For unwary users of a government satellite system that guides ships and airplanes, keeps cellular networks humming and helps surveyors lay out property lines, next weekend could be marred by a disorienting flashback.

The global positioning system, or GPS, blends signals from satellites to pinpoint the location of a radio receiver -- and anyone or anything holding it -- to within 50 yards or so. Where support from ground stations is added, the question of "Where am I?" can be answered within inches. The satellite signals also answer the question "What time is it?" down to tiny fractions of a second.

Unfortunately, the system's dazzling effectiveness depends in part on a bare-bones calendar that boils passing time down to the weeks since Jan. 6, 1980 -- currently 1,023 -- plus seconds. Sticking to such basics allows the satellites to communicate quickly, but the system is about to run out of the allotted digital space for such timekeeping.

The limit will become apparent all over the world 13 seconds before 7 p.m. EDT on Saturday. Like a car's odometer reaching 100,000 miles, the system's week count will revert to zero instead of moving to 1024.

There are "some unknowns and uncertainties" about what happens next, warned John Lovell, director of quality for Trimble Navigation Ltd., a leading manufacturer of global positioning equipment.

Some confused receivers will stop working. Others will generate bad data or display 1980 dates. Still others, peering at the spots in the skies where the satellites were in January 1980, will spend hours trying to lock on to the signals.

"Users should not rely on GPS where there is a risk to life, critical data or property," Lovell said.

Experts say that for the 24 satellites broadcasting the signals and for the Defense Department ground stations that control the system, the rollover will be a nonevent, like the hands on a watch sweeping past 12. They also expect smooth sailing for well over 90 percent of the estimated 8 million global positioning radio receivers in government and civilian hands.

But some receivers, especially older models, read Week 0 as that long ago week in early 1980 when the calendar started ticking. No one knows how many receiver owners with defective equipment have ignored or missed warnings to prepare for the rollover. Lovell and others believe tens of thousands of malfunctions are quite possible, perhaps more.

"The only way to know what will happen with a device is to check with the manufacturer," said Lt. Lee Putnam, spokesman for the U.S. Coast Guard Navigational Center in Arlington, Va. "You have to have the serial number as well as the model since some models were modified to become compliant during production."

Some manufacturers are charging customers for upgrades, a practice that plaintiffs' lawyers are gearing up to challenge, said Salvatore Graziano, a lawyer with the class-action firm of Milberg, Weiss Bershad Hynes & Lerach in New York. Milberg and others have filed similar lawsuits against software companies that have required customers to pay for Year 2000 upgrades.

The government has warned in general terms that the global positioning rollover poses "serious hazards." In some of the worst scenarios envisioned privately by officials, boaters foolish enough to rely solely on recreational GPS navigation in foggy conditions could run aground. Businesses like cellular networks that rely on GPS signals to synchronize electronic equipment or banks that use them to time-stamp transactions could be disrupted if faulty equipment has not been upgraded or backed up with other high-precision clocks.

But experts say the potential global positioning rollover problems are much more limited than the Year 2000 challenge, are easier to isolate and, perhaps most important, generally simple to overcome. Gartner Group, an information technology consulting firm in Stamford, Conn., concluded that 40 percent of the faulty equipment manufactured before 1996 could be fixed by simply turning it off and then starting it up again after the rollover.

It helps that most of the industry's growth has come in the past five years as demand surged for consumer applications like electronic mapping systems for cars. The government's published system specifications began explicitly noting the rollover date as early as 1993 and the vast majority of equipment made since then took it into account.

"But there were probably products shipped as late as this year that are at risk since they may have incorporated older programming," warned Lovell.

Fortunately, airplanes, ships and other major users of global positioning navigation systems are designed with other aids like radar. They can function safely even if the global positioning system fails completely. And businesses with major applications have reportedly been aggressively testing their systems.

"We've been deluged with requests for testing help," said Charles Fay, vice president of worldwide sales for Global Simulation Systems Inc. of Fort Worth, Texas, the leading manufacturer of equipment that simulates the GPS satellite network.

In most companies, the same information technology departments leading the Year 2000 repair effort are also dealing with the satellite rollover. Defense Department agencies gearing up for any unanticipated problems during the rollover are using the weekend as a dry run for the contingency plans for dealing with computer disruptions over the New Year weekend, according to Col. James Armor, director of the joint armed forces office in Los Angeles that oversees the system.

But even if the satellite transition turns out to be smooth, government officials are cautioning against reading too much into a smooth transaction.

"People shouldn't get a false sense of security about the Year 2000 if there are no major rollover problems," said John Gribben, spokesman for the President's Council on Year 2000 Conversion. "They are two separate issues."

Not that many people are treating them that way. The council itself is providing rollover information on its information hot line (888 USA-4Y2K) and Trimble Navigation, based in Sunnyvale, Calif., calls the rollover a "dress rehearsal for the Year 2000."

In part because public fears about the behavior of high-technology systems have been heightened by publicity about Y2K, as the Year 2000 computer problem is known, equipment manufacturers have prepared for a flood of rollover inquiries with briefings for dealers and customer support centers on alert.

Thomas Hunter, vice president and general manager of Magellan Systems of Santa Clara, Calif., a subsidiary of Orbital Sciences Corp. that is among the leading makers of hand-held GPS receivers popular with boaters and hikers, said, "We won't go home Friday night assuming everything is going to be OK."

Related Sites

U.S. Coast Guard Navigational Center
http://www.navcen.uscg.mil/

Global Simulation Systems Inc.
http://www.gssl.co.uk/

Magellan Systems
http://www.magellangps.com/

Trimble Navigation Ltd.
http://www.Trimble.com/

President's Council on Year 2000 Conversion
http://www.y2k.gov/
- About - http://www.y2k.gov/text/abouty2k.html
- Y2k Organizations - http://www.y2k.gov/text/adgroups.htm
- Y2K Products - http://www.y2k.gov/text/product_compliance.html

Home Page