Module 16 - Pilotage
Clearing Bearings
What you will learn
Construct, label and monitor a clearing bearing on the correct reference, then act before the planned safe-side limit is crossed.
A clearing bearing converts a charted danger boundary into a simple cockpit limit. It is useful only when the safe inequality, bearing reference and avoiding action are unambiguous.
Plot a line from a conspicuous charted object that clears the danger by a deliberate margin. Measure the bearing in the vessel-to-object direction, shade or label the danger side, and test an instruction such as 'lighthouse not more than 025°T' from points on the intended route. The chart decides whether the safe instruction is not-more-than or not-less-than; no mnemonic can.
The suffix is part of the limit. A hand-bearing compass normally gives a compass bearing unless corrected, while an electronic display may be configured true or magnetic. Convert the limit for the instrument being used, or convert each observation, and label the result. Comparing 025°T directly with 025°C can erase the safety margin.
Monitor the trend early and allow for observation error, sea state and vessel motion. Take the pre-briefed action before the limit is crossed, then retake the bearing to confirm separation is increasing. A clearing bearing is one control, not a complete position, so cross-check it with depth, a transit, radar range, another bearing or a reliable electronic position.
Respond before a maximum bearing becomes unsafe
The plan says 'lighthouse not more than 025°T'. Corrected bearings rise from 021°T to 023°T and then 024°T while the yacht continues towards the boundary.
1. Read the trend
The bearing is approaching the maximum; 024° is not reassurance merely because it remains below 025°.
2. Use the planned response
Alter course or speed early enough to keep the bearing on the safe side while preserving traffic and depth margins.
3. Confirm separation
Retake the bearing and cross-check depth and position until the danger is clearly passed.
Sense check: A limit first acted on after 025° has already stopped functioning as a protective boundary.
Common mistake or limitation
- Not-more-than and not-less-than cannot be guessed from the number; draw and test the danger side.
- A true chart bearing and an uncorrected compass observation are not directly comparable.
Recap
- Plot a real danger clearance rather than a line through the hazard.
- Label the safe inequality and bearing reference together.
- Act on the trend and confirm that the avoiding action worked.
Optional quick check
Section 4 of 12
A 'not more than 025°T' limit is increasing through 024°T. What should the skipper infer?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
Practice advanced pilotage controls
The complete pilotage module connects clearing bearings with transits, depths, lights, contingencies and a cockpit-ready plan.