Fixing by Cross Bearings

Principle of Fixing by Cross Bearings

Fixing by cross bearings involves taking bearings to two (or more) known ground stations—such as VORs, NDBs, or visual landmarks—at the same time. Each bearing provides a line of position (LOP) on the navigation chart. The point where these lines intersect is the aircraft's position fix.

How to Perform a Cross Bearing Fix

• Tune and identify two suitable navigation aids.
• Take simultaneous bearings to each station (using RMI, ADF, or VOR indicator).
• Plot each bearing as a line from the respective station on your chart.
• The intersection of these lines is your position fix.

This method is most accurate when the bearings are roughly 60–120 degrees apart (ideally close to 90 degrees). If the angle between bearings is too small, the fix becomes unreliable due to increased error sensitivity.

Cross Bearings in Practice

• Used to check or update dead reckoning (DR) positions.
• Helps identify track errors caused by wind drift.
• Essential for calculating actual track, groundspeed, and for correcting heading using rules like the 1-in-60 rule.

Common Causes of Error

• Inaccurate bearing readings (instrument or human error).
• Poor geometry (bearings too close together).
• Station position uncertainty or signal interference.

Example

If an aircraft receives a bearing of 045° from VOR A and 120° from VOR B, plotting both lines from their respective stations on the chart, the intersection is the aircraft's position at that moment.

When to Use Cross Bearings

• When GPS is unavailable or as a backup.
• To verify DR positions on long legs.
• During navigation training and in exam scenarios.