USCG Exam PracticeRunning fix from a single object
When using the doubling-the-angle technique, a vessel on course 090°T observes a lighthouse at a relative bearing of 030° at 0800. The navigator intends to take the second bearing when the relative bearing doubles to 060°. If the vessel is making 8 knots and the elapsed time between bearings is 18 minutes, what is the vessel's distance off the lighthouse at the time of the second bearing?
- A. 8.0 nautical miles
- B. 4.0 nautical miles
- ✓ 2.4 nautical milesCorrect
- D. 3.6 nautical miles
Why C is correct
By the doubling-the-angle rule, distance off at the second bearing equals the distance run between the two bearings. Distance run = 8 knots × (18/60) hours = 2.4 nautical miles. Therefore the vessel is 2.4 nm from the lighthouse at the time of the second bearing. (Bowditch Ch. 7 §703)
Cited:Bowditch Ch. 7 §703