[GRASS-dev] Streams extraction from streams map

Florian Kindl florian.kindl at uibk.ac.at
Thu May 3 06:27:15 EDT 2007

On May 02 [17:12], Markus Neteler wrote:
> I tried this v.strahler recently but it didn't work (it is in the GRASS
> Addons SVN) - for me. Maybe it's still under development. But yes,
> this would probably do the job.

Yes, v.strahler assigns a common identifier to all connected segments.
The code is in forest2tree.c:
StrahForestToTrees() makes use of Vect_get_line_nodes() and
Vect_get_node_line() to accomplish this.

Hints on why the code fails are more than welcome.

A word on why Vect_get_node_line() is hidden in StrahGetNodeLine():
I tried to implement "sloppy" mode where lines need not connect in a
topologically correct way but merely share nodes within a certain distance.
However, this adds a lot of complexity and isn't the point of v.strahler
at all (better run v.clean instead) - so it's defunct for now.

As far as the module "is still under development": well, it should be,
but for the moment I don't find the time. Feel free to hack on the
code if you have a good idea.


Florian Kindl
Institute of Geography
University of Innsbruck
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