Compass Add East for True (CADET)

A mnemonic stating that easterly compass error is added when converting a compass direction towards true.

“Compass Add East for True” forms CADET. Starting with a compass bearing or heading, apply deviation to obtain magnetic, then variation to obtain true; easterly corrections are added and westerly corrections subtracted under the usual signed-angle convention.

The reverse conversion reverses the arithmetic. Mnemonics can prevent sign errors only when the starting and required reference are identified, current variation is used and vessel-specific deviation is taken from reliable data.

1. C — Compass: Start with the compass bearing, the direction the compass shows on board.
2. AD — Add: Tells us to add Deviation and/or Variation if it is Easterly (as per the E in the mnemonic)
3. E — Easterly: If Deviation or Variation is East, add it to the Compass Bearing. (Therefore, if subtract if Deviation or Variation is West)
4. T — True: The final result after applying these adjustments is the True bearing.

Adjustments for Variation

This handy mnemonic helps us remember which way to apply adjustments for bearings. Magnetic (compass) to True, True to Compass, Easterly Variation or Westerly Variation. CADET (Compass Add East for...More Details

Day Skipper Theory, Knowing where you are!, Passage Planning and Making, Plotting Positions

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Adjustments for Deviation

This handy mnemonic helps us remember which way to apply adjustments for bearings. Magnetic (compass) to True, True to Compass, Easterly Variation or Westerly Variation.  CADET (Compass Add East...More Details

Day Skipper Theory, Knowing where you are!

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