<div dir="auto">Hi Stefan and Sebastian, thanks a lot for your suggestions.<div dir="auto">Azzurra</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il mer 5 mag 2021, 15:30 Sebastian Gutwein <<a href="mailto:bas@rdgland.com">bas@rdgland.com</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>In the QGIS toolbox there is a Saga algorithm called Terrain Surface Convexity that does calculate convexity or concavity. I have never used it. <br></div><div><a href="http://www.saga-gis.org/saga_tool_doc/2.2.3/ta_morphometry_21.html" target="_blank" rel="noreferrer">http://www.saga-gis.org/saga_tool_doc/2.2.3/ta_morphometry_21.html</a></div><div><a href="https://sourceforge.net/p/saga-gis/discussion/354013/thread/3fadd3e7/" target="_blank" rel="noreferrer">https://sourceforge.net/p/saga-gis/discussion/354013/thread/3fadd3e7/</a></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, May 5, 2021 at 4:14 AM Stefan Giese (WhereGroup) <<a href="mailto:stefan.giese@wheregroup.com" target="_blank" rel="noreferrer">stefan.giese@wheregroup.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>one process could be:</p>
<ul>
<li>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</li>
<li>substract the filtered from the original<br>
</li>
<li>select values > or < your cutoff</li>
<li>convert this into polygons</li>
</ul>
<p>see
<a href="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" target="_blank" rel="noreferrer">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</a>
for further reading</p>
<p>Hope this helps</p>
<p>Stefan<br>
</p>
<div>Am 05.05.2021 um 10:02 schrieb Azzurra
Lentini:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_default" style="font-family:tahoma,sans-serif">Hi
list,</div>
<div class="gmail_default" style="font-family:tahoma,sans-serif">I
need to find the convex and concave areas from a dtm raster
file. Do you have any suggestions? </div>
<div class="gmail_default" style="font-family:tahoma,sans-serif">Thanks </div>
<div><br>
</div>
-- <br>
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