August 5, 1999
Drivers, Boaters, Pilots and Hikers Warned of False Readings with
Some GPS-Based Satellite Navigation Systems
WASHINGTON, D.C. (SafetyAlerts)
- Federal agencies anounced today that the Y2K bug may cause inaccurate or false readings
in some Global Positioning System GPS unts. The U.S. Consumer Product Safety Commission,
U.S. Department of Transportation, U.S. Department of the Interior, U.S. Department of
Agriculture and Federal Trade Commission were all involved in the issuance of this
GPS is a satellite-based system that allows those
who use GPS receivers to determine their location. Used in cars, boats, planes and as a
hand-held navigational tool, some GPS receivers may not interpret correctly the
End-of-Week (EOW) Rollover beginning August 22, 1999, and the Year 2000 (Y2K)
"bug" on January 1, 2000, resulting in false readings. Drivers, recreational
boaters and pilots, hikers, campers, hunters and fishermen are among those who may rely on
The EOW rollover occurs every 1,024 weeks-about once every 20 years. GPS calculates time
by counting the number of weeks since January 6, 1980 - up to a maximum of 1,023 weeks. On
August 21, 1999, the GPS week "counter" will rollover from week 1,023 to week
zero and could be interpreted by some GPS receivers as an invalid date.
The Y2K computer problem stems from the fact that many computer programs use a two-digit
date field and assume the year is 19xx. When the year 2000 arrives, a two-digit date
becomes '00' and could be interpreted by some GPS receivers as an invalid date.
Those who depend on older GPS receivers for geographic locations at sea, on land or in the
air could experience the following problems if their system is not EOW rollover- and
- It will appear to be working, but display
inaccurate positions, times or dates.
- It will be unable to locate the satellites,
resulting in the receiver not working.
- It will take more time than usual to locate the
Owners of GPS receivers should check with the GPS
receiver manufacturer to find out if their GPS receiver is EOW rollover- and Y2K-
compliant. The Y2K hotline at (888) USA4Y2K has a list of receiver manufacturers and
contacts. Operators are available from 9 a.m. to 8 p.m. EDT Monday through Friday and
recorded information is available anytime. Information also is available on the Coast
Guard web site at www.navcen.uscg.mil/gps/geninfo/y2k/default.htm.