WATCHOUT - Loss of GPS leads to groundings, disruption and delay
In this series, we take a look at issues affecting the safety of mariners and the lessons that can be learned from incident reports and examples. The following case studies and analysis have been provided by Gard P&I Club
Example One: Coral collision
A vessel experienced a loss of GPS signal in the Red Sea and consequently relied on the Estimated Position (EP) function of its ECDIS for navigation towards the port. Hours later, the crew observed an unusual sea surface coloration, which they mistakenly believed was seaweed. The vessel ran aground on corals at a speed of 11.3 knots, incurring substantial damage to its bottom plating and double bottom ballast tanks – and the coral reef.
To ascertain the exact grounding site, the safety manager contacted the flag state. They were able to confirm the vessel’s position using the IMO’s LRIT (Long Range Information and Tracking System) – and found it was more than 40 nautical miles away from the estimated position displayed on the ECDIS.
Example Two: Desert disruption
While preparing to depart a port in the Red Sea after cargo operations, a vessel experienced severe GPS interference, showing it as being inland in a desert. Other nearby vessels were similarly affected by GPS disruption. The Master deemed it unsafe to depart without a functional GPS. The interference lasted over a week, delaying the vessel’s departure and leading to a lengthy dispute between the owners and charterers.
Lessons learned
These two case studies highlight several key points:
- GPS interference is a real and present danger, particularly in regions of geopolitical tension, as it can render primary navigation systems unreliable.
- These disruptions force seafarers to make critical ‘go/no-go’ decisions with contrasting choices and outcomes, as observed in the two cases above.
- The first case underscores the dangers of trusting an Estimated Position (EP) derived from ECDIS when underlying GPS data is compromised – especially when there are no conspicuous objects in the vicinity for visual cross-referencing.
- The successful use of LRIT in the first incident, operating on a different satellite communication frequency than GPS, emphasises the vital role of tracking systems other than GPS play in confirming a vessel’s actual location.