sigh. OK flat earth pedes. I’m going to spill the beans. I work in defense/aerospace for the evil military industrial complex. I’ve worked several projects that require precise math to determine very accurate locations. We’re talking use of satellites in ORBIT. To triage anything useful out of a set of satellites you have to account for earth’s curvature.

As someone else said in this thread, for small areas you can “cheat” by pretending the earth is flat when performing calculations. But for large areas and anything else requiring precision, you must account for the earth’s curvature, otherwise coordinates will cease to be even remotely accurate. I worked on a project some years ago where the system cheated when determining coordinates for radar plots. The customer provided funding to convert to whole earth coordinates instead (i.e. account for curvature) to get more accurate coordinates.

But don’t take my word for it. Get out of the house, book a flight or cruise around the world, and go see for yourself. You can see the curvature from a higher altitude. Shucks, take up mountain climbing. You kids need to get out more.