Given the size in pixels and an assumed size, you can work out

This was prompted by this video:

Source: https://www.youtube.com/watch?v=4IvY41SQMZ8&t=1856s

Which is very long and slow, but discusses the math around 30 minutes in. They use an estimated FOV of 38.5.

For something the size of a bird this seems to raise issues, assuming the math and measurements are correct, then given a "bird" height of 0.25 feet (3 inches) the speed comes out at around 500 mph

The smaller things get, the less likely it is that they are travelling so smoothly under their own power, and the more likely it is that it's the drone motion. But to get something to around 20 mph requires a height of 0.01 feet, or 0.12 inches (3 mm), and it's at 4x as wide as it is long, so about 0.48 inches (12mm). This is about the size of a piece of paper from my shredder.

Like:

This is somewhat consistent with @purpleivan's "slow bug" recreation at https://www.metabunk.org/posts/227878/

I'm not sure how the earlier motion fits into this though.

- the angular size (pixels * FOV /1920)
- distance (size/2)/(tan (angular size/2)
- the speed (difference in distance for one frame)*60 feet per second (*3600/5280 for mph)

This was prompted by this video:

Source: https://www.youtube.com/watch?v=4IvY41SQMZ8&t=1856s

Which is very long and slow, but discusses the math around 30 minutes in. They use an estimated FOV of 38.5.

For something the size of a bird this seems to raise issues, assuming the math and measurements are correct, then given a "bird" height of 0.25 feet (3 inches) the speed comes out at around 500 mph

The smaller things get, the less likely it is that they are travelling so smoothly under their own power, and the more likely it is that it's the drone motion. But to get something to around 20 mph requires a height of 0.01 feet, or 0.12 inches (3 mm), and it's at 4x as wide as it is long, so about 0.48 inches (12mm). This is about the size of a piece of paper from my shredder.

Like:

This is somewhat consistent with @purpleivan's "slow bug" recreation at https://www.metabunk.org/posts/227878/

I'm not sure how the earlier motion fits into this though.

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