[GRASS-user] Building topologically correct stream network
marchesini at unipg.it
Thu Jul 23 09:41:02 EDT 2009
If I well remember, the problems of 0 values in the category data were
related to braiding or similar artifacts deriving from rasterization
r.strahler used with threshold not too small should clean network and
solve the task...
here  (in italian.. sorry...) you can find some pictures about this
sorry but it was more than one year ago and I don't remember well all
Il giorno mer, 22/07/2009 alle 19.35 -0700, Hamish ha scritto:
> stephen wrote:
> >> Well, I am not sure what I am going to do. I would look at the
> >> code, but I am not adept at C.
> none the less, it doesn't hurt to look, depending on how it is written
> it might be understandable / tweakable.
> > > What exactly is wrong with topology? The existence of these dangles?
> note the v.strahler help page makes special mention that if you used
> r.watershed you should check the topology. Maybe it makes a bitter deal
> out of that than is really the case?
> > Maybe there is nothing wrong. On further reflection the area that
> > I am trying to use this procedure on is very flat and there are
> > intermittent streams and wetlands (site visit) all over the
> > study area. These non-connected lines maybe showing
> > intermittentancy?
> do you see a "ladder effect" in the r.to.vect river network?
> (like a braided river with all joins at right angles)
> maybe that is the problematic topology the module is concerned about?
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