A method and device for calibrating radiation of synthetic aperture radar

Abstract

The invention provides a synthetic aperture radar radiation calibration method and device, and relates to the technical field of radar calibration. The method comprises the following steps: selecting a reference image corresponding to a synthetic aperture radar payload image to be calibrated; verifying whether the reference image satisfies a first imaging scene, and if the first imaging scene condition is satisfied, obtaining a verified reference image; registering the verified reference image with the synthetic aperture radar payload image to be calibrated; inverting the surface parameters according to the verified reference image, and obtaining the backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated; obtaining an absolute radiation calibration coefficient according to the backscattering coefficient, and completing the radiation calibration. The invention realizes an external calibration test process in which a reference device is omitted, expands the reference range of the distributed target standard, realizes the normalized monitoring of the calibration coefficient, and ensures the normalized monitoring of the calibration coefficient.

Description

Technical Field

[0001] The present invention relates to the field of radar calibration technology, and in particular to a synthetic aperture radar radiation calibration method and device. Background Art

[0002] Synthetic Aperture Radar (SAR) is widely used in important fields such as exploration, environmental monitoring, and soil and water monitoring. The unique imaging method of SAR technology enables it to ignore the influence of atmosphere and light compared with other sensors such as optical, infrared, and far infrared, thereby achieving all-weather, multi-angle ground photography and reconnaissance tasks. Therefore, with the help of the characteristics of SAR images, it is possible to overcome many interferences from terrain, light, and weather conditions. Even the mutual occlusion of trees on the ground can be alleviated to a certain extent, so it has a wide range of utilization value in many fields such as ground exploration. However, SAR data cannot directly obtain ground object parameters, and data conversion processing is required through radiation calibration.

[0003] SAR radiation calibration is an indispensable step in the quantitative acquisition of surface physical parameters (such as soil moisture and biomass). SAR radiation calibration establishes the relationship between the digital quantization value of SAR images and the backscatter coefficient value of ground objects, which is of great significance for the quantitative extraction and accurate interpretation of ground object target characteristics and electromagnetic information contained in SAR data. SAR radiation calibration is an important front-end processing of observing the physical characteristics of the target and the processing of end-to-end system performance. At the same time, it establishes the accurate relationship between the image and the backscatter coefficient of the ground object. The absolute radiation calibration coefficient is the key parameter that links the pixel grayscale value of the synthetic aperture radar image with the actual backscatter area or coefficient of the target. The accurate solution of this parameter is an important step in the calibration of synthetic aperture radar.

[0004] See also Figure 1 As shown in the figure, the existing SAR absolute radiation calibration methods are generally through single-point stable point targets with known true backscattering area values ​​(artificial calibrators deployed in a limited number of calibration fields) or uniform tropical rainforest targets whose backscattering coefficients do not change with the radar incident angle. These methods are largely limited by the satellite revisit cycle and have great deficiencies in the timeliness of calibration; absolute radiation calibration through the point target method requires the deployment of a large number of artificial calibrators. The development, transportation, installation, long-term field operation and maintenance of artificial calibrators consume a lot of manpower and material resources and have a long revisit cycle; the method of calibration through uniform tropical rainforests is limited by the limited number of natural tropical rainforest scenes and geographical space limitations, and can only be calibrated once in a while. These factors greatly limit the timeliness of calibration.

[0005] Therefore, the need for a SAR calibration that can reduce the manpower and material resources consumed in the experimental process while ensuring timeliness is an important issue that needs to be urgently addressed in the industry. Summary of the invention

[0006] The present invention provides a synthetic aperture radar radiation calibration method and device, which are used to solve the defects of the prior art that the calibration process consumes a lot of manpower and material resources and the timeliness cannot be guaranteed, realizes the external calibration test process that omits the placement of reference equipment, expands the reference range of distributed target standards, realizes the normalized monitoring of calibration coefficients, and ensures the normalized monitoring of calibration coefficients.

