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Pattern matrix for OGC "Equals" relation

P

Hello:

At https://docs.safe.com/fme/html/FME_Desktop_Documentation/FME_Transformers/Transformers/spatialrelations.htm the Pattern Matrix for OGC "Equals" relation is filled with some * characters .

However, Simple Features OGC 06-103r4 document (p. XXXV) at https://www.ogc.org/standards/sfa defines "Equals" relation with no * characters:

a.Relate(b, “TFFFTFFFT”)

To follow OGC specifications, shouldn't the matrix be filled up accordingly?

Thank you very much

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Best answer by markatsafe 16 June 2020, 00:51

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M
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@pmonteiro I'm not sure what the OGC specification you referenced is trying to tell us - I find that presentation very confusing as I odn't really understand the matrix algebra. But I'm pretty sure Equals is typically thought to be T*F**FFF*. Equals is equivalent to Within & Contains:

Within

 

T*F**F***

 

ContainsT*****FF*

 

EqualT*F**FFF*

 

Also defined for PostGIS here

P

@pmonteiro I'm not sure what the OGC specification you referenced is trying to tell us - I find that presentation very confusing as I odn't really understand the matrix algebra. But I'm pretty sure Equals is typically thought to be T*F**FFF*. Equals is equivalent to Within & Contains:

Within

 

T*F**F***

 

ContainsT*****FF*

 

EqualT*F**FFF*

 

Also defined for PostGIS here

Thanks Mark.

Googling a bit, found here that OGC definition is not fully compliant with some situations, such as equality between points: the boundary of a Point is by definition empty, whereas OGC states a non-empty intersection between boundaries of equal geometries: TFFFTFFFT.

Better to use T*F**FFF*, then.

Best regards.

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