[postgis-users] Re: Feautures omitted from ST_Buffer operation

[Chris Hermansen]

Will st_boundary() help?  Perhaps in conjunction with st_buildarea() and
/ or st_polygonize()?

You may Roger André wrote:
> So I have a partial solution, but it creates another problem for me. 
> I'm able to properly buffer all of the features in Papua New Guinea by
> doing an ST_Dump and blowing apart the multipolygon, then buffering
> the individual polygons:
>
> SELECT name, ST_Buffer((ST_Dump(the_geom)).geom, .12) AS the_geom
> FROM coastlines WHERE iso_3_code = 'PNG';
>
> However, now I need to reassemble the polygons and dissolve the
> internal boundaries.  Is that possible?
>
> Roger
> --
>
>
> On Wed, Mar 25, 2009 at 4:20 PM, Roger André <randre at gmail.com
> <mailto:randre at gmail.com>> 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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-- 
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
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