QGIS v3.4

I have a single shapefile layer with overlapping features. I wish to intersect the features against themselves and transpose the summary of attributes in the output. The image below will help explain the goal.

What sequence of processing tools should I use to do this? The output should leave me without any overlapping features.

enter image description here

  • You can try to use SAGA: Polygon self-intersection Algorithm under processing tools
    – eurojam
    Jul 29, 2019 at 11:27
  • @eurojam That's perfect, do you want to post this as an answer?
    – James B
    Jul 29, 2019 at 12:09
  • @James B: it's not like you described in your image: for each intersection you will not get one new column...for that reason it was only an idea commited as a comment
    – eurojam
    Jul 29, 2019 at 13:32
  • @eurojam You're right, for the most part this has worked by adding new 'ID' field separating each unique value by a pipe. There are some duplicate geometries. The duplicates do not summarise all the values in a single feature but randomly combine them across each overlapping feature. Proceeding this...I have tried the 'point on surface' algorithm followed by the 'join attributes by location (summary)' algorithm on a cleaned version (no duplicates) of the polygon shapefile. The result retains the longest chain of characters in any one of the duplicate geometries/points. Not a solution...
    – James B
    Jul 29, 2019 at 14:32
  • Are u ok with aggregating area types in a single column and a given separator character ?
    – Snaileater
    Jul 29, 2019 at 15:52

1 Answer 1


As it was pointed out by @eurojam, you can use "SAGA:Polygon self-intersection Algorithm under processing tools"; but in a PyQGIS script for including only required parameter options and to get desired layer.

For testing above approach, I created a single shapefile layer with overlapping features, similar to your shapefile, where it is not showing intersections by using transparency options:

enter image description here

PyQGIS script ran at Pyton Console of QGIS 3.4 it is as follow:

import processing

polys = QgsVectorLayer("/home/zeito/pyqgis_data/overlapped_features.shp","self_intersections","ogr")
output = "/home/zeito/pyqgis_data/intersection.shp"

After running it, resulting layer can be observed at below image:

enter image description here

It can be also observed that it was create a new field where it is recorded all nine single features or self intersections.

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