Fix

A fix is a geographical position determined by visual reference to the ground, by radio navigation aids, by celestial observation, or by other navigation means. A fix provides a known, confirmed position that updates the dead reckoning estimate and resets the navigation computation.

Types of Fixes

• Exact fix: Position confirmed by two or more independently crossing position lines (e.g., two VOR radials, VOR + DME, GPS position)
• Running fix: Calculated position using a single position line advanced by DR from a previous fix
• Radar fix: Position identified by ATC radar and provided to the pilot
• Visual fix: Ground feature positively identified and matched to the chart

Importance of Regular Fixes

DR errors accumulate over time. Regular position fixes are essential to maintain navigation accuracy, especially in featureless terrain or over water. GPS provides a continuous fix, but pilots should cross-check GPS with other available sources periodically, particularly for IFR operations.

Related Terms

See also: Dead Reckoning, Designated Intersection, Position Report.