[postgis-users] Feautures omitted from ST_Buffer operation

[Roger André]

Hi Chris,

I don't think it's a linestring.  I checked the sql load file I made, and
the table is defined in it as a MULTIPOLYGON:

SELECT AddGeometryColumn('','coastlines','the_geom','-1','MULTIPOLYGON',2);

Not really sure how else to test though.
--


On Wed, Mar 25, 2009 at 8:46 PM, Chris Hermansen <
chris.hermansen at timberline.ca> wrote:

> 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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> >
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>
>
> --
> Regards,
>
> 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
> 401 · 958 West 8th Avenue  · Vancouver BC · Canada · V5Z 1E5
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