Section 6

Getting Your Bearings

You can plot bearings on the chart in the same way that you plot courses. A plotted bearing is called a line of position or LOP because the boat's position is somewhere on the plotted line.

The illustrations in the previous lesson and below feature a lighthouse bearing 170°. Assuming local variation to be 0°, the true angle of the LOP is also 170°. The bearing was taken from the boat and therefore the boat's position is somewhere on a straight line between the lighthouse and the boat. This is represented on a chart by a line of position drawn towards the lighthouse, at the correct angle and long enough to pass through the boat's probable position.

Plotting an LOP

The method of plotting an LOP is similar to that of plotting a course. The bearing is corrected to true and, using the course plotter, transferred to the chart as a line draw towards the object.

The line should cut across the course line if one has been plotted, and it must be long enough to accommodate correct labeling. Examples in this program show the LOP extending all the way to the object of the bearing. This isn't strictly necessary.

The time of the bearing is written above the line and the direction below it. This differs from labeling a plotted course where the direction is placed above the line.

Beware the Reciprocal!

As with a plotted course, care must be taken not to draw the reciprocal of the bearing, or to label the bearing with the reciprocal. Beware: these are common mistakes.

See Sail Canada plotting and labeling of a Line of Position.

The LOP and
the Boat's Position

You can only get a rough idea of the boat's position with a single bearing and the resulting LOP: it must be somewhere along the LOP and within visual range of the object, but where?

Adding another bearing will provide an accurate position. This is the topic of the next lesson.