Lidar

Lidar (/ˈlaɪdɑːr/, an acronym of light detection and ranging or laser imaging, detection, and ranging, often stylized LiDAR) is a method for determining ranges by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the optical receiver. Lidar may operate in a fixed direction (e.g., vertical) or it may scan directions, in a special combination of 3D scanning and laser scanning.

A frequency addition source of optical radiation (FASOR) used at the Starfire Optical Range for lidar and laser guide star experiments is tuned to the sodium D2a line and used to excite sodium atoms in the upper atmosphere.

This lidar may be used to scan buildings, rock formations, et cetera, to produce a 3D model. The lidar can aim its laser beam in a wide range: its head rotates horizontally; a mirror tilts vertically. The laser beam is used to measure the distance to the first object on its path.

An airplane collecting treetop data over a Brazilian rainforest

In this view, the viewer flies down to the rainforest canopy and flies through the virtual leaves.

This visualisation shows an airplane collecting a 50 km swathe of lidar data over the Brazilian rainforest. For ground-level features, colours range from deep brown to tan. Vegetation heights are depicted in shades of green, where dark greens are closest to the ground and light greens are the highest.

LiDAR is used within terrestrial, airborne, and mobile equipment around the globe. It is commonly used to make high-resolution maps, with applications in surveying, geodesy, geomatics, archaeology, geography, geology, geomorphology, seismology, forestry, atmospheric physics, laser guidance, airborne laser swathe mapping (ALSM), and laser altimetry. It is used to make digital 3-D representations of areas on the Earth's surface and ocean bottom of the intertidal and near coastal zone by varying the wavelength of light. It has also been increasingly used in control and navigation for autonomous cars and for the helicopter Ingenuity on its record-setting flights over the terrain of Mars. Lidar has since been used extensively for atmospheric research and meteorology. Lidar instruments fitted to aircraft and satellites carry out surveying and mapping – a recent example being the U.S. Geological Survey Experimental Advanced Airborne Research Lidar. NASA has identified lidar as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar-landing vehicles.