Phantom Boats Drawing 'GPS Crop Circles' Keep Appearing Off the Coast of San Francisco

Phantom ships that appear to be sailing in circles off the coast of San Francisco have been discovered by an analyst examining vessel tracking data. Bjorn Bergman, from SkyTruth and Global Fishing Watch, has identified nine boats broadcasting signals that suggest they were around Point Reyes, northwest of the city, when they were actually thousands of miles away.

Commercial boats of a certain size are required by U.S. and international law to have automatic identification systems (AISs). These systems provide information on where a ship is on the ocean, helping to inform maritime radar and avoid collisions.

Bergman has worked with SkyTruth and Global Fishing Watch for six years. The latter is an organization that runs a project to map global fishing activity using AIS data from an open system, normally on larger vessels but also used by smaller fishing boats. Using this information, the team can compare AIS data with satellite information to any find boats that may be fishing illegally.

Last year, Bergman had noticed false AIS locations appearing for several ships off the coast of China. When they got too close to a certain point on the shore, the AIS was scrambled and they appeared to be several miles away from their true location. At the time, Bergman determined this was a deliberate disruption of the GPS rather than being a malfunction of the AIS.

He then started looking more broadly for false AIS signals, and found a strange pattern, with boats appearing above Point Reyes. "Although the circling tracks look similar in both locations, the vessels on the Chinese coast were at most a few miles from the circling tracks, while the vessels broadcasting tracks above Point Reyes are actually thousands of miles away," he wrote in a blog post.

There is no known connection between any of the boats and their true locations were scattered across the globe. Some of the boats were in locations where boats are known to have had GPS scrambled, such as the Suez Canal, while others were not. What was causing these boats to all of a sudden put out false AIS locations is unknown. Bergman said it could be related to some sort of malfunction with the GPS device, or it could be deliberate manipulation. But both theories come with problems.

Port Reyes was a U.S. Coast Guard site until 2015 when it was decommissioned, although volunteers continue to maintain the site. "It has a long history in maritime navigation," Bergman told Newsweek. "There must be some connection. I've got a lot of theories [but] we don't know One thing that could be plausible is that it's acting as a zero location because of the importance of this spot in developing maritime navigation systems. So if [a ship's] reception is blocked for whatever reason they're appearing there."

He said some have suggested the location is being deliberately selected to test a system where someone is artificially inputting data into the vessels. "It's an open question about what's being affected," he said.

Bergman hopes to find out more about the AIS devices being used on the nine ships that appeared above Point Reyes. If they were made by the same manufacturer, that would be a link that he could investigate further. That alone, however, would not explain the phantom circles. Manufacturers create thousands of devices, so even if they were the same make and model, why would only nine malfunction?

Todd Humphreys, associate professor of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin, researches technology relating to positioning, navigation and security. He told Newsweek the circles off Point Reyes were likely the result of GPS "spoofing" devices. This technology, he said, started to become more accessible around 2016.

"Fast forward to 2020 [and] what I think we're witnessing with the strange patterns...is the emergence of commodity off-the-shelf spoofing devices," he said. "Someone somewhere is selling cheap turnkey GPS spoofers...I think that's what's going on." He said over the last year there have been instances of ships off China, Iran and Africa transported to some strange location and "dragged around a circle."

"We know it's GPS spoofing because we also see it in the data from exercise apps. Usually the false location is near the true one, but in other cases it's half a world away, like Point Reyes for a ship off the coast of Africa."

Humphreys said the most likely motive is to ward off drones and to hinder the enforcement of oil sanctions. "It's pretty remarkable that there hasn't been a concerted crackdown on this, given how important GPS is for safe navigation," he said. "If I'm right and cheap spoofers are now for sale, you can bet a lot more 'GPS crop circles' will show up in the coming months and years, with negative implications for ships, aircraft, and ordinary turn-by-turn directions."

Dana Goward, president of the Resilient Navigation & Timing Foundation, said he also believes GPS spoofing devices are responsible. "This might be for the purpose of concealing the vessels' movements for some reason," he told Newsweek. "Almost certainly these devices have become available for purchase on the internet from sites that specialize in GPS jamming and spoofing equipment. Maritime is a lightly governed domain and there are lots of reasons to conceal the movements of vessels or individuals."

He said it is not clear why the tracks are circular, but it could be a feature of the hardware and software of the spoofing device. The track pattern may have only become apparent once the devices started being used. What the significance of Port Reyes was, Goward says, is a "complete mystery."

"I served with the Coast Guard for 40 years retiring as the U.S. maritime navigation authority. I can't imagine how a closed radio station could have anything to do with a navigation issue. Pretty darn sure it is just a coincidence."

Bergman said he now plans to continue monitoring data for more false AIS locations. He hopes to see if he can get more information from the nine ships' AIS broadcasts. "Maybe there's a way to tell if this is something that came out of a receiver or if it was synthetically produced," he said. "Hopefully I'll get some more information about that."

Goward says the potential widespread use of spoofing devices is very concerning. In the U.S., Congress has passed a law for terrestrial systems to back up GPS timing signals. This should make receivers highly resistant to interference. "Furthermore, the system must be expandable into a navigation system that can be used when GPS is not available," he said.

This article has been updated to include more information on Global Fishing Watch.