Chart Navigation & Plotting · Distance Off — Bow and Beam
Using bow-and-beam bearings, an object bears 45° on the bow and later is abeam (90°). The distance run between the two bearings equals:
- AHalf the distance off when abeam
- BTwice the distance off when abeam
- CThe distance off the object when abeam✓ Correct
- DThe distance to the horizon
Explanation
When the relative bearing goes from 45° (4 points) to 90° (abeam), the isosceles geometry makes the distance run between bearings equal to the distance off the object at the beam bearing — a quick running-fix shortcut.
Authority: Bowditch (Pub. No. 9), distance by bearings
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