LiDAR: How does it work?

LiDAR, or Light Detection and Ranging, is a remote sensing technology that uses laser light to measure distances and create detailed, three-dimensional maps of the environment. The basic principle of LiDAR involves emitting laser pulses towards a target, measuring the time it takes for the light to travel to the target and back, and using this information to calculate distances. Here's a step-by-step explanation of how LiDAR works:

• Laser Emission: LiDAR systems use lasers, typically in the form of near-infrared or visible light, to generate short pulses of laser beams. The lasers used in LiDAR systems are low-divergence lasers, meaning they emit a focused beam of light.

• Emission of Laser Pulses: The LiDAR instrument emits rapid pulses of laser light towards the target area. These laser pulses are often emitted in a circular or conical pattern, covering a wide field of view.

• Interaction with Surfaces: When the laser pulses encounter objects or surfaces in the environment, a portion of the light is reflected back towards the LiDAR sensor. The time it takes for the light to travel from the source to the target and back is precisely measured.

• Time-of-Flight Measurement: LiDAR calculates distances by measuring the time it takes for the emitted laser pulses to travel to the target and return. The formula for distance (D) is given by: D = (Speed of Light x Time) / 2 Since the speed of light is constant, the time measurement is used to determine the distance to the target.

• Return Signal Detection: The LiDAR system's sensor detects the reflected laser pulses, or return signals. The sensor records the precise time at which each pulse is received.

• Multiple Returns and Point Cloud Generation: LiDAR systems often emit thousands of laser pulses per second. As a result, multiple return signals are received from different points on surfaces within the laser's field of view. The collected data points create a dense point cloud, which is a 3D representation of the surfaces and objects in the environment.

• Rotation or Scanning (for Mobile LiDAR): In mobile LiDAR systems, such as those mounted on vehicles or aircraft, a rotating mirror or scanning mechanism is used to direct laser pulses across the target area. This ensures comprehensive coverage of the surroundings.

• GPS and IMU Integration (for Georeferencing): LiDAR systems are often integrated with Global Positioning System (GPS) receivers and Inertial Measurement Units (IMUs). This integration provides accurate georeferencing, allowing the creation of precise 3D maps with spatial information.

• Data Processing: The raw data collected by the LiDAR system undergoes extensive processing. This includes filtering out noise, aligning data points, and converting the information into a usable format. The processed data is typically represented as a point cloud, where each point corresponds to a 3D coordinate in the environment.