Definition
Geographical range depends purely on the height of the light and the observer's eye. A common working formula is range in nautical miles equals 2.08 times the sum of the square roots of the two heights in metres, often simplified to 2.1 or, using feet, 1.17 times the square roots. For a light 40 metres high seen from an eye height of 2.25 metres, 2.08 times 6.32 plus 1.5 gives about 16.3 nautical miles.
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