Some GPS Units Face Rollover Crisis

As midnight strikes on Aug. 22, some trucking companies may be like Little Bo-Peep — unable to find equipment near and far because of a handicap in old global positioning satellite receivers.

Some GPS units — mostly those built before 1994 — are expected to become disoriented during the rollover from Saturday to Sunday. The receivers will be looking for the sun and the Earth in positions they occupied on Jan. 9, 1980, the day GPS time began.

The problem exists because the constellation of 24 satellites put into space by the Department of Defense was programmed to roll over after 1,024 weeks. Programmers of many older receivers did not account for the rollover.

Because receivers generally pinpoint their positions via transmissions from three satellites, a failure to find a signal could result in inaccurate readings or no readings at all.

According to several experts, trucking companies that use satellite systems from well-managed providers are less likely to experience any interruptions. But carriers that bought GPS receivers built in the early- to mid-1990s may want to check the compliance status of their units.

Faulty devices may lose contact with the satellites and result in significant inconveniences for companies and drivers.

For the full story, see the August 9 print edition of Transport Topics. Subscribe today.