Is your older GPS device about to go bonkers?


Do you own any GPS devices or 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 occur in April.

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 simple: just check that its software is up to date.

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 this coming April 6th.

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.

Read more at The Verge

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I’ve also been informed that my old TomTom will no longer be updated. Perhaps this is industry wide.

Roger Marble

Garmin info and reply.
Looks like not much to worry about unless you use a GPS as your timepiece.


I had a 10 ten year old Magellan and we set out on a trip 5 weeks ago. My friends were making fun of me and this “old” unit and suggested I get a new garmin. So I did.
We are in Arizona and California and so far the “new” garmin has steered us wrong about a 3 rd of the time. Even to RV parks that have been at. Location for 30 years.
Two days ago I pulled out the old Magellan and put the same address in both units.
Yep New Garmin was a half a mile out. Magellan was accurate.
Some say do an update. But this is a new unit and I should not have to do an update right out of the box.

Roy Ellithorpe

April Fools!


I’m curious of the source for this information… I worked for Orbital Sciences Corporation and Magellan in when GPS was first being built out and I dont recall 10 bit counters because that would be strange data alignment-wise. Further, the week number is mainly used only for display in any unit I’ve seen and has absolutely nothing to do with the nanosecond timer that produces the location triangulation. Certainly “never say never” but this is actually news to me…


I work for a timing company in August of 99. Between this and Y2K we kept several people employed and very busy for over a year and a half before this. The US government even had a task force to handle potential problems that would be caused by the GPS rollover and Y2K. Nothing eventful happened and life went on.


Is this how cell fones work too? Seems they go just so long and – walla, like magic – no software updates anymore.

Tommy Molnar

Gee, you mean my aging Magellan Meridian Platinum handheld GPS that I use for Geocaching could be rendered useless? They just don’t make things like they used to . . . . 🙂

Bob Godfrey

Funny how they don’t tell you this stuff when you originally purchase the product.

David Lange

How can I check?


So … what does it take to cure the GPS reset problem if you have an older GPS.