Curve of the earth visualized and measured

Earth’s shape has been measured many times.  It’s curvy.

If the earth is a sphere then the horizon must drop from the apparent level, sometimes called “eye level”.

This is predicted to be very slight so any measurements must be capable of more precision than the predicted dip.

 

If the earth is a sphere then the horizon must curve left to right.

This is predicted to be very slight so any measurements must be capable of more precision than the predicted curve.

 

If the earth is a sphere vertical lines must diverge.

This is predicted to be very slight so any measurements must be capable of more precision than the predicted divergence.