I am performing a morphometric analysis of dolines using QGIS 3. The analysis consists of determining the longest axis (the union of the two most distant points of the polygon) and the shortest axis which is the longest line perpendicular to the major axis and it is inside the polygon.

I could determine the major axis by the distance matrix, as they answered me in my previous question, but I have not been able to find the line perpendicular to this one.

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  • not sure if I understood your question correctly, but maybe a ready-made solution will solve your question...gis.stackexchange.com/questions/295648/… – Cyril Mikhalchenko Feb 12 '19 at 6:58
  • hello, is exactly what I need to calculate, but I do not understand well how to select the points to make the Delaunay triangulation and generate the line perpendicular to the major axis (line L) – John Feb 12 '19 at 16:23
  • I added a fragment of the picture with the image of the map object selection tool...when you select a point, it should be highlighted in yellow... – Cyril Mikhalchenko Feb 12 '19 at 16:42
  • If I understand the method @Cyril recommended, you need points on the boundary of the polygon. You can extract them with the extract vertices tool. If you need more points than just the vertices, you can use one of the densify tools to add more vertices, then extract vertices again. – csk Feb 12 '19 at 20:32
  • together, with csk we will definitely help Johny and lead him to victory ...:-) – Cyril Mikhalchenko Feb 13 '19 at 7:32

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