PostGIS Polygons – Deleting Small Gaps (Slivers) Between Polygons

deletepolygonpostgispostgresqlslivers

I try to delete the slivers that appeared when I have merged some polygons.

I have two different cases:enter image description here

For the CASE 1, no problem I fill the gap with:

CREATE OR REPLACE FUNCTION sliver_killer(geometry,float) RETURNS geometry AS
$$ SELECT ST_BuildArea(ST_Collect(a.geom)) as final_geom
FROM ST_DumpRings($1) AS a
WHERE a.path[1] = 0 OR
(a.path[1] > 0 AND ST_Area(a.geom) > $2)
$$
LANGUAGE 'sql' IMMUTABLE;

UPDATE merged SET geom = sliver_killer(geom,50::float);

A function that fill all the gaps smaller than x square meter.

BUT for the CASE 2, when the small gaps are "open" I can't manage to fill those gaps.

I have try something like: buffer(1) followed by buffer(-1) but of course I obtain some rounded corners. Did someone have a true solution ?

Best Answer

Ok I found an answer:

You can avoid to get rounded corner by adding the parameter 'join=mitre' to st_buffer:

So it work perfectly fine with:

SELECT st_buffer(st_buffer(geom,1,'join=mitre'),-1,'join=mitre') FROM mygeotable;

EDIT

If the buffer is too large st_buffer(geom,10,'join=mitre') produce from time to time some strange results (the polygones become spiky). So to avoid this effect it's safer to preserve the old boundary with st_intersection:

SELECT st_intersection(st_buffer(st_buffer(geom,-1,'join=mitre'),1,'join=mitre'),geom) FROM mygeotable;
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