[postgis-users] FW: Support in ST_ConvexHull syntax

[Sandro Santilli]

On Thu, Oct 20, 2011 at 12:09:01PM +0000, Gery . wrote:
> 
> 
> or should be 3 in my table! Bingo! after running: "select st_ndims(st_convexhull(st_collect(geom)) from splitbeam_point;" I got 3 instead of 2, so I put this3 into my table and ready! that did the trick. Now I'm wondering why this has to be 3, I mean, this is a 2D polygon, I think I'll realize that after keeping reading.
> 
> Thanks again Sandro, you were very helpful,

You could have forced your output to 2d using ST_Force_2d,
if that's what you needed.

Why you get a 3d convexhull from a 2d input I don't know.
Are you sure your input geometries are 2d ?
Check st_ndims against all stages: geom, st_collect(geom)

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