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I have polygons intersection in single layer. I want polygon in yellow frame and use polygon intersection to calculate area , how to do this?


In the processing toolbox, there is a tool named Polygon self-intersection that can be used to extract the intersection polygon in the same layer:

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Input file:

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Using the tool:

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After running the tool:

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Then you can calculate the area.

I am using QGIS 3.4.2

  • thank you. it work fine. If I want to show polygon intersection specifically. How to do ? – p wat Dec 12 '18 at 2:19
  • @pwat I am not sure how you can show the intersection, but the only thing that can come to my mind is to use the symbology. Go to Layer Properties -> Categorized -> Select ID column or Area column -> Classify your polygons based on ID or Area. You can delete unwanted classes in the style, if necessary – ahmadhanb Dec 12 '18 at 2:27
  • thank you. after I use self-intersection value in attribute of intersection is null how to fix this? – p wat Dec 12 '18 at 2:30
  • 1
    @pwat What value? if it is area attribute, you should select the row, then select the area field from the drop-down list and write $area and click on update selected. If this is not you question, then it is better to ask another question on another thread and make your question clear because you can only ask one question at a time. – ahmadhanb Dec 12 '18 at 2:35

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