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Is there function to delete the areas of overlap between polygon features to achieve visualized results? enter image description here

Id like to check for each geometry (row) if a geometry is intersected, or in other words if a geometry is overlapped by another. If this is the case Id like "erase" the overlap from the other geometry without creating a hole. When there is no direct way to delete the overlap, is it possible to create new features from the overlaps, and then filter them out by a certain size treshold?

Maybe there is a simple way I did not see but please excuse PostGIS is new to me.

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  • Is this related to gis.stackexchange.com/questions/363025/… ?
    – dr_jts
    May 27 '20 at 17:37
  • Yes I'd like to know it in general.
    – DrSnuggles
    May 27 '20 at 17:41
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    From the picture above, you could split (ST_Split) a polygon p1 with the exterior ring of a polygon p2 if they overlap. So now you have one big polygon p1, one small polygon p1 and the polygon p2: keep only the biggest polygon area grouped by the polygon ID (something like: .... GROUP BY id HAVING(MAX(ST_AREA(geom)))
    – obchardon
    May 28 '20 at 7:46
  • But how do you know which boundary is the correct boundary ?
    – obchardon
    May 28 '20 at 7:49
  • Considering your other questions concerning this issue; what are you going to do with theses buffers? For most tasks other than pure visuals, buffers can (and IMO should) be avoided (e.g. proximity/spatial relation analysis). And for visualizing them, the rendering application will usually do a better job at sorting out border issues than an approach on the geometric level. For reference: check out my answer here for a (different, but related) visual effect, and note the other answer that has a solution on the geometric level, both in QGIS.
    – geozelot
    May 29 '20 at 11:32
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I've used this and it is good for detecting overlaps

Check whether table has overlapping polygons, in PostGIS?

Remove the limit and make it into a table as

CREATE Table my.table AS
SELECT *
FROM my_table a
INNER JOIN my_table b ON 
   (a.geom && b.geom AND ST_Relate(a.geom, b.geom, '2********'))
WHERE a.ctid != b.ctid

The table will potentially have the ids on which you can search and come back to your source table, perhaps modify only on that list of ids.

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