What do isogonic lines represent on a chart?

Isogonic lines, also known as isogons, on a chart represent magenta lines that connect points of equal magnetic variation. Magnetic variation, or declination, is the angle between magnetic north and true north. This variation changes depending on your geographic location, and understanding it is crucial for navigation, especially for pilots using magnetic compasses.

By referencing isogonic lines, pilots can determine the degree of variation that they need to account for when converting between magnetic and true headings and when calculating their flight path. This is vital for ensuring accurate navigation and avoiding drift due to the difference between the two north references.

Other concepts, such as lines of equal elevation would relate to contour lines, boundaries of airspace pertain to regulatory limits, and routes of navigation aids do not specifically address magnetic variation. Each of these subjects serves a distinct purpose in aviation navigation but does not capture the role of isogonic lines.