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The Pitfalls of Being Overly Reliant on GPS

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When the Guide Goes Missing

Do we rely too much on GPS? Electronics expert Tim Bartlett explores the potential for GPS failure and what we should do to head it off.

Brad Parkinson knows a thing or two about satnav.

GPS Satellite

Forty-something years ago, as a newly-promoted Air Force Colonel, he took charge of an obscure and almost entirely theoretical research program called 621B, and nurtured it into bloom as the first working prototype of what we now know as GPS.

Parkinson has long since retired from the Air Force, but—as Professor Parkinson now, rather than Colonel—he is still regarded as one of the fathers of GPS, and a world-leading expert on the system.

So when Parkinson says that “GPS is not infallible,” it’s worthwhile to listen.

In some ways, GPS is a victim of its own success. When work began on the development of civilian GPS receivers, they were expected to achieve an accuracy of about 100 meters, and it was hoped that they might be commercially viable if the price could be held down to $10,000 each—equivalent to about $40,000 today.

But now, cellphone manufacturers pay about $2 each for one-chip GPS receivers, and build them into millions of phones every year. And as the price has fallen, accuracy has improved, allowing civilian GPS to be used for all sorts of things that Parkinson and his fellow pioneers never imagined, from tracking pets to monitoring the movement of the Earth’s crust; for timing bank transactions and power-supply switch-overs, and for navigating every kind of vehicle from bicycles to container ships.

“This blanket reliance on GPS,” says Parkinson, “could leave us vulnerable.” The fundamental problem is that this crucial global utility depends on a constellation of increasingly elderly satellites.

The oldest was launched in 1990, with a designed working life expectancy of 7½ years. Nineteen others—in a constellation of 32—are also past their use-by date.

Realistic Onboard Backup

At sea, well away from land, most of the man-made problems afflicting GPS don’t apply. Oh, we may still find that space weather degrades our receiver’s accuracy, or makes it inclined to lose lock on satellites, but we are not likely to suffer deliberate jamming or spoofing. And even if we do ... what is there to hit? 

The problems are more likely to affect us close inshore, where we are nearer to man-made interference, and where the need for accuracy is greater.

You can forget that old Loran receiver you ripped out 15 years ago, though. Even if you can still figure out how to connect it up and which buttons to press, it won’t work! 

And while a growing number of today’s GPS receivers are now able to handle the Russian Glonass signals—and will soon be able to use the European Galileo satellites—they are just as liable to blocking, jamming, and spoofing as GPS.

Chart-radar matching—locating your position on a chart by moving it around to match a radar image—is an interesting concept, but it can’t be achieved, in practice, on the MFDs produced by any of today’s mainstream manufacturers. The nearest you can get to it is by putting the chart and radar picture side by side, (and at the same scale) and then panning and scrolling the chart image until it matches the radar image.

So for the time being, the best onboard backup is likely to be a paper chart and some knowledge of good ol’-fashioned piloting. If nothing else, it’s worth reading up on how to use range lights and how to fix your boat’s position by cross bearings, downloading a chart of the approaches to your home port from, and getting an app for your iPhone such as Compass Eye, Hand Bearing Compass, or Theodolite, or any of several Android apps called Camera Compass to take bearings of landmarks ashore.

But a bigger problem is that their transmitters are solar-powered, and more than 12,000 miles from the Earth’s surface. Of course they use high-gain antenna systems to direct their signals towards the earth, rather than squirting power uselessly into space. But by the time their 25-watt transmission signals reach ground level, they are so thinly spread as to be barely recognizable over the everyday crackle of background radiation.

It doesn’t take much to block or jam such a tenuous link, or to confuse a GPS receiver by sending misleading signals that are marginally more powerful than the real GPS signals. In 2011, for instance, the Iranian government claimed that an unmanned spy plane had been tricked into landing in Iranian territory by “spoofing” its GPS guidance system into believing that it was in neighboring Afghanistan, while North Korea has been waging a series of GPS jamming attacks against South Korea since 2010.

Last year, a professor at the University of Texas at Austin and his grad students fooled the GPS navigation system of a superyacht so the autopilot followed a different course than the crew thought it was on. Of course, they did it with the crew’s consent, to prove a point.

But you don’t have to be a terrorist, a rogue state, or even an academic to dabble in a bit of electronic sabotage.

New Jersey trucker Gary Bojczak wasn’t trying to change the world when he plugged a $20 “privacy protection device” into the cigar-lighter of his truck—he just wanted to stop his boss from checking up on his movements.

His little jammer disrupted the GPS-based navigation system at nearby Newark Airport, however, and cost Bojczak nearly $32,000 in fines after he was caught by an FCC enforcement officer.

But the biggest culprit of all is the sun. Several times a week—sometimes even several times a day—it produces solar flares and “coronal mass ejections” that hurl billions of tons of charged particles into space at millions of miles per hour.

When these charged particles hit the Earth’s atmosphere, they create the spectacular Aurora Borealis—but on a less sunny note they can also distort the path taken by GPS signals as they travel through the atmosphere. At best, they can cause errors in GPS fixes, or the temporary loss of signal. At worst they could knock out a satellite or two.

Of course GPS isn’t the only navigation system available today. Many current “GPS” receivers are already capable of using the Russian Glonass system, and the European Galileo system is finally starting to make progress. But relying on them is like carrying a can of gas for your car—useful only in one particular kind of breakdown.

If sabotage or a solar storm disrupt GPS signals, they will disrupt Glonass and Galileo as well. What we need is a back-up system that is completely different.

Instead of a high-frequency, low-powered, satellite system, how about something that is low-frequency, high-powered, and land-based? Sounds like Loran, in fact. But perhaps an improved, upgraded, and modernized version of Loran, promising greater accuracy and reliability than the old Loran C, and with a catchy new name for the iPhone era, such as eLoran?

The idea’s not at all far-fetched. South Korea has chosen to protect itself against the increasingly aggressive jamming of GPS by reviving its Loran transmitters, and the UK has already declared part of its eLoran chain operational.

Now, at last, the U.S. is starting to play catch-up. Amongst other things, the 2015 Coast Guard Authorization Bill reverses its funding cut of five years ago, and puts an end to the teardown of the old Loran C masts and transmitters to leave them ready for a refurb and make-over to eLoran.

Great news, I’d say.

This article originally appeared in the June 2014 issue of Power & Motoryacht magazine.