Module 16 - Pilotage
Clearing Bearings
What you will learn
Construct, label and monitor a clearing bearing on the correct bearing reference and respond before its safe-side limit is crossed.
A clearing bearing converts a charted danger boundary into a simple cockpit limit. Its power comes from stating the safe side explicitly and comparing like with like: true with true, or a correctly converted compass observation with its matching limit.
On the chart, draw or imagine a line from a conspicuous object that clears the danger by the chosen margin. Measure its true bearing in the direction from the vessel towards the object, shade or label the danger side, and write an unambiguous instruction such as 'lighthouse not more than 025°T'. Test the wording from points on the intended route.
The suffix matters. A hand-bearing compass produces a compass bearing unless corrected; a plotter may display true or magnetic depending on configuration. Convert the planned limit for the instrument being used, or convert the observation, and label the result. Comparing 025°T directly with 025°C can erase the intended margin.
A clearing bearing is a limit, not a track to chase. Monitor it early enough to detect the trend, allow for observation error and vessel movement, and take the pre-briefed avoiding action before the boundary is crossed. Cross-check with depth, position and the physical scene because the object may be misidentified or obscured.
Respond to an increasing maximum bearing
The plan says 'lighthouse not more than 025°T'. Corrected bearings rise from 022°T to 024°T while the yacht is still moving towards the hazard boundary.
1. Read the trend
The bearing is approaching the maximum safe limit; 024° is not reassurance simply because it is still 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 hazard is clearly passed.
Sense check: A clearing limit that is first acted on after 025° has already stopped being a protective boundary.
Common mistake or limitation
- 'Not more than' and 'not less than' cannot be guessed from the number; the danger side must be drawn and tested.
- A true chart bearing and an uncorrected compass observation are not directly comparable.
Recap
- Draw the hazard boundary with a real clearance, not through the danger.
- Label the safe inequality and bearing reference together.
- Monitor the trend and confirm the avoiding action has worked.
Optional quick check
Section 4 of 8
The plan says 'lighthouse not more than 025°T' and corrected bearings rise through 025°T. What does that mean?
Practice advanced pilotage controls
The complete pilotage module connects clearing bearings with transits, depths, lights, contingencies and a cockpit-ready plan.