[GRASS-user] Extraction 3D vectors ridges/Thalweg from raster DEM ?

[image]

Hello,

Thank you very much for your reply. I made some tests following your
recommandations. For information, the surface of my raw raster DEM is 15.000
km². Resolution : 1 pixel X & pixel Y = 30 meters. (SRID 2154 UTM).

1/"r.watershed": the main input parameter seems to be the minimum size for
each basin. I typed 10 (unit pixels i think). I think it's a low value. I
would like know how enter a coherent value. How to ensure that our input
value is coherent?

2/"r.watershed" process generates several new raster layers. Could you
confirm to me that for *streams* r.thin & r.to.vect process i have to select
the third layer generated called "water_segments". And for the basins i have
to select the 4th layer called "Basin label"? 

3/For basins and the v.extract process. I made a test with v.extractwhere.
But i don't find how to enter the value type=boundary. For information i'm
working with easy GUI interface via Qgis., no with command lines interface.

4/ The final vector output data for streams seems to be rather coherent.
However, my basins vector segmentation seems to be really too detailed and
inexploitable.

Please find below usefull SS showing : A: My raster raw data /
B:Streams_vect_3D / C: Basins_labels_raster D: Basins_area_vector

A
<http://osgeo-org.1560.x6.nabble.com/file/n5094142/SS_raw_DEM.jpg> 

B
<http://osgeo-org.1560.x6.nabble.com/file/n5094142/SS_streams_vect_3D.jpg> 

C
<http://osgeo-org.1560.x6.nabble.com/file/n5094142/Basins_label_raster.jpg> 

D
<http://osgeo-org.1560.x6.nabble.com/file/n5094142/Basin_area_vect.jpg> 



If you can throw light for me. Thanks.

With kind regards. 




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