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Diffences between PostGIS's ST_IsValid and FME's GeometryValidator


katrinw
Participant
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Hi,

I am facing the problem mentioned in the title, especially when I want to detect Self-Intersections in 2D. FME detects a lot more Self-Intersections while PostGIS is fine with the geometry.

What are the reasons?

As we want to build up a standard quality gate for our data, I need to be certain that both ways - either using PostGIS or FME - act in the same way. What is the configuration then for FME to match the behaviour of PostGIS’s ST_IsValid function?

Thanks in advance! :-)

4 replies

ebygomm
Influencer
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  • Influencer
  • May 23, 2025

What settings are you using in the GeometryValidator - OGC should be close to PostGIS ST_IsValid?

 

Do you have an example of a geometry that FME reports as having self intersections but reports as valid in PostGIS?


katrinw
Participant
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  • Author
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  • May 23, 2025

I tried different settings (see screenshot). I attached one example. :-)


ebygomm
Influencer
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  • Influencer
  • May 23, 2025

That will pass a check if you’re checking OGC which is what ST_IsValid is checking so the result in FME is consistent with ST_IsValid

The OGC standard considers duplicate consecutive points to be valid, FME reports them as self intersections *if* you are specifically looking for self intersections


katrinw
Participant
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  • Author
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  • May 23, 2025

So, you say PostGIS’s ST_IsValid function is similar to The FME GeometryValidator Issue “OGC Compliant”.

And then the question other way around: Is there a PostGIS function that is similar to FME’s GeometryValidator Issue “Self-Intersections in 2D”? 


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