USCG Exam PracticeDead reckoning — DR plot maintenance
Which statement best describes why DR accuracy degrades over time?
- A. Electronic navigation systems introduce increasing signal error with elapsed time
- ✓ Cumulative errors from instrument, observation, plotting, and computation sources accumulate and the vessel may not have held the planned courseCorrect
- C. Set and drift cannot be measured accurately enough to apply to any DR plot
- D. Piloting fixes become less reliable as the vessel moves farther from landmarks
Why B is correct
Bowditch Ch. 1 §102 states DR accuracy degrades over time and must be confirmed by external fixes. Bowditch Ch. 23 §2301 identifies the specific error sources — instrument, observation, plotting, computation, and the assumption the vessel held its planned course — as the reason cumulative error grows.