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)? Regards, Shao On Mon, 27 Apr 2020 at 13:18, Bo Victor Thomsen <[email protected]> wrote: > (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); > > Then, > > 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? > > Regards, > > Shao > > _______________________________________________ > postgis-users mailing > [email protected]https://lists.osgeo.org/mailman/listinfo/postgis-users > > -- > Med venlig hilsen / Kind regards > > Bo Victor Thomsen > > _______________________________________________ > postgis-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/postgis-users
_______________________________________________ postgis-users mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/postgis-users
