Chart Navigation & Plotting · Plane Sailing
A vessel steams 20 nautical miles on a course of 045°(T). The difference of latitude made good is approximately:
- A20.0' (nm)
- B10.0' (nm)
- C14.1' (nm)✓ Correct
- D28.3' (nm)
Explanation
Difference of latitude = distance × cos(course) = 20 × cos 45° = 20 × 0.707 ≈ 14.1 nautical miles (minutes of latitude). The departure (east-west) is also 20 × sin 45° ≈ 14.1 nm.
Authority: Bowditch (Pub. No. 9), plane sailing
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