Polish Researchers Detect Ship-Based GPS Jammers in Baltic Sea

 

A study carried out by Polish GNSS researchers has determined that the GPS interference observed in the Baltic recently exhibits capabilities beyond commercial grade, and it appears to emanate from ships in transit - not from a fixed land-based source in Kaliningrad, as some analysts have speculated. If accurate, the apparent discovery of powerful ship-mounted transmitters would help explain the shifting pattern of GPS disruption in the region. It would also align with past reports of high-power radio equipment fitted aboard vessels in the Russian "shadow fleet." 

The study monitored GPS disruption at ground level with a sensor installed at Gdynia Maritime University, 75 miles east of central Kaliningrad. It was mounted high enough for a line-of-sight radio horizon of about 20 nautical miles offshore (depending on transmitter antenna height). This is enough to reach out into the Gulf of Gdansk, but not far enough to cover the main east-west sea lanes of the central Baltic, where the vast majority of the region's traffic occurs. 

Over a period of six months beginning in June 2024, the sensor picked up 84 hours of GNSS interference, including 29 hours in October alone. Events lasted for up to seven hours at a time, and caused horizontal positioning errors of up to 100 feet - enough to affect navigation in confined waterways. 

Multi-constellation jamming (GPS, GLONASS, BeiDou and Galileo) was observed through September 2024; the pattern changed to multi-tone interference from October onwards. This interference "likely originated from a mobile maritime source, given its periodic occurrence and movement patterns," the researchers wrote. 

The ground-level disruption affects maritime interests, and did not correlate with observations of ADS-B aircraft navigational system disruption at higher altitude. Since the ground-level GNSS events aren't detected by airborne ADS-B monitoring, the team called for setting up a terrestrial sensor network for GNSS disruption with geolocation capabilities, which would be used to spot the offending vessels and identify them for possible enforcement action. 

"The interference . . . exhibited noticeable fluctuations in power levels, suggesting that the jamming source was in motion. Given the system's radio horizon, which primarily covers a portion of the Baltic Sea, and assuming that the interference source was not located within Poland’s borders, the most plausible explanation is that the jamming originated from a vessel in international waters," the researchers concluded.