So i had some snarky remarks but i'll cut it out.
How many meters would you guess is the shadow from the wing? If you say less than 10 than that's easily good enough to know where the airplane is.
He only used the shadow to get relative positions so speeds estimated are as accurate as possible. The change of sun angle during takeoff is negligible.
Regarding the angle described in an earlier post, there is some distortion but the analysis isn't nearly as bad as you make it out to be.
Instead of just disregarding what they did maybe use some trigonometry to approximate the errors made using their techniques.