http://www.nga.mil/MSISiteContent/StaticFiles/Calculators/range.html
Geographic Range
Given the Height of the Light Above Sea Level and the Height of the Eye
of the Observer above Sea Level Compute the Geographic Range
Height of the Light aboveSea Level (specify units):
feet
meters
Height of the eye of the Observerabove Sea Level (specify units):
feet
meters
Geographic Range (distance to the horizon) :
(Nautical Miles)
