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

[Sean Gillies]

Howard, don't forget OGC URNs! And xlink traversal for GML ;)

Daniel Morissette wrote:
> I like the concept. I would rather read that we are using and extending 
> support for an existing repository, than reading that we are creating 
> our own repository, but I am not aware of an actual central repository 
> somewhere that will accept user-contributions ... so I guess this is 
> really filling a void.
> 
> Note that I am not an expert in OGC SRS and other projection 
> authorities, so there may well be something that exists already and that 
> I'm just not aware of.
> 
> Anyway, the extension seems simple and flexible enough to be extended to 
> support other types of repositories someday, so I'm cool with it.
> 
> Daniel
> 
> 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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> 
>