Which duration is a commonly accepted maximum for a running fix?

• A. 10 minutes
• B. 30 minutes
• C. 60 minutes
• D. 15 minutes

Answer: (B)

A running fix relies on updating your position as you move by obtaining lines of position from observations taken at intervals while underway. Because the vessel is constantly shifting, the later you wait between observations, the more your fix will reflect drift and changes in speed or course rather than your current spot. Thirty minutes is the commonly accepted maximum because it keeps the fix current enough to be reliable while allowing time to gather sufficient observations. At typical speeds, you can move several nautical miles in that interval, which is about the range where the intersecting lines of position still meaningfully represent your present location. Shorter intervals would improve accuracy but require more frequent observations; longer intervals would let drift accumulate too far, reducing reliability.