Marine Glossary

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danger bearing

The maximum or minimum bearing to a landmark for safe passage of an off-lying danger. As a vessel proceeds along a route, the bearing of a fixed point on shore, such as a lighthouse, is measured frequently. As long as the bearing does not exceed the limit of the predetermined danger bearing, the vessel is on a safe course.

Sometimes navigators will mark these bearings on the chart as NMT 205 M or NLT 045 M, etc for "Not More Than" or "Not Less Than," which is a traditional terminology.

But we could label this differently if we choose: instead of labeling the safe when bearing as "not less than 200 M" (meaning we must have have, say, 205, 220, 234, etc), we could in our own chart or notebook write: we are safe when the bearing remains "greater than 200 M."

When using this procedure we are standing on deck with a bearing compass continually measuring the bearing to the target object, which we are doing no matter where we are on the chart, and no matter which way the boat is headed.

Likewise, when we decide what the specific danger bearing should be, we are not considering the location of the boat. All we are looking at is the target light or landmark and the hazard we want to avoid, plus some safety margin around that target.

We have these course resources that discuss the procedure:

video| https://www.youtube.com/watch?v=Mm33xjLXLzs

and

article| https://davidburchnavigation.blogspot.com/2022/04/danger-bearing.html