Pilotage
What Is a Clearing Bearing? Staying Clear of Hidden Dangers
Published · Last checked October 2026
A clearing bearing is a line drawn on the chart from a conspicuous landmark, passing safely clear of a hazard such as a rock or shoal. You note its bearing and label it 'not more than' (NMT) or 'not less than' (NLT). Underway you take hand-bearings of the landmark: as long as the bearing stays on the safe side of the limit, you are clear of the danger, without needing to fix your position.
How to draw a clearing bearing
- Pick a conspicuous, charted object ahead of or behind the hazard, so the bearing to it changes slowly.
- Draw a line from the object that passes the danger with a safety margin.
- Measure the bearing of that line from seaward towards the object, and convert it to magnetic for use with a hand-bearing compass.
- Shade or hatch the dangerous side of the line.
- Label it NMT or NLT so there is no doubt when you are at sea.
NMT or NLT?
Imagine yourself on the safe side looking at the landmark. If moving towards the danger would make the bearing larger, the limit is 'not more than'. If it would make the bearing smaller, it is 'not less than'.
| Situation | Danger lies | Label |
|---|---|---|
| Heading north towards a lighthouse, rocks to the west of the track | Left of the line (bearing increases as you move left) | NMT, e.g. NMT 010°M |
| Heading north towards a lighthouse, shoal to the east of the track | Right of the line (bearing decreases as you move right) | NLT, e.g. NLT 350°M |
Using it underway
- Take regular hand-bearings of the landmark as you approach.
- If the bearing goes past the limit, turn away towards the safe side at once.
- Have a second clearing bearing or a transit ready for the next leg.
- Check depth as a back-up: a contour can act as a clearing line too.
Clearing lines without a compass
A transit can do the same job. If you keep two objects 'open' so that one stays to the left of the other, you are on the safe side. This avoids compass errors altogether. Both methods are part of pilotage planning on the Day Skipper course.