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| geographic range The maximum distance at which the curvature of the earth and terrestrial refraction permit an aid to navigation (light or unlighted object) to be seen from a particular height of eye without regard to the luminous intensity of the light. The best present knowledge for this range is where H is the height of the object above the water and HE is the height of the observer's eye above the water, both in feet. The factor of 1.17 has changed a bit over the years as scientists learned more about low angle refraction, but the 1.17 is the best value now for standard atmospheric conditions and the one that should be used on the water and indeed on any training quiz or certification exam. |
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