USCG Exam PracticeCourse to steer to compensate for current
A vessel departs a fix at 0800 steering 000°T at 10 knots. The current sets 270°T at 4 knots. At 0900 the navigator plots the DR position and then constructs an EP. Which procedure correctly produces the EP?
- ✓ From the 0900 DR position, lay off a vector in the direction 270°T for a distance of 4 nautical miles; the end of that vector is the EPCorrect
- B. From the 0800 fix, lay off the current vector for the full hour and label that point the EP without plotting a DR position
- C. Average the 0800 fix and the 0900 DR position and label the midpoint the EP
- D. From the 0900 DR position, lay off a vector in the direction 090°T (reciprocal of set) for 4 nautical miles to correct for the current
Why A is correct
Bowditch Ch. 8 §803 directs the navigator to first plot the DR position, then from that DR position lay off the current's set and drift for the elapsed time. Set is 270°T and drift is 4 knots; in one hour the current displaces the vessel 4 miles in the direction 270°T. The end of that vector is the EP, plotted as a dot inside a square.
Cited:Bowditch Ch. 8 §803