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.
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
--
Adrien
(attachments)
On Sat, Mar 30, 2019 at 5:30 PM Micha Silver <tsvibar@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
grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user
–
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918
grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user
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@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
grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user
–
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918
grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user
--
Adrien
