And another cautionary example – meteorologists routinely publish Mean Sea Level Pressure maps, even over the Tibetan plateau, and the geodetic details have been routinely ignored for decades.
From: Ed Parsons [mailto:eparsons@google.com]
Sent: Wednesday, July 22, 2015 10:16 AM
To: Joshua Lieberman; simon.cox@csiro.au
Cc: public-sdw-wg@w3.org
Subject: Re: RFC 5870 - A Uniform Resource Identifier for Geographic Locations ('geo' URI)
Yes matters sometimes.. to some people.. It is equally a generalisation to say that geodetic details are relevant to everyone using global coordinates on the web !
Ed
On Wed, 22 Jul 2015 at 03:01 Joshua Lieberman <jlieberman@tumblingwalls.com<mailto:jlieberman@tumblingwalls.com>> wrote:
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<mailto:simon.cox@csiro.au> wrote:
Just became aware of this (via the GeoJSON list)
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
Simon
--
Ed Parsons
Geospatial Technologist, Google
Mobile +44 (0)7825 382263
www.edparsons.com<http://www.edparsons.com> @edparsons
Received on Tuesday, 4 August 2015 15:02:55 UTC