Y2K Problem....

Mike DiMuzio (mdimuzio@cisnet.com)
Fri, 01 Jan 1999 19:11:50 +0000

	MSNBC news web page had a article today on
the upcoming dates of when Y2K problems will surface.  One
date in particular stood out:
----------------------------------------
AUG. 22, 1999
                                The Global Positioning System, the network of
                         satellites that allows planes, trains and other
infrastructures
                         to identify the precise location of a receiver on or
above the
                         earth’s surface, reaches the end of its built-in
calendar at
                         midnight, Greenwich Mean Time, on Aug. 22. The system
                         will roll over and start at the beginning of the
calendar again,
                         operating for approximately 20 years (1,024 weeks to be
                         exact). Some people expect massive logistical errors on
this
                         date. 
				If a company or agency is using an older GPS receiver,
                         manufactured before 1994, there is a chance that the
                         rollover will affect the management of traffic. The GPS
                         system does count time in weeks (actually it’s weeks 0
-
                         1,023, for a total of 1,024, which some argue is
another
                         problem, that GPS systems won’t be able to deal with a
“0”
                         week. It won’t be a problem.) However, the week does
not
                         come into play in a GPS calculation, except at the
instant
                         the system rolls over. GPS calculations deal in
milliseconds.
                         A GPS receiver determines its position by triangulating
                         difference in the time it takes for signals from two
GPS
                         satellites to reach it, a matter of milliseconds. The
only time
                         the week would enter into the calculation is as the
system
                         rolls over from Week 1,023 to Week 0.
                                A GPS receiver that is not prepared for the date
                         rollover would think that one or both of the satellites
had
                         taken 18 years to send a signal that should have taken
less
                         than a second. It could not calculate its position
accurately.
                         In some cases, the receiver would simply fail to
function, but
                         in most cases it would just produce a weird reading.
Most
                         commercial users of GPS have upgraded their systems.
For
                         example, the Federal Aviation Administration, a major
user
                         of GPS data, has upgraded its systems to handle the
system
                         rollover, as have airlines.
                                If the GPS system rollover does cause problems,
it will
                         be in routing of traffic. An airport with an outdated
GPS
                         receiver would have to revert to ground-based
positioning
                         systems, like radar. But, as noted, the likelihood of a
GPS
                         system error is low, because almost all hardware in the
U.S.
                         has been upgraded.

-------------------------------------
Full story is at http://www.msnbc.com/news/227483.asp

Mike
-- 
41.087N  80.722W 330 meters

Mike DiMuzio    mdimuzio@cisnet.com