Soil radiation shielding device and method for foundation microwave radiometer

Abstract

The invention relates to the technical field of microwave remote sensing, in particular to a soil radiation shielding device and method for a foundation microwave radiometer. The shielding device comprises a microwave radiometer, an automatic lifting platform, a shielding net and a terminal console, the microwave radiometer is placed on the upper end face of the automatic lifting platform and erected on a forest canopy, and the shielding net is laid on soil below the forest canopy to be detected. The terminal console is in electric control connection with the microwave radiometer and used for adjusting the observation angle and azimuth angle of the microwave radiometer, and the terminal console is in electric control connection with the automatic lifting platform and used for adjusting the height of the automatic lifting platform. The soil radiation shielding device and method for the ground-based microwave radiometer aim at solving the problem that the ground-based microwave radiometer cannot shield surface soil radiation when measuring forest canopies in the field.

Description

Technical Field

[0001] The invention relates to the technical field of microwave remote sensing, and in particular to a soil radiation shielding device and method for a ground-based microwave radiometer. Background Art

[0002] Passive microwave remote sensing is a key means to obtain surface soil moisture, especially the low-frequency L band (1.4GHz) is sensitive to soil moisture. In nature, there is a vertical structure of layered media, including soil, leaf litter, snow, forest and atmosphere. Decoupling the radiation energy of different media is the key to achieving high-precision inversion of surface soil moisture. Ground-based microwave radiometers are the main method for verifying satellite remote sensing observations, and they play a key role in studying the radiation transmission parameters of the medium and the radiation transmission coupling process between different media. When using ground-based radiometers to measure the radiation brightness temperature of different media, the radiation coupling effect of other media on the target material is often ignored, resulting in deviations in the radiation brightness temperature of the target medium. For example, in field measurements, ground-based radiometers are often set up under trees to observe upward through horn antennas or set up above the canopy to observe downward to obtain the radiation brightness temperature of the canopy. However, the soil microwave radiation will be reflected by the forest canopy or penetrate the canopy and enter the sensor, which makes the observed canopy brightness temperature higher, affecting the accuracy of the solution of the canopy radiation transmission parameters.

[0003] Shielding the microwave radiation from other media is an effective way to accurately measure the brightness temperature of the target material. However, there are few studies on the surface soil radiation shielding methods and shielding devices for ground-based microwave radiometers. At the same time, there is a water vapor transmission effect between the soil and the atmosphere, and how to follow the real natural state also brings challenges to shielding soil microwave radiation.

[0004] Therefore, the inventor provides a soil radiation shielding device and method for a ground-based microwave radiometer. Summary of the invention

[0005] (1) Technical issues to be solved

[0006] The embodiments of the present invention provide a soil radiation shielding device and method for a ground-based microwave radiometer, which solves the technical problem that the ground-based microwave radiometer cannot shield the surface soil radiation when measuring the forest canopy in the field.

[0007] (2) Technical solution

[0008] The first aspect of the present invention provides a soil radiation shielding device for a ground-based microwave radiometer, comprising a microwave radiometer, an automatic lifting platform, a shielding net and a terminal control console, wherein the microwave radiometer is placed on the upper end surface of the automatic lifting platform and erected above the forest canopy, the shielding net is laid on the soil below the forest canopy to be detected, the terminal control console is electrically connected to the microwave radiometer and is used to adjust the observation angle and azimuth of the microwave radiometer, and the terminal control console is electrically connected to the automatic lifting platform and is used to adjust the height of the automatic lifting platform.

[0009] Furthermore, the shielding mesh is a metal mesh with a mesh size of 1 to 10 mm.

[0010] Furthermore, the single layer thickness of the shielding mesh is 1 to 2 mm.

[0011] Furthermore, the shielding net is made of stainless steel.

[0012] Furthermore, the observation frequency of the microwave radiometer is 1.4 GHz, the wavelength is 21 cm, the field of view angle of the antenna is 10° to 15°, and the observation angle is 45° to 55°.

[0013] Furthermore, the maximum lifting height of the automatic lifting platform is 10m.

