USCG Exam PracticeDead reckoning — DR plot maintenance
A navigator advances a 0600 LOP along the DR track to 0700 and crosses it with a 0700 LOP to obtain a running fix. Compared to a fix obtained from two simultaneous LOPs at 0700, which statement about this running fix is correct, and what is the primary reason?
- A. The running fix is equally accurate because both LOPs reference the same charted object
- ✓ The running fix is less accurate because advancing the LOP introduces any DR errors accumulated between 0600 and 0700Correct
- C. The running fix is more accurate because it incorporates a longer observation baseline
- D. The running fix is less accurate solely because observation error is doubled when the same object is used twice
Why B is correct
Bowditch Ch. 7 §702 explicitly states the running fix is less accurate than a fix from simultaneous LOPs. The reason is that advancing the first LOP along the DR track incorporates all DR errors — including those from set, drift, and course-keeping — accumulated over the interval between observations, per Bowditch Ch. 23 §2301 and §2302.