Actually I want to add on to the gyro compass thought. After thinking about it, this device will not operate at all on a flat earth, it will only operate correctly on a rotating round earth, there is a slight compensation that has to be engineered into the machine in order for it to be accurate in the northern hemisphere and the Southern hemisphere. There is not a flat earther alive that would understand it, even if I went into painfully long explantations with graphs and pictures, and the simple fact that you can easily look up how they work online. But if you really wanted to collect that 3 Bitcoins, be my guest. Try to show him how one works, research it yourself, it is a device that will literally only work on a spherical earth, and ships have them, and they do work.