[postgis-users] GEOS union() error

[Lee Keel]

Hello list.

I am trying to get a multipolygon from a union of buffered linestrings.  See
attached (bad_drawing.jpg) to see what I am trying to achieve.  I have some
linestrings, I want to buffer each line by 400 feet, then combine all of
those buffers to create one multipolygon.  My thought was to do something
like:

select geomunion(buffer(the_geom, 400)) as the_geom from main

However, when I do this, then I get the following error:

NOTICE:  TopologyException: side location conflict
(901411,1.03413e+006,1.03413e+006)

ERROR: GEOS union() threw an error!
SQL state: XX000


Now my guess is that the geomunion is throwing the error because the buffers
overlap and of course that would be an invalid polygon.  So, could someone
purpose a different approach to doing this?  Or tell me what I am doing
wrong.


 <<bad_drawing.jpg>> 

Thanks in advance,
Lee
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