[email protected] wrote:
The geometries themselves look okay, they specify polygons that have
some area.
Unfortunately, computing area is not indicative of valid geometries. For example, consider this polygon that has a hole
that extends outside of the polygon, but still returns an area ... whatever that might mean.
SELECT ST_IsValid(geom), ST_Area(geom)
FROM (
SELECT '
POLYGON(
(1 1, 1 4, 4 4, 4 1, 1 1),
(2 2, 5 6, 6 6, 6 5, 2 2)
)'::geometry AS geom
) AS foo;
NOTICE: Self-intersection at or near point 4 3.5
st_isvalid | st_area
------------+---------
f | 5
(1 row)
Any more things to look at would be much appreciated.
As Regina eluded to, if you've ruled out geometry validity as the problem, it may be st_union is running into precision
issues. Try putting your geometries through ST_SnapToGrid()
Cheers,
-- Kevin
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