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GPS proves vulnerable in experiment


During a presentation on the limitations of Global Positioning System (GPS), Capt. Andrew Schofield realized the yacht under his command was vulnerable.

He was listening to GPS expert Todd Humphreys explain his experiments where students spoofed GPS and sent a helicopter drone on a new course. Spoofing is when one program masquerades as another; falsifies data, tricks the system and takes control.

Humphreys is assistant professor in the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas and is director of the radionavigation laboratory. He presented his findings at the South by Southwest conference in Texas in March.

As president of the Professional Yachting Association and captain of the 213-foot (65m) M/Y White Rose of Drachs, Schofield wanted to see what this could mean for yachts, so he invited Humphreys to run a spoofing experiment onboard the yacht.

“The owner of our boat was happy for the UT team to be aboard and for this information to be made public,” Schofield said by phone.

During the experiment, Humphreys and his team used a laptop, a small antenna and an electronic GPS spoofer they built for $3,000. The GPS coordinates on the bridge indicated the yacht was on a straight course, but in reality, the vessel was steered off course by a student on the sundeck.

And the exact thing they feared would happen did.

“Someone can introduce a fake signal and there’s not much we can do,” Schofield said. “Just a few meters offside can be serious. It’s one thing to control a yacht, but imagine a 350m container ship. The potential financial damage is huge.

“And it’s not just GPS in the U.S.,” he said. “It’s pertinent to the Russian GLONASS [Global Navigation Satellite System] and European Union Galileo.”

Today’s yachts are guided by satellites, not stars. Although captains are trained to navigate with sextant, paper charts and dead-reckoning, most of them use GPS as their primary tool.

But captains still need to look out the window, said Capt. Ted Morley, chief operations officer at Maritime Professional Training in Ft. Lauderdale.

“There is innocuous and intentional spoofing out there,” he said. “It is inherent in the world of electronics. All of our real training equipment is basically spoofed. We feed false signals for the training environment” in the school’s simulator.

Morley still uses the basics of navigation when at sea and he cautions captains to be aware of potential electronic failure on the bridge.

“Some of the newer captains are over-reliant on computers, especially when the autopilot and GPS are connected and there is no human,” Morley said. “It can be scary.

“We forget GPS is a navigational aid,” he said. “Navigating is a process, a skill. If you are not a good navigator, GPS cannot replace that.”

He reminds captains that basic navigational skills are still required for licensing.

“Celestial and paper, they are un-spoofable,” Morley said. “There is no way to spoof-proof your GPS.”

After hearing about the experiment on M/Y White Rose of Drachs, Capt. Tedd Greenwald of M/Y Go Fourth pulled out his old charts and looked at the “zillions” of marks from his dead reckoning hourly plots.

“Sometimes I wonder why I still have my charts and plot, but they make me feel good,” he said. “I mean, we have two iPads, two iPhones, separate computers for navigation and more. But the weak link is the GPS.

“Now I know why I still do them,” he said of the GPS spoofing. A navigator since before GPS, he remembers when navigation tools were a compass and a log book.

“These days, everyone swears by GPS,” said Jay Verkey, owner of Lauderdale Compass in Ft. Lauderdale.

Jay Verkey, owner of Lauderdale Compass in Ft. Lauderdale. Photo by Dorie Cox

Jay Verkey, owner of Lauderdale Compass in Ft. Lauderdale. Photo by Dorie Cox

But his customers tell tales of lost power and dark electrical screens, thankful for their basic, non-electric compass on board. As to the potential for spoofing a compass, Verkey said it seems unlikely.

“I don’t think there is any way to affect a compass on that scale,” he said. “There is no way a compass can be remotely influenced. It is a mechanical device. They are infallible, as far as I know.”

Since there is little to prevent such a spoofing, some are concerned that the experiment only served to give bad guys more ideas.

“To the people that say we shouldn’t tell others about this, this is a friendly wake-up call,” Schofield said. “This [GPS] is a large part of our lives.”

Dorie Cox is associate editor of The Triton. Comments on this story are welcome at

Click to see video by Humphreys on GPS spoofing.

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About Dorie Cox

Dorie Cox is editor of The Triton.

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