Chart Navigation & Plotting · Compass Error — Gyro
A gyrocompass reads 089.0° when the true bearing of a range is 091.0°. The gyro error is:
- A2.0° West
- BZero
- C180.0°
- D2.0° East✓ Correct
Explanation
True is greater than gyro (091 vs 089), so the gyro reads low — the error is easterly. Gyro error 2.0°E is added to gyro readings to obtain true (mnemonic: 'compass least, error east').
Authority: Bowditch (Pub. No. 9), compass checks
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