[postgis-devel] How are these concepts managed in PostGIS?

[Martin Davis]

Tolerance in the way that Oracle uses it is not supporting in PostGIS.  
Instead, functions such as spatial predicates and overlay operations (eg 
intersection) are computed using the full precision of the DP floating 
point numbers.  (Intternally GEOS does support the concept of a 
user-defined precision model, but this isn't exposed in PostGIS).

I'll let someone else speak to M-value support.

Jorge Arévalo wrote:
> Hi,
>
> I'd like to know if these two concepts are taken into account in
> PostGIS, and where to find information on how are they managed. They
> are concepts used in Oracle Spatial:
>
> - Tolerance (distance that two points can be apart and still be
> considered the same):
> http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28400/sdo_intro.htm#i884589
>
> - Unit of measurement support (particularly, creating an user-defined
> unit of measurement):
> http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28400/sdo_objrelschema.htm#i1010145
>
> I'm not finding this information in PostGIS manual
> (http://postgis.refractions.net/documentation/manual-svn/).
>
> Many thanks in advance, and best regards,
>
> --
> Jorge Arévalo
> Internet & Mobilty Division, DEIMOS
> jorge.arevalo at deimos-space.com
> http://mobility.grupodeimos.com/
> http://gis4free.wordpress.com
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>   

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022