Chart Navigation & Plotting · Compass — Amplitude
Using sin(amplitude) = sin(dec) ÷ cos(lat), for declination N12° at latitude 36°N, the amplitude is about:
- AE25°N
- BE12°N
- CE15°N✓ Correct
- DE36°N
Explanation
sin A = sin 12° ÷ cos 36° = 0.2079 ÷ 0.8090 = 0.2570, so A = 14.9° ≈ 15°. Named from east toward the pole of the declination: E15°N (true rising bearing ≈ 075°).
Authority: Bowditch (Pub. No. 9), Amplitudes
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