fix
A non-waypoint terrain feature used to make a determination of location.
fix: a ground landmark pilots use to know where they are
A fix is a confirmed position, established by visual reference to a distinctive terrain feature or structure on the ground. Unlike a waypoint, which is a predetermined coordinate in flight planning software, a fix is something a pilot actually sees and uses to cross-check their location during flight. A prominent hill, radio tower, bridge, or water tower serves as a fix. The pilot identifies the feature visually, correlates it with the sectional chart or moving map display, and confirms their current position.
Fixes remain essential in visual flight rules (VFR) operations and as backup verification during instrument flight. A pilot flying under VFR is required to maintain situational awareness by reference to landmarks; establishing a fix every 5 to 10 minutes by identifying a charted feature is standard practice. In instrument conditions or over featureless terrain, fixes become less reliable, but remain useful for validating inertial navigation systems or GPS data. The fix is plotted on the chart and noted in the flight log with the time observed.
Variants and precision
A fix can be as simple as a single visual reference, or it can be a crossed fix, where two or more visible features are identified simultaneously to narrow position uncertainty to a small area. Electronic fixes, derived from VOR (VHF omnidirectional range) signals, GPS receivers, or NDB (nondirectional beacon) bearing lines, serve the same purpose: confirming actual location against expected position. In older practice, fixes were plotted manually by drawing bearing lines from radio stations; modern glass cockpits display position fixes in real time.
The term fix comes from navigation tradition shared with maritime practice, where a vessel's position is similarly established by reference to landmarks or celestial observation. In aviation, the fix bridges the gap between pre-flight planning and the reality of flight; it is a moment of verification, a ground truth that confirms the aircraft is where the crew believes it to be. Failure to establish regular fixes, or misidentification of a landmark, has contributed to loss-of-positional-awareness accidents, making the discipline of fixing a foundational element of flight safety.