ABSTRACT
Light detection and ranging (LiDAR), also called laser scanning, is an e§ective remote sensing system for acquiring threedimensional (3D) information about scanned objects, which has been widely applied in a broad range of disciplines since it was ¦rst developed less than two decades ago (Baltsavias, 1999a; Krabill et al., 2000). A LiDAR system integrates several accurate optical, electronic, mechanic, timing, and georeferencing units that make it enable to acquire 3D point measurements rapidly. LiDAR systems are mainly classi¦ed into two types based on the motions that occur when they collect data. Ÿe ¦rst category includes static terrestrial (or ground-based) LiDAR systems (usually mounted at a tripod) with a variety of scanning ranges, which are also called 3D laser scanners. Ÿe primary component of a terrestrial LiDAR system is a laser ranging unit to obtain the distance to the target. Integrating with one or two rotating mirror or prism that changes the direction of emitting laser pulses, the LiDAR system can scan and measure the distances to the surrounding objects. By calculating the obtained range and the scanning angle, the 3D coordinates of the scanned target are obtained. Because the mirror rotates in rapid speed with small-angle variation when the LiDAR operates, a huge number of dense and accurate point measurements, o¬en called point cloud, of the surfaces of scanned objects are obtained (Figure 17.1).
