Chart Navigation & Plotting · Compass — Azimuth
Observing a charted range that bears 045°T, your gyrocompass reads the range at 047°. What is the gyro error and how is it applied to observed gyro bearings?
- AGyro error 2°W (gyro reads high); subtract 2° from gyro bearings to get true✓ Correct
- BGyro error 2°E; add 2° to gyro bearings
- CGyro error 2°E; subtract 2° from gyro bearings
- DNo error; the gyro is correct
Explanation
True is 045° but the gyro reads 047°, so the gyro reads 2° high ('gyro best, error west') — a 2°W gyro error. When correcting a gyro bearing to true you subtract a westerly error: 047° − 2° = 045°T.
Authority: Bowditch (Pub. No. 9), gyro error by range or azimuth
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