Thanks for filing the bug. It's definitely something bad, I did a test where I buffered every country in the world and then underlaid the original shapefile in solid red. There are alot of random places showing though. The explode, buffer, union and re-assemble process seems to give correct results though.
Thanks again for the follow-up. -- On Thu, Mar 26, 2009 at 11:02 AM, Martin Davis <[email protected]>wrote: > Thanks for that. Nice test case! FWIW, this runs fine in JTS. Hopefully > someone on the GEOS side can take a look at this. > > Roger André wrote: > >> Ok, here is the WKB. Let me know if there are any problems with the file. >> -- >> >> On Thu, Mar 26, 2009 at 8:57 AM, Martin Davis >> <[email protected]<mailto: >> [email protected]>> wrote: >> >> I don't think this can be the problem - a buffer of a linestring >> should still produce a polygon. >> >> This is probably a bug in the GEOS buffer algorithm. It would >> help if you posted the WKB or WKB for the geometry. >> >> >> Chris Hermansen 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 >> -- >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> <mailto:[email protected]> >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> >> >> >> -- Martin Davis >> Senior Technical Architect >> Refractions Research, Inc. >> (250) 383-3022 >> >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> <mailto:[email protected]> >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> ------------------------------------------------------------------------ >> >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > > -- > Martin Davis > Senior Technical Architect > Refractions Research, Inc. > (250) 383-3022 > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users >
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