What does the term "isogonal" refer to?

The term "isogonal" refers to a line connecting points of equal variation, specifically in the context of magnetic variation. Magnetic variation is the difference between magnetic north and true north, and isogonal lines are important in navigation and aeronautical charts as they help pilots understand how the magnetic field varies across different geographic areas.

Understanding isogonal lines is essential for accurate navigation, as pilots must adjust their headings based on the magnetic variation to ensure they are on the correct course. This concept distinguishes isogonal lines from other similar terms such as isobars (equal pressure) or isotherms (equal temperature), which relate to different atmospheric and environmental measurements. Knowing this helps clarify how isogonal lines specifically pertain to navigational considerations in aviation.