[postgis-users] ST_Contains - WGS84

postgis.domain.thewild at spamgourmet.com postgis.domain.thewild at spamgourmet.com
Fri Jun 27 07:46:27 PDT 2008

+postgis+thewild+172cd4478a.postgis.domain.thewild#spamgourmet.com at spamgourmet.com 
a écrit :
> Markus Schaber - schabi at logix-tt.com a écrit :
>> I'm not really sure about that, it may be that the rubberbands get
>> mangled into curves in certain projections. And so vertexes from other
>> polygons might "jump" on the other side of the rubberband.
> Indeed, I would assume that too.
> Projections do not preserve parallelism, so I guess that the same 
> geometries projected in two different srids could have different 
> ST_Relate results.
> If you want "true results", I think you have to go for a real coordinate 
> space like 4326.

Thinking a bit more about it, maybe those spatial relation checks are 
always internally performed in unprojected coordinates.
That would be logical, since projections are just a representation of 
real things, relations should be checked on the real things rather than 
on their representations.

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