Slowly, the old rules of navigation are changing, and one of the oldest, which dates back before the days of sailing ships, is the rule about magnetic variation and compasses: “Variation East, Magnetic Least; Variation West, Magnetic Best.” That means, for example, that if you’re flying out of Presque Isle, Maine, and want to fly due west, you need to turn onto a compass heading of 290 degrees, because up there, the local variation is 20 degrees West and the variation rule says “West is best.” That is, adding magnetic to true makes it a bigger number, or “best.” But to fly due west out of, say, Seattle, where the variation is around 20 degrees East, you’ll need to head 250 degrees, because when the variation is East, you subtract magnetic from true, making your compass heading a smaller number, or “least.”
By now most of us have forgotten the East/West rule because we rarely need to apply it. Just about every heading we fly, such as VOR radials, ILS localizers, holding patterns, airway centerlines, runway headings and so forth have already been corrected to the local magnetic variation values on aeronautical charts, approach plates and other flight information data. But at ICAO’s Air Navigation Conference (ANC) last November, Nav Canada proposed that aviation should cease using magnetic references and use only directions relative to the geographic, or true, North Pole.
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