What does magnetic variation signify?

Magnetic variation, also known as magnetic declination, signifies the difference between magnetic north and true north. This variation is crucial for navigation because a pilot needs to understand how to accurately interpret their heading on a compass in relation to the actual geographic north pole.

The Earth's magnetic field is not aligned perfectly with its rotational axis, so the direction indicated by a magnetic compass differs from the true north direction indicated by geographic coordinates. The amount of this difference changes based on your geographical location and is expressed in degrees east or west. Pilots must apply this variation when cross-referencing their navigational charts and when inputting waypoints, ensuring safe and accurate flight navigation.

The other options pertain to different concepts: altitude variation relates to terrain differences, flight speeds are influenced by various factors such as wind or aircraft performance, and geographical changes affecting frequency transmission do not directly relate to magnetic variation. Understanding magnetic variation is fundamental for effective and safe navigation in aviation.