see also:

LiDAR, and LADAR, "light detection and ranging", "laser imaging, detection, and ranging", "3-D laser scanning, Lidar mapping"

Light Detection And Ranging is a method where the round-trip time of a laser reflection is measured using a time-to-digital converter (TDC). It is used 3-D laser scanning both airborne and stationary, for computer vision especially in autonomous vehicles and meteorological measurements. 

Please also read our detailed article on this topic.