The uses of LiDAR

Radar is a detection system that uses radio waves to determine the distance, angle, or speed of a target. It can be used to detect aircraft, ships, spacecraft, guided missiles, or motor vehicles, and even predict weather formation and detect terrain.
The radar system includes a transmitter that generates electromagnetic waves in the radio or microwave field, a transmitting antenna, a receiving antenna (usually the same antenna is used for transmitting and receiving), as well as a receiver and a processor to determine the properties of objects. The radio waves (pulses or continuous) from the transmitter are reflected by the object and then returned to the receiver, providing information on the position and velocity of the object.



The modern uses of radar are very diverse, including:

1. Air and ground traffic control and radar astronomy
2. Anti missile system
3. Collision prevention systems for ship radar positioning navigation marks and other ships and aircraft
4. Ocean monitoring system
5. Outer Space Surveillance and Fusion System
6. Meteorological precipitation monitoring
7. Altitude measurement and flight control systems, as well as missile target positioning systems
8. Ground penetrating radar for geological observation

High tech radar systems integrated with digital signal processing (DSP) and machine learning (ML) into artificial intelligence (AI), combined with deep learning (DL), can extract useful information from very high noise levels. Radar is a key technology mainly used by the auto drive system, in addition to sonar and other sensors. Other radar like systems utilize other parts of the electromagnetic spectrum.

LiDAR

An example is light detection and ranging (LiDAR), which mainly uses infrared light from lasers rather than radio waves. Some articles or books refer to LiDAR as LADAR, which means the same technology. With the emergence of autonomous vehicles, radar is expected to assist automated platforms in monitoring their environment, thereby preventing unnecessary accidents.

The detection mechanism of LiDAR is based on measurement methods, which use laser to irradiate the target and sensors to measure the distance to the target by measuring the reflected light. The difference in laser return time and wavelength can be used to form a digital 3D representation of the target. The name LiDAR is now used as the acronym for light detection and ranging (sometimes light imaging, detection, and ranging), originally a combination or combination of light and radar.

Lidar, sometimes referred to as 3D laser scanning, is a special combination of 3D scanning and laser scanning. It has applications on the ground, in the air, and in mobile applications. The optical radiation frequency plus source (FASOR) used for LiDAR and laser guided star experiments within the range of starfire optics is tuned to the sodium D2a line to excite sodium atoms in the upper atmosphere.

Lidar typically uses ultraviolet (UV), visible light, or near-infrared (IR) light to image objects. It can target many different materials, including non-metallic objects, rocks, rain, compounds, aerosols, clouds, and even single molecules. Narrow laser beams can map physical features at very high resolution; For example, an aircraft can draw a terrain map with a resolution of 30 degrees Celsius (12 inches) or higher.

In the example of airborne LiDAR, it is simply airborne laser scanning, a type of laser that is connected to the aircraft during flight, creating a 3D point cloud model of the landscape. This is currently the most detailed and accurate method for creating digital elevation models, which can replace photogrammetry. Compared to photogrammetry, a major advantage is the ability to filter out vegetation reflections from point cloud models, creating a digital terrain model that represents ground hidden by trees, such as rivers, paths, cultural sites, etc.



In the category of airborne LiDAR, there is sometimes a difference between high-altitude and low altitude applications, but the main difference is that the accuracy and point density of the data obtained at higher altitudes are reduced. See Figure 1.3. In Figure 1.3, we observe the schematic diagram of the airborne LiDAR scanning to generate parallel lines at measurement points. Although there are other scanning mode methods, this is the most common one.

Compared to most other technologies, using LiDAR to collect elevation data has several advantages. The main features include higher resolution, centimeter accuracy, and the ability to perform ground detection on forest terrain. [Image]  Schematic 

Lidar has become an established method for collecting highly dense and accurate elevation data in landscapes, shallow water areas, and project locations. This active remote sensing technology is similar to radar, but uses laser pulses rather than radio waves. Lidar is usually collected in flight or from an aircraft, allowing it to quickly collect large areas of data points. Airborne lidar can also be used to create shallow water depth models.