What are isogonic lines used for in navigation?

Isogonic lines are specifically used in navigation to show areas of equal magnetic variation on a map. Magnetic variation, or declination, refers to the angle difference between magnetic north (the direction your compass points) and true north (the direction along the earth’s surface towards the geographic North Pole). These variations can significantly impact navigation, especially in aviation, where accurate headings are crucial for safe flight.

By using isogonic lines, pilots and navigators can determine how much to adjust their compass readings to align with true north, which improves accuracy in navigation and ensures that their planned flight paths align with the intended destinations. This is particularly important for long-distance flights where the effects of magnetic variation can accumulate, leading to significant navigational errors if not accounted for.

In contrast, other options do not accurately represent the purpose of isogonic lines in navigation. For example, while airspace boundaries are important for aviation regulations and safety, they do not relate to magnetic variation. Likewise, navigational aids serve different functions, such as providing geographical reference points rather than depicting magnetic variation. Additionally, terrain altitude is represented through contour lines or elevation markers, which is unrelated to the concepts of magnetic variation represented by isogonic lines.