Yes, thats right, and I tried this with g.region zoom=basin<x> for example. But I have to merge more than one area and they could be distributed far away each other, in worst case.
Regards, Christian. Zitat von Michael Barton <[EMAIL PROTECTED]>: > If you run g.region to set the computational region to just the area of each > basin before doing the other calculations, it might run a lot faster. > > Michael > > > On 5/15/08 5:02 AM, "[EMAIL PROTECTED]" > <[EMAIL PROTECTED]> wrote: > > > Date: Thu, 15 May 2008 14:00:14 +0200 > > From: Christian Schwartze <[EMAIL PROTECTED]> > > Subject: [GRASS-user] Multiple usage of r.water.outlet > > To: grass-user@lists.osgeo.org > > Message-ID: <[EMAIL PROTECTED]> > > Content-Type: text/plain; charset=ISO-8859-1 > > > > Dear GRASS user, > > > > the problem I have is using r.water.outlet for some scripting in Python. > Below > > I > > want to explain the proceeding in detail. It should be mentioned in advance > > that > > the necessary drainage raster has nearly 10000 rows and columns, so it's > not > > really small... > > I have a point shape file (or generally point coordinates, more than 100 > > pairs) > > that presents the input for multiple calls of r.water.outlet. To produce a > map > > representing the corresponding watersheds of all these points I thought of > the > > three following approaches: > > > > (A) At certain intervals (of the r.water.outlet iteration) I sort the > > previous > > calculated basins by area and use the resulting and ascending order as an > > input > > for r.patch. So the basins can not hide each other. > > > > (B) At certain intervals I execute r.cross for overlaying the previous > basins. > > > > (C) I use r.mapcalc in every iteration step with an expression like > > "allbasins = allbasins + > > > if(isnull(allbasins),basin<x>,if(allbasins>=1&&basin<x>==1,<newBasinID>,allbas > > ins))" > > where allbasins is initially a "novalue" raster. > > > > > > All methods above are working right, but have the same lack: the > performance - > > too slow! > > Remember that the working raster has an extent of 10000x10000 pixel. The > > single > > calculated basins and their extents compared to entire drainage raster are > > very > > small (see the attachment). While the duration of r.water.outlet is barely > > acceptable, the merging step (regardless of the technique in A, B or C) > takes > > too long. > > What do you think about the three approaches for a script in Python and how > > can > > i minimize the performance problem when bringing the basins together within > a > > large area? Many thanks for any advice! > > > > Regards, > > Christian. > > __________________________________________ > Michael Barton, Professor of Anthropology > Director of Graduate Studies > School of Human Evolution & Social Change > Center for Social Dynamics & Complexity > Arizona State University > > phone: 480-965-6213 > fax: 480-965-7671 > www: http://www.public.asu.edu/~cmbarton > > > _______________________________________________ > grass-user mailing list > grass-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-user > ---------------------------------------------------------------- This mail was sent through http://webmail.uni-jena.de _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user