[GeoJSON] Removing CRS from GeoJSON

[Simon.Cox at csiro.au]

Looking back in the archives, in the thread with this subject line, I see comments like



>>  I don't know of a good web service ... that provides axis order information for arbitrary CRS URN,

FWIW - EPSG do provide a service to look up their CRS here: http://www.epsg-registry.org/
The web API is http://www.epsg-registry.org/indicio/query?request=GetRepositoryItem&id=urn:ogc:def:crs:EPSG::27700 for example. You get GML back, from which the axis order (and everything else) can be deduced, with a little work.

Of course the underlying problem with URNs is that you need to know this kind of thing in order to resolve them, and every URN scheme has a different resolver (if at all!). Not very helpful to most people. That's why in 2010 OGC changed its approach and prefers http URIs (i.e. URLs) for all new definitions, leveraging DNS instead. And all the old URNs are mapped directly to URLs with this pattern:

urn:ogc:def:crs:EPSG::27700 --> http://www.opengis.net/def/crs/EPSG/0/27700

You still get GML back, but the service is pretty reliable. Somehow the word has not got out - perhaps because URNs are still mentioned in some of the specs which have not been updated since the policy change. But if you look across the web landscape, URNs are clearly an obsolete technology.

The GeoJSON spec (section 3) recommends the OGC URN syntax, as preferable to the old EPSG:27700 syntax. Maybe a minor update to recommend the OGC URL syntax instead (or as well), and then at least you can have something that usually resolves directly?

Or maybe the IETF process is the opportunity to make such a change? Would it be helpful if I were to submit a formal comment through the IETF lists to do this?


Simon J D Cox
Research Scientist
Land and Water
CSIRO

E simon.cox at csiro.au<mailto:simon.cox at csiro.au> T +61 3 9252 6342 M +61 403 302 672
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