3D Point Cloud Data Processing - Open Source Geospatial Tools: Applications in Earth Observation - page 256

Quantised
Full
Waveform
Echo

Quantised
Discrete
Echo

Returned
Echo

Infra-red
Pulse

c. 1ns*

Terrain

* In a vacuum light will travel approximately 0.3m in 1ns

Fig. 15.1 Discrete echo and full waveform airborne laser scanning

light comprising a continuous waveform. The returned echo can be represented as
in Fig. 15.1 . 1
Traditional LiDAR instruments capture discrete laser pulses, where each emitted
pulse results in a discrete number of returns (first, second, ... , last). The number
of returns received depends on sensor technology and the target that was hit. If the
pulse is absorbed by the target, a single pulse might not be returned, as is frequently
the case when the target hit is water. Vegetation typically returns up to three pulses,

1 Graphics by Anthony Beck, licensed under the Creative Commons Attribution-Share Alike 3.0
Unported license.