What is the maximum duration allowed for a running fix in practice?

• A. 5 minutes
• B. 20 minutes
• C. 30 minutes
• D. 45 minutes

Answer: (C)

A running fix is an ongoing position estimate that you update as you move, using lines of position from observations or dead reckoning. The key idea is that your uncertainty grows the longer you go without fresh data, because your actual track can differ from your assumed track due to changes in course, speed, currents, leeway, and various instrument or measurement errors. To keep the position reliable, you should refresh the running fix at regular intervals, with about 30 minutes being the practical upper limit. If you let it go longer, the accumulated uncertainty can become too large to trust, which is why 30 minutes is the maximum duration in practice. Shorter intervals are fine when conditions demand tighter accuracy, but it’s the 30-minute ceiling that's being tested.