SAT-JAM: Ships must learn to navigate without GPS

A researcher in Denmark who has developed a new system for tracking satellite navigation interference from space has a stark warning for the shipping industry in today’s Maritime CEO interview: GPS can no longer be considered a dependable means of navigation.

Kian Bostani Nezhad, a PhD researcher at the Technical University of Denmark (DTU), believes the maritime industry needs a fundamental rethink of its reliance on satellite positioning.

“GNSS interference has become a perpetual problem,” he tells Maritime CEO. “Everyone who uses GNSS must change their mindset from GNSS being a primary and dependable navigation solution, to it being a supplement to other navigation methods.”

Nezhad is the creator of SAT-JAM, a freely accessible online platform launched in September that maps GNSS interference detected by satellites orbiting hundreds of kilometres above Earth.

The project began with an unexpected conversation last year.

“I heard a spacecraft operator complain about their spacecraft having problems with GNSS over Europe,” he recalls. Intrigued, Nezhad searched for publicly available navigation data collected by low-Earth-orbit satellites and discovered several European Space Agency missions providing the information. Every mission he examined showed evidence of interference.

Nezhad then submitted a research abstract to the Advanced Maui Optical and Space Surveillance Technologies conference in March, before developing SAT-JAM, inspired by GPSJam, a website tracking interference experienced by aircraft.

His findings demonstrate that disruption affecting ships in the Baltic, Black Sea and other maritime hotspots is not confined to the Earth’s surface. Satellites operating 400 to 600 km above the planet can also experience degraded positioning signals.

The platform uses publicly available European Sentinel satellite data, updated as new observations become available, to identify where spacecraft experience interference. However, Nezhad stresses an important distinction between detecting interference and locating its source.

“SAT-JAM does not show where GNSS interference originates from, but where spacecraft measure the GNSS interference,” he explains. “The actual source, and the measurement can be far apart, due to the high altitude of satellites.”

The distinction matters for shipowners attempting to understand the geographical spread of jamming and spoofing. Satellite measurements cannot automatically be interpreted as evidence of interference affecting vessels directly beneath them.

Nezhad’s research background also includes maritime surveillance. His master’s thesis explored applying facial recognition algorithms to satellite imagery to identify and re-identify individual ships.

Asked what practical advice he would offer shipowners facing increasingly unreliable satellite navigation, Nezhad identifies two priorities.

First, operators should keep pace with improvements in GNSS receiver technology, particularly controlled reception pattern antennas (CRPA), which can suppress interfering signals.

His second recommendation is more fundamental – seafarers must learn to navigate without GNSS.

“I know it is easier said than done, but GNSS interference has become a perpetual problem,” he stresses.

Britain warned shipowners earlier this month that satellite navigation can no longer be relied upon in major shipping regions, urging crews to practise operating without GPS. New guidance from the Maritime and Coastguard Agency highlights growing jamming and spoofing threats across the Baltic, Black Sea, Middle East Gulf and East Asia, affecting everything from ECDIS and AIS to autopilots and port systems. 

Maritime intelligence firm Windward recorded an average of 5,131 daily jamming incidents during the third quarter. The MCA recommends regular navigation drills, alternative positioning methods and greater awareness of equipment vulnerabilities.

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