Lines on charts that connect points of equal magnetic variation are called what?

• A. Isogonals
• B. Isogonic Line
• C. Parallels
• D. Isolines

Answer: (B)

Magnetic variation changes with location, so pilots use lines on charts that connect all points with the same variation. These are called isogonic lines. They show how much you must adjust a compass heading to get the true heading, and they indicate whether the variation is east or west along that line. The zero-variation line is called the agonic line. While some texts might use similar terms, the standard aviation term for these lines is isogonic line. Parallels are lines of constant latitude, and isolines is a general term for lines of equal value, but isogonic lines specifically refer to lines of equal magnetic variation.