In a flat Earth, the difference between 5-minute altitudes will not remain consistent. Make a graph of records if you need to. If there was no degree of roundness in the Earth, there would be abrupt changes in the altitude. **But as long as the rate of change of the altitude meter remains relatively consistent, the Earth must be round, with no sudden, jagged edge.** Consider my experiment very carefully. Do not miss any piece of logic.

Why do you think that the altimeter on an airplane would have jagged changes in readings on a flat earth? I don't understand the thinking behind this experiment.

Here's another case in point: the Earth is so huge, that the human could not directly see how much the shape of its terrain changes on average. If we were to walk from one point of a circle, or oval, and cover the smallest imaginable distance, that is very akin to walking about a mile around the Earth. The difference could hardly be found. For people who have studied basic Calculus techniques: When you zoom in enough on the curve of a graph, you see a tangent line appear. The tangent line, by definition, is a line, which is flat. But you know that this flatness is a simplification derived from a curve. It appears flat, but it is already known to be a constituent, an infinitesimal section, of the curve. Likewise, the human eye, with such a small distance observed, sees flat land where it is truly a super small section of a round planet. If I made a mistake with my reasoning, inform me.

Here's another case in point: the Earth, flat or round, does not have smooth terrain regardless of its overall shape. It has mountains, gorges, crevices, like a sharp, confusing, disproportionate graph. But I am using averages, nevertheless, to determine whether or not the Earth is flat. How do I get these averages? With the experiment I suggested already.

If you guys would like me to conduct a deeper analysis on the topic, with or without the notion of experimentation (i.e., common sense, logic), reply.

If anyone spots a flaw in my current analysis, again, reply, and make sure to criticize me at your leisure. I don't give a damn about my "feelings." I am not being sarcastic, I promise that my emotions are never affected by insult.

There may be a language barrier, but I don't understand your proposals. In the "walking around in a circle" experiment, what observations are we meant to make?

On the topic of the jagged edge, I am referring to the outer circle of the flat Earth. If the Earth is flat, it should one circular shaped "edge" per se, right? Think about it: If it's not a sphere, and it it has two flat sides, on the top and bottom, then the jagged edge would be between both flat sides, as in a circle's visible circumference. So: if the plane were to circumnavigate around the entire Earth, flat or not, then surely, it would cross over this jagged edge. Readings of altitude would change drastically if the path of the plane were to maintain a constant, circular pace while crossing this edge.

Walking around in a giant circle, one would not notice that great a change, depending on how much of the circle was covered. If you covered, say, a quarter of the circle, it would be obvious that you are walking in a circle. If you were to around 1/720 of the circle, or half a degree, or pi/360 radians of the circle, next to no difference could possibly be observed. The second situtation is the case when it comes to the Earth. Many people claim that the Earth is flat because they do not notice this change; this, however, does not justify a perception of the world as flat, since the Earth is merely too big to observe without measuring longer distances. In a practical case, it is impossible to observe walking distances to prove that the Earth is flat. It is still plausible to say that the Earth is round if you cannot detect such walking changes in a planet that is huge and spherically-shaped.