[GRASS-user] intersection of network-lines and areas

achim ak7 at jupiter.uni-freiburg.de
Mon Mar 2 10:24:35 EST 2009

Hi Markus,

thanks for these fine answers.

I used the new r.watershed-version, which is very fast and can handle
massive gids like r.terraflow (in grass64)

Yes, r.waterflow produces very good results, including stream-segments.
But I would have to vary the threshold manually and many times to get
all basins.

I attach an example-jpg to illustrate my point of view...


Markus Metz schrieb:
> achim wrote:
>> I have many rivers flow into sinks. 
> Sounds like r.terraflow output.
>> So I have to define the points, where the river-network has its extreme
>> points/where the points with highest accumulation-values are.
> In case of r.watershed, the stream segment output is more precise.
>> I understand, that I need only one point for r.water.outlet:
>> -> how do I find out the E and N of the starting-cell? Its a CELL and
>> there are falling many coordinates within.
> Any set of coordinates falling within that cell should do.
> BTW,  r.terraflow flow direction must be modified before it can be used
> with r.water.outlet.
>> -> how do I give r.water.outlet a list of my desired "starting-cells"
>> (their coordinates)
> You could call r.water.outlet repeatedly in a script.
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