Chart Navigation & Plotting · Electronic — Position Accuracy
On an ECDIS, why should you verify the GNSS position against an independent source such as visual bearings or radar ranges when piloting in confined waters?
- ABecause GNSS is always less accurate than DR
- BBecause ECDIS cannot display radar
- CTo detect undetected GNSS error, datum mismatch, or sensor failure before grounding — never rely on a single positioning source✓ Correct
- DOnly to satisfy logbook requirements
Explanation
A single positioning source can fail or carry undetected error (signal degradation, spoofing, datum offset, antenna fault). Good practice cross-checks the electronic fix against independent visual/radar LOPs, especially in pilotage waters where errors are least forgiving.
Authority: Bowditch (Pub. No. 9); IMO ECDIS performance standards; bridge resource management
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