USCG Exam PracticeThree-bearing fix and cocked-hat triangle
A navigator takes a bearing of 045°T to lighthouse Alpha and plots the LOP. Fifteen minutes later, after running 2.0 nm on course 090°T, the navigator takes a bearing of 358°T to the same lighthouse. The first LOP is advanced 2.0 nm along the 090°T track. The resulting position is BEST described as:
- A. A fix, because two LOPs to the same object were used
- ✓ A running fix, less accurate than a simultaneous two-object fixCorrect
- C. A fix equivalent in accuracy to a three-bearing simultaneous fix
- D. A doubling-the-angle fix, valid only when the second bearing is exactly double the first relative bearing
Why B is correct
Advancing the first LOP along the DR track and intersecting it with the second LOP produces a running fix. It is less accurate than a simultaneous fix because any DR error — from current, speed error, or leeway — is incorporated into the advanced LOP. Bowditch Ch. 7 §702.
Cited:Bowditch Ch. 7 §702