[GRASS-user] Re: highest and lowest point in catchment

[Daniel Victoria]

Maybe something like this...

For each catchment you run r.info -r to get the highest and lowest
value of the DEM (use a MASK for the catchment and r.info -r DEM).

Then, with r.mapcalc you select the highest and lowest areas that you
obtained with r.info. After that you can vectorize the areas selected
and do v.db.update to get coordinates.

It would be nice to put this all into a script if you have too many catchments.
One problem would be that you might not get a single pixel for the
high and low parts of the basin. It could be a small area...

Another thing. v.rast.stats can give you the max and min value for a
DEM for every catchment. It just wont give you the coordinates - not
that I know of...

Good luck
Daniel

On Jan 30, 2008 5:03 AM, Dr. Manuel Seeger <seeger at uni-trier.de> wrote:
> Thanks Richard,
> but elevation data is on a raster map.
> The idea I had was to generate point vector files with the highest and
> lowest point and then generate the colums with y and y coordinates...
> but it seems to me like a complicated way and I was wondering if there
> is a possibility to do that with r.mapcalc.... I think the functions are
> ther, but how combining?
>
> Perhaps someone knows a way?
>
> Thanks
> MAnuel
>
> Richard Chirgwin schrieb:
>
> > grass-user-request at lists.osgeo.org wrote:
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> >> Today's Topics:
> >>
> >>    1. highest and lowest point in catchment (Dr. Manuel Seeger)
> >>    2. SHELL Variable problem: Workaround (Peter L?we)
> >>    3. Re: SHELL variable not set (Martin Wegmann)
> >>    4. Re: SHELL variable not set (Glynn Clements)
> >>    5. Re: SHELL variable not set (Hamish)
> >>    6. Re: SHELL variable not set (Markus Neteler)
> >>    7. Re: Building wxgrass vdigit (Martin Landa)
> >>    8. segment_format error with r.watershed (Wes Kent)
> >>    9. union features of vector (Alfredo Alessandrini)
> >>   10. Re: Snap across layers (Martin Landa)
> >>
> >>
> >> ----------------------------------------------------------------------
> >>
> >> Message: 1
> >> Date: Tue, 29 Jan 2008 10:01:20 +0100
> >> From: "Dr. Manuel Seeger" <seeger at uni-trier.de>
> >> Subject: [GRASS-user] highest and lowest point in catchment
> >> To: GRASSLIST <grass-user at lists.osgeo.org>
> >> Message-ID: <479EEB60.6050606 at uni-trier.de>
> >> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
> >>
> >> Hello all,
> >> I hope the questions does not seem too simple, but I have now no real
> >> good idea how to solve this simple problem:
> >>
> >> I need to find the highest and the lowest point within catchments
> >> WITH their coordinates (and to get the information about altitude and
> >> coordinates, of course)
> >>
> >> thanks for hints!
> >>
> >> manuel
> >>
> >>
> > Manuel - hope I'm not being silly here, but I'd consider just using an
> > SQL select directly to the data store.
> >
> > Select max( <altitude column> ), <latitude column>, <longitude
> > column>, <any other column you want> from <table> where <boundary
> > conditions of catchment>
> > Select min( <altitude column> ), <latitude column>, <longitude column>
> > <any other column you want> from <table> <boundary conditions of
> > catchment>
> >
> > If you have to, you could extract only the catchment to a separate
> > vector, so that you don't need to fool around with complex boundary
> > conditions.
> >
> > But I'm sure that a genuine Grass expert will have a simpler solution
> > than this ...
> >
> > Cheers,
> > Richard
> > _______________________________________________
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> > grass-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user
> >
>
>
> --
>
> _______________________________________________________________________
> Dr. Manuel Seeger
> Wiss. Assistent                         Scientific Assistant
> Physische Geographie                    Dpt. of Physical Geography
> FB VI - Geographie/Geowissenschaften    Geography/Geosciences
> Universität Trier                       University of Trier
> D - 54286 Trier
> Tel.:   +49-651-201 4557
> Fax:    +49-651-201 3976
> Web:    http://www-neu.uni-trier.de/index.php?id=9607
>
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