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This video attempts to determine the location of an object within a scene, using the motion of the camera and the resulting parallax of known objects at different depths as cues for the unknown object’s distance from camera. There are two reasons this will not work: The unknown object is moving. It’s position relative to the camera is changing and this will either counter or exaggerate the perceived parallax. With only 1 angle on the scene, this makes parallax an unreliable cue for depth, and 2) The unknown object does not pass behind or in front of any other objects in the scene, apart from the far mountain range. The tree line claim is better explained by the difficulty the camera sensor is having in resolving detail from noise and the small size of the object at that point in time. The most we can confidently say is that it is between the mountains and the camera. Later, the video attempts to determine the position of the drone relative to the operators and their vehicle. It asserts a field of view of 35 degrees, on an assumed 50mm lens. The DJI Inspire 1 has a diagonal FOV of 94 degrees, a horizontal FOV of 82 degrees, on a 20mm lens. All the resulting distance, real world size, and pixel size equivalent measurements are therefore wrong. (As an aside, though it is already wrong: the video also asserts a distance of ~12" from camera to motor arm. The Inspire has a forward mounted (i.e not centered to the body) camera that can rotate 360 degrees, so I’m not sure we can tell if it is the far or near strut that swings into view. This would then seem to be another unfounded measurement). The analysis in this video is fundamentally flawed. Parallax of a moving object is unreliable, and the camera specs used are wrong. Other things the video fails to address: The top speed of the Inspire is around 80km/h, or 73ft/s. Even half that speed would have a significant effect on the perceived motion of something small and nearby. The video does not explain the lack of atmospheric perspective on the object when it is claimed to be 2-3 miles away, despite the mountainside it is allegedly travelling down and over displaying soft details, low contrast, and blue shifted colour - useful depth cues. Our unknown object remains the same luminance and the same colour over the course of its journey.
This is excellent! Thanks for taking the time to write this. I'll address what I can. True the object "seems" to be moving and we can't say how, but only observe it relative to the surroundings. BUT, we have to consider all of the findings together and not individually. The object is tiny in the frame. You are indeed correct about parallax being unreliable (or I might say non-definitive.) But considered in conjunction with the other facts we can at least test some assumptions. That's what I have done. How far away would a bug have to be to appear that small in frame and then how close would it have to be to exit frame that large? Distance, plus size, plus parallax I think gives us something to consider. I have shown that it is POSSIBLE that the object disappears behind the ridgeline for 2 frames. This could be the result of other effects as you point out. (I have actually started to think it is flipping end-over-end.) Regardless, non-definitive. However, this is again where we must consider the size of the object and the change in size over time. I found that (by tracing the path) the object goes from 1 pixel (actually less than as it has trouble resolving) to over 50 pixels at exit. It's measurable in the frame, so I'm not guessing. That's a 5000% or 50 times increase in size in just under ONE SECOND. Consider the findings together not separately. The videographer could settle this one, but your assumption is not correct (I have reached out to Brian Hanley for this). The Inspire 1 could be purchased with the X5 camera that comes with a default lens, but is changeable with other micro four-thirds lenses. And there are indeed options for the range of 50mm (here's a 45mm on an Inspire 1). The field of view is definitely ~35deg as can easily be measured by landmarks in the frame and triangulation. Again, regardless I did not rely on either the focal length or the field-of-view in my findings. I showed in the video a scale drawing I have from DJI of the drone and the camera position. The forward positioning is important and helps determine that the camera is looking towards the rear where the control arm would be visible. Looking forward it is impossible for the camera to see the control arm. As such it is simple to measure the distance on the scale drawing from the center of the gimbal to the crossbar in view where it meets the rotor housing. It could certainly be off by some based on camera/lens dimensions, etc. But it's close enough to test assumptions, and that's what I did. Yes! You are definitely on to something here. I am aware that the drone speed should calculate into the findings and chose to negate it. However this speed can be calculated because we can determine (with landmarks) quite definitively where the drone is located. The movement of the drone is important as it is what causes the parallax. This should be revisited, but I do not believe the drone travels at it's top speed and therefore in one second it's distance covered is negligible. But that's opinion. Good catch! This has been answered by other comments, and I believe even your own comment mentions that the camera is having trouble resolving it. It's super tiny and fast as #, or large and distant and fast as #. Either one is fast and provable. Dude, thanks for challenging this video with this kind of logic. I really think it's what helps us get better. None of us can defeat CGI. But if it's real world then these conversations are vital. Cheers!