Dear list
Great, how powerful expressions are in QGIS!
I have two polygon layers, one with parcels and one with forests. In a virtual
field of the layer parcels I'm trying to calculate the area covered with
forest. I can sum the area of intersecting forests in a virtual field with the
follwing expression:
coalesce(
array_sum(
overlay_intersects(
layer:= 'forest',
expression:= area(@geometry)
)
)
, 0)
But @geometry doesen't return the intersecting area. It returns the whole
polygons, that partly intersect the parcel. So I could add an additional
intersection():
coalesce(
array_sum(
overlay_intersects(
layer:= 'forest',
expression:= area(
intersection(
@geometry, geometry(get_feature_by_id()
)
)
)
)
, 0)
@geometry is calculated in the context of the layer forests. How could I access
the geometry of the parcel inside of overlay_intersects()? get_feature_by_id()
doesn't seem to help, since I don't see a way to get the actual ID of the
parcel.
It is not possible to return @geometry as expression in overlay_intersects and
do the intersection outside.
Does any one have an idea, how I could get the intersected area?
Thank you. Bruno
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