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How to Use a Rotating Plotter

Pilots use rotating plotters, which are specialized slide rules capable of measuring distance and angle, to plan flight courses and distances. Specifically, pilots use this tool to determine the exact true course -- or direction the airplane will travel over the ground -- they must take to reach their destination, and the exact distance between the origin and destination. While a rotating plotter may seem like a jumble of spinning parts and random lines to a non-aviator, you can learn to use this device with a few simple steps.

Things You'll Need

Aeronautical chart
Rotating plotter
Marker

Instructions

Measure Distance
- 1
  Find two airports, denoted by blue or magenta circles, on your aeronautical chart. Draw a course line with your marker connecting the two airports, using the edge of the plotter like a ruler to ensure the line is straight.
- 2
  Flip the plotter over to the side marked "nautical miles," which is the common measurement of distance in aviation. Place the black line marked "0" over the center of the first airport symbol. Move the plotter so that it runs down your line and intersects both airports.
- 3
  Move your finger to the "destination" airport. Read the number on the plotter next to the destination airport -- that is your distance in nautical miles.
Determine True Course
- 4
  Move your plotter to a place where your course line intersects a "line of longitude," which are thin, black, ticked lines running north to south. Place the plotter's golden metal circle over the center of your course line.
- 5
  Adjust the rotating plotter's disc so that "0" is on the line of longitude.
- 6
  Read the number directly on your course line. This number is your true course.

Aviation