[GRASS-user] r.watershed - Cleaning vector streams

[Adrien André]

Thank you for your help,

i'll try r.stream.extract

I do have set a small threshold value but it is on purpose.
The streams i am trying to model are not hydrological.

Best regards,

Adrien

Le 19-03-31 à 09 h 48, Markus Metz a écrit :
>
>
> On Sat, Mar 30, 2019 at 5:30 PM Micha Silver <tsvibar at gmail.com 
> <mailto:tsvibar at gmail.com>> wrote:
> >
> >
> > On 29/03/2019 22:03, Adrien André wrote:
> >
> > Hello,
> >
> > following the wiki doc about stream extraction [1], once the stream 
> layer thinned and vectorized,
> > there are many small arcs i would like to remove (see attached 
> capture [2]).
> >
> > So, with the underlying drainage direction map [3], and the 
> resolution r, i would like to delete segments
> > - about r*sqrt(2) long
> > - whose azimuth is more than 45° different from the pixel value 
> under its starting point.
> >
> >
> > This might be possible, but I think the best approach would be to 
> choose the correct threshold value for r.watershed from the start.
> >
> > Trying to manually "fiddle" with the stream network will most likely 
> leave you with disconnected segments, or other inconsistencies.
>
> +1
>
> Please try r.stream.extract in order to get a clean vector stream 
> network. The approach r.thin + r.to.vect creates noise and does not 
> always follow flow directions.
>
> Markus M
>
> >
> >
> > But i still haven't figured a way to achieve this.
> >
> > Do you have any advice ?
> >
> > Thank you,
> >
> > Best regards,
> >
> > [1] 
> https://grasswiki.osgeo.org/wiki/Creating_watersheds#Display_first_results
> > [2] https://framapic.org/1exdxrdqxemw/ytuVxiBp2FKh.png
> > [3] https://grass.osgeo.org/grass74/manuals/r.watershed.html
> >
> >
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> >
> > --
> > Micha Silver
> > Ben Gurion Univ.
> > Sde Boker, Remote Sensing Lab
> > cell: +972-523-665918
> >
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-- 
Adrien

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