3 min read


Featured Image

According to GPS data, the nine ships were sailing in circles off Point Reyes, just north of San Francisco, California. In reality, the vessels were floating in locations as diverse and far away as the Norwegian Sea, Eastern Mediterranean, and Nigerian coast.

Bjorn Bergman, an analyst for environmental oversight groups SkyTruth and Global Fishing Watch, noticed the pattern of false GPS broadcasts earlier this year following similar reports of “ghost ships” circling ports in China. In December 2019, Bergman and his colleagues at SkyTruth reported on systematic GPS interference occurring at 20 sites on the Chinese coast, mostly oil terminals and government installations. Ship tracking data condensed into strange circles up to a few miles away from the vessels’ actual positions. Another GPS source, the fitness app Strava, confirmed that according to their data, this interference was not a malfunction of automatic identification system (AIS) onboard ships, but rather a problem with the underlying GPS system.

“ghost ships” circling ports in China

Source: SkyTruth

Bergman has been closely surveying global maritime satellite data since the China spoofing circles incident. In contrast to the ghost ships observed off the Chinese coast, the GPS signals broadcasting near Point Reyes were coming from vessels quite literally across the world.

GPS signals broadcasting near Point Reyes were coming from vessels across the world

Source: SkyTruth

Bergman presented his findings at the Resilient Navigation and Timing Foundation’s annual meeting on May 5. He said the cause of the false GPS signals is still a complete mystery. He is unsure whether the circular tracks off the coast of California are caused by the same thing as those off the coast of China.

“It could just be some weird malfunction in the AIS system or it could be more significant with GPS manipulation of some sort occurring,” Bergman said of the GPS signals near Point Reyes.

The false GPS signals is still a complete mystery

Source: SkyTruth

Todd Humphreys, associate professor of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin, told Newsweek that he thinks the circles above Point Reyes are the result of GPS spoofing: deliberate GPS interference and transmission of inaccurate coordinates.

"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 to Newsweek. "Someone somewhere is selling cheap turnkey GPS spoofers...I think that's what's going on."

Humphreys noted that similar circular patterns have been observed in ship data near Iran and Africa. As Bergman said in his RNT foundation presentation, these instances may be linked to operations around oil terminals.

The growing accessibility of low-cost spoofers is increasing risk for this form of interference, according to Humphreys. "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," he said.

As spoofing attacks become easier and cheaper, mass markets will need to answer with easy-to-install, cost-efficient spoofing protection. Regulus Cyber is the first company to offer this kind of technology: a standalone software solution that can detect and mitigate spoofing attacks. Regulus Cyber’s Pyramid GNSS is the ideal defense against the low-cost spoofing attacks mentioned by Humphreys – the Pyramid GNSS is reliable, affordable, and applicable across all GNSS industries. You can read more about Regulus Cyber’s Pyramid GNSS here: https://www.regulus.com/

Learn More About Maritime Solutions


“2020 RNT Foundation Annual Meeting.” YouTube, Resilient Navigation and Timing Foundation, 14 May 2020, www.youtube.com/watch?v=33AlxsUEin4&feature=youtu.be&t=1

Emmert, Samantha. “AIS Ship Tracking Data Shows False Vessel Tracks Circling above Point Reyes, near San Francisco.” Global Fishing Watch, Global Fishing Watch, 26 May 2020, https://globalfishingwatch.org/data-blog/circling-above-point-reyes/

Osborne, Hannah. “Phantom Boats Drawing 'GPS Crop Circles' Keep Appearing Off the Coast of San Francisco.” Newsweek Online, Newsweek, 5 June 2020, www.newsweek.com/ships-gps-crop-circles-san-francisco-1509012

Thomsen, Michael. “Mysterious GPS Signals Reveal GHOST SHIPS Sailing in Wide Circles off the Coast of San Francisco.” Daily Mail Online, Daily Mail, 8 June 2020, www.dailymail.co.uk/sciencetech/article-8400397/Mysterious-GPS-signals-reveal-GHOST-SHIPS-sailing-wide-circles-coast-San-Francisco.html

13 min read

GPS Is Easy to Hack, and the U.S. Has No Backup

On August 5, 2016, Cathay Pacific Flight 905 from Hong Kong was heading for an on-time arrival at Manila’s Ninoy Aquino...

1 min read

2 years since the Tesla GPS hack

In June 2019, Regulus Cyber's experts successfully spoofed the GPS system of a Tesla Model 3 vehicle. This experiment...

1 min read


The modern world relies heavily on the accuracy of the position, navigation and timing of the Global Positioning...