Study: Baltic GPS Disruption Comes From a Tactically-Controlled Network

The Baltic is a notorious hotspot for GPS interference, particularly in the region around the Russian exclave of Kaliningrad. But pinning down the extent and the nature of the problem requires careful research. A team from GPSPatron and Gdynia Maritime University have carried out that work - first with shore-based data collection, and now with on-the-water data from a research vessel at sea.

Between June and October, the joint team used a sophisticated interference detector aboard the research vessel Imor on trips near the Polish coastline, including several approaches to the maritime boundary with Kaliningrad. The sensor suite was built to detect interference with GPS, Galileo and GLONASS - three out of the four GNSS satellite constellations - in order to identify simultaneous attacks on multiple channels.

The intensity of jamming (and the research vessel's itinerary) varied over the course of the study. Jamming was most intense in late June and July, when GNSS positioning was unavailable off Gdansk about 17 percent of the time. The power level of the interference became stronger as the vessel went further out into Gdansk Bay, away from the port. In addition, strong spoofing components targeting the GPS and BeiDou constellation signals were detected when offshore - not in port.

"This spoofing–jamming combination is a widely used technique. Full multi-constellation spoofing would require generating all GPS, Galileo, GLONASS, and BeiDou signals across multiple frequency bands," the researchers observed. "In practice, this is complex and costly. For this reason, real-world interference systems typically spoof only GPS — the primary navigation constellation — and simultaneously jam all other GNSS signals. This prevents the receiver from performing any constellation cross-checks and forces it to rely solely on the forged GPS solution."

The characteristic sign of this GPS spoofing technique is the "ship-on-land" aberration. The ship's GPS sensor picks up the spoofed position and feeds it to the AIS transceiver on the bridge, which then retransmits it - broadcasting a message that the ship is wherever the spoofing signal says it is. On AIS, this displays as a cluster of "ships" that appear to be sharing the same false position, sometimes orbiting in circular tracks, often located on land.

The signal combination is not some form of accidental interference, the researchers suggest. The data point strongly towards a network of transmitter station sites, which operate on multiple bands and change continuously in strength. Some of the recorded spectral patterns of the jamming show artifacts consistent with analog radio equipment, while others are more refined, indicating that the operator is using several different generations of transmitter equipment. In addition, the team found that the GPS spoofing signal is itself partially jammed by other stations in the network. Most persuasively of all: these interference methods all turn on and off at the same time.

"Taken together, these observations point to a distributed, multi-node interference system, where several independently operating transmitters—likely of different generations and purposes—are synchronized to work as a single electronic warfare network," the researchers concluded.

This poses an ongoing threat to shipping, the team warned. By tampering with GPS and all three satellite-navigation alternatives, the jamming network can throw off ECDIS systems, confuse watchstanders and VTS operators, disrupt some types of autopilot systems, and generally raise the risk of collision.

"The findings demonstrate that GNSS spoofing in the southern Baltic is not a theoretical threat—it is an operational reality already affecting vessels daily. The risks to maritime safety, port operations, and environmental security are immediate and significant," the team concluded.