Due to the Curvature of the Earth, the Maximum Distance $D = \sqrt { 2 r h + h ^ { 2 } }$

Short Answer

Due to the curvature of the earth, the maximum distance D that you can see from the top of a tall building of height h is estimated by the formula $D = \sqrt { 2 r h + h ^ { 2 } }$ where r = 3960 mi is the radius of the earth and D and h are also measured in miles. How far can you see from the observation deck of a tower, 1,000 ft above the ground?