QGIS Overlapping Features – How to Find Overlapping Areas in Same Polygon Layer

Question

I'm working with QGIS to find overlapping area's in a polygon layer.

Some more info :
The Layers contains multiple circles ( buffers ) and i need to find where there is an overlapping area of 3 or more circles. And based on how many circles overlap they have to get a different color / style.

Does anybody know a fast workflow for this?

Answer 1

QGIS 3.4

1. Make sure your polygon layer has a unique id field, such as id or fid.
2. Run Union tool (Processing Toolbox > Vector overlay). It will return a new Union layer.
3. Open the attribute table of this Union layer, and create an integer field with an expression as below: count("id", group_by:=geom_to_wkt($geometry)) ...... if your id field name is "id".