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

From: Joshua Lieberman <jlieberman@tumblingwalls.com>
Date: Tue, 21 Jul 2015 22:00:18 -0400
Cc: public-sdw-wg@w3.org
Message-Id: <A13D0438-4491-45FA-9A5C-5E0EA2B76854@tumblingwalls.com>
To: simon.cox@csiro.au
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
> 


Received on Wednesday, 22 July 2015 02:00:50 UTC

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