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Over the curve of the water

eye hlight Hhorizon

Each height has its own distance to the horizon, 1.17 × √(feet) nautical miles. Add the two to get the geographic range.

Skill 8 · Light risingProblem 11003

Height of eye 20 ft: when should the light show?

On a clear night your height of eye is 20 ft. You are closing a light listed as 135 ft high, nominal range 15 nm.

Find its geographic range (how far off its light first clears the horizon for you) and the distance at which you should first see it. Take the nominal range as its luminous range on this clear night.

Use the horizon distance d = 1.17 × √h (nm, h in feet). Tolerance: 0.15 nm.

Given
Height of eye20 ft
Height of the light135 ft
Nominal range15 nm
nm
nm
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