USCG Exam PracticeVisual piloting — three-bearing fixes, danger bearings
A navigator takes a bearing of 310°T on a lighthouse and plots the LOP. Twenty minutes later, after running 3.0 nm on course 060°T, the navigator takes a second bearing of 350°T on the same lighthouse. The navigator advances the first LOP 3.0 nm along the 060°T track and plots the intersection with the second LOP. Which statement about this position is most accurate?
- A. It is a fix of the highest accuracy because two LOPs were used
- ✓ It is a running fix, less accurate than a simultaneous fix, because the first LOP was advanced along the DR trackCorrect
- C. It is equivalent to a simultaneous fix because both bearings were taken on the same object
- D. It is a doubling-the-angle solution valid only if the second bearing is exactly double the first relative bearing
Why B is correct
Bowditch Ch. 7 §702 defines a running fix as the result of advancing a first LOP along the DR track to the time of a second observation, and explicitly states it is less accurate than a fix from simultaneous LOPs. Any error in the DR track — from current, leeway, or speed error — is carried into the advanced LOP and therefore into the running fix position.