Re: Points from Polygon

Yes, that's right.  ST_Boundary will convert the polygon to
[multi]linestrings which you can then use to extract the points.

These have examples that should help:
http://postgis.refractions.net/documentation/manual-svn/ST_PointN.html
http://postgis.refractions.net/documentation/manual-svn/ST_NPoints.html
http://postgis.refractions.net/documentation/manual-svn/ST_GeometryN.html

Mike, nice solution with your function.  Have to give that a try sometime.
-- Kevin

tommy408 wrote:
> How can I extract points from all the vertex of a polygon?
>
> I see there are ST_NPoints and ST_PointN for linestring.  But nothing for
> polygons.  Maybe convert polygon to linestring then linestring to points?
>  
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