Federal Agencies Warn Drivers, Boaters, Pilots and Hikers of False Readings with Some GPS-Based Satellite Navigation Systems

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 are warning about possible false receiver readings with navigation systems that rely on the Global Positioning System (GPS).

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 GPS receivers.

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 Y2K-compliant:

- 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 satellites.

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/.

Addition

GPS End-of-Week Almanac Notice:

On August 19, 1999, the first End-of-Week (EOW) related update to the Global Positioning System (GPS) Almanacs will occur. This almanac will be for week 0000. Almanacs are approximate orbital data parameters for all GPS satellites. The approximate orbital data is used to preset the GPS receiver with the approximate position and carrier Doppler frequency of each satellite in the constellation. All almanacs for week 0000 will be updated in the entire GPS satellite constellation within 24 hours of the first satellite update. GPS receivers that are not fully compliant with the GPS Interface Control Document ICD-GPS-200-C, which contains specifications for GPS code implementation, may experience GPS receiver malfunctions once the almanacs are uploaded.

Users should contact respective GPS receiver manufacturers about ICD-GPS-200-C compliance. More information on EOW and Y2K is available on the Coast Guard web site at www.navcen.uscg.mil/gps/.