Which lines connect points of equal difference between true and magnetic north?

The lines that connect points of equal difference between true north and magnetic north are known as isogonic lines. These lines represent the variation or declination angle, which is the angle between the direction of true north (geographic north) and the direction to magnetic north (as indicated by a magnetic compass).

Declination varies depending on where you are on the Earth's surface, influenced by factors such as the Earth's magnetic field. By understanding isogonic lines, navigators and pilots can adjust their headings to account for this variation, ensuring accurate navigation.

In the context of the other terms, isotropic relates to properties that are uniform in all directions, isogonal would refer to lines of equal angular measurement rather than magnetic variation, and isobaric pertains to lines of constant pressure, which is not relevant to magnetic declination.