Chart Navigation & Plotting · Distance Off — Bow and Beam Bearings
You take a relative bearing of 045° on the port bow of a lighthouse, then a beam bearing (090° relative) later, having run 3.0 nm between the two. What is your distance off the lighthouse when abeam?
- A4.2 nautical miles
- B1.5 nautical miles
- C3.0 nautical miles✓ Correct
- D6.0 nautical miles
Explanation
In the 45°/90° (bow-and-beam) special case, the distance run between the two bearings equals the distance off when abeam. Run of 3.0 nm gives a beam distance of 3.0 nm — a quick distance-off without trigonometry.
Authority: Bowditch (Pub. No. 9), bow-and-beam bearings
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