[Telepathic Intruder]

Wrong. The formula is 8" per mile squared.

Wrong again. That is a parabolic function. The earth is a sphere, not a parabola. The formula for circle is R²=X²+Y².

R (earth's radius) is about 4,000 miles, so using miles, CURVATURE=4,000 - (square root of (16,000,000 - distance²)).

It just happens to be that 8" per mile squared is a good approximation using small distances.

[Travis McGee]

See 54 for the math geekery.

[philman_36]

Wrong again.
Nope, you even say as much...

It just happens to be that 8" per mile squared is a good approximation using small distances.

It's a good approximation for ANY distance.

Earth Curvature Calculator

1 mile	0.00013 miles = 0.67 feet
2 miles	0.00051 miles = 2.67 feet
5 miles	0.00316 miles = 16.67 feet
10 miles	0.01263 miles = 66.69 feet
20 miles	0.05052 miles = 266.75 feet
50 miles	0.31575 miles = 1667.17 feet
100 miles	1.26296 miles = 6668.41 feet
200 miles	5.05102 miles = 26669.37 feet
500 miles	31.5336 miles = 166497.53 feet
1000 miles	125.632 miles = 663337.65 feet