Hello,
I am trying to simplify a polygon by reducing the precision using ST_Union with
the gridSize parameter ( I am using postgis 3.1 and GEOS 3.9.1). I have read
that it is possible to do that by a union of a geometry with an empty geometry
(http://blog.cleverelephant.ca/2020/12/waiting-postgis-31-3.html). However,
does not works for me ( maybe is my fault because I am new with postgis). I
have tried as follows:
CREATE TABLE public.error_union_empty
(
geom geometry(MultiPolygon),
gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass),
CONSTRAINT error_union_empty_pkey PRIMARY KEY (gid)
);
INSERT INTO error_union_empty
(SELECT ST_union(geom,ST_GeomFromText('POLYGON EMPTY'), 0.001152) geom
FROM f_polygon);
But the result is an empty table.
Then I tried to do the same but by doing the union with the polygon himself,
and this approach seems to work ok.
CREATE TABLE public.error_union_empty2
(
geom geometry(MultiPolygon),
gid integer NOT NULL DEFAULT nextval('fallo_gid_seq'::regclass),
CONSTRAINT error_union_empty2_pkey PRIMARY KEY (gid)
);
insert into error_union_empty2
select ST_CollectionExtract(ST_union(f_polygon.geom,f_polygon.geom, 0.001152))
geom
from f_polygon;
Why is not working the first approach? Have I missed something in the query?
Any help or comments are welcome.
Does anyone knows if is expected to have a simplify with gridsize in the
future?
Thanks!
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