GPS Rollover

Forget Year2000 for a while. Are you ready for 21 August 1999 ? On this date, at 23:59:47 UTC, certain navigation equipment using GPS (Navstar Global Positioning System) technology will fail or operate slower than normal. It is also possible that some computer systems may be affected, since GPS receivers are sometimes used to provide an accurate time signal for distributed networks.

Wrapup article

Various people in report odd problems, patches applied etc. with Garmin, Magellan units.

It is unlikely that the position reported by GPS receivers will be significantly in error. However, units may lose lock or take more time to acquire satellites, and not give a fix for ten minutes or longer. It is therefore not a good time to connect the autopilot to the GPS and go below to cook dinner (you are, of course, obliged to keep a proper watch in any case..)

See the following sites for a brief technical description:

The Cruising World page also has a list of affected systems.

See also this list of affected systems reported by Marc Brett (

GPS Upgrades

Manufacturers: 3S Allen Osburne Ashtech Austron Avcan Azimuth Bancomm CMT Corvallis CSI Datum Delnorte Eagle Furuno Garmin Hopf Humminbird Interphase Japan Radio Leica Lowrance Magellan Magnavox Marconi Motorola Novatel Raytheon Simrad Spectrum Starlink Trimble Universal Avionics

Many GPS products must have a firmware upgrade to be Y2K/rollover compliant. This usually means obtaining a ROM chip from the manufacturer or dealer, opening up the device and swapping the chip. Some devices may be upgradeable by connecting them to a PC and running a special program, while others may require unsoldering parts and should be left to a specialist in most cases to retain product warranty.

GPS Satellites and Ground Stations

The satellites and ground stations are maintained by the US military. Here is their website giving details of the server-side rollover issues:

GPS Receivers