How angles become location — and why one bearing is never “just one bearing”
Contents
Use the links below to jump to any section:
- What a Bearing Actually Represents
- True, Magnetic, and Relative Bearings in Practice
- The Concept of a Line of Position
- Why One Bearing Is Still Valuable
- Two Bearings and the Creation of a Fix
- Bearing Spread and Fix Geometry
- Running Fixes and Advancing a Line
- Bearing Accuracy and Human Error
- When Bearings Disagree
- Professional Bearing Discipline on the Bridge
1. What a Bearing Actually Represents
A bearing is an angle, but operationally it is much more than that.
When you take a bearing to a charted object, you are not saying “the lighthouse is over there.”
You are saying:
“The ship lies somewhere along this line relative to that object.”
That statement is powerful. It converts a momentary observation into a geometric constraint.
Navigation is the art of stacking constraints until only one position remains possible.
2. True, Magnetic, and Relative Bearings in Practice
Bearings are measured in different reference frames, and confusion here causes early errors.
A true bearing is referenced to true north and aligns directly with the chart.
A magnetic bearing is referenced to magnetic north and must be corrected.
A relative bearing is measured from the ship’s head and must be converted before plotting.
On the bridge, all three are used. What matters is not the type, but that the officer knows which one they are holding and how it connects to the chart.
Most bearing errors are not angular mistakes. They are reference mistakes.
3. The Concept of a Line of Position
When a bearing is plotted on the chart, it becomes a line of position.
That line does not say “the ship is here.”
It says “the ship is somewhere along this line.”
This is why a single bearing is never useless. It removes an entire half of the chart from possibility.
Every additional line of position reduces uncertainty further.
Navigation works by narrowing, not guessing.
4. Why One Bearing Is Still Valuable
A single bearing cannot give a fix, but it can still:
- confirm the ship is on the correct side of a danger
- verify progress along a track
- detect unexpected set or drift
- provide reassurance when combined with depth or transit
Professional navigators use single bearings constantly without announcing it. They are checking reality continuously, not waiting for perfect fixes.
5. Two Bearings and the Creation of a Fix
Two bearings taken to two separate charted objects create two lines of position.
Where they intersect is the ship’s position.
This is the simplest fix geometry and the most commonly used in coastal waters.
The reliability of that fix depends not on precision of plotting, but on the angle between the bearings. Shallow crossing angles produce uncertainty. Strong crossing angles produce confidence.
This is geometry, not luck.
6. Bearing Spread and Fix Geometry
The quality of a fix is governed by geometry.
Bearings taken to objects that are close together in direction will intersect poorly. Bearings spread widely across the horizon intersect cleanly and decisively.
Experienced watchkeepers instinctively choose objects that “frame” the ship.
This instinct is learned, not memorised.
7. Running Fixes and Advancing a Line
Sometimes only one good object is available.
In that case, bearings taken at different times can be combined with the ship’s movement to create a running fix.
The earlier bearing is advanced along the ship’s estimated track to the time of the second bearing. The intersection then reveals position.
Running fixes require honesty about speed and course. If those inputs are wrong, the fix will be wrong.
They reward discipline and punish assumption.
8. Bearing Accuracy and Human Error
Bearings are only as good as the person taking them.
Common errors include:
- misidentifying the object
- reading the compass incorrectly
- delaying between bearings
- failing to account for ship movement
The most dangerous error is false confidence. A precise-looking bearing to the wrong object is worse than no bearing at all.
9. When Bearings Disagree
When plotted bearings do not intersect neatly, something is wrong.
Possible causes include:
- object misidentification
- poor geometry
- ship turning during observation
- compass error
- plotting mistake
A “cocked hat” is not failure. It is feedback.
Professional navigators investigate disagreement instead of averaging it away.
10. Professional Bearing Discipline on the Bridge
On a professional bridge, bearings are:
- taken deliberately
- plotted promptly
- questioned when unexpected
- used to verify, not decorate
They are part of a continuous awareness loop.
Bearings tell you where you are.
Lines of position tell you where you can’t be.
Between those two truths lies safe navigation.
Closing Perspective
Bearings and lines of position are the language of terrestrial navigation.
Once understood, they appear everywhere: in fixes, in transits, in ranges, in pilotage, and even in radar interpretation.
This is the skill that allows a navigator to remain calm when electronics disappear.
Tags
bearings · lines of position · coastal navigation · chartwork · bridge watchkeeping · visual navigation