LiDAR (Light Detection and Ranging) is a remote sensing technology that is used mostly for measuring the specific distance to a target. It facilitates with 3D information of the target, after compiling the data collected by LiDAR sensors.
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Although LiDAR technology was used for the first time in the 1960s when laser scanners were attached to the aircraft, though the technology did not get a proper boost at that time. After the introduction of GPS (global positioning system) in the 1980s, LiDAR started its applications in measuring the geographic locations.
As like other technologies such as radar, which uses radio waves, and sonar uses sound waves as well as to measure the distance to a specific target, LiDAR uses light pulses to measure the distance.
The general LiDAR technology consists of four basic elements laser, GPS, IMU (inertial measurement unit), and computer. A laser is used as a light pulse to scan the field or object from every side. Different wavelengths of laser lights are used in LiDAR, depends on the environment in which the LiDAR is used. GPS is used to locate the object that carries the LiDAR system, and also the coordinates of the target. As LiDAR is mostly used by planes, for various purposes, IMU is used to measure the plane tilt during flying, as it is important for accurate measurement. A computer is used to collect the data that LiDAR system records during its scanning process, and determine the distance of the target.
In the LiDAR system, the light pulses are sent to the target and then return to the LiDAR system. The speeds of pulses, of some LiDAR systems, are calculated for about 150,000 pulses per second. Now to calculate the distance of a target from LiDAR system, speed of the light, and time, that takes the light to hit the target and return back to LiDAR system, are used as the basic components in the calculations.
The formula to calculate distance looks like this:
((time travel) * (speed of light))/2
The formula will show how far the light actually reaches its target. In the case of the LiDAR system in planes, there are some other factors which also need to be determined during the calculation, such as altitude, turbulence, and pulse angle from the plane.
There are mainly two types of LiDAR systems used, mobile LiDAR system and static LiDAR system. As the names suggest, the mobile LiDAR system mostly consists of sensors, GPS and cameras which are attached to the moving object, and calculate distances and identify various targets on its way. The static LiDAR system is mostly attached to a static object and scans the surrounding environment.