I don't get this. His image says "we should not see the ground at an angle of -3.3 degrees if the Earth is a sphere" when that's (about) exactly what we should see. And if the Earth was flat, his theodolite should be reading just below 0 degrees.
Form the video: "I placed the cross-hairs down to -3.3°, which is where the horizon should be." (on a globe earth).
But the cross-hairs point lower than the horizon.
I get what he's trying to do. He's not sighting the crosshairs on anything. He's just tilted down until he got the 3.3-3.4° "dip" angle that would be the calculated angle between a horizontal line and the line tangent to the earth, coincident with the horizon, from about 37,000'. That's correct.
The crosshairs guides on the screen are static. As the phone tilts, the scale on the right scrolls to display the amount of tilt away from horizontal. So (if calibrated and if accurate) the crosshairs when the gauge is reading 3.3° would be on the globe horizon line from 37,000'.
In the image, he's seeing Lake Erie above the horizon (cross hairs).
Isn't he?
Calibration is certainly an issue. So is precision with these apps. I have Theodolite on my phone, and back in this thread you can find examples of me trying to use it. But I was trying to detect "dip" of around the granular limit of the app's scaling (+/- 0.1°) and found it very difficult, even with a tripod, to measure to that degree of precision.
Not to mention that constant calibration and accuracy of the accelerometers of the phone. It quickly became novelty tool for what I wanted it for. From an airplane in flight, I don't see how you could trust the dip angle measurement down to the tenth of a degree. It's possible he took video and just captured a frame in which he had the dip close, but that still doesn't ensure accuracy of the reading.
However, 3.3 or 3.4° I suppose is close. His point can be made even if the calibration is off a couple tenths of a degree since he's at an elevation where whole degrees matter more than tenths.
What I hope to draw focus on isn't the accuracy of the tool, but his interpretation of what he's seeing. I guarantee you if I had been on a flight, sighted a horizon, put the crosshairs on it and it read out -3.4° and posted it on this board as evidence that the horizon dips and the earth is curved, Tom (at least) would be all over it. As I've said before, I invite the critiques. It's good to be challenged. But critique should be balanced. The same degree of inspection and critique should be made for any argument or evidence presented for either side of the flat/globe debate. What I was hoping from Tom was a recognition that JT's slide from that video may not be supportive of what he's claiming.
Tom is not unique. We all tend to latch onto, without skepticism, evidence claims that support what we believe. And we'll put a magnifying glass to those that contradict what we think we know. If you're only interested in "winning" a debate or strengthening an affirmed tenet, then that makes sense. But if you're are being honest about wanting to get at the truth, then that's misguided approach. You have to be as skeptical of evidence for either side and as rigorous in evaluating it.
I received a lot of critique (some constructive) on my attempts to detect (not measure) horizon dip. I would expect a truth seeker to apply that same degree of rigorous questioning of evidence presented to claim the horizon is at eye level.