Rules of the Road — Practice Questions

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A navigator is maintaining a DR plot in open water using only course steered and speed through the water. No external fix has been obtained for 4 hours. Which combination of factors from the source material BEST explains why this DR plot may contain significant positional error, and what action is required?

1. APiloting is unavailable in open water, so the navigator must switch to celestial navigation; no DR plot maintenance is required
2. BCumulative errors from instrument, observation, plotting, and computation sources compound over time, and the DR assumption that the vessel has held the planned course ignores set and drift; the plot must be confirmed against external fixes whenever possible
3. CThe running fix method should replace DR after two hours because simultaneous LOPs are more accurate; the DR plot should be abandoned
4. DElectronic navigation is the principal real-time reference and renders DR plot maintenance unnecessary on modern vessels