Originally Posted by
parabellum
.Scott:
Surely, before any information from shadows can be included you must know the height of the sun above the horizon, its position relative to the aircraft etc. also, just minor movement of the hand holding the smartphone will change the picture. Throughout this thread assumptions have been made without knowing any of the relevant trigonometry which has just been ignored.
I only need to know that the shadow remains at the same relative position to the plane - within a meter or two.
Of course, you may want to know distance from the end of the runway to a particular spot on the plane - such as the nose or the landing gear. And I do not have those offsets.
As other posters have noted, since the sun angle does not appreciably change during the take off roll, and the wing stays approximately the same distance above the surface during that time, the shadow makes for a good indicator. It is moving with the plane.
As far as the distances are concerned: I used a runway map, compared it to photographs of the airport to verify that it was true, downloaded it to my computer, brought it up in paint, and examined it at the pixel level.
Then I used the 2011 meters and the runway end markers to establish the exact scale. All other measurements were based on that.
Perhaps the biggest contributor to error was the timings. If I had downloaded the video, I could have stepped through it frame by frame and gotten timing good to about 70 milliseconds. But since I viewed them from the web, those timing were probably only good to about 200 ms.