Yep, absolutely right - I meant Union, not intersection!
Kevin Neufeld wrote:
Martin Davis wrote:
I was able to rebuild your polygon this way:
1. extract the exterior ring - you may want to add to this subquery
all
the interior rings if you have any
2. extract all the points of the ext ring as ordered pairs (ie as
point1-point2, point2-point3, point3-point4, ....)
3. recreate line segments from all these ordered point pairs, removing
duplicates.
4. rebuild the polygon using st_buildarea()
Would this trick work on every polygon? By construction my polygons
have no interior ring.
Knowing that you have no holes definitely helps.
Another thing you might be able to try is to:
- convert the polygon to a linestring
- call intersection on it with a single point from the linestring
(this effectively nodes the linework)
- polyognize the resulting linework back to a polygon
Nice. You mean union, not intersection though, right Martin? Because
the intersection of a point and a line is a point.
This is better than my solution cuz generate_series actually has
issues when the number of points in a line is more than a few thousand
(probably due to internal storage and toast tables).
So, your query would become:
SELECT ST_BuildArea(geom) AS geom
FROM
(
-- Re-node the linear ring
SELECT St_Union(geom, St_Startpoint(geom)) AS geom
FROM
(
-- The exterior ring of your polygon
SELECT ST_ExteriorRing(
'POLYGON((
9.50351715087891 47.3943328857422,
9.50386047363281 47.3943328857422,
9.50351715087891 47.3943328857422,
9.50248718261719 47.3943328857422,
9.50214385986328 47.3939895629883,
9.50180053710938 47.3943328857422,
9.50145721435547 47.3939895629883,
9.50111389160156 47.3936462402344,
9.50145721435547 47.3936462402344,
9.50145721435547 47.3939895629883,
9.50214385986328 47.3939895629883,
9.50248718261719 47.3939895629883,
9.50386047363281 47.3943328857422,
9.50351715087891 47.3943328857422))'::geometry) AS geom
) AS ring
) AS fixed_ring
-- Kevin
-------------
Kevin Neufeld
Software Developer
Refractions Research Inc.
300-1207 Douglas St.
Victoria, B.C., V8W 2E7
Phone: (250) 383-3022
Email: [EMAIL PROTECTED]
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--
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
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