I have a shapefile containing 6 classes of polygons on QGis 3.14. Some of these polygons overlap each others, but they're not geometry errors or duplicates, just polygons with different attributes. However I need to have maximum one entity at any place. So, I'd like to obtain, for each overlapping area, a new entity containing the attributes of the polygons that overlap. I can't make an intersection on a single layer, and the union tool gives me two polygons with equal geometries.

What should I do ?

  • The SAGA Self-intersection tool did the job, thank you, merci beaucoup.
    – HeelRom
    Commented Jun 29, 2020 at 15:42

1 Answer 1


In QGIS 3, I can suggest paying attention to the SAGA's tool Polygon Self-Intersection that is placed in Processing > Toolbox under SAGA > Vector Polygon tools > Polygon self-intersection.


Check also @Kazuhito's answers in this article Summing up values of overlapping polygons in QGIS.

Maybe one-day @xunilk will translate his article in English.


  • 1
    Actually, @Kazuhito's answer using the aggregate tool with the geometry group-by function is perfect, after an union or even a spatial joint ! While the self intersection polygon tool deletes the other field's entries in intersecting feature's attribute tables. Thank you ;)
    – HeelRom
    Commented Jul 1, 2020 at 14:54

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