[postgis-users] polygons inside polygon

[Jorge Gustavo Rocha]

Hi Paul,

Maybe you can try to apply a ST_ConvexHull. The resulting geometry 
ST_touches the most outer polygon. Can you try that or this not make sense?

Regards,

Jorge

On 30/11/21 10:42, paul.malm at lfv.se wrote:
> Thank you Marcin!
> 
> I’m not sure if I understand you correct. Here is what I tried to do to 
> get the outer most polygons:
> 
> Select * from "org" Where "fid" IN(
> 
> select distinct on (t1.fid) t1.fid
> 
> from "org" t1,"org" t2
> 
> where ST_Area(t1.the_geom)>ST_Area(t2.the_geom)
> 
> and ST_intersects(t1.the_geom,t2.the_geom)
> 
> order by t1.fid,ST_Area(t2.the_geom) desc)
> 
> AND "fid" NOT IN (
> 
> select distinct on (t1.fid) t2.fid
> 
> from "org" t1,"org" t2
> 
> where ST_Area(t1.the_geom)>ST_Area(t2.the_geom)
> 
> and ST_Intersects(t1.the_geom,t2.the_geom)
> 
> order by t1.fid,ST_Area(t2.the_geom) desc);
> 
> I’m still getting polygons inside other polygons.
> 
> Kind regards,
> 
> Paul
> 
> *Från:*postgis-users <postgis-users-bounces at lists.osgeo.org> *För 
> *Marcin Mionskowski
> *Skickat:* den 30 november 2021 08:40
> *Till:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Ämne:* Re: [postgis-users] polygons inside polygon
> 
> *Klicka bara på länkar och öppna bilagor om du litar på avsändaren och 
> vet att innehållet är säkert.*
> 
> 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 
> <https://url11b.mailanyone.net/v1/?m=1mrxkX-0008NY-3a&i=57e1b682&c=E3fbWP_UxOp_aLqY_yLoWpoHnd9en_osfYJj-MVUi5KueBYHM1BjtHCJY7dzm-LB011qRSoveVUqU8Wbo-SQYSOYr9IMVYP063lEVQCr3G9ErfMMDLx0JWLLcyDsdbz4OsKdCpzFuBZU-g6Zf2gdwauTuWm-WmCCd-yXe9BTojKOCWOHXliBKmmUzJm2IMYt21G3fa06qgsJNMVB57og9hfef8SNtdDMCfyM41WFZcL6sAWT7ulje7X4_yE-ywIBR2t6-OHWw7iVq5THHQ_FPz6JAbbD-P0i4FQ6Ze6X30U>) 
> below is my take on this:
> 
> select distinct on (t1.id 
> <https://url11b.mailanyone.net/v1/?m=1mrxkX-0008NY-3a&i=57e1b682&c=9KJuH3f7Mex6ks3lu5cPQvny5O6XFhyh-eH6svguvEFAWIQVxt2r_IF0pHeMBwTmQ0XE2xxmCMWnaDbfaMp5XAI5b_Dcd0CClUb5RGp_7jG34xScneDpX0vYGQ4vngdzDwWvGm-5Vrd9D1J_a38Rof5Lup9vwpMo_mGHYNGYu4f1wTbn36eA3P8CNM6_0ioVin4dzKvW5LcIMv9Lun1VjfK4qpwRVaVWuelYCEa3WiGmNGu1zEEv9fA7t7zcNFT0>) 
> t1.id 
> <https://url11b.mailanyone.net/v1/?m=1mrxkX-0008NY-3a&i=57e1b682&c=9KJuH3f7Mex6ks3lu5cPQvny5O6XFhyh-eH6svguvEFAWIQVxt2r_IF0pHeMBwTmQ0XE2xxmCMWnaDbfaMp5XAI5b_Dcd0CClUb5RGp_7jG34xScneDpX0vYGQ4vngdzDwWvGm-5Vrd9D1J_a38Rof5Lup9vwpMo_mGHYNGYu4f1wTbn36eA3P8CNM6_0ioVin4dzKvW5LcIMv9Lun1VjfK4qpwRVaVWuelYCEa3WiGmNGu1zEEv9fA7t7zcNFT0>,t2.id 
> <https://url11b.mailanyone.net/v1/?m=1mrxkX-0008NY-3a&i=57e1b682&c=MB1btGDh1LRWWz9_qH-7fMRyiv5SylMmhNclzuXCnly7_WjBFSzNNi8uoxskAeJ4w4vgf__otNnIlUBwzIcTXhXbUpsTFsuilzyfmYd9zwlz05eB_sxpFqejtXwlOFEeYlEQLMRezJUhez4-Az3YSqWptDxKMQo3xICyLgQ_J7X-Y60pOXOjXiF2bxqaDL7qbXenH7LOd0rsTK8ovDtTM0OQ4EBcMuXDxIvRB7k1Wb5YS5ejXpy-7iOFHBuUUIEB>
> 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 
> <https://url11b.mailanyone.net/v1/?m=1mrxkX-0008NY-3a&i=57e1b682&c=9KJuH3f7Mex6ks3lu5cPQvny5O6XFhyh-eH6svguvEFAWIQVxt2r_IF0pHeMBwTmQ0XE2xxmCMWnaDbfaMp5XAI5b_Dcd0CClUb5RGp_7jG34xScneDpX0vYGQ4vngdzDwWvGm-5Vrd9D1J_a38Rof5Lup9vwpMo_mGHYNGYu4f1wTbn36eA3P8CNM6_0ioVin4dzKvW5LcIMv9Lun1VjfK4qpwRVaVWuelYCEa3WiGmNGu1zEEv9fA7t7zcNFT0>,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 <mailto: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
> 
>     1_LFV_svensk_96
> 
>     Paul Malm
> 
>        Operations / AIM Flyginfo SE
> 
>     	
> 
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J. Gustavo
-- 
Jorge Gustavo Rocha
Departamento de Informática
Universidade do Minho
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