The wingspan of an F-15 is about 45’ and I’m guessing a urban 2 lane street with parking on both sides is about the same. Based on the picture above, i’m thinking somebody with some math skills could come up with an altitude estimate?
Low flying jet almost wacked me
- Thread starter Trackedout
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N017RW
Premium Pilot
Fair enough.
My experience with falling aircraft over the decades is they rarely drop.
There will be some horizontal component.
My experience with falling aircraft over the decades is they rarely drop.
There will be some horizontal component.
The aircraft is subsonic so there is no shock wave per se. I see some evidence of a disturbance around 3 seconds after it passes, but with the speed of sound in air being around 330 m/s that would put the aircraft much higher.
Unfortunately the size of the shadow doesn't tell you anything because it doesn't change with height - it simply becomes more diffuse around the edges.
N017RW
Premium Pilot
Exactly sar...
Let's just say you hope to prove the plane is at/near 500ft (~0.15 km).
The sun is so far away (~150 million km) that the divergence of its rays in the last 0.15 km of altitude is so small that the shadow is virtually the same size as the airplane because the rays are virtually parallel.
Let's just say you hope to prove the plane is at/near 500ft (~0.15 km).
The sun is so far away (~150 million km) that the divergence of its rays in the last 0.15 km of altitude is so small that the shadow is virtually the same size as the airplane because the rays are virtually parallel.
Correct. The only variable that you have to work with is the size of the source - since the sun is not a point source the rays from different parts of the sun subtend different angles at the object, and produce shadows that are offset by an amount that is a function of distance to the image plane (i.e. the distance from the aircraft to the ground). Unfortunately, adding in the issue of motion blur, that's a tough measurement to make from a video.
Well just as a sanity check, since there is one frame where both the core shadow and the outer edge of the shadow (left wing tip) are fairly well defined, and orthogonal to the direction of motion so no motion blur, I ran that calculation. The distance between the edge and the core of the shadow on the ground looks to be about 1.5 meters, and since the sun subtends an angle of 0.52°, that puts the distance of the shadow from the aircraft at:
1.5/(2.tan(0.52/2)) = 155 m (508 ft)
1.5/(2.tan(0.52/2)) = 155 m (508 ft)
Nice catch - thanks for sharing. The size of the shadow and setting off the car alarms alone indicates he was less than 400 ft. There are flight rules us drone pilots are expected to follow; aircraft (even military) are required to do the same. You have the evidence to report it to the nearby military base you think is responsible. We had Air Force jets buzzing a place where I worked. Our Director called the Air Force Base, got a profound apology, and we never saw a plane again. They do take such reports serious generally. Still, a classic nice few seconds of video.
N017RW
Premium Pilot
N017RW
Premium Pilot
N017RW
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Yip watched few times awsome but scary,hate to be jet washed, it would have been even cooler if you panned up after he passed,(next time ay)
Cool...............better add that be 2 pairs of undies ........
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**** I never even thought of that. I was facing the right way but I was too focused on getting down
Given the geometry of casting a shadow from the sun, the size of the shadow yields no information about the airplane altitude. HOWEVER, the edge blurring does tell you something. The lower the aircraft, IE: closer to the target, the more distinct (sharp) the shadow will be.
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