What defines magnetic variation at a specific location on Earth?

Magnetic variation, also known as magnetic declination, is defined as the angle between the horizontal component of the Earth's magnetic field and True North. This angle varies by geographic location and can change over time due to changes in the Earth's magnetic field. Knowing this variation is essential for navigation because it allows aviators and mariners to adjust their compass readings to align with True North, which is necessary for accurate navigation.

The horizontal component of the magnetic field refers specifically to the aspect of the magnetic field that lies along the Earth's surface, as opposed to the vertical component, which points downward towards the Earth's core. In navigation, understanding how the magnetic field interacts with True North enables pilots to make accurate course corrections and enhances safety during flight operations.

This definition is fundamentally important for flight planning and situational awareness, as miscalculations involving magnetic variation can lead to navigational errors. Knowing the precise angle of magnetic variation at a specific location allows pilots to compensate for it and maintain their intended flight path accurately.