Distance measurements based on time-resolved data acquisition
LIDAR, which is an acronym for LIght Detection And Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances). LIDAR instruments send laser pulses in the direction of the target and then measure the time taken for each light pulse to bounce back using suited single photon sensitive detectors. Because light moves at a constant and known speed, a LIDAR instrument can then calculate the distance between itself and the target with high accuracy. A similar technique is Satellite Laser Ranging (SLR) in which a global network of observation stations measures the round trip time of flight of ultrashort laser pulses to satellites equipped with retroreflectors. It is the most accurate technique currently available to determine the geocentric position of an earth satellite with millimeter level precision. This data is then used as a basis for advanced geodesy applications.