Bad title! This works only in a flat universe. I mean, only if Earth is FLAT! On a convex Earth (say, a sphere), you should get a value smaller than 3.1415926

Bad title! This works only in a flat universe. I mean, only if Earth is FLAT! On a convex Earth (say, a sphere), you should get a value smaller than 3.141592653589793... So it should be titled: How to prove or disprove flat-Earthers.