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 >
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