UK MCA issues guidance on operating ships without reliable GNSS

The UK Maritime and Coastguard Agency published Marine Guidance Note MGN 719 (M+F), on operating in GNSS-denied and degraded environments, on 1 October 2026. It responds to rising jamming, spoofing and signal loss, with reported interference concentrated around the Black Sea, the Baltic, the Gulf and East Asia.\n\nThe note is advisory. It lists shipboard, shore-based, timing-dependent and fishing systems that rely on satellite positioning, navigation and timing, including ECDIS, AIS, VTS and survey-grade GNSS and RTK. It urges operators to map dependencies, detect interference, verify positions independently and drill crews in radar fixing, visual navigation, celestial navigation and dead reckoning. UK government estimates from 2023 put a seven-day outage at £1.5bn for the maritime sector. A sovereign eLoran network is planned, with initial timing capability in 2028 and full position and navigation capability by 2030.

Why it matters: GNSS interference is now treated as a routine operational risk, including for survey-grade GNSS and RTK work at sea. Practitioners, including those operating in African waters and ports, can use the dependency-mapping approach to audit their own positioning and timing exposure.