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2 Answers

Track crossing multiple Isogonals

Asked by: 4316 views , , , ,
General Aviation, Private Pilot, Student Pilot

Hi.

How would i calculate the magnetic variation if the track crosses multiple isogonals?

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2 Answers



  1. Bob Gardner on May 28, 2016

    Of the elements involved in dead reckoning navigation: True Course, Wind Direction and Velocity, Variation, and Deviation, variation is the least important, You draw the course line and measure the distance, but everything else is either forecast, estimated, or based on outdated information. The Coast and Geodetic Survey is supposed to update the variation on aeronautical charts but tight budgets make it a low priority.

    As a low time pilot I’m sure that you are hand-flying the airplane. You can’t steer a consistent course within .5 or 1.0 degree, so why obsess about it? Use the variation from the midpoint of your flight for planning and devote your worry beads to the woefully inaccurate Winds and Temperatures Aloft Forecast.

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  2. Skyfox on Jun 02, 2016

    Considering the length of a flight plan that would cross multiple isogonic lines, you should have checkpoints at least that distance apart regardless of the isogonic lines. Where I live they’re about 55 miles apart. So, it would simply be a matter of having a checkpoint at least once every isogonic line (or at a midpoint between each line) and adjust your flight plan accordingly.

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