What is the GPS Week Number Rollover (WNRO)?
The GPS system is world renowned for its ability to provide accurate and reliable positioning and timing information worldwide. The GPS satellites transmit to users the date and time accurate to nanoseconds. However, back in 1980, when the GPS system first began to keep track of time, the date and time was represented by a counter that could only count forward to a maximum of 1024 weeks, or about 19.7 years. After 1024 weeks had elapsed, this counter “rolled over” to zero, and GPS time started counting forward again. This first rollover occurred in August of 1999. The second rollover will occur on April 6, 2019.
Is My Device Affected?
For many years, Garmin has anticipated and prepared for this event. Regardless, Garmin has been performing exhaustive testing of current and legacy devices to determine if they will be affected by the GPS week number rollover. Our testing shows the vast majority of Garmin GPS devices will handle the WNRO without issues.
What is the Effect of a GPS Week Number Rollover Issue?
For GPS devices that are affected, after the rollover occurs, an incorrect date and time will be displayed. This incorrect time will also be used to timestamp track logs, compute sunrise and sunset, and other functions that rely upon the correct date and time. However, the positioning accuracy will not be affected. The device will continue to deliver the same positioning performance as before the rollover.
Gary, Gary, Gary,
You don’t need a $30,000 GPS simulator to verify if a GPS product in your inventory has the rollover bug. You simply ask the supplier to certify that they don’t have the rollover bug. They use their _$100,000_ GPS simulator If needed, but usually it’s done with a trivial code review.
If the supplier can’t provide such a certification, then they are no longer a supplier. This tends to persuade them to certify.
If you as an air carrier (or any other critical GPS consumer) fail to ask for such a certification in time to field a replacement, that’s your fault.
You might not be aware, but zero US air carriers had any unplanned downtime from the GPS rollover. I can’t say the same thing for certain Asian air carriers :)
-mel via cell
On May 1, 2019, at 8:39 PM, Gary E. Miller <gem@rellim.com> wrote:
Yo Mel!
On Thu, 2 May 2019 03:30:03 +0000
Mel Beckman <mel@beckman.org> wrote:
I’m also an FAA licensed A&P mechanic, and have worked for airlines
in fleet maintenance. Air carriers have extremely thorough systems
reviews, by law, through the Airworthiness Directive program, which
started identifying 2019 GPS rollover vulnerabilities in ... 2009!
Nobody was surprised. If any GPS systems “went nuts”, it was through
the incompetence and negligence of their owners.
How many GPS owners happen to have $30,000 GPS simulators to check
their $300 GPS/NTP servers? Some of mine did, most did not.
Seems to me the negligence is in the GPS manufacturer that failed to
notify their customers.
To be fair, Avidyne and Telit did notify their customers, but not with
a fix or enough lead time to swap out the units.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem@rellim.com Tel:+1 541 382 8588
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