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Old 19th March 2019, 10:15   #1
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Default GPS week number rollover event on 6th April, 2019

I have been following reports on GPS week number rollover event on 6 April 2019. I am not sure how does it impact us? Last time it happened on 21 August 1999, however usage of GPS at that time was not as widespread as today.

US Department of Homeland Security Memorandum

The GPS Internal Navigation Time Scale “GPS Time” is based on the weighted average of GPS satellites and ground station clocks. GPS Time is used for user navigation solutions. A nanosecond error in GPS Time can equate to one foot of position (ranging) error. The WN parameter is provided via a ten (10) bit parameter – or “counter.” The valid range of values for the WN parameter is 0 to 1023 (or 1024 total values). The WN parameter is incremented by one each week. At the end of the 1024th week, the counter experiences a rollover (resets) to 0. Each WN rollover event defines a new GPS Time Epoch. The WN value is referenced to the start of the current GPS Time Epoch. The last WN rollover was August 21, 1999. GPS Time is currently in the second Epoch. The next WN rollover is April 6, 2019.

GPS satellites have a little-known ‘Millennium Bug’ problem of their own

Designed in the 1970’s, the computer systems on the GPS satellites represent weeks using a 10-bit number. This has a maximum value of 1024. After 1024 weeks have passed, or 19.7 years, the number rolls back to zero. This extremely rare event has only ever happened once. It’s expected to occur again on April 6, later this year.

Older GPS devices are facing their own mini Y2K bug next month, But most products will be protected by a simple software update

The bug isn’t disastrous and should only hit a small number of GPS devices, but for those impacted the results could be severe, resetting the receiver’s time and corrupting its location data. Only older devices are at risk, though, and if you’re just using a commercial device the fix is quite simple: just check that its software is up to date.

This Is The 1 Day Security Experts Say They Won't Get On a Plane (It's In a Few Weeks' Time)

The effects would be more widespread [today] because so many more systems have integrated GPS into their operations.
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