Measuring the Curvature of the Horizon with a Level

[Jesse3959]

I'm not sure if I posted this already but here's a measurement I made of the water surface horizon through a theodolite from about 56 feet above sea level: Source: https://youtu.be/IqAZuqSSmfw

 

[DavidB66]

Flat Earth debunker Bobby Shafto, who does some great work, has successfully replicated Rory's 'horizonomatic' method from a height of nearly 500 meters and obtained a nice clear result. See his short YouTube video here:
Source: https://www.youtube.com/watch?v=KWUAuAvzxyc