Soil moisture is the basic condition for crop growth and development and an important parameter for crop yield forecast. At the same time, it is also an important environmental factor and process parameter in hydrology, meteorology and other scientific research fields, so it is of great significance for the study of soil moisture. At present, in many remote sensing soil moisture monitoring methods, the use of microwaves to monitor soil moisture is the focus of research, in addition to the use of more sophisticated soil temperature and humidity recorders and other detection instruments. Because microwaves have strong penetrating power to clouds, they are able to work in all weathers without being limited by light conditions, and long-wavelength microwaves can penetrate vegetation and have a certain ability to penetrate soil, which is closely related to soil moisture and dielectric constant. These characteristics make microwave remote sensing have its unique advantages in soil moisture monitoring and occupy an important position in this field.
Basic Principles of Microwave Remote Sensing for Monitoring Soil Moisture Microwave remote sensing is the use of sensors to receive microwave signals emitted or reflected from various parts of the ground to extract and analyze useful information. In the soil moisture monitoring, the microwave is sensitive to moisture, making it a very effective method for remote sensing of soil moisture. Using microwave remote sensing data to monitor soil moisture includes two methods: passive microwave remote sensing and active microwave remote sensing. The detection principle is based on the significant difference in the dielectric constants of water and soil. The difference between the passive and active methods lies in the characteristics of their means and their different characteristics for the target sensor. Passive sensors rely on receiving microwaves emitted by ground objects themselves, such as microwave radiometers, microwave scatterometers, etc., to measure soil moisture by measuring soil brightness temperature, soil brightness temperature is determined by soil dielectric constant and soil temperature, and dielectric constant It is related to temperature and soil moisture, so the soil temperature can be used to invert the soil moisture; the active type emits a microwave beam from the sensor and then receives the echo reflected or scattered by the ground object, such as a side-looking radar, which measures the backscattering of the soil. The coefficient, the soil backscatter coefficient is mainly determined by the dielectric constant and the soil roughness, the dielectric constant is determined by the soil moisture, so the radar can be used to better invert soil moisture.
Selection of microwave remote sensing soil moisture monitoring method In the process of conducting remote sensing microwave monitoring of soil moisture in an area, it is necessary to select an appropriate microwave radiation or scattering model, which requires a certain degree of understanding of the specific conditions on the ground, and it is possible to obtain high accuracy The results, such as whether exposed, if not, the type of vegetation, characteristics and other information. In the comparison of master and passive, active microwave method has become the main way to monitor soil moisture. It has greater potential, especially in the smaller area, and radar monitoring has become more and more widely used. Then, in addition to choosing the appropriate scattering model as the calculation method, some parameters of the radar itself are also crucial. According to the characteristics of the soil roughness and vegetation structure, etc., the best incident angle and polarization method are used to invert the soil moisture. . Soil information can also be more accurately expressed in combination with soil models and dielectric constant models.
Microwave remote sensing soil moisture retrieval has a history of 30 years. It has been successfully applied to soil moisture monitoring systems to assist soil moisture monitoring. At present, the inversion method is still the focus and focus of research.
The research and application of passive microwave remote sensing monitoring of soil moisture have been relatively mature technologies and models. The spatial resolution of passive microwave remote sensing image is relatively low, which is suitable for studying a large area. However, there is still a long way to achieve a practical global soil moisture inversion, and the influence of vegetation and surface roughness on the soil moisture inversion has not yet been affected. It is fundamentally resolved and needs further study. In recent years, with the research and rapid development of spaceborne passive microwave remote sensing, passive microwave soil moisture inversion is rapidly moving towards the globalization of high spatial-temporal resolution.
Active microwave soil moisture inversion is still in the starting stage relative to passive microwave soil moisture inversion. The advantages of active microwave remote sensing signal and high spatial resolution of the image make up for the inadequacy of passive microwave remote sensing to monitor soil moisture and soon become The main force in various methods for monitoring soil moisture. However, it is more affected by surface roughness and vegetation. To overcome this defect, experts and scholars have done a lot of research on radar soil moisture model and parameters, and achieved certain results. At present, the imaging radar system is developing toward the direction of multi-band, multi-polarization, multi-mode, full-polarization, interferometry, and multi-parameter full-polarization interference. The research on active microwave remote sensing soil moisture will receive more extensive attention.
The development of aerospace and aviation causes more and better support platforms for microwave remote sensing. The ability of microwave remote sensing to obtain surface information becomes stronger and stronger, and more and more information is available and more comprehensive. At the same time, data processing methods and methods are also becoming more and more perfect, which makes microwave remote sensing monitoring soil moisture has a wider and wider application prospects.
