Re: [Geopriv] Question on draft-linsner-geopriv-relativeloc-01

Date: Wed Jul 11 2007 - 03:42:11 EDT

Perhaps the semantics for the expression of a z value should be grounded
in geodesy best practices, such as feet above mean sea level. MSL is
defined as the zero elevation for a local area. The zero surface
referenced by elevation is called a vertical datum. An alternative is to
base height measurements on an ellipsoid of the entire earth, which is
what systems such as GPS do. In aviation, the ellipsoid known as World
Geodetic System 84 is increasingly used to define mean sea level.

Just a thought. We need to insure that the definition used in the document
is unambiguous.



----- Original Message -----
To: Marc Linsner
Cc: Geopriv
Sent: Friday, July 06, 2007 1:16 PM
Subject: [Geopriv] Question on draft-linsner-geopriv-relativeloc-01

Hi Marc, list,

First, I find this draft to be marginally useful. There will be some
cases where such relative offsets are helpful, but I expect not too many.

That said, I have a comment/question on Z dimmension. Sec 4 sez:
        "If the altitude (Z) parameter is expressed, it is assumed to
  utilize locally significant ground level (the ground directly below

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Received on Wed, 11 Jul 2007 03:42:11 -0400 (EDT)

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