Laser profilers measure 1D range profiles and operate in different environments, like spaceborne, airborne and indoor. Most of them operate top-down on flying platforms, but as well bottom-up is possible, e.g. in meteorology for cloud monitoring.
It is the simplest application of the LIght Detection And Ranging technique. It transmits a short pulse of energy (visible or near-infrared radiation) and detects 'echo', by measuring the time delay and knowing the speed of propagation of the pulse, the range from the instrument to the surface can be measured.