Re: draft-ietf-geopriv-dhcp-lci-option-oo.txt

From: nabbott@telcordia.com
Date: Tue May 13 2003 - 10:40:01 EDT

Marc,

I suggest that a codepoint be added in Section 2 of "Internet
draft-ietf-geopriv-dhcp-lci-option-oo.txt" to represent the North American
Datum 1983 (NAD83) in addition to WGS84.

Fred Latham, a colleague who participates in the Open GIS Consortium,
provided the following background as rationale for this additional
codepoint.

NAD83 is an earth-centered (or geocentric) datum with reference point at
the center of the earth.
It is derived from Geodetic Reference System (GRS80), developed by USDOD
from satellite measurements.
(WGS84 is also derived from GRS80, although from a different reference
point.)
NAD83 has been adopted as the official datum by federal civilian agencies,
including the US Census Bureau, USGS, and US Geological Survey.
Internationally, several Canadian provinces and government agencies such as
the Canadian Department of Energy, Mines and Resources use NAD83. Mexico
has
also adopted NAD83 as its official datum.

WGS84 was developed by US Defense Mapping Agency. This datum is a global
datum based on electronic technology which is still to some degree
classified.
WGS-84 is becoming the base datum for the processing and
conversion of data from one datum to any other datum.
The Global Positioning System (GPS) is based on this datum.

The difference between WGS-84 and NAD83 is small, and is generally
considered to be insignificant.
NAD83 and WGS84 are close enough to be called the same for non-geodetic
applications like Search and Rescue (the difference is about 2 meters).

Since a number of existing GIS databases used in Public Safety
implementations do use NAD83,
it seems reasonable to include this codepoint for the this application, one
of whose purposes is to support emergency calling.

Thanks,
Nadine Abbott
Received on Tue May 13 11:01:18 2003

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