What does a clearing bearing actually do?
A clearing bearing creates an observable limit around a charted danger. Instead of waiting for a complete position fix, the navigator monitors the bearing of a suitable fixed object. Crossing to the danger side warns that the vessel is approaching or entering the protected area.
It is useful because the decision has been made before workload increases. The chart work establishes the boundary and its safe side; the observation afloat answers a simpler question: are we still on the intended side?
The line does not show the vessel's exact position. Many points can share the same bearing, so use it alongside depth, visual cues, electronic position information and the rest of the pilotage plan.
How is a safe clearing bearing plotted?
Start with a current, suitable-scale chart and identify the danger that needs a margin. Select a fixed, charted object that should be visible and identifiable during the relevant part of the passage.
Plot a line from that object so it clears the danger by the margin appropriate to the vessel and circumstances. Account for charted depth, height of tide, positional uncertainty, the width of the hazard, expected track error and the consequences of getting it wrong.
Record whether the plotted value is true, magnetic or compass and keep every value in the pilotage plan consistent. If a handheld compass observation will be compared with a true charted bearing, the required conversion must be completed before it is needed.
How do you avoid confusing the safe side?
Do not rely on memory such as “greater is good”. Bearing values wrap through north, and the relationship can reverse depending on the object and direction of travel.
Mark a test position clearly on the safe side of the line and check what the object would bear there. Write an instruction that names both the object and the safe relationship, then verify it with a second person during the briefing.
On the chart or pilotage card, shade or label the danger side. A visual boundary is much harder to reverse under pressure than an isolated three-digit number.
When should the bearing be monitored?
Begin while there is still room and time to respond. Establish the object's identity from position, shape, colour, light character or surrounding features before treating its bearing as evidence.
Monitor the trend, not only one reading. A steady movement towards the limit should prompt an early check of position, course and environmental effects. Reaching the limit should trigger the action decided in the plan, which may be altering course, slowing, stopping the approach or moving to the abort area.
A clearing bearing that first becomes visible beside the hazard provides little protection. Visibility range, darkness, background lighting and possible obstruction should be considered when choosing the object.
What else belongs beside it in the plan?
Pair the boundary with a planned track, depth limits, wheel-over or turn points, expected buoyage and lights, a position-fixing method and an abort point. Traffic and collision-avoidance duties remain active even when the navigation boundary looks comfortable.
Use current official charts and local information for real navigation. This explanation teaches the reasoning; it cannot supply a bearing or margin for a particular vessel, chart or passage.
Primary sources
Compass Revision is an independent revision aid and is not affiliated with or endorsed by the RYA. Check current official publications, charts, forecasts and local directions before making a real passage or safety decision.