[postgis-users] unioning a buffer - bug?

[Lee]

Forgot to mention, I have tried this on a couple other polygon and polyline 
tables with similar results.

 





________________________________
From: Lee <quimby5 at yahoo.com>
To: postgis mailing list <postgis-users at postgis.refractions.net>
Sent: Mon, September 13, 2010 10:07:06 AM
Subject: [postgis-users] unioning a buffer - bug?


So after some googling I see similar problems, but no solutions posted.

I am trying to union a buffer, but the query is returning no results.  Here is 
ultimately what I would like to achieve:

select st_union(st_buffer(the_geom,0.1)) as the_geom from 
base.current_assessment_parcel

Here are some troubleshooting steps I have taken to try narrow it down:

select st_isvalid(the_geom) a from base.current_assessment_parcel group by a
TRUE

select st_isvalid(st_buffer(the_geom,0.1)) a from base.current_assessment_parcel 
group by a
TRUE

select st_isvalid(st_union(the_geom)) from base.current_assessment_parcel
TRUE

select st_isvalid(st_union(st_buffer(the_geom,0.1))) from 
base.current_assessment_parcel
NOTICE:  TopologyException: found non-noded intersection between 586714 
4.95189e+006, 586714 4.95189e+006 and 586714 4.95189e+006, 586739 4.9519e+006 
586714 4.95189e+006
Total query runtime: 859 ms.
1 row retrieved.
(returns blank record)


 And just for fun
select st_isvalid(st_buffer(st_union(the_geom),0.1)) a from 
base.current_assessment_parcel
TRUE


I guess my next step would be to try the snap to grid functions, but the first 
query above should work, shouldn't it?

Any help appreciated. Thanks.
Lee
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