Re: RFC 5870 - A Uniform Resource Identifier for Geographic Locations ('geo' URI)

An excellent cautionary tale. For example, the 3D default coordinate system is cited as EPSG:4979, with optional elevation relative to the WGS84 geoid. However, 4979 elevation is relative to the WGS84 ellipsoid, not the geoid the RFC cites. There is a defined WGS84 gravimetric geoid (EGM96) that varies from the ellipsoid by around +/-100m over the earth, and is approximated by a coarse coverage in most modern GPS units while neglected in older ones. Unfortunately the geodetic details matter. 

-Josh

> On Jul 21, 2015, at 8:08 PM, simon.cox@csiro.au wrote:
> 
> Just became aware of this (via the GeoJSON list)
> 
> https://tools.ietf.org/html/rfc5870#section-3.4.5 <https://tools.ietf.org/html/rfc5870#section-3.4.5>
> I’ve added it to the BP ref list https://www.w3.org/2015/spatial/wiki/BP_References <https://www.w3.org/2015/spatial/wiki/BP_References>
> Simon
>