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GPS Week Rollover 2019

On April 6, 2019, GPS satellite week counting will be reset to zero.


GPS satellites are able to provide receivers with the correct time and date.
The information is split into two parts: it provides the correct week number and then the correct number of seconds in the week. This allows the receiver to translate the time and date into a more usual format such as day, month, year and time of day.

The field containing the week number is a 10-bit binary number. This limits the range of week numbers to 0-1023.
This means that when a receiver reaches week 1023, it will start over from zero.

Thus resetting to zero occurs around every 20 years. The previous reset was on August 21, 1999 and the next will take place April 6, 2019.

What this means for Westerstrand products:

Over the past 20 years of production we have had 3 different GPS chip solutions for external GPS receivers.

-2013: Trimble chip (included in GPS part numbers 122980-00 and 122982-00)
2013-2016: SIRFstarIV (also used in our analog clocks)
2016-: GTop chip MT3339

Chips MT3339 and SIRFstarIV are ready for the reset, but we are unfortunately having difficulty in obtaining information about the Trimble chip as it is an end-of-life product (EOL).
We have some indications that the Trimble chip will zero during 2024, but this has not been confirmed.

Thus there is a high risk that GPS receivers with the Trimble chip will fail to function properly.

What this means for Westerstrand customers:

To be on the safe side, we recommend replacing GPS receivers that use the Trimble chip.

Please contact us for further information!