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I'm trying to understand the behavior of a single laser pulse in a traditional airborne lidar.

I understand that the multiple return values are representative of the surface that reflected the initial pulse. However, does a single pulse from the laser, return each reflection individually to the sensor? Or does a single pulse from the laser continue through it's path, capturing each reflection along it's way until returning to the sensor?

So if a system can capture 300k pulses per second, are those 300k pulses released and captured? Or is that 100k +/- pulses returning 300k values?

Lidar Pulse returns

Example photo: Does each disturbance in the waveform return it's own pulse to the sensor? If so, how the sensor understand the laser is continuing? And if that is also true, where does the energy come from to continue the pulse further?

marked as duplicate by John Powell, radouxju, Ian Turton Dec 22 '15 at 9:52

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The pulse is emitted, the light "spreads" out as it continues its path down, much like a flashlight. No external energy is needed once the light is emitted. The diagram you have shows it quite well. Neither the sensor nor the light understand the light is continuing, it is just that when the light hits more distant objects it takes longer to return than closer objects. One light pulse out but multiple possible returns from the original pulse. Part of the outbound light hits the top of the canopy and returns, another part makes it through the canopy to a branch and returns, another part makes it to the ground and returns. Hundreds of thousands of pulses are sent out per second, many never make it back but enough do.

"However, (i) does a single pulse from the laser return each reflection individually to the sensor? Or (ii) does a single pulse from the laser continue through it's path, capturing each reflection along it's way until returning to the sensor?"

Most similar to the first one (i) you state.

This nice video explains it well.

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