A ROUGH RULE FOR THE INTERVISIBILITY OF POINTS ON OR JUST ABOVE THE EARTH'S SURFACE

Abstract

It has been shown in an earlier number of the Empire Survey Review (iv, 24, 70) that if an observer whose eye is at sea level in a calm sea sees an object at a distance s, so that it appears to be on the horizon, then the height of that object above sea level is given by h=Ks2 where K=12?kr; being the coefficient of refraction and r the mean radius of the earth.