LiDAR (Light Detection and Ranging) is an active optical ranging system analogous to radar but using near‑infrared or visible photons instead of microwaves. The most tried and tested LiDAR technology, topographic/altimetric lidar, emits short laser pulses, measuring how long they take to return, and converting these time‑of‑flight measurements plus precise platform position and attitude into dense 3D point clouds or profiles of surfaces and vegetation. The newly emerging differential absorption lidars use two wavelengths to retrieve gas concentrations (e.g. CO₂, H₂O) while Doppler lidars measure the frequency shift to infer atmospheric wind profiles.
