Joining two polygons where they overlap the most in QGIS

Question

I have two layers: district (with lots of districts) and an object layer. I want to add the information where the object lies in the most to the object.

For example: this object lies the most in district B, so it should add 'B' to a column in the objects attribute table.

I tried spatial joins but i am not getting what i am searching for.

Does anyone know how to get there?

Answer 1

Use QGIS expressions with this expression:

array_first (
    overlay_intersects( 
        'Districts',  -- Replace with the name of the layer
        $id,
        sort_by_intersection_size:='des'
    )
)

The parameter sort_by_intersection_size works since QGIS 3.24, see visual changelog.

Answer 2

Let's assume there are two polygon layers one called 'grid_test' (green) and the second called 'grid_test2' (orange), see image below.

Apply the "Join attributes by location" tool with the 2 — Take attributes of the feature with largest overlap only (one-to-one) for the 'Join type':

and get the output like this: