The Application of Laser and Radar in Laser Rangefinder
The Laser Xiyuantai Ranging Instrument Network is an active remote sensing technology that measures the distance between the sensor and the target object through the laser emitted by the sensor (LiDAR). This technology can be divided into two categories based on the different detection targets: air detection and ground detection. The aim of airborne laser ranging is to determine the physical and chemical properties of the atmosphere by emitting a laser beam into the air and receiving the echoes reflected by suspended particles in the air. The main goal of ground laser ranging is to obtain surface information such as geology, terrain, geomorphology, and land use status. According to the classification of sensor platforms, laser ranging can be divided into four categories: satellite based (satellite based), airborne (aircraft based), vehicle based (vehicle based), and positioning (fixed point measurement).
Laser ranging technology began in the 1960s, and by the 1970s and 1980s, laser technology had become an important component of electronic ranging equipment. LIDAR (Light Detection And Ranging) usually refers to airborne ground to ground laser ranging technology, and in Chinese terms, LiDAR is commonly used to refer to LIDAR. In the United States, since the 1970s, multiple agencies including NASA, NOAA, and the Department of Defense Surveying and Mapping (DMA) have started developing LIDAR type sensors for ocean and terrain measurements. In Europe, research on laser ranging has started almost simultaneously with the United States. Unlike the United States, they are committed to developing satellite platform laser ranging radar systems, focusing more on the development and research of airborne platforms and their matching laser radar systems, and have achieved considerable success.
By the 1990s, with the development of airborne GPS technology and portable computer systems, the stability and reliability of LIDAR systems had been greatly improved, and they gradually began to be commercialized in Europe. Relevant applied research was also carried out in Europe.
Compared to other remote sensing technologies, the research on LIDAR is a very new field, both in improving the accuracy and quality of LIDAR data and enriching the application technology of LIDAR data. Unlike remote sensing imaging technology, LIDAR system can quickly obtain three-dimensional geographic coordinate information of the surface and corresponding ground objects (trees, buildings, surface, etc.), and its three-dimensional characteristics meet the mainstream research needs of today's digital earth.
With the continuous progress of LIDAR sensors, the gradual increase in surface sampling density, and the increase in the number of recoverable waves for a single laser beam, LIDAR data will provide richer surface and object information. By filtering, interpolation, classification, segmentation, and other processing on the surface 3D point set collected by LIDAR, various high-precision 3D digital terrain models can be obtained. Surface features can also be classified and recognized, and 3D digital reconstruction of surface features such as trees and buildings can be achieved. 3D forest and 3D city models can be drawn, and virtual reality can be constructed. On the basis of virtual reality, more detailed ground feature analysis can be conducted to analyze the forest land and its individual trees