Basic Principles of Microwave Remote Sensing for Monitoring Soil Moisture Microwave remote sensing is the use of sensors to receive microwave signals emitted or reflected from various parts of the ground to extract and analyze useful information. In the soil moisture monitoring, the microwave is sensitive to moisture, making it a very effective method for remote sensing of soil moisture. Using microwave remote sensing data to monitor soil moisture includes two methods: passive microwave remote sensing and active microwave remote sensing. The detection principle is based on the significant difference in the dielectric constants of water and soil. The difference between the passive and active methods lies in the characteristics of their means and their different characteristics for the target sensor. Passive sensors rely on receiving microwaves emitted by ground objects themselves, such as microwave radiometers, microwave scatterometers, etc., to measure soil moisture by measuring soil brightness temperature, soil brightness temperature is determined by soil dielectric constant and soil temperature, and dielectric constant It is related to temperature and soil moisture, so the soil temperature can be used to invert the soil moisture; the active type emits a microwave beam from the sensor and then receives the echo reflected or scattered by the ground object, such as a side-looking radar, which measures the backscattering of the soil. The coefficient, the soil backscatter coefficient is mainly determined by the dielectric constant and the soil roughness, the dielectric constant is determined by the soil moisture, so the radar can be used to better invert soil moisture.
Selection of microwave remote sensing soil moisture monitoring method In the process of conducting remote sensing microwave monitoring of soil moisture in an area, it is necessary to select an appropriate microwave radiation or scattering model, which requires a certain degree of understanding of the specific conditions on the ground, and it is possible to obtain high accuracy The results, such as whether exposed, if not, the type of vegetation, characteristics and other information. In the comparison of master and passive, active microwave method has become the main way to monitor soil moisture. It has greater potential, especially in the smaller area, and radar monitoring has become more and more widely used. Then, in addition to choosing the appropriate scattering model as the calculation method, some parameters of the radar itself are also crucial. According to the characteristics of the soil roughness and vegetation structure, etc., the best incident angle and polarization method are used to invert the soil moisture. . Soil information can also be more accurately expressed in combination with soil models and dielectric constant models.
Microwave remote sensing soil moisture retrieval has a history of 30 years. It has been successfully applied to soil moisture monitoring systems to assist soil moisture monitoring. At present, the inversion method is still the focus and focus of research.
The research and application of passive microwave remote sensing monitoring of soil moisture have been relatively mature technologies and models. The spatial resolution of passive microwave remote sensing image is relatively low, which is suitable for studying a large area. However, there is still a long way to achieve a practical global soil moisture inversion, and the influence of vegetation and surface roughness on the soil moisture inversion has not yet been affected. It is fundamentally resolved and needs further study. In recent years, with the research and rapid development of spaceborne passive microwave remote sensing, passive microwave soil moisture inversion is rapidly moving towards the globalization of high spatial-temporal resolution.
Active microwave soil moisture inversion is still in the starting stage relative to passive microwave soil moisture inversion. The advantages of active microwave remote sensing signal and high spatial resolution of the image make up for the inadequacy of passive microwave remote sensing to monitor soil moisture and soon become The main force in various methods for monitoring soil moisture. However, it is more affected by surface roughness and vegetation. To overcome this defect, experts and scholars have done a lot of research on radar soil moisture model and parameters, and achieved certain results. At present, the imaging radar system is developing toward the direction of multi-band, multi-polarization, multi-mode, full-polarization, interferometry, and multi-parameter full-polarization interference. The research on active microwave remote sensing soil moisture will receive more extensive attention.
The development of aerospace and aviation causes more and better support platforms for microwave remote sensing. The ability of microwave remote sensing to obtain surface information becomes stronger and stronger, and more and more information is available and more comprehensive. At the same time, data processing methods and methods are also becoming more and more perfect, which makes microwave remote sensing monitoring soil moisture has a wider and wider application prospects.
Full hydrostatic drive, easy to operate, change direction fast. Needn't repeated repaired the road. Adopt larger power engine and can fits working on highland. The machine's turning, vibration and walking all depend on hydraulic system. The machine is mainly used to compress on the asphalt, sand soil and gravel. It is also used to compact road in the school.
1. Equipped with Gasonline or diesel engine
2. Imported Sao hydraulic motor
3. Imported lufthansa variable pump Motor 475
4. Operating radius is small, can work in a small area
5. Surface spray, beautiful appearance, rust corrosion
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