So back on topic.
We can all see the curvature of the Earth in every high altitude photo.
If a passenger jet is not flying high enough to show the curvature from left to right, it still shows the curvature away from the viewer.
The horizon does not continue to rise to the vanishing point as it should on a flat Earth. Instead it curves down, away, out of sight. It does this in all directions. This is simple easy proof that the Earth is a globe.
I agree - you need quite a bit of precision to measure the curvature of the horizon in a 60 degree field of view camera shot from 40,000 feet. The sky is rarely clear enough to see a defined horizon at that distance anyway.
My thread here is merely to dispel one more common FET argument.
If at some future time, we have a nice photo of a clear horizon that exhibits measurable curvature - then when the FE'ers call foul on account of window-distortion artifacts - we are ready with an answer here.
1) There can be no horizontal curvature because windows are curved to fit a horizontal cylinder.
2) There can be no appreciable distortion in the vertical direction because curved windows of uniform thickness comprise a convex lens backed by a concave lens of *almost* identical radius. The radius of the outside of the lens would be the radius of an airplane fuselage - several meters - and the radius of the inside lens would be just a few millimeters less because of the thickness of the plastic.
3) There is no observed bending of straight lines in actual photography.
But yes - until some photos (eg from Concorde) appear that clearly show curvature, this is just a "back-stop" argument to prevent future complaints.