GPS Clock Rollover – Will my Satnav work after the 6th April?

models were quite large and came at a huge cost of over $2,000. Since 1991, GPS receivers have become much smaller and now built into many everyday items including phones, tablets and satellite telephones such as those made by Iridium, Thuraya and Inmarsat. GPS is also used by some IT systems as a reference point for accurate time.

Old GPS from the 1990’s

The clock system used by the GPS system is completely different to the time format of hours, minutes and seconds we all use. On April the 6th, 2019, the clock system used by GPS will reach its highest number and will the roll over to zero and start again. This is very similar to the computer clock problem which was known as the Millennium Bug or Y2K.

Recent press reports have hyped up the GPS roll over as a big problem. One executive from Trend Micro stated at a conference recently that he will not be flying on the 6th April. So do we have a problem? Absolutely not. We have been here before as the GPS clock system last rolled over in 1999 with no major problems created. Planes did not fall out of the sky, and everybody’s sat-nav did not stop working. So in this article, I am going to explore the science between the GPS clock and explain what we will all remain safe and why GPS technology will keep running.

GPS depends upon its clock system

The GPS systems uses accurate atomic clocks for a time reference. Time is used to calculate distance based on the speed that radio waves take to travel from  the satellites to GPS receiver. A minimum of four satellites are needed to calculate a three dimension fix  (Latitude, Longitude and Altitude).

As GPS needs highly accurate time keeping, the time signals from the GPS system is also used by IT systems as a time reference. One example of this in action is the computer systems used to trade stock and shares around the world.

The GPS system is digital which means that data is managed using binary code (ones and zeros). Days, Hours, Minutes and seconds is a format which does not work in computing, so binary counters are used to measure time in a different format which is easier to use. Software on the GPS units convert the GPS binary time to the normal format we all use.

The counter used to measure weeks is known as “10 bit binary” which means that a maximum 1024 weeks are counted before the counter is goes round the clock and back to zero. The GPS clock started in 1980 and the first time the counter reached its maximum count took place in August 1999. There were no major issues back then.

Does the clock roll over present a risk?

Several newspapers in the UK has published some alarming articles predicting disaster. The SUN is one example of scaremongering which has no scientific grounding. Many responsible commentators have added comments to some of these news articles questioning the poor content written by people who do not have any idea about the technology. The truth of the roll over is this – The GPS system will continue to operate and nobody has any reason to worry! So here is the reality check:

  • SatNav and other systems using GPS technology will stop working?  Untrue!  The clock rollover occurred in 1999, GPS manufacturers have been aware of this issue for a long time and have built function into the design of systems to cope with the rollover. It is unlikely that anyone will have an issue with a GPS purchased anytime over the past 5 years or more.
  • Some leading commentators have said that there could be issues with flights and other forms of transport?  Untrue! Ships and aircraft use multiple technologies to navigate in addition to GPS. Many modern satellite communications also use the Chinese and Russian navigation systems as well as the USA GPS system.
  • Cell phones and satellite phones will stop working as they lose their time reference? Untrue!  Phones normally get their time reference from the communications network. Some modern phones also include the Russian and Chinese versions of GPS,

Conclusion:  Ignore the press hype which predicts doom and gloom. GPS will carry on working as normal. Most systems will have the capability to handle the roll over. For that extra reassurance, people can update the software (known as firmware) on older GPS receivers so they can be 100% sure that there will not be an issue.

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