Laser scanners are sophisticated systems which emit an array of timed laser pulses and measure the reflected return pulse. This information is used to detect the elapsed time or phase shift, as well as the strength of the returning light intensity. These systems usually feature a fixed laser source, with the scan action created by rotating or oscillating mirrors.
Alternately, fibre arrays can be used to generate a scanning pattern. Advanced airborne lasers allow for multiple returns from each outgoing pulse, as well as a “Full Waveform” return for further processing. The resulting data gathered from this process can be used to create rich 3D models of features and landscapes.
However, it’s important to note that the last pulse return is not necessarily from the ground and must be verified through ground truth data.