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

[Roger André]

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> 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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