Use your plotter to determine the true course (TC), the total distance of
your flight, and the distance between each checkpoint.
Place the small hole in the center of the protractor section over a
meridian (line of longitude), and then align either the bottom or top
edge of the ruler section with your course line, as shown below.
In the illustration above, the TC, which is read on the scale over
the meridian, is 042°. The reciprocal (return) course is 222°.
Make sure that you use the proper scale for your direction of flight.
Meridians are not parallel lines. They converge at the poles. Therefore,
course measurements should be made near the midpoint of each segment.
If your course is nearly north or south and does not cross a meridian,
place the hole of your plotter over a parallel (line of latitude), and use
the inner scale as shown below.
Measure the total distance of the course, as well as the distance between
checkpoints with the ruler section.
Use the scale that is appropriate to your chart (Sectional,
Terminal Area Chart, or World Aeronautical Chart).
You should generally use the nautical mile scale for most