Magnetic Variation

Magnetic variation is the angular difference between true north and magnetic north at a given location on the Earth. Because navigational charts are aligned to true north while an aircraft compass points to magnetic north, variation must be applied to convert a true track to the correct magnetic track to fly. Variation is depicted on charts as isogonic lines and changes slowly over time.

Key Points

• •The angular difference between true north and magnetic north at a specific location.
• •Varies depending on geographical location and is shown on charts as isogonic lines.
• •Changes slowly over time due to shifts in the Earth's magnetic field.
• •Applied to a true track — by adding or subtracting — to obtain a magnetic track.

Related Terms