What is a line connecting points of equal variation from true north called?

The term used for a line that connects points of equal variation from true north is "isogonal." In the context of navigation and cartography, isogonal lines represent areas where the magnetic declination, or variation from true north, is the same. This concept is crucial for navigators who need to adjust their compasses to account for the differences between magnetic north and true north, particularly in regions where magnetic declination varies significantly.

Isobars, on the other hand, relate to atmospheric pressure and indicate lines of equal pressure on weather maps, while isotherms denote lines connecting points of equal temperature. Equidistant refers to a distance measurement where equal intervals are maintained, not specifically related to compass variations. Understanding these definitions helps clarify the specific function and significance of isogonals in navigation.