USCG Exam PracticeDead reckoning — DR plot maintenance
A navigator plots a DR position but suspects current is affecting the vessel's track. The best action to verify the DR and correct for current is to:
- A. Increase speed to reduce the time current can act on the vessel
- B. Advance the most recent LOP along the DR track and accept the running fix as equivalent to a simultaneous fix
- ✓ Obtain an external fix from simultaneous LOPs and compare it to the DR position to determine set and driftCorrect
- D. Continue the DR plot and check against a fix only after reaching the destination
Why C is correct
Bowditch Ch. 1 §102 requires DR to be confirmed by external fixes whenever possible. Bowditch Ch. 23 §2302 explains that comparing the fix to the DR position reveals the set and drift acting on the vessel. Bowditch Ch. 23 §2301 warns that cumulative errors must be checked against fixes whenever possible.