Thanks to another forum member here I now have a really great case to prove to you the Earth is a globe.
1) They are a hostile source, so they have no reason to be bias in my favour, so these are the best sources to make my case.
2) It's using modern technology so we are not stuck arguing like we are in the 1600's and it's a repeatable observation for a significant amount of people, as I don't have a camera as good as his but it's certainly possible for many people.
3) The answer to his question is simply that his calculations are wrong.
4) The irrefutable proof is that the water is higher in the distance at the horizon than it is at the base of the oil rigs, with 'Habitat' also being higher than 'Platform C' now if the Earth were flat than this is simply impossible, but if the Earth is a globe then this makes total sense, as there is an incline until we reach the horizon which is exactly what we see, he has simply got his calculations wrong somewhere in regards to the curvature and thus location of the horizon, but it's irrefutable proof of curvature and thus a globe Earth.
5) As an added extra, you can then get a telescope and take a look at the Moon and some Planets and see that everything around us is also a globe.
God Bless