Section 5

Plotting Basics

5.1

Plotting a Course

Lesson 1.3 pointed out the importance of the nautical chart for boaters and lesson 4.3 explained how the compass is used to determine a boat's heading and course. Now let's plot a boat's course on the chart. The tool to use is the course plotter. Other tools that can be used to plot a course are parallel rules and the cockpit plotter.

Note: Your course plotter is included in your student kit.

Course Plotter

A course plotter allows a navigator to plot a line of a precise direction on a chart by using a meridian of longitude as the reference to true north.

To plot a course...
1. Place the plotter on the chart with its centre point on a meridian near the starting point of the course line.
2. Keep the centre point on the meridian and rotate the plotter until the course direction on the compass scale is lined up with the meridian.
3. Slide the plotter up or down the meridian until either outer edge touches the starting point. This edge is then used to plot the course.

Some course plotters have a second compass scale offset 90° to the first enabling the plotter to be used with the latitude reference lines. This is helpful for directions that are awkward to plot using longitude, such as those close to 000° and 180°.

Labeling the Plotted Course Line

The plotted line is labeled with the course direction, preceded by C, for course. Put a space after the C. The convention is to place the course label, in this case "C 080" on top of the line and away from the starting point. Note that the degree symbol is not used (to keep the chart clutter-free).

Watch Out!
  A common mistake is to plot the reciprocal of a course by drawing the line in the wrong direction from the starting point. It's a good idea to visualize the general direction of the course (north, northeast, southwest, etc.) before drawing the line.

 

Using the Course Plotter:
Video Demonstration and Exercises

We've created five short videos that show how to use the course plotter, as well as get some practise.

First, download and print the three Video Exercise Sheets.

Exercise Sheet 1 (pdf)
Exercise Sheet 2 (pdf)
Exercise Sheet 3 (pdf)
Now, click on YouTube to go to the coastalnaviation.com channel and view the videos. YouTube

 

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