A new DR position must be plotted at every course change, every speed change, at each fix, and ______.

A. at every change of watch
B. whenever visibility drops below 1 mile
✓ at least once each hourCorrect
D. at least every 30 minutes in all waters

Why C is correct

The DR plot is updated at course changes, speed changes, fixes, and at minimum once per hour — more frequently in pilot waters. Watch changes and visibility thresholds are not listed triggers.

Cited:Bowditch Ch. 8 §801

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A new DR position must be plotted at every course change, every spe… — USCG Exam Practice · CaptainsGround