What is the term for the line that connects points of zero magnetic variation?

The term that refers to the line connecting points of zero magnetic variation is known as the Agonic Line. This is significant in navigation and aviation because it indicates where magnetic north aligns precisely with true north, leading to a magnetic declination of zero in those areas. Pilots and navigators use this information to correct for differences when relying on magnetic compasses.

In contrast, isogonal lines connect points of equal magnetic variation but do not indicate zero variation. Magnetic declination refers more broadly to the angle between magnetic north and true north, while variation line is a more generic term that could be confused with isogonals. Understanding the distinction and the significance of the Agonic Line is essential for accurate navigational practices.