Contents I. Introduction
Light-based measuring techniques were firstly used in calculating the air density in the upper atmosphere just by reading the intensity of a searchlight beam’s reflection. Later, and instead of using continuous light beams, the cloud-base height measurement was obtained by calculating the time taken by a light pulse to travel to the cloud and back to the ground [1]. Back in 1953, Middleton and Spilhaus introduced the Light Detection and Ranging (LiDAR) as a range measuring technique [2], which was initially a portmanteau of the terms light and Radar [3]. However, only with the invention of new techniques such as Dennis Gabor’s holography method in 1945 and the laser in 1960 [4], the LiDAR principle was introduced as we know it nowadays: it can measure distances by simply calculating the round-trip time of a laser pulse traveled to the target and back [5]. Nonetheless, and since E.D Hinkley has published his LiDAR textbook in 1976 [6], the evolution of LiDAR has been primarily associated with the improvement of hardware components and measuring techniques, rather than the development of new disrupting measuring principles [7].
