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Is this weekend’s ‘rollover’ event the Y2K of GPS?

OK, this just doesn’t seem possible! It’s been 20 years since the big Y2K scare. Seriously, it’s true.

Back then, tons of people were freaking out and stocking up of food, water and batteries. All because in the computer world, years were abbreviated to “99” instead of 1999. So no one knew what would happen with computer systems and power grids when the calendar flipped from 99 to 00 on Jan. 1, 2000.

Fortunately, nothing disastrous happened and we’re all fine. Whew! The thing is, we’re about to have another event similar to that, but in the world of GPS.

Are we doomed with the GPS rollover?

The Global Positioning System (GPS) does more than just tell you how to get to that hard-to-find restaurant you’ve been dying to try. It also supplies precise timing information, called Coordinated Universal Time (UTC), to critical systems that includes communications and power grids.

Plus, GPS transmits accurate dates and times to receivers by providing them with the current week and the number of seconds that we are into the week. The receiver then translates these figures into a more readable month, day, year and time of day format.

Here’s the problem: these timestamps are encoded in a 10-bit field, which means the week number can only accommodate 1,024 integer values. So every 1,024 weeks, which is a little less than 20 years, the counter needs to reset back to zero and start over.

This system began on Jan. 6, 1980, and rolled over for the first time on Aug. 21, 1999. Nearly 20 years later, here we go again. The counter hits the 1,024 week mark on April 6, 2019 and we’ll reset back to zero.

Since GPS requires accurate timing to determine precise locations (a nanosecond error in time equals one foot in position error), not only will your GPS receiver display the wrong date and time, it will output the wrong coordinates too.

This could cause headaches for older data and navigation systems that rely on GPS for accurate timing and location.

It’s not as scary as it sounds

The reality is, you probably won’t be impacted at all unless you have a really old GPS. If you have a GPS unit built after 2010, or a GPS receiver that has received firmware updates in the last 10-15 years, you should be fine.

Manufacturers have prepared for the 2019 GPS week rollover and it’s likely that most modern GPS systems conform to the compatible ICD-200/IS-GPS-200 standard.

However, there is still a chance that your system could glitch-out on you. Your GPS unit could misinterpret the rollover and turn back its clock to Jan. 6, 1980. So the first thing you need to do on April 6 is make sure your GPS is displaying the correct date and time.

If it says that you’re in the 1980s, you can most likely correct it with a firmware update. Check the owner’s manual to find out how to get the update if you don’t know how.

DHS guidelines for safe rollover

To ensure critical systems that rely on GPS won’t be affected by the 2019 rollover, the Department of Homeland Security (DHS) has these recommendations for Critical Infrastructure owners and operators:

  • Investigate and understand their possible dependencies on GPS for obtaining UTC
  • Contact the GPS manufacturers of devices they use to obtain UTC to:
    A) Understand the manufacturers’ preparedness for the April 6, 2019, rollover
    B) Understand the actions required by critical infrastructure and other owners and operators to ensure proper operation through the rollover
  • Ensure the firmware of these devices is up to date

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