[0014] Furthermore, the automatic lifting platform includes a base, a lifting mechanism and a platform, one end of the lifting mechanism is hinged to the platform, the other end of the lifting mechanism is hinged to the base, and the microwave radiometer is installed on the platform.

[0015] Furthermore, a plurality of rollers are installed on the lower end surface of the base.

[0016] A second aspect of the present invention provides a shielding method using the soil radiation shielding device for a ground-based microwave radiometer, comprising the following steps:

[0017] The microwave radiometer is fixedly installed on the automatic lifting platform;

[0018] Respectively connecting the microwave radiometer, the automatic lifting platform and the terminal control console;

[0019] The microwave radiometer is used to observe the black body and liquid nitrogen respectively, obtain the brightness temperature of the cold end and the brightness temperature of the hot end, and establish an equation group through the voltage values ​​of the cold end and the hot end and the radiation brightness temperature of the two ends to solve the calibration coefficient;

[0020] Starting the automatic lifting platform, and controlling the automatic lifting platform to rise to a set height through the terminal console, and adjusting the antenna incident angle and antenna azimuth of the microwave radiometer;

[0021] The horn antenna is directed downward to measure the radiation energy of the surface soil, the brightness temperature value is calculated by the calibration coefficient and the voltage value, and the first observation data is recorded;

[0022] A shielding net is laid in the same ground range to cover the surface soil, the horn antenna is pointed downward to measure the same ground range, and the second observation data is recorded;

[0023] By comparing the first observation data and the second observation data, determining the effect of shielding soil radiation;

[0024] According to the judgment result, the azimuth angle of the microwave radiometer is adjusted to observe the forest canopy;

[0025] The radiation brightness temperature of the canopy is obtained according to the radiation transfer equation, and the microwave emissivity of the canopy is obtained according to the physical temperature of the trunk.

[0026] Furthermore, after obtaining the microwave emissivity of the canopy according to the physical temperature of the tree trunk, the method further includes:

[0027] After the field measurement is completed, the measurement data is saved, and the microwave radiometer and the automatic lifting platform are controlled to reset through the terminal console.

[0028] (3) Beneficial effects

[0029] In summary, the present invention ensures the water vapor interaction between the soil and the atmosphere through the shielding net, avoids the uncertainty of radiation brightness temperature measurement caused by the device, can effectively shield the soil microwave radiation from the surface, and improves the accuracy of radiation transmission parameters of the target medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a schematic diagram of the structure of a soil radiation shielding device for a ground-based microwave radiometer provided by an embodiment of the present invention;

[0032] Figure 2 It is a flow chart of a soil radiation shielding method for a ground-based microwave radiometer provided in an embodiment of the present invention.

[0033] In the figure:

[0034] 1-microwave radiometer; 201-base; 202-lifting mechanism; 203-platform; 204-roller; 3-shielding net; 4-terminal console. DETAILED DESCRIPTION

[0035] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments, and covers any modification, replacement and improvement of parts, components and connection modes without departing from the spirit of the present invention.

[0036] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the present invention are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0038] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting" and "installation" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] Figure 1 is a schematic structural diagram of a soil radiation shielding device for a ground-based microwave radiometer provided by an embodiment of the present invention, such as Figure 1 As shown, the device may include a microwave radiometer 1, an automatic lifting platform, a shielding net 3 and a terminal control console 4. The microwave radiometer 1 is placed on the upper end surface of the automatic lifting platform and erected above the forest canopy. The shielding net 3 is laid on the soil below the forest canopy to be detected. The terminal control console 4 is electrically connected to the microwave radiometer 1 and is used to adjust the observation angle and azimuth of the microwave radiometer 1. The terminal control console 4 is electrically connected to the automatic lifting platform and is used to adjust the height of the automatic lifting platform.

[0040] Specifically, when measuring in the field, the ground-based microwave radiometer is usually set up above the forest canopy, and then the radiometer horn antenna is observed downward. The radiation energy entering the horn antenna mainly comes from three parts: ① the brightness temperature of the forest canopy itself, ② the energy of soil radiation reflected by the forest canopy, and ③ the radiation of soil radiation passing through the forest canopy. In order to accurately obtain the brightness temperature of the forest canopy itself, methods must be taken to shield the microwave radiation from the soil.

