[geos-devel] GEOS and Writing SRID values

Charlie Savage cfis at savagexi.com
Thu Sep 13 23:39:42 EDT 2007

> PostGIS uses -1 as the default "unknown" SRID. Unfortunately, ISO uses 
> 0.  So we remain tempted to flip to 0. It is the one of the major 
> "breaking" changes we would have to do to get to SQL/MM conformance (the 
> others are changing the type numbers for ZM geometry variants in AsBinary).

Since GEOS generally seems to use 0, how about we stick to that?

> Are we suffering a terminology breakdown here? You're talking about SRID 
> in WKB, but the WKB spec doesn't include SRID.  Only the EWKB 
> implementation, which is our own concoction, does that.  As long as the 
> changes don't end up breaking the standards compliant WKB output, things 
> should be OK... I wonder what others think?

Yes, understood.  Except GEOS's wkb output also includes dimension 
information.  That's not part of the original WKB spec, but I see hints 
that it was later added (although I've never actually seen the document).

I think what Frank and I were thinking about is the way to go - keep WKB 
the same by default but let clients change settings if necessary.  Since 
GEOS is used extensively with PostGIS, it sure would be helpful for it 
to also support EWKB fully.

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