USCG Exam PracticeDead reckoning — DR plot maintenance
A vessel steers 090°T at 10 knots. A current sets 180°T at 2 knots. Which statement correctly describes the relationship between the vessel's course steered and course made good?
- A. Course made good equals course steered because drift acts perpendicular to the heading
- ✓ The vector sum of the course steered and the current vector gives the actual course over groundCorrect
- C. Course made good is derived by subtracting the drift vector from the course steered
- D. Set and drift affect only speed made good, not the direction of the track over ground
Why B is correct
Bowditch Ch. 23 §2302 states that the vector sum of the intended course through the water and the current vector gives the actual course over ground. A current setting 180°T will deflect the track southward, changing both direction and speed made good.
Cited:Bowditch Ch. 23 §2302