[0041] This shielding device not only meets the needs of large-scale ground-based microwave remote sensing experiments in the field, but can also be installed in the laboratory for controlled experiments. It is not only suitable for shielding soil radiation, but also can shield the radiation brightness temperature of other media such as snow and forest canopy.

[0042] The ground-based microwave radiometer 1 includes a receiver and a horn antenna, with a total weight of 22 kg. The automatic lifting platform 2 is driven by a lifting mechanism with a built-in battery to automatically lift, and the safe lifting weight does not exceed 200 kg.

[0043] The shielding device ensures the water vapor interaction between the soil and the atmosphere through the shielding net 3, avoids the uncertainty of radiation brightness temperature measurement caused by the shielding device, can effectively shield the soil microwave radiation from the surface, and improves the accuracy of radiation transmission parameters of the target medium.

[0044] As an optional implementation, the shielding net 3 is a metal net with a mesh aperture of 1 to 10 mm. A metal net with a mesh aperture of 1.2 mm is cleverly designed as a shielding device. Its mesh aperture should be much lower than the L-band wavelength, ensuring the water vapor interaction between the soil and the atmosphere, while also shielding the L-band soil microwave radiation. Tests have found that it has a good shielding effect.

[0045] As an optional embodiment, the single layer thickness of the shielding net 3 is 1-2 mm, and the shielding net 3 is made of stainless steel. The metal net is thin and tough, with a thickness of about 1 mm and a weight of about 3 kg. It can be directly rolled up through the crossbar, so the whole device is light and easy to install.

[0046] As an optional implementation, the observation frequency of the microwave radiometer 1 is 1.4 GHz, the wavelength is 21 cm, the field of view of the antenna is 10° to 15°, and the observation angle is 45° to 55°. The field of view of the antenna is related to the performance of the sensor, usually 10° to 15°, and the observation angle can be consistent with the satellite incident angle and can be set to 45° to 55°.

[0047] As an optional implementation, Figure 1 As shown, the automatic lifting platform includes a base 201 , a lifting mechanism 202 and a platform 203 , one end of the lifting mechanism 202 is hinged to the platform 203 , the other end of the lifting mechanism 202 is hinged to the base 201 , and the microwave radiometer 1 is installed on the platform 203 .

[0048] Specifically, the automatic lifting platform has a built-in battery to drive the lifting mechanism to perform automatic lifting, the safe lifting weight does not exceed 200kg, and the maximum lifting height is 10m. The battery assembly has a built-in large-capacity rechargeable lithium battery, which is installed on the base 201 to power the receiver of the microwave radiometer 1, the automatic lifting platform and the terminal console 4, and also acts as a counterweight to stabilize the support base.

[0049] As an optional implementation, a plurality of rollers 204 are installed on the lower end surface of the base 201 .

[0050] Figure 2 FIG. 1 is a flow chart of a soil radiation shielding method for a ground-based microwave radiometer provided by an embodiment of the present invention. Figure 2 As shown, the method may include the following steps:

[0051] S101. Fix the microwave radiometer on the automatic lifting platform.

[0052] Specifically: move the lifting platform vehicle to a flat and hard open ground, spread out the four corner legs to ensure that the lifting platform is solid and stable. Fix the tripod on the lifting platform, and then fix the microwave radiometer receiver and horn antenna on the tripod.

[0053] S102, respectively connect the microwave radiometer, the automatic lifting platform and the terminal control console.

[0054] Specifically, the microwave radiometer receiver and the horn antenna are connected by wires, the microwave radiometer receiver and the terminal console (which can be a computer terminal) are connected by wires, and the elevator and the terminal console are connected by wires. The microwave radiometer, elevator and computer terminal are uniformly powered by the distribution box (battery) under the lifting platform.

