Chart Navigation & Plotting · Distance Off — Bow and Beam Bearings
You note a light broad on the bow at a relative bearing of 045°, then again when it is abeam (090° relative). You ran 3.4 NM between the two bearings. How far off is the light when abeam?
- A3.4 NM✓ Correct
- B1.7 NM
- C4.8 NM
- D2.4 NM
Explanation
The bow-and-beam bearings (45° and 90° relative) form an isosceles right triangle, so the distance off when abeam equals the distance run between the two bearings: 3.4 NM. This is a quick way to get distance off without a fix.
Authority: Bowditch (Pub. No. 9), Distance by Two Bearings
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