Worked examples
| Distance | Curvature drop | Note |
|---|---|---|
| 1 mi | 8.0 in | barely noticeable |
| 3 mi | 6.0 ft | small boat hull starts hiding |
| 10 mi | 66.6 ft | geometric, no refraction |
| 20 mi | 266 ft | distant shoreline obscured |
Common questions
How much does the Earth curve per mile?
The drop is about 8 inches over the first mile, but it grows with the square of distance, so 10 miles is roughly 66 feet, not 80 inches.
What does the 7/6 refraction correction do?
Light bends slightly in the atmosphere, so true objects appear higher than geometry predicts. The 7/6 factor inflates the effective radius and reduces the apparent drop by about 14 percent.