Hi Stefan and Sebastian, thanks a lot for your suggestions. Azzurra Il mer 5 mag 2021, 15:30 Sebastian Gutwein <[email protected]> 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) < > [email protected]> 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 >> >> -- >> Adjunct Professor University "Roma Tre" >> Gis Applied for Environmental studies >> Risk modelling & Hydrogeology >> Consultant DFID-UK, United Nations, EU projects >> AZZURRA LENTINI >> ++++++++++++++++++++++++++ >> Italy Mobile Tel.: **(39) 338 24 40 676 >> ++++++++++++++++++++++++++ >> SKYPE azzurrahydro >> ++++++++++++++++++++++++++ >> >> *[email protected] <[email protected]>* >> >> *[email protected] <[email protected]> * >> ++++++++++++++++++++++++++ >> *Par respect pour l'environnement,* >> >> *n'imprimez ce mail qu'en cas d'absolue nécessité* >> >> >> >> >> >> >> _______________________________________________ >> Qgis-user mailing [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> >> -- >> Mit freundlichen Grüßen >> Stefan Giese >> Projektleiter/Consultant >> ---------------------------------------------------- >> Aufwind durch Wissen! >> Web-Seminare und Online-Schulungen >> bei der www.foss-academy.com >> ---------------------------------------------------- >> WhereGroup GmbH >> Schwimmbadstr. 2 >> 79100 Freiburg >> Germany >> >> Fon: +49 (0)761 / 519 102 - 61 >> Fax: +49 (0)761 / 519 102 - 11 >> [email protected] >> Geschäftsführer: >> Olaf Knopp, Peter Stamm >> Amtsgericht Bonn, HRB 9885 >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >
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