[0007] The present invention provides a synthetic aperture radar radiation calibration method, comprising the following steps:

[0008] Selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold;

[0009] Verifying whether the reference image satisfies a first imaging scene condition, and obtaining a verified reference image if the first imaging scene condition is satisfied;

[0010] The verified reference image is registered with the synthetic aperture radar payload image to be calibrated, and the geometric relationship and resolution of the verified reference image are converted to be consistent with those of the synthetic aperture radar payload image to be calibrated;

[0011] Inverting the surface parameters according to the verified reference image, and obtaining the backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated;

[0012] According to the backscattering coefficient, an absolute radiation calibration coefficient is obtained to complete the radiation calibration.

[0013] According to the synthetic aperture radar radiation calibration method provided by the present invention, verifying whether the reference image satisfies the first imaging scene condition, and if the first imaging scene condition is satisfied, obtaining the verified reference image; specifically comprising the following steps:

[0014] Acquire the surface root mean square height of the imaging scene of the reference image, and determine whether the imaging scene of the reference image meets the first imaging scene condition according to scene parameters; wherein the scene parameters include the radar carrier wave number, radar incident angle and incident frequency of the synthetic aperture radar used to generate the synthetic aperture radar payload image to be calibrated, and soil moisture content;

[0015] If the imaging scene of the reference image satisfies the first imaging scene condition, retaining the reference image to obtain the verified reference image;

[0016] If the imaging scene of the reference image does not meet the first imaging scene condition, the reference image is deleted and a new reference image is selected.

[0017] According to the synthetic aperture radar radiation calibration method provided by the present invention, the verified reference image is registered with the synthetic aperture radar payload image to be calibrated, and the geometric relationship and resolution of the verified reference image are converted to be consistent with the synthetic aperture radar payload image to be calibrated, which specifically includes the following steps:

[0018] Taking the synthetic aperture radar payload image to be calibrated as the reference image;

[0019] Using the corners and other points in the reference image as control points, a first translation registration is performed on the pixel positions corresponding to the synthetic aperture radar payload image to be calibrated and the verified reference image;

[0020] The pixel positions corresponding to the synthetic aperture radar payload image to be calibrated after the first registration and the verified reference image are subjected to a second translation registration through a maximum correlation function method, and the geometric relationship and resolution of the verified reference image are converted to be consistent with those of the synthetic aperture radar payload image to be calibrated.

[0021] According to the synthetic aperture radar radiation calibration method provided by the present invention, surface parameters are inverted according to the verified reference image, and the backscatter coefficient of the synthetic aperture radar payload image to be calibrated is obtained according to the surface parameters and the synthetic aperture radar payload image to be calibrated, which specifically includes the following steps:

[0022] According to the grid length of the synthetic aperture radar payload image to be calibrated, the verified reference image and the synthetic aperture radar payload image to be calibrated are grid-divided, and the verified reference image and the synthetic aperture radar payload image to be calibrated are both divided into grids with a side length of l×l; wherein l is the correlation length;

[0023] According to the divided verified reference image, a backscatter coefficient of the verified reference image is obtained; wherein the backscatter coefficient of the verified reference image includes a backscatter coefficient of the verified reference image in a horizontal transmission and horizontal reception polarization direction and a backscatter coefficient of the verified reference image in a vertical transmission and vertical reception polarization direction;

[0024] Inverting the surface parameters according to the backscatter coefficient of the verified reference image; wherein the surface parameters include the real part of the surface dielectric constant and the surface root mean square height;

[0025] According to the surface parameters and the self-attitude data of the synthetic aperture radar payload image to be calibrated, the backscattering coefficient of the synthetic aperture radar payload image to be calibrated is obtained; wherein the self-attitude data includes the incident angle and the wave number, and the backscattering coefficient of the synthetic aperture radar payload image to be calibrated includes the backscattering coefficient of the synthetic aperture radar payload image to be calibrated in the horizontal transmission and horizontal reception polarization direction and the backscattering coefficient of the synthetic aperture radar payload image to be calibrated in the vertical transmission and vertical reception polarization direction.

