USCG Exam PracticeEstimated position from current set & drift
A vessel's DR position at 1400 is determined. The current has a set of 090° T and a drift of 2 knots. One hour has elapsed. How is the estimated position (EP) constructed from the 1400 DR position?
- ✓ Lay off a vector in the direction 090° T for a distance of 2 nautical miles; the end of that vector is the EPCorrect
- B. Lay off a vector in the direction 270° T for a distance of 2 nautical miles; the end of that vector is the EP
- C. Apply 2 knots to the course steered and replot the entire DR track from the last fix
- D. Average the set with the course steered and plot a new course line from the last fix
Why A is correct
Bowditch Ch. 8 §803 directs the navigator to lay off the current's set and drift for the elapsed time from the DR position. With set 090° T and drift 2 kts over one hour, the displacement vector is 2 NM in the direction 090° T. The end of that vector is the EP, plotted as a dot inside a square.
Cited:Bowditch Ch. 8 §803