News Item

GPS timing rollover coming up

For the second time, we are about to encounter as GPS Week Number rollover event.

The transmitted GPS navigation message includes a 10-bit parameter that represents Week Number (WN). Thus, the WN parameter in the GPS navigation message 'rolls over' to zero every 1,024 weeks - starting from 0000Z on 6 January 1980. The next, second, WN rollover will occur on 6 April 2019.

A GPS device that conforms to the latest IS-GPS-200 specification and provides UTC should not be adversely affected. However, according to the US Dept of Homeland Security, tests of some GPS devices revealed that not all manufacturer implementations will correctly handle the 2019 WN rollover. Additionally, some implementations interpret the WN parameter relative to a date other than 5 January 1980 - these devices should not be affected by the WN rollover in April 2019, but may experience a similar rollover event at a future date.

Hence, the Dept of Homeland Security strongly recommends that all GPS receiver owners with critical time dependency:
- investigate and understand their possible dependencies on GPS for obtaining UTC
- contact the GPS manufacturers of devices they use to obtain UTC
- understand the manufacturers’ preparedness for the WN rollover
- understand their own actions required to ensure proper operation through the rollover
- ensure that the firmware of their devices is up-to-date

The full Dept of Homeland Security statement is at the link below . .

  • 10 April 2018
  • RIN

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