[geos-devel] WkbReader and Z-geometries

[Oyvind Idland]

On Thu, Aug 4, 2011 at 11:22 PM, Sandro Santilli <strk at keybit.net> wrote:

> On Thu, Aug 04, 2011 at 07:46:39AM +0200, Oyvind Idland wrote:
> > Oh.. sweet chaos!
> >
> > The lack of a WKB-spec with Z (and M) ordinates seems to have triggered a
> > bunch of WKB-flavours, such as
> > - OGR's "Two-and-a-half-D extensions for Simple Features"
> > - FDO's FGF-format
> > - Postgis EWKB
> >
> > I found the EWKB proposal here, but probably not the latest:
> >
> http://postgis.refractions.net/pipermail/postgis-devel/2004-December/000710.html
> >
> > As far as I can see, it is fairly similar in structure as the SQL/MM,
> except
> > for the optional SRID. The object-type ID's are of course not the same.
> >
> > In addition, SQL/MM specifies CircularString/CurvePolygon/CompundCurve
> etc
> > aswell, would be nice to have these implemented in GEOS aswell (PostGIS
> has
> > done some work here, not sure what)
> >
> > I got two versions of the SQL/MM spec in PDF, the earliest (2nd edtion)
> > dates from 2002. I'll send you the newest right away.
> >
> > For now, I'll try to make a simple hack on the existing WkbReader.
> >
> > Would be nice with a more united WKB-world...
>
> Please use an enum for different WKB types, it's the best we can have.
> I confirm any extension support comes from PostGIS EWKB, which is
> documented in doc/ZMSgeoms.txt, which is the document submitted as
> proposal to the OGC (not sure about the outcome of that).
>
> --strk;
>
>
OGC is currently working on harmonization with ISO, and they will probably
adopt SQL-mm part 3 (3D coordinates, WKB, etc):

http://www.opengeospatial.org/projects/groups/sfswg


-- Oyvind
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