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SESK: Stuff Everyone Should Know · sesk.info/pilot-isogonic-lines

On aeronautical charts, what do broken magenta isogonic lines connect?

Points of equal magnetic variation.

  1. Points of equal elevation
  2. Points in the same time zone
  3. Points of equal magnetic variation ✔

Why: Variation is the angle between true north and magnetic north, and it changes with location. Isogonic lines join places with the same variation so pilots can convert true course to magnetic.

Huh, didn't know that: The line where variation is zero, so true and magnetic north line up, is called the agonic line.

The dad joke
Parallel lines have so much in common. It's a shame they'll never meet.
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Sources

  1. Pilot's Handbook of Aeronautical Knowledge, Chapter 16 Navigation (FAA-H-8083-25C) https://www.faa.gov/sites/faa.gov/files/18_phak_ch16.pdf

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