Hi Achim,
i usually produce the river network starting from the flow accumulation,
not from the flow direction. If you have a raster elevation map you can
get it using r.watershed.
Then, i make as follows:
r.mapcalc 'log_accumulation=log(abs(accumulation)+1)'
r.mapcalc 'inf_river=if(log_accumulation>6)'
6 is a treshold value for the log_accumulation, it is a good value for
me but you maybe can try other values. It produces a binary map.
Then:
Raster -> Transform features -> Thin linear features to reduce at 1pixel
the lines of the binary raster inf_river and create the new file in_river.
Finally, with r.to.vect you can transform the raster in_river in a
vector map.
Hope this helps
Margherita
Message: 8
Date: Wed, 20 May 2009 16:45:56 +0200
From: achim <[email protected]>
Subject: [GRASS-user] IN: raster-flow-direction OUT:vector-network?
To: grass-user <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-15"
Hello,
I am searching for a good idea to convert a raster-flow-direction map
into a vector-network map.
Probably I will have to write a script. If it is possible at all...
In case of writing a script it mean to me: how to produce a line within
r.mapcalc?
Has anyone a hint?
Cheers,
achim
PS:for illustration I attached a little picture
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End of grass-user Digest, Vol 37, Issue 35
******************************************
--
Ing. Margherita Di Leo
Ph.D. Student
Methods and Technologies for Environmental Monitoring
Department of Environmental Engineering and Physics (DIFA)
University of Basilicata
Campus Macchia Romana
85100 - Potenza
Italy
Office: +39-0971205363
Fax: +39-0971205160
E-mail: dileomargherita AT gmail DOT com
Skype: dileomargherita
URL: http://www.difa.unibas.it/A_Manager_PP.do?azione=visualizzaHomePage&id=106
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