[postgis-users] ST_Contains - WGS84

Markus Schaber schabi at logix-tt.com
Mon Jun 30 03:38:20 PDT 2008

Hi, postgis.domain.thewild at spamgourmet.com,

postgis.domain.thewild at spamgourmet.com wrote:

> 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.

No, they should be performed in exactly the projection which was used
to acquire the data. Only using that projection can guarantee that the
vertexes are connected with straight lines.

And one must use a carthesian coordinate system in that projection.


Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in Europe! www.ffii.org

More information about the postgis-users mailing list