[0055] S103, using a microwave radiometer to observe the black body and liquid nitrogen respectively, obtain the brightness temperature of the cold end and the brightness temperature of the hot end, and establish an equation group through the voltage values ​​of the cold end and the hot end and the radiation brightness temperature of the two ends to solve the calibration coefficient;

[0056] S104, start the automatic lifting platform, and control the automatic lifting platform to rise to a set height through the terminal console, and adjust the antenna incident angle and antenna azimuth of the microwave radiometer.

[0057] Specifically: Carefully remove weeds on the ground, try to ensure the ground is flat and has a sufficient range (3m*5m), and do not damage the state of the surface soil. Start the power supply of the lifting platform distribution box, control the work platform to rise to a height of 8m through the computer terminal, and adjust the incident angle (47.5°) and azimuth (0°, observing the open space) of the microwave radiometer antenna through the computer terminal.

[0058] S105, measuring the radiation energy of the surface soil with the horn antenna pointing downward, calculating the brightness temperature value through the calibration coefficient and the voltage value, and recording the first observation data.

[0059] Specifically: the horn antenna is pointed downward to measure the radiation brightness temperature of the surface soil, and the observation data within 5 minutes is recorded on the computer terminal, and the average value is recorded. At the same time, a handheld infrared thermometer is used to measure the physical temperature of the soil.

[0060] S106. Lay a shielding net in the same ground range to cover the surface soil, measure the same ground range with the horn antenna facing downward, and record the second observation data.

[0061] Specifically: lay a 3m*5m metal mesh (single layer is sufficient) on the same ground area to cover the soil layer, observe the same ground area with the horn antenna facing downward for 5 minutes, and record the average value.

[0062] S107. Determine the effect of shielding soil radiation by comparing the first observation data and the second observation data.

[0063] S108. Based on the judgment result, adjust the azimuth angle of the microwave radiometer to observe the forest canopy.

[0064] Specifically, when the shielding effect is reliable, the azimuth angle of the microwave radiometer can be adjusted (90°, toward the vegetation) to observe the forest canopy, while a handheld infrared thermometer can be used to measure the physical temperature of the tree trunks.

[0065] S109. Obtain the radiation brightness temperature of the canopy according to the radiation transfer equation, and obtain the microwave emissivity of the canopy according to the physical temperature of the tree trunk.

[0066] Specifically, a metal mesh is laid under the forest canopy to shield the upward radiation of the soil layer. The radiation brightness temperature of the canopy can be obtained according to the radiation transfer equation. According to the physical temperature of the tree trunk, the microwave emissivity of the canopy can be calculated using the following formula (2).

[0067] According to the law of conservation of energy, the radiation brightness temperature Tb observed by the L-band ground-based microwave radiometer mainly includes three parts: the radiation of the forest canopy itself, the radiation of the soil passing through the forest canopy, and the radiation of the soil reflected by the forest canopy, which can be expressed as:

[0068] Tb=e canopy ·T canopy +γ canopy ·Tb soil +r canopy Tb soil (1)

[0069] Where e, γ and r represent the emissivity, transmittance and reflectivity of the forest canopy, respectively, and Tb canopy represents the physical temperature of the canopy, Tbsoil In order to accurately obtain the radiation brightness temperature of the forest canopy, the present invention proposes a method of shielding soil radiation, so formula (1) can be expressed as:

[0070] Tb=e canopy ·T can opy (2)

[0071] Where Tb represents the forest canopy radiation brightness temperature, which is measured by a radiometer. Therefore, as long as the physical temperature of the canopy is known, the emissivity of the canopy can be obtained.

[0072] As an optional implementation, after obtaining the microwave emissivity of the canopy according to the physical temperature of the tree trunk in step S109, the method further includes:

[0073] Step S110: After the field measurement is completed, the measurement data is saved, and the microwave radiometer and the automatic lifting platform are reset through the terminal console.

[0074] Specifically, the power supply of the distribution box is cut off, all wires are recovered, and then the microwave radiometer receiver, horn antenna and tripod on the workbench are disassembled. The four corner legs of the lifting platform are folded up and the lifting platform is towed away by a tractor. The metal mesh on the ground is rolled up by a handheld horizontal bar and placed in a wooden box to prevent damage. At this point, the installation and recovery of the soil radiation shielding device for the ground-based microwave radiometer are completed.

