Two confident screens, one uncertain receiver
A merchant vessel is approaching a coastal waypoint after several hours in open water. Both electronic displays show the ship close to the intended track, and their symbols appear stable. The officer notices, however, that the radar ranges to two identified charted objects no longer agree with the expected distances. A visual bearing, obtained where the weather permits, also appears inconsistent with the electronic position. The displays receive their position from the same GNSS source. Traffic remains present ahead, and the next planned leg passes closer to a charted shoal. There is room to reduce speed and delay the turn while the bridge team investigates. The pilot has not yet boarded, and the master is available to be called.
1. Why are the two screens not independent confirmation?
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They share the same underlying position source. Compare the available radar and visual evidence, assess uncertainty, call the responsible support and avoid proceeding into a reduced-margin leg on an unexplained fix.
2. What should be reassessed before executing the next leg?
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Reassess position, source integrity, stopping and maneuvering room, traffic and the actual under-keel and lateral margins. A valid planned route does not remove the need for reliable execution evidence.