How to Plot a Bearing on a Chart — Step by Step

To plot a bearing on a chart, take the compass bearing of a charted object, correct it for deviation and variation to get a true bearing, then set your plotter to that bearing and line its edge up on the object. Draw the line from the object out to sea, roughly where you think you are. You are somewhere on that line. Two or three such lines crossing give you a fix.

What you need

A chart of the area and a soft pencil (2B) with an eraser.
A Breton-style plotter or parallel rule.
A hand-bearing compass, or the steering compass if the object is ahead.
The variation from the chart's compass rose, and your deviation card if using the steering compass.

Step by step

Pick a good object: charted, unmistakable and fairly close, such as a lighthouse, church spire or headland.
Take the bearing and note the time and log reading.
Convert to true. A hand-bearing compass used away from steel has negligible deviation, so just apply variation: going from magnetic to true, subtract westerly variation and add easterly. Remember 'Variation West, Magnetic Best; Variation East, Magnetic Least'.
Set the plotter to the true bearing, aligning its grid with the chart's meridians or parallels.
Line up the edge of the plotter on the object, with the direction arrow pointing from you towards the object.
Draw the position line in the area where you think you are, not all the way across the chart.
Label it with the time and an arrowhead at the end pointing to the object.

Converting a magnetic bearing to true
Variation	Rule	Example
2° W	Subtract	065°M becomes 063°T
2° E	Add	065°M becomes 067°T

Turning bearings into a fix

One bearing tells you only that you are somewhere on a line. Take a second and third bearing quickly, of objects ideally 60 to 120 degrees apart, and plot them the same way. Where they cross is your fix. Three lines rarely meet at a point: the small triangle they form, the 'cocked hat', shows the accuracy. See the three-point fix guide.

Three position lines from three landmarks crossing to form a small triangle, the cocked hat — Three bearings crossing give a fix; the size of the cocked hat shows its quality.

Practise in the position fixing lesson.

Related guides

Frequently asked questions

Do you plot magnetic or true bearings?

Usually true, so they line up with the chart's grid. Some plotters let you set variation and plot magnetic directly, but the result must be the same line.

Why draw the arrow towards the object?

A bearing is measured from you to the object. Arrowheads pointing at the landmark make it clear which line came from which object when you check your work later.

How accurate is a hand-bearing compass?

In a small boat you can typically read it to within a few degrees. At 5 miles, 3° of error moves the line about a quarter of a mile, so closer objects give better fixes.

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