Hi Martin, everyone; The polygons were converted to linestrings in the previous step, and I've checked...
Martin Davis wrote: > Did you convert your polygons to linestrings? If not, then you are > running the union operation on polygonal geometry. This is the usual > source of topology errors (which are caused by robustness & precision > issues in the underlying linework). > > Chris Hermansen wrote: >> Hi folks; >> >> I posted something a few days back on a noding problem I'm having, and >> received no answer. At this point I have more details and I think there >> is something seriously wrong. >> >> This is Postgis 1.3.1 and GEOS 3.0.0rc4. >> >> The Postgis Wiki has an example of putting two somewhat overlapping >> polygon networks together: >> >> http://www.postgis.org/support/wiki/index.php?ExamplesOverlayTables >> >> Basically, two tables of polygons are converted into linestrings and put >> in a third table. >> >> Then, the table of linestrings is noded; in the Wiki, the code given is: >> >> CREATE TEMP TABLE noded_lines AS >> SELECT St_Union(the_geom) AS the_geom >> FROM all_lines; >> >> Right, my problem! I have two tables with multi-polygons. I convert >> them to polygons. I use isValid() on their geometries to make sure that >> they are in good shape. >> >> Then! I run the "noding query" - which I might add takes a >> loooooooooooooooong time - and in the end I see: >> >> dustin=# create temp table step2 as >> dustin-# select st_union(geom) as geom from step1; >> NOTICE: TopologyException: found non-noded intersection between >> 1.40568e+06 507100, 1.40568e+06 507100 and 1.40568e+06 507100, >> 1.40568e+06 507100 1.40568e+06 507100 >> ERROR: GEOS union() threw an error! >> >> OK, now to me this doesn't seem at all fair! If the st_union() command >> is supposed to node the linework then WHY is complaining about non-noded >> intersections? >> >> Thanks in advance for any light you can shed on this! >> >> > -- Regards, Chris Hermansen · mailto:[EMAIL PROTECTED] 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. _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
