itishappy 2 days ago

Time of flight ranging is used in nature by bats and whales/dolphins.

2
maxbond 2 days ago

My back of the napkin estimate is that a human using time of flight ranging would be unable to distinguish between an object directly in front of their face and 8.6 meters away[1]. I think human echolocation uses a different mechanism (presumably relating to amplitude)?

Skimming the Wikipedia article[2], it seems like animals do use time of flight, but also Doppler shifting.

(As a side note, some animals have apparently evolved active countermeasures to echolocation!? It seems obvious in retrospect but incredibly cool.)

There's interesting research into the mechanisms of human echolocation [3], but it was over my head. My impression was that the jury is out as far as the precise mechanisms involved but that there's a lot of evidence to be considered, I'm sure someone with a better background would get more out of it than I did.

(I'm just curious about the mechanism, I agree that LIDAR has natural analogs.)

[1] Speed of sound * 25ms, 25ms being the rule of thumb I've memorized for the minimum interval for two sounds to register as distinct from each other. This is just folk wisdom I've picked up hacking on audio, so perhaps I'm mistaken.

[2] https://en.wikipedia.org/wiki/Animal_echolocation

[3] https://durham-repository.worktribe.com/preview/1375913/1963...

jaimex2 2 days ago

Both primarily use their eyes. Look it up.