What is remote sensing technology?

In ancient mythology, the Monkey King, the Great Sage of Qitian, was able to know what was happening in distant places. But, you know what? In our real life, there is also this magical guy, that is, remote sensing technology. What is remote sensing technology? It is a new technology that uses electromagnetic signals to perceive the target, its nature and state from a distance without direct contact with the target.

/kloc-remote sensing technology came out in the 0/9th century. As early as 1839, people used it to get the first photo. 1858, the French conducted the first aerial photography experiment with balloons over Paris. After the invention of 1903 aircraft, aerial photography developed rapidly. 1957 When the first man-made satellite was launched, remote sensing devices were installed on the satellite, and methods of radio reconnaissance and detection from space began to appear. Since then, remote sensing technology has entered the practical stage and become a comprehensive detection technology. American strategic communication satellites perceive the truth of distant military targets through modern radio instruments and equipment. Since 1960s, remote sensing technology has been applied to various sectors of the national economy, such as agriculture, forestry, hydrology, geology, ocean, surveying and mapping, environmental protection, engineering construction and many other aspects. 1972, the United States launched the first earth resource satellite, and for the first time, people saw the whole picture of the earth completely with the help of electromagnetic waves, and obtained extremely rich ground features. With the development of space technology, human beings have obtained a lot of valuable information from the universe through remote sensing technology. This shows that the investigation and exploration of unknown fields by remote sensing technology has entered a new stage.

What is the principle of remote sensing technology we are talking about? As we all know, all objects on the earth can radiate electromagnetic waves, receive electromagnetic waves from objects through remote sensors, and then understand the state and attributes of objects through optical and electronic technologies, and then obtain relevant information.

Remote sensing system is a unified collective, and its members include: remote sensor, remote sensing platform, information transmission equipment and information processing equipment. The most important one is the remote sensor, whose main task is to feel the electromagnetic wave information from the target, which is usually served by high-resolution cameras, TV cameras, multi-spectral scanners and so on. Remote sensing platform is used to install remote sensors. Information transmission equipment is used for information transmission between remote sensing platform and ground objects. Information processing equipment is the place to process the received information, which mainly includes image processing equipment, color synthesizer and electronic computer.

Remote sensing system families can be classified. According to the carrier of remote sensor, it can be divided into ground remote sensing, aerial remote sensing and space remote sensing; According to different working principles, it can be divided into: active remote sensing and passive remote sensing; According to different remote sensing methods, it can be divided into visible light remote sensing, infrared remote sensing, ultraviolet remote sensing and microwave remote sensing. No matter how classified, each type of remote sensing system has great power in capturing remote sensing information, especially space remote sensing technology, which is used to obtain military information in many countries. By the mid-1980s, more than 3,000 man-made satellites had been launched all over the world, of which more than 70% were directly or indirectly used for military purposes, and all kinds of remote sensors were installed, which could continuously detect and monitor the ground environment. Visible light remote sensing has high resolution and can clearly understand the objects on the ground; Infrared remote sensing can work day and night and can identify camouflage on the ground; Multispectral remote sensing is superior, which has all the advantages of visible light remote sensing and infrared remote sensing. Microwave remote sensing has higher resolution and can pass through clouds, vegetation and ground. Military targets such as airport runways, taxiing planes and missile launchers can be clearly seen in the photos obtained by reconnaissance satellites, and the types of tanks and vehicles can also be distinguished. To sum up, their advantages are: wide reconnaissance range, not limited by geographical conditions, rapid and accurate target discovery, etc. Look, isn't the ability of remote sensing amazing?

In fact, there are many things that remote sensing can do. For example, the application of remote sensing technology in weapon guidance can greatly improve the hit accuracy. Remote sensing technology can provide 25 minutes early warning time when it is used to detect incoming strategic ballistic missiles. The application of remote sensing technology in military reconnaissance and military mapping can reduce the navigation error of aircraft and ships, thus improving the combat effect. The application of remote sensing technology in geology can study global geological phenomena, help to discover new mineral resources, predict earthquakes and volcanoes, and provide detailed information on sediment movement and estuary evolution. The application of remote sensing technology in marine hydrology can provide clues for finding groundwater, and can also measure the depth of seawater, providing a basis for the development of marine undertakings. When remote sensing technology is applied to agriculture and forestry, it can make a large-scale investigation of agricultural conditions, grasp the timing of irrigation, drainage, fertilization and pest control, so as to take corresponding measures, estimate forest resources, measure soil quality and pasture conditions, and create conditions for the development of agriculture and animal husbandry. The application of remote sensing technology in environmental monitoring can observe air pollution, help find pollution sources, check the damage of vegetation, and take better measures to protect the ecological environment.

In fact, different information obtained by remote sensing technology often overlaps. Therefore, it is necessary to study the electromagnetic characteristics of the target and master the general law of the interaction between electromagnetic waves and objects in order to accurately obtain more useful information from remote sensing images.

The development trend of remote sensing technology in the future is: from passive remote sensing to the combination of passive remote sensing and active remote sensing; From single electromagnetic wave remote sensing to multi-wave remote sensing; From half-day remote sensing to all-weather remote sensing; From qualitative remote sensing to quantitative remote sensing. As time goes by, with the continuous progress and in-depth development of science, remote sensing technology will become more and more extraordinary!