[Qgis-user] convex and concave areas

[Sebastian Gutwein]

In the QGIS toolbox there is a Saga algorithm called Terrain Surface
Convexity that does calculate convexity or concavity. I have never used it.
http://www.saga-gis.org/saga_tool_doc/2.2.3/ta_morphometry_21.html
https://sourceforge.net/p/saga-gis/discussion/354013/thread/3fadd3e7/

On Wed, May 5, 2021 at 4:14 AM Stefan Giese (WhereGroup) <
stefan.giese at wheregroup.com> wrote:

> one process could be:
>
>    - smooth the DTM by a neigbourhood analysis. The width depends on the
>    size of your convex and concave areas. you can use a mean filter or lowpass
>    for example
>    - substract the filtered from the original
>    - select values > or < your cutoff
>    - convert this into polygons
>
> see
> https://www.researchgate.net/profile/Hazen-Russell/publication/277324326_A_semi-automated_esker_detection_method_EDM_for_improved_quantification_of_glaciated_landscapes/links/5567b6ca08aeab77721eac23/A-semi-automated-esker-detection-method-EDM-for-improved-quantification-of-glaciated-landscapes.pdf
> for further reading
>
> Hope this helps
>
> Stefan
> Am 05.05.2021 um 10:02 schrieb Azzurra Lentini:
>
> Hi list,
> I need to find the convex and concave areas from a dtm raster file. Do you
> have any suggestions?
> Thanks
>
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