[0075] It should be clear that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. In addition, for the sake of brevity, a detailed description of known methods and technologies is omitted here.

[0076] The above are only embodiments of the present application and are not limited to the present application. For those skilled in the art, the present application may have various changes and variations without departing from the scope of the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A soil radiation shielding device for a ground-based microwave radiometer, characterized in that: The invention comprises a microwave radiometer (1), an automatic lifting platform, a shielding net (3) and a terminal control console (4); the microwave radiometer (1) is placed on the upper end surface of the automatic lifting platform and erected above the forest canopy; the shielding net (3) is laid on the soil below the forest canopy to be detected; the terminal control console (4) is electrically connected to the microwave radiometer (1) and is used to adjust the observation angle and azimuth of the microwave radiometer (1); and the terminal control console (4) is electrically connected to the automatic lifting platform and is used to adjust the height of the automatic lifting platform.

2. The soil radiation shielding device for a ground-based microwave radiometer according to claim 1, characterized in that: The shielding net (3) is a metal net, and its mesh diameter is 1 to 10 mm.

3. The soil radiation shielding device for the ground-based microwave radiometer according to claim 2, characterized in that: The single layer thickness of the shielding net (3) is 1 to 2 mm.

4. The soil radiation shielding device for a ground-based microwave radiometer according to claim 2, characterized in that: The shielding net (3) is made of stainless steel.

5. The soil radiation shielding device for ground-based microwave radiometer according to claim 1, characterized in that: The observation frequency of the microwave radiometer (1) is 1.4 GHz, the wavelength is 21 cm, the field of view angle of the antenna is 10° to 15°, and the observation angle is 45° to 55°.

6. The soil radiation shielding device for ground-based microwave radiometer according to claim 1, characterized in that: The maximum lifting height of the automatic lifting platform is 10m.

7. The soil radiation shielding device for ground-based microwave radiometer according to claim 1, characterized in that: The automatic lifting platform comprises a base (201), a lifting mechanism (202) and a platform (203); one end of the lifting mechanism (202) is hinged to the platform (203); the other end of the lifting mechanism (202) is hinged to the base (201); and the microwave radiometer (1) is installed on the platform (203).

8. The soil radiation shielding device for the ground-based microwave radiometer according to claim 7, characterized in that: A plurality of rollers (204) are mounted on the lower end surface of the base (201).

9. A shielding method using the soil radiation shielding device for a ground-based microwave radiometer according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: The microwave radiometer is fixedly installed on the automatic lifting platform; Respectively connecting the microwave radiometer, the automatic lifting platform and the terminal control console; The microwave radiometer is used to observe the black body and liquid nitrogen respectively, obtain the brightness temperature of the cold end and the brightness temperature of the hot end, and establish an equation group through the voltage values ​​of the cold end and the hot end and the radiation brightness temperature of the two ends to solve the calibration coefficient; Starting the automatic lifting platform, and controlling the automatic lifting platform to rise to a set height through the terminal console, and adjusting the antenna incident angle and antenna azimuth of the microwave radiometer; The horn antenna is directed downward to measure the radiation energy of the surface soil, the brightness temperature value is calculated by the calibration coefficient and the voltage value, and the first observation data is recorded; A shielding net is laid in the same ground range to cover the surface soil, the horn antenna is pointed downward to measure the same ground range, and the second observation data is recorded; By comparing the first observation data and the second observation data, determining the effect of shielding soil radiation; According to the judgment result, the azimuth angle of the microwave radiometer is adjusted to observe the forest canopy; The radiation brightness temperature of the canopy is obtained according to the radiation transfer equation, and the microwave emissivity of the canopy is obtained according to the physical temperature of the trunk.

10. The shielding method according to claim 9, characterized in that: After obtaining the microwave emissivity of the canopy according to the physical temperature of the tree trunk, the method further includes: After the field measurement is completed, the measurement data is saved, and the microwave radiometer and the automatic lifting platform are controlled to reset through the terminal console.

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