[postgis-devel] Motion: vote for considering SRID <= 0 as "unknown"

Chris Hodgson chodgson at refractions.net
Tue Oct 4 10:11:59 PDT 2011

Sandro Santilli wrote:
> On Tue, Oct 04, 2011 at 03:54:28PM +0100, Mark Cave-Ayland wrote:
>> My only comment would be what do the various standards (SQL-MM/OGC)
>> say about SRID values? As long as they don't specify anything, I
>> guess we have a bit more freedom to interpret the specification as
>> fits best with PostGIS.
> All I can find about SRID in OGC SFS 1.1:
>  Before a geometry can be constructed and inserted into a table,
>  the corresponding row for its SRID must exist in the
>  SPATIAL_REFERENCE_SYSTEMS table, else construction of the geometry
>  will fail.
> There's no mention of the possibility for a geometry to have _no_ srid.
> The SRID field in spatial_ref_sys and geometry_columns is of type
> "integer" (but there's no case of "unsigned" in the whole document so
> that isn't necessarely a sign of the fact that we should support <0).
> The SQL/MM doesn't seem any different in that reguard. 
> In both there's no concept of "unknown" srid.
I thought the entire motivation for switching to the unknown=0 semantic 
was for some kind of standards compliance... if this isn't in any 
standard, why are we doing it again? (I'm seriously asking the question 
- what is the positive side of this change?)


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