basic concept
The term remote sensing comes from the English "Remote Sensing", which is literally translated as "distant perception", and it has been translated into remote sensing for a long time. Remote sensing is a comprehensive technology for earth observation developed in the 1960s. Since the 1980s, remote sensing technology has made great progress, and the application of remote sensing technology has become increasingly widespread. With the continuous progress of remote sensing technology and the deepening of the application of remote sensing technology, the future remote sensing technology will play an increasingly important role in the construction of China's national economy. The scientific meaning of remote sensing usually has two interpretations, broad and narrow: Broad interpretation: all long-distance detection without contact with the target. Narrow interpretation: using modern optical and electronic detection instruments, not in contact with the target, recording the electromagnetic wave characteristics of the target from a long distance, and revealing the characteristics, properties and changes of the target itself through analysis and interpretation .
The composition of the system
Remote sensing is a comprehensive technology for earth observation. Its realization requires both a complete set of technical equipment and the participation and cooperation of multiple disciplines. Therefore, the implementation of remote sensing is a complicated system engineering. According to the definition of remote sensing, the remote sensing system is mainly composed of the following four parts:
1. Information source Information source is a target that needs to be detected by remote sensing. Any target has the characteristics of reflection, absorption, transmission and radiation of electromagnetic waves. When the target interacts with the electromagnetic waves, the electromagnetic characteristics of the target will be formed, which provides the basis for obtaining information for remote sensing detection.
2. Information acquisition Information acquisition refers to the detection process of using remote sensing technology equipment to receive and record the electromagnetic wave characteristics of the target. The remote sensing technology equipment used for information acquisition mainly includes remote sensing platforms and sensors. Among them, the remote sensing platform is a vehicle used to carry sensors, and balloons, airplanes, and artificial satellites are commonly used; sensors are instruments and equipment used to detect the electromagnetic wave characteristics of targets, and cameras, scanners, and imaging radars are commonly used.
3. Information processing Information processing refers to the technical process of using optical instruments and computer equipment to correct, analyze, and interpret the acquired remote sensing information. The role of information processing is to correct or analyze and interpret the remote sensing information, grasp or remove the errors of the original remote sensing information, sort out and summarize the image features of the detected target, and then identify and extract Useful information.
4. Information application Information application refers to the process in which professionals apply remote sensing information to various business fields for different purposes. The basic method of information application is to use remote sensing information as the data source of geographic information system for people to inquire, count and analyze it. The application fields of remote sensing are very wide. The main applications are: military, geological and mineral exploration, natural resources survey, map surveying, environmental monitoring, and urban construction and management.
Principles of Remote Sensing
The propagation of vibration is called a wave. The propagation of electromagnetic vibration is electromagnetic waves. Electromagnetic wave bands can be divided into γ-rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves and radio waves according to the wavelength from short to long. The shorter the wavelength of the electromagnetic wave, the stronger its penetration. The electromagnetic wave band used for remote sensing detection is the spectral band from ultraviolet, visible, infrared to microwave. The sun acts as a source of electromagnetic radiation, and the light it emits is also an electromagnetic wave. Sunlight must pass through the earth's atmosphere from the universe to the surface of the earth. When sunlight passes through the atmosphere, it will be affected by the absorption and scattering of sunlight by the atmosphere, thus attenuating the energy of sunlight passing through the atmosphere. However, the effect of the absorption and scattering of sunlight by the atmosphere varies with the wavelength of sunlight. The spectral band with high transmittance when sunlight passes through the atmosphere is usually called the atmospheric window. The spectral bands of the atmospheric window are mainly: ultraviolet, visible and near infrared bands. Any objects on the ground (that is, targets), such as the atmosphere, land, water bodies, vegetation, and artificial structures, etc., have reflection and absorption under the condition that the temperature is higher than absolute zero (ie 0 ° k = -273.15 ° C) , Transmission and radiation characteristics of electromagnetic waves. When sunlight illuminates the earth's surface from the universe through the atmosphere, objects on the ground will reflect and absorb electromagnetic waves composed of sunlight. Because the physical and chemical properties of each object and the wavelength of the incident light are different, their reflectivity to the incident light is also different. The law of various objects reflecting the incident light is called the reflection spectrum of the object. Remote sensing detection
Classification of remote sensing
In order to facilitate professionals to study and apply remote sensing technology, people classify remote sensing as follows from different angles:
1. Classification by remote sensing platform equipped with sensors
According to different remote sensing platforms used in remote sensing detection, remote sensing can be classified as:
Ground remote sensing, that is, setting the sensor on a ground platform, such as vehicle, ship, portable, fixed or movable elevated platform, etc .;
Aeronautical remote sensing, that is, placing sensors on aircraft, such as balloons, model airplanes, airplanes, and other aircraft;
Space remote sensing, that is, placing sensors on spacecraft, such as artificial satellites, spaceships, space laboratories, etc.
2. Classification according to the working mode of remote sensing detection Remote sensing can be classified as:
Active remote sensing, that is, the sensor actively emits electromagnetic waves of a certain wavelength to the detected target, and then receives and records the electromagnetic waves reflected from the target;
Passive remote sensing, that is, the sensor does not emit electromagnetic waves to the detected target, but directly receives and records the electromagnetic waves reflected by the target or solar radiation emitted by the target.
3. According to the working band of remote sensing detection, remote sensing can be classified as:
For ultraviolet remote sensing, the detection band is between 0.3 and 0.38um; for visible light, the detection band is between 0.38 and 0.76um;
Infrared remote sensing, its detection band is between 0.76 ~ 14um; microwave remote sensing, its detection band is between 1mm ~ 1m; multi-spectral remote sensing, its detection band is in the range of visible light and infrared band,
Microwave remote sensing multi-spectral remote sensing
4 Application areas or topics:
Environmental Remote Sensing Atmospheric Remote Sensing Resources Remote Sensing Ocean Remote Sensing Geological Remote Sensing Agricultural Remote Sensing Forestry Remote Sensing
Characteristics of remote sensing technology
Remote sensing is a comprehensive technology for earth observation. Its emergence and development are not only the objective needs for people to recognize and explore the natural world, but also have unmatched characteristics with other technical means. The characteristics of remote sensing technology can be summed up in the following three aspects: 1. Wide detection range and fast data collection. Remote sensing detection can make observations on a large area from the air and space in a short time, and obtain Remote sensing data of value. These data expand people's visual space, create extremely favorable conditions for macroscopically grasping the status quo of ground objects, and also provide valuable first-hand information for macroscopically studying natural phenomena and laws. This advanced technology is irreplaceable compared with traditional manual work. 2. Remote sensing can dynamically reflect the changes of ground objects. Remote sensing can periodically and repeatedly observe the same area, which helps people to find and dynamically track changes in many things on the earth through the obtained remote sensing data. At the same time, study the law of change in nature. Especially in monitoring weather conditions, natural disasters, environmental pollution, and even military targets, the use of remote sensing is particularly important. 3. The data obtained is comprehensive remote sensing detection. The remote sensing data acquired in the same period and covering a wide range of areas, these data comprehensively display many natural and human phenomena on the earth, and macroscopically reflect the forms of various things on the earth. And distribution, it truly reflects the characteristics of geology, landform, soil, vegetation, hydrology, artificial structures and other features, and comprehensively reveals the correlation between geographical things. And these data have the same trend in time.
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