[postgis-users] Intersection errors out with null directed edge

[Chris Hermansen]

I used Paul's command and here's an excerpt of what I found:

clh=# select gid from v2007 where not st_isvalid(the_geom);
NOTICE:  Self-intersection at or near point 1.01727e+06 886743
NOTICE:  Self-intersection at or near point 1.06218e+06 960196
NOTICE:  Self-intersection at or near point 1.07742e+06 956155
NOTICE:  Self-intersection at or near point 1.08071e+06 960386
NOTICE:  Ring Self-intersection at or near point 1.08938e+06 959268
...
  gid   
--------
    190
  75287
  77089
...
(27 rows)

This is great, super-useful in fact!  Thanks a lot!!!

On Fri, 2007-14-09 at 10:26 -0700, Chris Hermansen wrote:
> Thanks, Martin, I will give those a try and report back on what I find
> out.
> 
> On Fri, 2007-14-09 at 10:01 -0700, Martin Davis wrote:
> > Currently your only option is to run isValid on your geometry table.  It 
> > will identify any geometries which are not valid. 
> > 
> > To see the actual nature and location of the errors you will have to 
> > export them to another tool (such as JUMP or JTS TestBuilder) to see the 
> > actual nature & location of the errors (Providing similar functionality 
> > is on the ToDo list for PostGIS)
> > 
> > Martin
> > 
> > 
> > Chris Hermansen wrote:
> > > Hello again;
> > >
> > > So with GEOS 3.0.0RC4 the problem now becomes:
> > >
> > > TopologyException: EdgeRing::computePoints: found null Directed Edge
> > >
> > > I believe there is in fact something wrong with the data.  However the
> > > TopologyException does not identify the source of the problem.
> > >
> > > In looking through the mailing list archives, I see questions around
> > > this issue have come up in the past (eg September 2006).  I don't see
> > > anyone suggesting ideas on how to find the offending data elements.
> > >
> > > Also, trolling through google doesn't seem to turn up anything.
> > >
> > > Does anyone have any ideas on how to explore the data to look for
> > > problems such as this.
> > >
> > > Thanks in advance!
> > >
> > > On Thu, 2007-13-09 at 11:31 +0200, Andreas Laggner wrote:
> > >   
> > >> Hi Chris,
> > >>
> > >> as i had this errors i installed postgis with GEOS 3.0, and such an 
> > >> errors never occurs again! I am not sure, but postgis 1.3.1 can be built 
> > >> with GEOS 2.2 too......just run the query select postgis_full_version(); 
> > >> and check your version of GEOS.
> > >>
> > >> cheers      Andreas
> > >>
> > >>
> > >> Chris Hermansen schrieb:
> > >>     
> > >>> Hi folks;
> > >>>
> > >>> I had this problem today:
> > >>>
> > >>> AssertionFailedException: EdgeRing::computePoints: found null Directed
> > >>> Edge
> > >>>
> > >>> I see in the archives that there are others who have suffered this, back
> > >>> in 2006 and then in 2005, but there don't seem to be any offerings of
> > >>> techniques to either repair the code or the data - and based on the
> > >>> error above, I'm not sure which is ultimately at fault.
> > >>>
> > >>> Does anyone have some more up-to-date thought on this?
> > >>>
> > >>> I'm running postgis-1.3.1 on Ubuntu with the packaged postgresql-8.2
> > >>> installed.
> > >>>
> > >>> 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.