How often should a fix be compared with an unrelated positioning source?

Comparing a fix with an unrelated positioning source every 15 minutes is crucial for maintaining navigational accuracy and safety at sea. This practice helps to identify any discrepancies between the primary navigation method being used and an alternative source, which may include GPS, radar, visual landmarks, or other navigational aids. The 15-minute interval is often recommended, especially when navigating in areas of concern, such as congested waters or during limited visibility. This frequency allows for timely adjustments and increases confidence in positional accuracy, which is vital for effective decision-making and operational safety.

Longer intervals, such as half-hour or hour comparisons, might not detect shifts in position or potential navigational errors quickly enough, which could potentially lead to unsafe situations. Hence, the 15-minute benchmark is a proactive measure to ensure continuous situational awareness while navigating.