Johannes, Thank you very much for the useful suggestions. I greatly appreciate your comments! I'll post my results once I work through things.
Best, Tom On Wed, Nov 12, 2014 at 7:42 AM, Johannes Radinger < [email protected]> wrote: > Hi Tom, > > what comes into my mind is following approach (not tested): > > 1) calculate flow direction using r.watershed for each pixel of your map > 2) transforming raster to vector points (r.to.vect), adding some columns > for your results (X, Y, ID). This step should provide you already with > unique IDs for your cells/points. > 3) With v.to.db you can update the X and Y coordinate of your cell center > and together with the raster resolution you can get the lower left corner > as desired. > 3) By knowing the flow direction for each point you should be able to > calculate the X and Y coordinate of the downstream cell (adding or > substracting your cell dimensions from the cell center, correct for > diagonal flow). When you know X and Y of your downstream cell then you > should be able to also get the ID of the downstream cell (most probably a > SQL query I guess) > > Maybe there are easier ways.... > > hope it works, > Johannes > > On Wed, Nov 12, 2014 at 5:10 AM, Thomas Adams <[email protected]> wrote: > >> All: >> >> I need to generate an ascii text file from a flow direction grid that >> consists of (among a couple other things that don't really matter at this >> point) for each pixel: >> >> (1) a unique integer identifier (1 -- N) for the pixel >> (2) the integer identifier of the downstream pixel (assuming there is >> ONLY one) >> (3) the x,y location of the pixel (presumably, the lower left corner of >> the pixel) >> >> has anyone already done something like this? >> >> It's needed (along with some header information) as an input file for a >> gridded distributed hydrologic model, identifying the flow connectivity >> from pixel to pixel for streamflow routing purposes. I have already >> formulated conceptually how to do this, but if someone has already done >> such a thing, why reinvent the wheel?? >> >> Any help is appreciated. >> >> Regards, >> Tom >> >> >> _______________________________________________ >> grass-user mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/grass-user >> > > -- Thomas E Adams, III 718 McBurney Drive Lebanon, OH 45036 1 (513) 739-9512 (cell)
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