[postgis-users] Strange Exceptions

[Paul Ramsey]

Validity is a terrible chicken and egg problem. Ideally, people would 
only have valid geometries. So we could enforce a "valid-only" load 
rule. But then how to people load their data, if they have a few invalid 
geometries? Do we silently drop them? Then how to they find and fix 
them? If we let people load invalid geometries (and we pretty much have 
to) then how do we keep people from running validity-sensitive tests on 
them? Etc, etc, etc.

Markus Schaber wrote:

> Hi,
> 
> On Mon, 26 Jan 2004 10:37:54 -0800
> Paul Ramsey <pramsey at refractions.net> wrote:
> 
> 
>>Make sure you check all your geometries with isvalid() before you
>>start trying to intersect them. Invalid geometries are the #1 cause of
>>failures in the other functions.
> 
> 
> That was a good hit, it points out that I have some non-valid geometries
> in my database. So I think I now have to make them valid.
> 
> I just found out that all ExteriorRings are valid. So I can work with
> the ExteriorRings only until the problem is solved. ATM, I suspect that
> there are some points of interior rings that lie on the border or
> outside of the exterior ring...
> 
> Thanks,
> Markus
> 


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      | Paul Ramsey
      | Refractions Research
      | Email: pramsey at refractions.net
      | Phone: (250) 885-0632
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