[GRASS-user] Hydrological grass question: main channel length for each subbasin
wortmann at pik-potsdam.de
Mon Feb 17 02:16:00 PST 2014
this is what I meant by looping over each subbasin, but that is exactly
what I would like to avoid as it would take a lot of time for 1000+
subbasins and I dont really need all the other analysis.
On 02/16/2014 05:58 PM, Thomas Adams wrote:
> 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.
> On Sun, Feb 16, 2014 at 11:07 AM, Michel Wortmann
> <wortmann at pik-potsdam.de <mailto:wortmann at pik-potsdam.de>> 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
> 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.
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