Just another (incomplete) idea! On Fri, 2008-02-08 at 10:19 -0200, Daniel Victoria wrote: > 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.
(a) Here "r.stats -ng" to get pixel values with coordinates (?) and export in file (like x,y,z) (b) Do a numeric sort (sort -n) according to z value sort -n -k3 input_file.txt | tail -1 #### this is from http://lists.osgeo.org/pipermail/grass-user/2008-January/042520.html (c) Instead of only tail -1 grab both "head -1" (that would be the min) and "tail -1" (that would be the max) and so you have one "min" and one "max" even if you have small areas and then the rest... (?) > 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 <[EMAIL PROTECTED]> 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: > > > > > [EMAIL PROTECTED] wrote: > > >> Send grass-user mailing list submissions to > > >> [email protected] > > >> > > >> To subscribe or unsubscribe via the World Wide Web, visit > > >> http://lists.osgeo.org/mailman/listinfo/grass-user > > >> or, via email, send a message with subject or body 'help' to > > >> [EMAIL PROTECTED] > > >> > > >> You can reach the person managing the list at > > >> [EMAIL PROTECTED] > > >> > > >> When replying, please edit your Subject line so it is more specific > > >> than "Re: Contents of grass-user digest..." > > >> > > >> > > >> 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" <[EMAIL PROTECTED]> > > >> Subject: [GRASS-user] highest and lowest point in catchment > > >> To: GRASSLIST <[email protected]> > > >> Message-ID: <[EMAIL PROTECTED]> > > >> 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 > > > _______________________________________________ > > > grass-user mailing list > > > [email protected] > > > 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 > > > > _______________________________________________ > > > > grass-user mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/grass-user > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user -- Nikos Alexandris . Department of Remote Sensing & Landscape Information Systems Faculty of Forestry & Environmental Sciences, Albert-Ludwigs-University Freiburg . Tel. +49 (0) 761 203 3697 / Fax. +49 (0) 761 203 3701 / Skype: Nikos.Alexandris . Address: Tennenbacher str. 4, D-79106 Freiburg i. Br., Germany
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