Fix

A determined vessel position obtained from observations or reliable position data.

A traditional fix is plotted from two or more position lines observed at the same time or corrected to a common time. Electronic navigation systems can provide a direct position fix from GNSS or another suitable positioning source.

Every fix has uncertainty arising from observations, geometry, chart data and equipment. It should be identified by time and method and checked for plausibility against depth, visual information, previous movement and other available sources; it differs from a dead-reckoning or estimated position.