I thought this drone imagery of a horizon from a friend was interesting:
A couple of semi-transparent horizontal lines added for reference:
These are apparently from some very high quality lenses that do not distort when viewed directly down and thus these horizontal curvatures only occur on the horizon.
If you have some ideas for experimentation or would like to see some specific scenario this person is willing to do whatever you'd like to see... so let me know and I'll set it up!