RE: Year 2000 - A Strange Date

Mike_Stouffer@aal.org
Tue, 13 Jul 1999 09:31:23 -0500

My understanding of is that many (all?) GPS systems have a built-in
"almanac" that tells approximately where satellites are found in the skies,
at any particular time. If the date is wrong inside of the GPS receiver,
it will look up the wrong "almanac" page, and either not find the satellite
where it's expected, or mistake one satellite for another. This may cause
havoc with the position-finding (triangulation) algorithms in the GPS
receiver. You may find that the receiver suddenly fails to find your
location on the globe, or reads out an incorrect location.

Because not all GPS systems are up-and-running all the time, the problems
may occur sometime after August 21st, on power-up. Also, if corrective
measures are applied incorrectly to the GPS when it fails, the problems may
be compounded. Like the Y2K problem, this isn't a problem whose
repercussions can be easily estimated or foreseen. I'm going to be
interested in the how the GPS rollover plays out, since it may be a good
indication of how people will react to the larger Y2K problem (i.e. risk
mitigation and management, insurance issues, legal issues). It may even be
seen as a "silly non-problem" when we look at things in retrospect.

I do believe, though, that it would be prudent to be on the ground when the
GPS clock rolls over at midnight on August 21st.

Mike Stouffer
Mike_Stouffer@aal.org

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