USCG Exam PracticeLeeway allowance in plotting
A navigator obtains a single line of position (LOP) at 0800 and advances it along the DR track to intersect with a second LOP taken at 0830. The resulting position is best described as which type of fix, and what is its primary limitation?
- A. A fix from simultaneous LOPs; it is limited by the angle of cut between the two bearings
- ✓ A running fix; it is less accurate than a fix from simultaneous LOPs because it depends on the assumption that the DR track accurately represents the vessel's movement between observationsCorrect
- C. A running fix; it is more accurate than a simultaneous fix because it incorporates elapsed time and distance run
- D. A dead reckoning position; it cannot be used as a fix because no simultaneous observations were made
Why B is correct
Bowditch Ch. 7 §702 defines a running fix as one obtained when LOPs cannot be taken simultaneously, with the first LOP advanced along the DR track to the time of the second observation. It is explicitly described as less accurate than a fix from simultaneous LOPs. Bowditch Ch. 23 §2301 further notes that navigational errors include the assumption that the vessel held the planned course, which directly affects the reliability of an advanced LOP.