Three Norths

The ladder

T → variation → M → deviation → C. True Virgins Make Dull Company. Every question is one or two steps on this ladder, in one direction or the other.

Going down (chart → compass)

West is best, East is least. Add a westerly error, subtract an easterly one. …add Whisky.

045°T + 4°W = 049°M + 2°W = 051°C

Going up (compass → chart)

CADET: Compass, ADd East, True. Add an easterly error, subtract a westerly one.

051°C − 2°W = 049°M − 4°W = 045°T

Which compass?

Steering compass: variation and deviation. Hand-bearing compass: variation only, no deviation card.

Habits examiners like

Three figures always: 007°. A suffix always: T, M or C. Wrap through 360: 358 + 5 = 003. Look deviation up by the ship's heading, never by the bearing of an object.

Keys

Enter checks, Enter again moves on. Alt+←/→ change stage. Progress is saved in this browser.