Navigation General · Distance
The approximate distance to the visible horizon (in nautical miles) for an observer can be estimated as 1.17 times the square root of the:
- AVessel's speed in knots
- BBarometric pressure
- CHeight of eye in feet✓ Correct
- DLatitude in degrees
Explanation
Distance to the sea horizon (NM) ≈ 1.17 × √(height of eye in feet). This horizon distance, summed with the light's own horizon distance, gives a light's geographic range — the basis of 'raising' and 'dipping' lights.
Authority: Bowditch (Pub. 9); distance to horizon
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