[postgis-users] Feautures omitted from ST_Buffer operation

Chris Hermansen chris.hermansen at timberline.ca
Wed Mar 25 20:46:08 PDT 2009

This sounds to me like you might be buffering a linestring and not a
polygon.  Is that possible?  Ie are the countries represented as
outlines (linestrings) rather than polygons?

Roger André wrote:
> Hi All,
> I'm having some problems with features that are being returned from an
> ST_Buffer operation in PostGIS.  When I try to buffer the extents of
> Papua New Guinea, a large region in the middle of its extents is
> omitted.  You can see a visual representation of this at
> http://lagerratrobe.blogspot.com/2009/03/problem-with-postgis-stbuffer.html
> If I just select the country itself, I get back all of the features
> that I'm expecting.  In the image I've posted above, the black area
> indicates the results of that query.
> I am using postgresql-8.3.5, and postgis-1.3.3.  My select statements
> is as follows:
>     select name, Buffer(the_geom, .12) from coastlines where
> iso_3_code = 'PNG';
> I've tried this using both a free countries shapefile, as well as an
> ESRI one, and get the same results.  I'm a bit baffled, and unsure if
> I have a problem with both data sets, or in my query, or...?  If
> someone else has had a similar problem in the past, and can shed some
> light on it, I'd greatly appreciate it.
> Thanks in advance,
> Roger
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Chris Hermansen         mailto:chris.hermansen at timberline.ca
tel+1.604.714.2878 · fax+1.604.733.0631 · mob+1.778.232.0644
Timberline Natural Resource Group · http://www.timberline.ca
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