Subject: RE: Geographic location representations?

From: [email-masked]
Date: Thu, 28 Jun 2001 12:11:40 +0100

I agree with previous comments to this group... although there are 'better'
datums, the WGS-84 ellipsoid is the most commonly used, and thus should be
the prime consideration, but don't devise an encoding scheme that prevents
the inclusion of other ( even regional datums) at a later date.

You might like to have a look at the work that has been progressing over the
past few years in ETSI/ANSI/ITU-T/3GPP...

The latest version of the 3GPP spec 23.032 v4.0.0 is available at;

ftp://ftp.3gpp.org/Specs/2001-03/Rel-4/23_series/23032-400.zip

The 'Geographic Area Description' goes significantly further than any other
proposals that I have seen thus far... it makes the leap from trying to
simply describe a single point to describing a geographic area, with a suite
of 'shape descriptions' that are independent of the method used to determine
location. It also has the concept of transporting the accuracy, or
'confidence' level of location information (this information can't be
inferred as it is very dependant on the locating technique used!).

As an aside, the latest version of the GAD has an extension to encode
velocity information (can you imagine it... '911 help, I'm at 25,000 feet
and going down fast'!!)

...however, back on track...

Consistency has been achieved thought the many diverse telecoms
standardisation fora ('GAD' in GSM/3GPP, ISUP and INAP 'Calling Geodetic
Location' in ITU-T/ETSI/ANSI), and I feel that any encoding used within the
IP world (if not identical) should have simple interoperability with those
already defined for the Telecoms and Wireless 3G worlds.

Regards

Simon