[postgis-users] polygons inside polygon

[Marcin Mionskowski]

Assuming (1) your problem is not trivial (you have more then one "outer
most" polygon) and (2) there can be only one type of spatial relationship
(polygons are properly contained
https://postgis.net/docs/ST_ContainsProperly.html) below is my take on this:
select distinct on (t1.id) t1.id,t2.id
from t t1,t t2
where ST_Area(t1.geom)>ST_Area(t2.geom)
and ST_Intersects(t1.geom,t2.geom)
order by t1.id,ST_Area(t2.geom) desc;
Enclose this in CTE and then just select "outer" polygons based on left
column and "inner" based on right column.

wt., 30 lis 2021 o 07:30 <paul.malm at lfv.se> napisał(a):

>
>
>
>
> Hi,
>
> I have a polygon layer where polygons are inside other polygons (could be
> polygons in polygons in polygons…).
>
> I would like to separate them in 2 different layers, one layer with the
> outer most polygon and one layer with all polygons that has a surrounding
> polygon.
>
> Is there a smart way to do this in SQL?
>
>
>
> Thanks,
>
> Paul
>
>     [image: 1_LFV_svensk_96]
>
>   Paul Malm
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