A new technical study has recorded a marked escalation in GNSS interference in the southern Baltic Sea, with shipborne measurements indicating a shift from simple jamming to coordinated spoofing–jamming activity near the maritime boundary of Kaliningrad.
The follow-up research, shared with the UK Defence Journal by GPSPatron, expands on a land-based monitoring project we reported on last year. The previous phase, conducted with Gdynia Maritime University, documented persistent multi-constellation jamming from a fixed sensor ashore. This latest six-month campaign placed a GP-Probe TGE2 system aboard a research vessel operating from the Port of Gdańsk between June and October 2025, capturing interference exactly as it affects ships under way.
The results suggest a material change in the electronic warfare environment. According to the report, the strongest events now blend forged GPS signals with simultaneous jamming of GLONASS, Galileo and BeiDou. The authors argue this imposes reliance on spoofed GPS inputs while denying access to independent satellite ranges. They recorded 83.5 percent GNSS availability in the worst period and more than four days of spoofing across June and July, including nearly 30 continuous hours inside a 48-hour window.
Spectral analysis points to several emitters rather than a single system. Four distinct signatures were identified: a spoofing transmitter, two chirp jammers in different bands and a broadband analog-like jammer covering the full L1 band. The report states the near-simultaneous activation of these components implies a centrally coordinated network, while differing spectral fingerprints suggest multiple sites.
The technical profile has also changed. The earlier study highlighted clean, constellation-matched wideband jamming associated with modern systems. The new dataset shows simpler chirp jamming at higher power, combined with spoofing and older RF hardware with frequency instability. That mix, the authors say, indicates an environment where legacy high-power systems and newer spoofing tools are being used together.
Interference strength rises sharply offshore. Signals that appear weak in Gdańsk become significantly stronger in open water, increasing by up to 15 dB as the vessel approaches waters facing Kaliningrad. That spatial gradient underpins the paper’s conclusion that maritime operators bear the brunt of disruption, with fewer effects detectable on shore-based infrastructure.
Stefan Majinovic of GPSPatron told us the findings offer a “rare, data-driven view” of a rapidly evolving threat picture and that the company is making raw data available for further scrutiny. The full report, including spectrograms and methodology, is available on GPSPatron’s website.