Re: [dhcwg] Fwd: Working Group Last Call: Location Configuration Information for GEOPRIV
Andrew Daviel <andrew@daviel.org> Wed, 02 July 2003 10:12 UTC
Received: from optimus.ietf.org (ietf.org [132.151.1.19] (may be forged)) by ietf.org (8.9.1a/8.9.1a) with ESMTP id GAA00369; Wed, 2 Jul 2003 06:12:33 -0400 (EDT)
Received: from localhost.localdomain ([127.0.0.1] helo=www1.ietf.org) by optimus.ietf.org with esmtp (Exim 4.20) id 19Xeam-0000db-R2; Wed, 02 Jul 2003 06:12:00 -0400
Received: from odin.ietf.org ([132.151.1.176] helo=ietf.org) by optimus.ietf.org with esmtp (Exim 4.20) id 19XYDR-0003Tv-IM for dhcwg@optimus.ietf.org; Tue, 01 Jul 2003 23:23:29 -0400
Received: from ietf-mx (ietf-mx.ietf.org [132.151.6.1]) by ietf.org (8.9.1a/8.9.1a) with ESMTP id XAA26049 for <dhcwg@ietf.org>; Tue, 1 Jul 2003 23:23:24 -0400 (EDT)
Received: from ietf-mx ([132.151.6.1]) by ietf-mx with esmtp (Exim 4.12) id 19XYDN-0004mI-00 for dhcwg@ietf.org; Tue, 01 Jul 2003 23:23:25 -0400
Received: from h24-87-63-73.vc.shawcable.net ([24.87.63.73] helo=home.daviel.org ident=root) by ietf-mx with esmtp (Exim 4.12) id 19XYDL-0004mF-00 for dhcwg@ietf.org; Tue, 01 Jul 2003 23:23:23 -0400
Received: from localhost (IDENT:andrew@localhost [127.0.0.1]) by home.daviel.org (8.11.6/8.10.2) with ESMTP id h623N8D18393; Tue, 1 Jul 2003 20:23:08 -0700
Date: Tue, 01 Jul 2003 20:23:07 -0700
From: Andrew Daviel <andrew@daviel.org>
To: John Schnizlein <jschnizl@cisco.com>
cc: Robert Elz <kre@munnari.OZ.AU>, dhcwg@ietf.org, geopriv@mail.apps.ietf.org
Subject: Re: [dhcwg] Fwd: Working Group Last Call: Location Configuration Information for GEOPRIV
In-Reply-To: <4.3.2.7.2.20030620151602.0200e778@wells.cisco.com>
Message-ID: <Pine.LNX.4.53.0307011944440.15517@home.daviel.org>
References: <4.3.2.7.2.20030620061756.0468bf98@funnel.cisco.com> <4.3.2.7.2.20030620061756.0468bf98@funnel.cisco.com> <4.3.2.7.2.20030620151602.0200e778@wells.cisco.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset="US-ASCII"
Sender: dhcwg-admin@ietf.org
Errors-To: dhcwg-admin@ietf.org
X-BeenThere: dhcwg@ietf.org
X-Mailman-Version: 2.0.12
Precedence: bulk
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=unsubscribe>
List-Id: <dhcwg.ietf.org>
List-Post: <mailto:dhcwg@ietf.org>
List-Help: <mailto:dhcwg-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/dhcwg>, <mailto:dhcwg-request@ietf.org?subject=subscribe>
On Fri, 20 Jun 2003, John Schnizlein wrote: > Thank you for the probing questions. Clarification embedded in context: > > At 08:38 AM 6/20/2003, Robert Elz wrote: > >The definitions of altitude in that draft need work. > > > >Metres (positive and negative) is simple enough, but relative to > >what? Unless I missed it, I could find no definition of what is 0. > > Zero is defined by the datum, at least for those we know. > To cover any cases where it is not, we propose clarifying text as follows: > If MU = 1, an AltRes value 0 would indicate unknown altitude. > The most precise Altitude would have an AltRes value of 30. > Unless otherwise defined by datum, a value of 0 is with respect > to mean-low-tide. > > >If the assumption is that it is to be "mean sea level" then which sea? > >If it is to be above (+ or - below) ground level, which ground level > >within the designated area given by the latitude and longitude (sloping > >ground). > > It is our understanding that mean low tide is well defined, since > political and personal land-ownership boundaries are based on it. It depends on the jurisdiction. For instance, it is different in Canada and the US - one uses mean lower low water and the other uses lowest normal tide or something as a nautical chart datum. Defining elevation seems to be more problematic than defining position. If consumer-grade GPS has a horizontal resolution between 5-30 metres, that's good enough to give a street or maybe a room in a building. But the vertical resolution may be double that, and that's 3 floors at best, even assuming you have ground level sorted out properly. Other navigation techniques such as LORAN (obsolescent) or cellphone-signal based may not give elevation at all. On the other hand, from what I read, survey-grade differential GPS is currently capable of excellent accuracy (15cm or better), but this is unlikely to be available in inexpensive mobile devices. The European GALILEO service will provide greater accuracy than GPS, and I think I read somewhere that it may penetrate buildings and dense vegetation better. Augmentation systems such as SBAS, WAAS, EGNOS seem to provide enhanced accuracy to 3-5 metres, so maybe within a decade we will have inexpensive devices able to discern which floor they're on ... http://www.magellangps.com/en/products/aboutgps/ etc. Andrew Daviel Vancouver Webpages _______________________________________________ dhcwg mailing list dhcwg@ietf.org https://www1.ietf.org/mailman/listinfo/dhcwg
- [dhcwg] Fwd: Working Group Last Call: Location Co… Ralph Droms
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Robert Elz
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… John Schnizlein
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Robert Elz
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Andrew Daviel
- RE: [dhcwg] Fwd: Working Group Last Call: Locatio… Marc Linsner
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Henning Schulzrinne
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… creediii
- [dhcwg] Unit of Measurement...? James M. Polk
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… John Schnizlein
- [dhcwg] Re: Unit of Measurement...? James M. Polk
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… James M. Polk
- RE: [dhcwg] Fwd: Working Group Last Call: Locatio… Marc Linsner
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Henning Schulzrinne
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Greg Troxel
- [dhcwg] Re: Unit of Measurement...? Henning Schulzrinne
- [dhcwg] Re: Unit of Measurement...? Greg Troxel
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Greg Troxel
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Greg Troxel
- [dhcwg] Re: Unit of Measurement...? Carl Reed
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Dominic Pinto
- Re: [dhcwg] Fwd: Working Group Last Call: Locatio… Carl Reed