[postgis-users] Problems following the Examples Overlay Tables on Wiki

[Chris Hermansen]

Ladies and gentlemen;

I'm trying to follow the Wiki example by Kevin Neufeld on overlaying tables.

I get all my linework from my two polygon tables into a third table just
fine.

When I get to the point of noding, up comes the following situation:

dustin=# CREATE TABLE step2 AS
dustin-# SELECT st_union(geom) AS geom
dustin-# FROM step1;
NOTICE:  TopologyException: found non-noded intersection between
1.40568e+06 507103, 1.40568e+06 507100 and 1.40568e+06 507100,
1.40568e+06 507100 1.40568e+06 507100
ERROR:  GEOS union() threw an error!
dustin=#

I find this greatly puzzling as I thought the whole point of this
exercise was to put nodes into the linework... I must be missing
something very simple!

This is PostGIS 1.3.1 and GEOS 3.0.0.RC4 running against vanilla Ubuntu
7.04 PostgreSQL, I think 8.2.

Thanks in advance!

-- 
Regards,

Chris Hermansen · mailto:clh at timberline.ca
tel:+1.604.714.2878 · fax:+1.604.733.0631
Timberline Natural Resource Group · http://www.timberline.ca
401 · 958 West 8th Avenue · Vancouver BC · Canada · V5Z 1E5

C'est ma façon de parler.