Airborne LIDAR is the use of light from an aircraft-mounted laser to detect or measure objects. LIDAR is an acronym for light detection and ranging, a detection technology that emits beams of photons with wavelengths in the ultraviolet, infrared, or visible light region of the electromagnetic spectrum. When the photons hit and reflect off an object, the LIDAR detects the scattered light and interprets it to provide information about the target. LIDAR is very similar to radar, which uses radio waves in the same way that LIDAR uses light, but LIDAR can be far more precise because it uses electromagnetic radiation with much shorter wavelengths. Airborne LIDAR is used for purposes such as mapping and surveying, in scientific fields such as biology and geology, and in military detection equipment.
The most common use of airborne LIDAR is to study and measure the topography, or surface features, of the Earth. A LIDAR device mounted on an aircraft can scan the ground below with greater precision and resolution than conventional aerial photography, allowing it to detect and measure even very small or subtle terrain features. The global positioning system, a satellite-based navigation system, is used to precisely track the passage of time and the movement of the aircraft as it flies to create a record of exactly where the LIDAR system was at each moment of the survey. This allows airborne LIDAR surveys to produce extremely accurate and detailed topographic maps. LIDAR can also penetrate vegetation, such as the canopies of trees, and so can accurately map terrain obscured from normal aerial observation due to forests or jungles.
The great precision possible with airborne LIDAR means that repeated surveys can detect very small changes over time. This makes it useful in the study of natural phenomena such as the movement of glaciers and geological faults, which occur extremely slowly over thousands or millions of years and so require very precise measurements to detect and measure. It can also show gradual changes in the landscape caused by natural forces such as wind and water erosion. Aerial LIDAR surveying is also used in agriculture, providing information on soil composition, topography, and erosion patterns. It can also measure trees and vegetation, making it useful for the management of forests.
Airborne LIDAR is additionally helpful in the study of underwater areas. It is implemented in bathymetry, the measurement of sea beds and lake floors, to map shallow areas such as coastlines and rivers. This makes it possible to accurately survey an area more rapidly than could be done with sonar carried by ships. It is also useful for studying very shallow or hazardous areas where bringing a ship is impractical or dangerous and for studying environmentally sensitive areas without intruding on the local ecology. In military applications, LIDAR systems carried by helicopters can detect naval mines.