[Qgis-user] convex and concave areas

[Azzurra Lentini]

Hi Stefan and Sebastian, thanks a lot for your suggestions.
Azzurra

Il mer 5 mag 2021, 15:30 Sebastian Gutwein <bas at rdgland.com> ha scritto:

> 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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