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Older GPS devices are facing their own mini Y2K bug next month


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Do you own any GPS devices or use equipment that relies on GPS to function? If so, now is probably a good time to check whether or not those products are protected against the GPS Week Number Rollover issue — a sort of mini Y2K Bug for GPS receivers that will come into affect from April 6th this year.


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.


TomTom has told customers “if you frequently update your device there’s no need to worry” as it’s already rolled out a fix. (You can also check if your device is affected using its serial number here.) Garmin says it’s currently testing its devices for any problems but that “the vast majority of Garmin GPS products handle the event without issue.” And an official memorandum from the Department of Homeland Security says any GPS receivers running the latest IS-GPS-200 standard and connected to UTC “should not be adversely affected.”


If you’re not sure about whether your device is covered, contact the manufacturer.


The rollover issue itself is caused by the fact that GPS systems count weeks using a ten-bit parameter. This means they start counting at week zero and reset when they hit week 1,024. The first count (or “GPS epoch”) started on January 6th, 1980, and the first reset took place on August 21st, 1999. That means the next one is due April 6th this year.


When the rollover happens older devices may reset their date, potentially corrupting navigation data and throwing off location estimates. GPS relies on precise timing data to operate, and each nanosecond the clock is out translates into a foot of location error.

All this is why some have compared the issue to a sort of mini Millennium, or, Y2K Bug for GPS receivers that will come into affect from April 6th this year. Bug. That was also caused by a number rollover problem, as a lot of early software recorded the year using a two-digit code (“78” for “1978” and so on) that reset when clocks hit the year 2000.


However, it’s worth noting that just because the next GPS week reset is scheduled for April 6th, actual errors might kick in later. As telecoms testing company Spirent noted in a blog post, some devices may have restarted their week count later — for example, when the manufacturer compiled their firmware. As Spirent’s Guy Buesnel writes, that means “the impact won’t necessarily be felt on rollover day itself. In fact, it’s much more likely that an affected receiver won’t start outputting erroneous data until long after the 6 April 2019.”


So: the best thing to do is check your device is up to date and, if in doubt, read these guidelines from the DHS about what to do next.



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