The story
Contraction of grid (magnetic) variation.
Etymology from Wiktionary, CC BY-SA 4.0.
grivation
Today it means: The angle, at any point on the surface of the Earth, between grid north and magnetic north. Full definition →
Today it means: The angle, at any point on the surface of the Earth, between grid north and magnetic north. Full definition →
Contraction of grid (magnetic) variation.
Etymology from Wiktionary, CC BY-SA 4.0.