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Three arrows showing grid, true and magnetic north.
Also known as: Declination diagram, North arrows diagram, Grid magnetic angle
The declination diagram shows how far magnetic north differs from grid north at the date of the map. Magnetic north drifts, so the printed figure is dated and an old map's value is wrong by an amount worth knowing before navigating on it.
Shows the angular difference between true north, grid north and magnetic north at the map's stated date.
Contexts: Maps
Carries a date and an annual rate of change because magnetic north moves, so the printed value is correct only for the year given.
Contexts: Maps
Distinguishes three separate norths, of which only true north is fixed by geography.
Contexts: Maps
Three straight lines radiating from a common point at slightly different angles, each capped with a distinct arrowhead or star and labelled.
The plain north arrow is one of the three this diagram distinguishes.