Chart Navigation & Plotting · Distance to Horizon
Distance off can be found by 'distance by vertical angle' when you know the object's charted:
- AColor
- BHeight and you measure its vertical (sextant) angle✓ Correct
- CMagnetic bearing only
- DNominal range of its light
Explanation
When a charted object's height is known, measuring its vertical angle with a sextant and entering Bowditch's tables (or the formula) yields distance off — a useful single-object range when only one landmark is visible.
Authority: Bowditch, American Practical Navigator (Pub. 9), distance by vertical angle
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