The UK Maritime and Coastguard Agency (MCA) has told shipowners and seafarers that they should no longer assume satellite navigation will always be available. In new guidance, MGN 719, the agency points to growing jamming and spoofing of GNSS signals in the Baltic, the Black Sea, the Persian Gulf and parts of East Asia.

Back to basics on the bridge

The MCA wants crews to regularly practise navigating without satellites: taking radar fixes and visual bearings, using celestial navigation and working out positions by dead reckoning.

More than just the chart

The risk goes well beyond electronic charts. AIS, autopilots, radar, gyrocompasses and distress communications can all be affected. On shore, vessel traffic services and port logistics systems are exposed as well.

The numbers behind the warning

A UK government study estimates that a seven-day GNSS outage would cost the British maritime economy around £1.5 billion, of which £1.3 billion would fall on port operations. Windward recorded an average of 5,131 GPS interference events per day in the third quarter, affecting more than 124,000 ships. In a Royal Institute of Navigation survey, 14% of respondents said GNSS disruption had put them in an unsafe situation. In the Black Sea, four tankers reported false positions, and one vessel appeared about 12,000 km away from where it actually was.

Backup still years away

The UK's land-based backup, eLoran, is still under construction. Initial timing services are expected in 2028, with full positioning and navigation planned for 2030.

What it means for shippers

Signal interference in busy trade lanes can slow vessels, disrupt port operations and make tracking data less reliable. Importers should allow extra buffer in schedules for cargo moving through affected regions and check ETAs with their forwarder rather than relying only on AIS tracking.