Clearing bearings: construct and monitor a safe boundary

A clearing bearing uses the bearing of a charted object to define one edge of safe water. Plot the boundary so it clears the danger by a deliberate margin, measure its true bearing at the charted object, and write down which side of that line is safe. The instruction might be 'keep the lighthouse bearing not less than 045°T', but the safe inequality must come from your plot rather than a memorised rule.

Before using the boundary with a steering or hand-bearing compass, convert the plotted true bearing to the compass reference you will actually observe and allow for the accuracy of the charted object, compass, sea state and observer. At the first safe opportunity, check that the observed trend moves in the direction your plan predicts. If it approaches the limiting value, take early action; do not wait to cross the boundary.

A clearing bearing is a monitoring control, not a complete position. Cross-check it with depth, a transit, a second bearing, radar range or a reliable electronic position. In the cockpit plan, record the object, reference (true, magnetic or compass), limiting value, safe side, expected trend, action point and abort action. This practical use is distinct from constructing danger angles between two charted objects in the chartwork module.