[postgis-users] TopologyException and ST_Intersection

[Bob and Deb]

People should be cautioned that some polygons might disappear when using a
buffer of 0.  Does Postgis 2.0 have this problem with makevalid?
On Jun 25, 2012 7:47 AM, "Nicolas Ribot" <nicolas.ribot at gmail.com> wrote:

> > Hi Nicolas,
> > This is great.  However, we are running POSTGIS="1.5.3"  Is this
> possible in
> > this version?  If not, is there a workaround as I don't think we will be
> > able to upgrade that quickely?
> >
> >
>
> Hi Derek
>
> Yes indeed, there is a trick on postgis < 2.0 to clean polygons: try
> using st_buffer(geom, 0.0). This method is often able to rebuild a
> valid polygon from an invalid one. I also saw on the list (and tested
> myself) that st_buffer(st_buffer(geom, -1), 1) could clean some
> polygons that are not cleaned with only a 0 unit buffer.
>
> Nicolas
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