $Revision: 62060 $ but trying to use
> > version $Revision: 62364 $. You need to rebuild GRASS GIS or untangle
> > multiple installations.
>
> Mhh, "this should not happen" issue. In a winGRASS installer there
> should not be any version mixture.
> Helli, Martin, any ideas?
>

Did you update G7 without updating the r.stream* perhaps? I'm not sure if
this would lead to the error above mentioned, but to give it a try, please
remove and then reistall the r.stream modules using g.extension

>
> [...]
>
>
> > I also have two more questions:
> > - Should I set the computational region to the whole raster map I am
> using
> > or to the vector map defining my basin? (I tried both alternatives and
> > r.basin writes something a bit different on the screen depending on what
> I
> > use)
>
> This is a question for the author of r.basin, I don't know.
>

The vector map defining your basin is actually an output of the module. You
should set the computational region to include the closing section and the
area above it up to the ridges (the top of the mountains). This is the best
guess on where your basin is more or less contained. If your entire raster
is reasonably small, it is OK to set the computational region to the whole
raster, otherwhise, you should try to include the ridges that define your
basin of interest. If your selection is wrong, you'll be able anyway to
detect it because your basin will extend to the limits of your
computational region. In this case you will know that you should extend the
computational region.

>
> > I am using a mask based on my vector map, so maybe the computations are
> > anyways done only for the area covered by the basin?
>
> ... also here.
>

No, the module does not reduce the region automatically. My suggestion
would be to set the computational region reasonably larger than the vector
and not to use it as a mask. This is because it could prevent including
cells that drain into the basin. You can prove it running r.watershed on
the raster masked by the polygon representing the basin. Query the flow
accumulation that you obtain (you can use r.mapcalc) to see if there are
negative values. The negative values are conventionally used in r.watershed
to detect cels that are "incomplete" as sinks for other cells to drain
into.

Hope this helps,
madi



-- 
Best regards,

Dr. Margherita DI LEO
Scientific / technical project officer

European Commission - DG JRC
Institute for Environment and Sustainability (IES)
Via Fermi, 2749
I-21027 Ispra (VA) - Italy - TP 261

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

Disclaimer: The views expressed are purely those of the writer and may not
in any circumstance be regarded as stating an official position of the
European Commission.
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