[postgis-users] noding problem
chris.hermansen at timberline.ca
Tue Oct 23 14:30:43 PDT 2007
Sorry to take so long to get back on this!
How "isolated" do you want it? What I have right now is a three polygon
table that I wish to overlay on a 3378 polygon table.
Meantime, I'm working on making the problem smaller...
Kevin Neufeld wrote:
> Can you isolate the geometry that is causing the error? If geos is
> broken, it would be nice to have a test case.
> IE. Try noding half the lines at a time, then try noding half of a
> half, etc...
> -- Kevin
> 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:
>> 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
>> Thanks in advance for any light you can shed on this!
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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
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