Navigation General · Compass - Variation
The variation for a given area and the small annual change to apply are found:
- AOn the chart's compass rose✓ Correct
- BIn the Tide Tables
- COn the AIS display
- DIn the Nautical Almanac star charts
Explanation
The inner ring of the chart's compass rose gives the magnetic variation for a stated year plus the annual rate of change, so the navigator can update it to the current year before converting between true and magnetic directions.
Authority: Chart compass rose; Bowditch (Pub. 9)
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