GPS with Y2K problem this weekend!

["KHOO, John Kelvin" <john_khoo@xxxxxxxxxxxx>]

Global positioning receivers may become disoriented this weekend
August 17, 1999 
Web posted at: 12:18 PM EDT (1618 GMT) 
CNN's Rick Lockridge looks at the Global Positioning System date rollover

WASHINGTON -- Some of those increasingly popular satellite receivers that
tell you where you are may become disoriented this weekend unless they've
been adjusted. 
The result could be lost hikers and boaters, if they depend solely on the
new technology to guide themselves home. 
Originally designed for the military, the Global Positioning System now is
used widely by airlines, ships and in businesses and has also become popular
with recreational boaters and pilots, hikers, campers, hunters and
fishermen. 
GPS receivers determine locations by using signals from three or more of the
24 satellites in the system. To do this they need the exact time, and the
system determines time by counting the weeks since Jan. 5, 1980 -- up to
1,024. 
Then they reset to zero and start over. 
That moment arrives at 8 p.m. EDT Saturday. 
Unless they have been repaired earlier, some receivers may think it is Jan.
6, 1980, when the satellite clock resets, according to the Transportation
Department. 
The satellites use the week count system to account for variations in the
earth's orbit and rotation. That's why receivers not programmed to handle
the rollover could have problems determining location. 
Most receivers built since 1993 were designed to handle the rollover. Older
ones can be adjusted through either a new computer chip or changes in their
software. 
The Federal Aviation Administration issued a notice to airlines and pilots
in June advising of the pending rollover and urging checks to ensure
navigation systems have been adjusted if needed. 
The Air Transport Association, which represents the major airlines, says its
members are aware of the changeover and expect no problem. 
Most likely to have trouble are older, small handheld receivers, said FAA
spokeswoman Tammy Jones. 
Units that have not been fixed could experience any of several malfunctions:

Inability to locate satellites, which would result in receiver failure. 
Delays in locating the satellites. 
Appearance of correct functioning while displaying inaccurate positions,
times or dates. 
"GPS broadcasts do contain sufficient data to ensure that navigation need
not be affected" by the rollover, the Coast Guard reports on its Wide World
Web site. 
The Department of Defense says the date changes are not expected to affect
the operation the satellites or the Pentagon's ground control center. 
Owners of GPS receivers can determine whether their units are able to handle
the change by providing the manufacturer model numbers and other details. 
A list of manufacturers and contacts is available at the Coast Guard's Web
site: www.navcen.uscg.mil/gps/geninfo/y2k/default.htm. 

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