Isogonic Line
What is isogonic line?
An isogonic line connects points on an aeronautical chart that all have the same magnetic variation—the angular difference between true (geographic) north and magnetic north. These lines help you correct between true and magnetic headings as you move across the country. Think of it as a "same-variation" line; the special one where variation is zero is called the agonic line.
Also known as: isogonic line, isogonic lines, lines of equal variation
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