USCG Exam PracticeLatitude, longitude, and geographic coordinates
After drawing a course line between two charted points, a mariner walks parallel rulers to the nearest compass rose to read the true course. From which ring of the compass rose is the true course read?
- A. The inner ring, which displays magnetic directions
- B. The inner ring, because the parallel rulers must cross the magnetic north indicator
- C. Either ring, since variation is already applied to the course line
- ✓ The outer ring, which displays true directionsCorrect
Why D is correct
Bowditch Ch. 4 §406 specifies that the true course is read where the parallel ruler crosses the outer (true) ring of the compass rose. The inner ring displays magnetic directions and must not be used when plotting true courses.
Cited:Bowditch Ch. 4 §406