Problems seen when GPS resets on Aug. 21, 1999

September 21, 1998|By John Diedrich | John Diedrich,KNIGHT RIDDER TRIBUNE

When the government turned on the Global Positioning System satellite network in 1980, a nearly 20-year clock started ticking.

At exactly 6:59 p.m. Eastern Daylight Time on Aug. 21, 1999, the clock starts over at zero. And that could cause problems for some commercial GPS users.

GPS began as a tool to help the military. A ring of orbiting satellites shoot back readings to receivers, giving location in latitude and longitude. Just like the Internet, GPS now is used by millions, including farmers, truck drivers and surveyors.

Engineers programmed GPS satellites to run for 1,024 weeks or just over 19 years because of limited memory in the system's internal clock. When the time's up, the internal clocks start over for another 1,024 weeks.

The rollover won't have an impact on the 24 GPS satellites, which are operated from Schriever Air Force Base, or the government's receivers.

But some of the first generation commercial receivers built in the early 1990s might be affected. They weren't built with the rollover in mind and could freeze up or give slightly faulty readings.

Users should contact the company that manufactured their unit to check and get a possible fix.

Another problem facing GPS users is the millennium bug, which is expected to bite the world's computer systems on Jan. 1, 2000.

If the GPS receiver depends on an internal clock, the millennium change could freeze the unit. Just as importantly, GPS receivers might appear to malfunction if the computers they are hooked up to aren't fixed.

Officials in charge of GPS are anxious to notify the public about the possible impending problems.

"So many rely on GPS, we want to make sure people are aware of them," said Aaron Renenger, a spokesman for the military agency that manages the system.

Pub Date: 9/21/98

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