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

[Howard Butler]

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