Hm, bmende,
How to express that.
As you said, people on this forum are polite because you are the first of your specimen to come here. We didn't had to deal with the crowd of dementia fueled paranoiacs magically popping under every youtube video where a slight curvature of earth can be observed. You came here honest and polite and this is respected.
It doesn't change the fact that (and looking at the reaction of the various fellow
outerrans posting here, I'm not the only one), your opinions and "scientific" protocol are bonkers. You seems like a good chap, so no one here is going to lay anything more violent than a sensible chuckle.
Now, I provided you a valid protocol to test your ideas, and one even working no matter what your considerations are for the nature of this world. Two (really) distant referential, a map, a bearing, what's beyond the two. Simple. But it doesn't matter. I could bring up the non-linearity of the day-night cycle in different parts of the world and you would say it's not a proof, maybe that the sun is smaller than we think, a spot going over some parts of the world and not others.
It's a lost cause and I know it. So I won't try to change that, considering you are more interested by this quest of truth than a factual observation of the world, because this world can be very difficult to grasp sometimes and it's reassuring to think you are on to something, that everyone was wrong and you are right, because, and let's admit it, it feels good to think you carry a truth with some others like minded. Everyone does it, at different scale, for different things. Believing the earth is flat is just a rather extremist version of that process. One that could lead you always further, because you need to find "proofs", so there is always this ounce of doubt you can validate.
So I won't try no longer to change your opinion.
However, you are welcome to not post this non-sense here.
The Outerra initiative is a very serious organization and we know earth is not flat.
It's a quadrilateralized spherical cube, as demonstrated in this picture:
See? It fits perfectly:
Don't forget, if a concept can essentially be manipulated for unknown reasons to convince the major part of the population, it means the very opposite concept you try to prove can be equally forged. So everything is false, and it doesn't matter.
But earth is truly a quadrilateralized spherical cube, that's a fact.