[postgis-users] Finding a TopologyException

[Ben Madin]

G'day all,

I have a topology exception with a file I clean up with GRASS and exported back into PostGIS, which I discovered when I tried to merge provinces into countries:

CREATE TABLE new_country AS 
	SELECT country::varchar(3), st_union(the_geom) as the_geom
	FROM new_prov
	GROUP BY country;

NOTICE:  TopologyException: found non-noded intersection between LINESTRING (-0.204257 0.999226, -0.204257 0.99858) and LINESTRING (-0.204257 0.995743, -0.204257 0.999226) at -0.204257 0.999226

There is obviously information here on where the problem lies, but my entire project is in Lat / Long (EPSG:4326) in South East Asia, so I'm guessing this is not (nor is it on a unit square)

So :

How does the coordinates returned by the error relate to my geometry? or What do they mean? Can I use this information to find the problem part of the geometry.

(as an aside, changing the query to st_union(st_buffer(the_geom,0)) let it through (and it works as I wanted)

cheers

Ben