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Upcoming GPS Week Number Rollover: Problems for Older GPS Units

By Sue Richards last modified Mar 11, 2019 01:37 PM
On April 6th, 2019, GPS units manufactured ten or more years ago which have not had their firmware updated may well become unreliable.

Published: 2019-03-09 00:00:00
Topics: Communications , Equipment

The Global Positioning System (GPS) not only helps you understand your precise position but also supplies precise timing information (Coordinated Universal Time (UTC)).

GPS Time started on Jan 6, 1980. Back then, it used 10 bits to count GPS Week Numbers and could only count up to a maximum of 1,024 weeks (approx. 19.7 years). After 1,024 weeks the counter “rolled over’ to 0, and started counting again. This first occurred on August 21, 1999, count forward another 1,024 weeks and you arrive at April 6th, 2019 (just under 4 weeks away).

The main difference between the 1999 and 2019 rollovers is how widespread the use of GPS has become. If your unit is not designed to deal with the rollover it will display an incorrect date and time.

Newer GPS units from major manufacturers are most likely fully compliant with updated GPS Interface Control standards and should not experience problems during the upcoming rollover. However, those units manufactured ten or more years ago which have not been updated may very well become unreliable, including providing incorrect time tags which could corrupt navigation data.

GPS receivers affected would include GPS sensors and GPS receivers embedded within MFDs, chartplotting products, AIS receivers, and VHF radios.

Older devices may need an upgrade or a patch to work. Contact the manufacturer of your GPS to make sure the proper updates have been installed.

The Department of Homeland Security has published a bulletin on the upcoming rollover, as has the US Coast Guard.

Furuno – List of affected Units

Raymarine – Affected Units

Garmin – Statement


As Reported By:
Panbo – The Marine Electronics Hub
Alerts USA
Sail-World Cruising

Noonsite has not independently verified this information.

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