[TXnMA]

"i fail to see how it goes through the trees/leaves"

If you bombard a forest with a dense-enough "cloud" of laser pulses, statistically, some of them will "find holes between the leaves" and reach the ground -- and will be the last to be reflected back to the detector. By subtracting out all the "quick returns", all you have left is those that reflected back from the "bare ground".

Ideally, in a temperate area, you do the overflight in winter, when foliage is at a minimum...

But, I agree with you: getting enough pulses through a triple-canopy jungle must be a genuine challenge!

[Chode]

thank you sir