The fundamental question is, if you could linearly extrapolate from your position to infinity.
The fundamental question is, "is the horizon always at eye level?"
Is it? How do you know? How do you test to see if that's true?
Here's a flat earth demonstration using water level to claim the horizon does maintain at eye-level.
https://www.youtube.com/watch?v=IRTCCEB_QIg&t=177sHere's a globe earth guy using the same technique to claim it doesn't
https://www.youtube.com/watch?v=NqOQ_BCtqUI&t=6sHow can they come to different conclusions using the same technique?
I'd like to improve on the method.
Seeing this photograph gave me the idea to complement the water level with a squared frame of reference for lines of perspective:
Perspective, as in drawing 3D depth on a 2D canvas where art students are told the vanishing point is always on the horizon, is the flat earth reason given for the phenomena on the horizon by flat earth (sinking sun, ships disappearing hull first). So perspective plays a key role in the flat earth explanation. I'm sorry that I can't grasp the explanation for why that is so, but I can grasp a definitive claim like "the horizon is always at eye level" regardless of the rationale for such a claim.
So, is the horizon always at eye level? Does the perpendicular plane vanishing point for an observer at any elevation always coincide with the horizon?
It's not my claim. I'm just testing to see if it's true. If there's some way I'm misunderstanding the claim, and a 90 degree from plumb view is not where the vanishing line of a horizon will always be, regardless of elevation, then a flat earther endorsing the "the horizon is always at eye level" needs to explain why not. If the horizon can change angles depending on what I can see at varying distances without me doing anything to change my elevation, then how can it always be at eye level?
If there's something about my ignorance in understanding flat earth explanation for horizon and vanishing point that renders this method I've chosen flawed, then that needs to be explained to me. So far, I've not seen anyone try. The closest is the challenge of whether or not I'm looking at the "true horizon." Well, how do I know that. Explain that to me so I can incorporate it.