[postgis-users] geometry type issue
shishaozhong at gmail.com
Wed Apr 29 06:34:52 PDT 2020
Hello, Bo Victor Thomsen,
A very good point!
By the way, would ST_ConcaveHull for a point, leads to a point geometry?
Would ST_ConcaveHull for 2 points, leads to a line?
Would ST_ConcaveHull for 3 points, leads to a triangle (polygon)?
On Mon, 27 Apr 2020 at 13:18, Bo Victor Thomsen <bo.victor.thomsen at gmail.com>
> (not tested !!)
> UPDATE a_table AS a SET a.geom = b.cgeom from (select name,
> ST_ConcaveHull(ST_Collect(geom), 0.99) as cgeom from b_table group by name
> having count(*) >= 3) AS b WHERE a.name = b.name
> the "count(*) >= 3" removes point collections which will result in
> degenerative concave hulls
> Den 27-04-2020 kl. 12:29 skrev Shaozhong SHI:
> I added a new column.
> alter table a_table add column geom geometry(Polygon, 27700);
> update a_table set geom = (select ST_ConcaveHull(ST_Collect(geom), 0.99)
> from b_table where name = _name) where name = _name;
> It kept throwing up an error message saying: "geometry type point does not
> match polygon".
> I thought that a concavehyll is a polygon. That is why I created a
> polygon column for it.
> Can anyone help?
> postgis-users mailing listpostgis-users at lists.osgeo.orghttps://lists.osgeo.org/mailman/listinfo/postgis-users
> Med venlig hilsen / Kind regards
> Bo Victor Thomsen
> postgis-users mailing list
> postgis-users at lists.osgeo.org
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