Hello Bruno,
try it the other way around:
coalesce(
area(
intersection(
@geometry,
collect_geometries(
overlay_intersects(
'forest',
@geometry
)
)
)
),
0
)
In addition you can use the inner part in the geometry generator.
So you have a visual help to compare your results:
intersection(
@geometry,
collect_geometries(
overlay_intersects(
'forest',
@geometry
)
)
)
Mit freundlichen Grüßen
Ihre PV ANSPERGER mbH
Klaus Affeldt
Zentrale Kamp-Lintfort
Südstraße 25
47475 Kamp-Lintfort
Tel. +49 2842 9635-14
https://www.ansperger.de
A==============================================================================================
>>
>> 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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