[postgis-users] Still can't make sense of this error

[strk at refractions.net]

First of all you should isolate the two geometries giving you
the problem. Do it using oid or gid and a binary search.

Once you find the two geoms send an sql script issuing
the difference command so we can test it on newer GEOS versions.

If the problem is still there we'll see how JTS handles this
and hunt the bug if it does it cleanly.

--strk;

On Thu, May 19, 2005 at 09:20:05AM -0400, Mark Fenbers wrote:
> OK, now that we got the source of the message garbage out ot the way, I 
> need to restate my unresolved problem...
> 
> I'm consistently getting an error that I cannot make sense of.  Here's 
> the query I run:
> 
> SELECT 'ILN' AS "base radar",radid,
>    AsText(
>            Difference(
>                base_geom,
>                x_geom
>            )
>    )
>    FROM MJF WHERE radid != 'ILN'
>     AND IsValid(x_geom) AND IsValid(base_geom);
> 
> Here's the error I get::
> 
> NOTICE:  TopologyException: no outgoing dirEdge found (34380.5,521104)
> ERROR:  GEOS difference() threw an error!
> 
> If I change my query such that only one row is returned (such as adding 
> "LIMIT 1", or changing the WHERE clause from "!=" to "="), then I do NOT 
> get the error.   I get the error whether I use Difference(), 
> Intersection(), GeomUnion(), or the like, whenever more than one row is 
> returned.   The 'base_geom' contains a circular geometry returned from 
> the Buffer() function (to create a disk around point).  The x_geom is a 
> rectangle that I know intersects the circle (base_geom).  Any ideas how 
> to interpret this error or get around it?
> 
> Mark
> 


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