[Gdal-dev] Proposed Feature: Consumption of URL-based Spatial References

[Jan Hartmann]

Yes, this is a good idea. I am working with historical maps with their 
own projections (e.g. central meridian in Paris), and a central 
repository for those definitions would be very welcome. One wish: it 
would be nice to be able to name the projections, e.g. "Cassini" for the 
18th century French projection. Did you know BTW that our definition of 
the meter as 1/40000 of the globe circumference comes from work done for 
creating that projection?

Jan

Dr. J. Hartmann
Department of Geography
University of Amsterdam

Howard Butler wrote:
> All,
> 
> Chris Schmidt and I have been working on a website 
> <http://spatialreference.org> that reflects the EPSG spatial reference 
> codes database and user-contributed codes in a variety of output 
> formats.  The EPSG code database is never as up to date as you would 
> like, and we frequently tell people to hack their /usr/share/proj/epsg 
> database file with made up codes to support alternative projections.  If 
> we could consume URL-based spatial references with OSR, all that would 
> be required is someone adds the custom coordinate system definition to 
> the site and then everyone could refer to it at that location (hopefully 
> indefinitely).
> 
> As for the website itself, if it has uptake and people find it useful, 
> we will work to put it somewhere it can live for a very long time -- for 
> example OSGeo.  The source code (it's written in Django) will be made 
> available so anyone can stand up their own version of the site.
> 
> I would like to propose that an ImportFromUrl() method be added to 
> OSRSpatialReference that constructs a spatial reference given the 
> SetFromUserInput data retrieved at the given URL.  It would only need to 
> be as specific as that, and it wouldn't need to refer to 
> spatialreference.org.  Additionally, this mechanism could be used to 
> support GML SRS retrieval from URLs (which Frank mentioned was in the 
> spec) in the future.  This method would only be active if you have 
> included curl support, of course.  Maybe someday, if necessary, we do 
> some magical caching, but that'd be a premature optimization at this point.
> 
> Here's an example:
> 
> ogr2ogr -a_srs http://spatialreference.org/epsg/4326/proj4 -t_srs 
> http://spatialreference.org/user/6/proj4 world_borders.shp 
> world_borders_google.shp
> 
> Howard
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