[MetaCRS] IGNF Projection catalog?

[Christopher Schmidt]

On Thu, Dec 18, 2008 at 04:53:01PM +0100, Richard didier wrote:
> Le Mercredi 17 Décembre 2008 13:45, Christopher Schmidt a écrit :
> > Hi,
> >
> > I see that proj4js has a catalog for the IGNF projections:
> >
> >   http://trac.osgeo.org/proj4js/browser/trunk/tools/catalogues/IGNF
> >
> > I've googled, and found a couple places where these codes appear to
> > possibly come from:
> >
> >   http://www.geoportail.fr/partage/Professionnel/RIG/RIG.xml
> >  
> > http://svn.osgeo.org/gdal/trunk/gdal/ogr/ogrsf_frmts/geoconcept/geoconcept_
> >syscoord.c
> >
> > and the code mentions that:
> >
> >  " The following information came from GEO CONCEPT PROJECTION files"
> >
> > There is also:
> >   http://lambert93.ign.fr/index.php?id=28
> >
> > Which is in French, but mentions "+init=IGNF:LAMBE +to
> > +init=IGNF:LAMB93", which makes me think it might be related.
> >
> > Can anyone point to the canonical source for this data? is it the
> > RIG.xml, and is there a process used to convert these to WKT? (Or is
> > proj4 the canonical string format?)
> >
> 
> Hi Christopher,
> 
> The IGNF catalogue for PROJ4 has been integrated by me in the 1.6.1
> release (the last one).  It is produced from our internal DB that
> allows others catalogues like ignf-spatial_ref_syst.sql, qgis.sql,
> RIG.xml for different software.  Basically, the idea was that on
> PROJ.4 based software using our catalogue could directly benefits from
> our interpolation grid for NTF to RGF93.  I have also sent to PROJ4JS
> project python script to convert EPSG and IGNF files format of PROJ.4
> into JavaScript for PROJ4JS.

Didier,

Thanks for your help here.

The reason I'm asking is not directly related to wanting to use the codes
for transformations, but rather because I would like to have the most up
to date references included within SpatialReference.org.

Thus far, we have been doing our best to work as close to the 'source'
data as possible, and use the same translation pipeline that other
software would. The goal is to take the 'source' data and convert it to
WKT, which is what SpatialReference.org exposes.

It looks like it would be possible to use the spatial_ref_sys.sql files
provided to do this, but it's not clear to me if those files are updated
in line with something like the RIG.xml, or if they are a secondary
product. If the spatial_ref_sys files are converted from something else
-- which is publicly available -- I'd love to be able to know aht the
'something else' is, and use the same tools. If that's not possible,
then I just have to hope that the spatial_ref_sys.sql doesn't lag behind
:)

It looks like the RIG.xml has more of the information we need -- things
like domain of validity and so on -- though I'm somewhat scared of
converting the GML to WKT :) 

> In the coming month, the canonical source will be RIG.xml that will be hosted 
> under http://librairies.ign.fr/geoportail/resources/RIG.xml (there is already 
> a file there, it is not the final one). All other links you mentionned will 
> be redirected to it.

Okay. Are things like the spatial_ref_sys.sql files *more* final, or are
they sourced from the (still-incomplete) RIG.xml?

Regards, 
-- 
Christopher Schmidt
MetaCarta