"magnetic variation." YourDictionary, n.d. Web. 19 January 2019. <https://www.yourdictionary.com/magnetic-variation>.
magnetic variation. (n.d.). Retrieved January 19th, 2019, from https://www.yourdictionary.com/magnetic-variation
(plural magnetic variations)
(military, nautical, navigation) In navigation, at a given place and time, the horizontal angle between the true north and magnetic north measured east or west according to whether magnetic north lies east or west of true north.
(cartography) In cartography, the annual change in direction of the horizontal component of the Earth's magnetic field.
English Wiktionary. Available under CC-BY-SA license.