Objects disappearing bottom up without any curvature

With camera recording from the top of a railroad track, the distant vehicle crossing is slightly elevated up (perhaps 30 CM or 12 inches) and the bottom of the vehicles have disappeared even though there is no curvature found here.
0:00 Camera setup
0:28 Camera on rail
3:07 Man appears
5:00 Walking man disappears
5:05 Camera lifted and man reappears
6:25 Camera being lowered
6:55 Man disappeared yet again

[@RogHawk]

An undulating steel track with heat waves. Controls, maybe?

[@DirectCurrent4u]

No TRAIN CRASHES! 👎

[@phatsmall2007]

Measure it with theodolite first

[@oswald9723]

What proof that the ground here is actually flat ? What about the obvious refraction of the rails ? This has been attempted once but it just displayed the ground actually wasnt flat.

[@RayleighCriterion]

If you want this channel about railroad maintenance kzbin.info you will learn that railroads spend time and effort to make railroad tracks as level as possible to reduce wear and tear on the rail and the trains and cars riding on them. The section of railroad I used is actually slightly elevated at the far end, perhaps 1 foot or so. Which further reduces any chance of curvature drop occurring here. There is no real refraction here, the optical phenomenon is actually diffraction, the light rays are colliding and interfering with each other. This was not an observation of flatness, this was an observation that diffraction causes, in this case an entire person to disappear and meld into the scene. So what can happen over short distance close to a surface can also happen at greater distances with the observing point next to a surface, especially one with a high reflective index, like water.

[@oswald9723]

​@@RayleighCriterionheated metal rails warms the air above causing light to go through different densities of air, distorting the image and the real position of the man. That is refraction, don't know why you would try to deny that. Also I won't take your word about elevation.