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!
We actually could do that @sidharthabahadur... Much of the path for doing this is already done and laid out, but the only thing is missing is some funding. Contact me privately for further discussion...