Michel, If you do what you suggest, but first apply a MASK using each subbasin; so, when you calculate the statistics, they will be for one subbasin at a time; with a very simple script you could loop through each subbasin.
I hope this helps. Cheers! Tom On Sun, Feb 16, 2014 at 11:07 AM, Michel Wortmann <[email protected]>wrote: > Hi list, > I'm looking for a way to calculate the main channel length and width for a > large number of subbasins within a river basin. I understand that the > r.stream.* addon / R.basin gives me the main channel length along with a > tone of other statistics but only for one catchment. Of course, I could > loop over all my subbasins and calculate the statistics one by one, but I > fear that will be time consuming and I dont actually need all the other > analysis. > > I have got an efficient way to calculate the mainstream for each subbasin > as a vector, but I'm struggling to get from there to the distance of the > longest segment in each subbasin. Maybe someone has an idea to complete > this idea of a work flow: > > raster=mainstreams (thinned raster with unique categories for each > subbasin) > > r.to.vect to vectorise, this unfortunately gives me line segments crossing > over subbasin boundaries > > somehow make stream segments from each subbasin > > v.to.db to measure the distance of each line segment > > choose the longest distance for each subbasin > > > Any suggestions/help would be much appreciated. > Regards, > Michel > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user >
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