Garmin’s statement regarding the WNRO week number change

Garmin reports that some GPS-equipped devices may be affected by Week Number Rollover WNRO in April 2019.


What is a GPS Weekend Number Portability WNRO ?

The GPS system is world-renowned for its ability to provide accurate and reliable location and time information around the world. GPS satellites tell users the date and time precisely to within nanoseconds. However, in 1980, when the GPS system first began tracking time, the date and time were represented by a counter that digitally 10-bit encoded the number of the week. The counter could count up to a maximum of 1024 weeks, which is a period of about 19.7 years. Thus, the device calendar does not have the usual month and year it operates with weeks, which are recalculated to the format we are accustomed to, including the month and the year, thanks to the counter.

After 1024 weeks this counter is “reset” to zero, and the GPS time starts counting again. The first rollover event first rollover took place in August 1999. The second event second rollover will occur on April 6, 2019. Currently encoded in a 13 bit system, and the WNRO problem for most devices has been eliminated for the next 100 years.

How a problem with GPS Weekend Number Portability can affect your device?

Garmin would like to point out that GPS devices that are affected by this problem will display the wrong date and time after switching. This incorrect time will also be used to mark time in track logs, to calculate sunrise and sunset times, and for other functions that depend on the correct date and time. However, positioning accuracy will not be affected. The device will continue to provide the same positioning characteristics as it did before the week number change.

My device will be affected?

This problem will affect the currently outdated devices. For years, Garmin has been anticipating and preparing for this event. Despite this, Garmin is conducting exhaustive testing on existing and legacy devices to determine if they will be affected by the GPS week number change. Our tests show that the vast majority of Garmin GPS devices have no problem coping with WNRO.

For those devices that will be affected, the problem is solved by installing a reflash. Garmin Technical Center can be contacted in America

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