[0026] According to the synthetic aperture radar radiation calibration method provided by the present invention, an absolute radiation calibration coefficient is obtained according to the backscatter coefficient to complete the radiation calibration, which specifically includes the following steps:

[0027] According to the backscattering coefficient of the synthetic aperture radar payload image to be calibrated, and taking the grid as the unit, the absolute radiation calibration coefficient of each grid of the synthetic aperture radar payload image to be calibrated is obtained;

[0028] The average of the absolute radiation calibration coefficients of all grids is taken to obtain the absolute radiation calibration coefficient of the synthetic aperture radar payload image to be calibrated, and the radiation calibration is completed.

[0029] According to the synthetic aperture radar radiation calibration method provided by the present invention, it is verified whether the reference image satisfies the first imaging scene condition, and if the first imaging scene condition is satisfied, a verified reference image is obtained; the method further includes the following steps:

[0030] The synthetic aperture radar payload image to be calibrated and the reference image are preprocessed.

[0031] According to the synthetic aperture radar radiation calibration method provided by the present invention, the synthetic aperture radar payload image to be calibrated and the reference image are preprocessed, specifically comprising the following steps:

[0032] Determine a target scene area, select data of a synthetic aperture radar payload image to be calibrated and a reference image located in the target scene area, and obtain a cropped data set;

[0033] Performing orbit correction on the cropped data set to obtain a first corrected data set;

[0034] performing speckle filtering on the first corrected data set to obtain a filtered data set;

[0035] Relative radiation correction is performed on the filtered data set to obtain a second corrected data set, namely, the preprocessed synthetic aperture radar payload image to be calibrated and the reference image.

[0036] The present invention also provides a synthetic aperture radar radiation calibration device, comprising the following steps:

[0037] A reference image selection module, used for selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein the spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selection threshold;

[0038] A uniform bare ground verification module is used to verify whether the reference image satisfies a first imaging scene condition, and if the first imaging scene condition is satisfied, a verified reference image is obtained;

[0039] A registration module is used to register the verified reference image with the synthetic aperture radar payload image to be calibrated, and convert the geometric relationship and resolution of the verified reference image to be consistent with the synthetic aperture radar payload image to be calibrated;

[0040] A backscatter coefficient acquisition module is used to invert the surface parameters according to the verified reference image, and obtain the backscatter coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated;

[0041] The radiation calibration module is used to obtain an absolute radiation calibration coefficient according to the backscatter coefficient to complete radiation calibration.

[0042] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of any one of the synthetic aperture radar radiation calibration methods described above are implemented.

[0043] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of any one of the synthetic aperture radar radiation calibration methods described above are implemented.

[0044] The synthetic aperture radar radiation calibration method and device provided by the present invention are an absolute radiation calibration method and device for SAR real data under realistic conditions. Different from the traditional absolute radiation calibration method, the image data after the calibration of the calibrated satellite-borne or airborne payload correction is used as the reference data of the radar cross section (RCS) to solve the absolute radiation calibration coefficient of the synthetic aperture radar payload image to be calibrated, and verify whether the reference image meets the first imaging scene, so as to obtain the verified reference image, which can effectively screen the reference area and reduce the influence on the subsequent radiation calibration caused by the data not meeting the bare ground requirement. By aligning the reference image with the synthetic aperture radar payload image to be calibrated, the geometric relationship and resolution of the verified reference image are converted to be consistent with those of the synthetic aperture radar payload image to be calibrated, and the synthetic aperture radar payload image to be calibrated is used as the reference image during the alignment, and the reference image is aligned so that the alignment accuracy reaches To the pixel level, the matching between images is more accurate, and the traditional absolute radiation calibration method is avoided through inversion, so that the acquired backscattering parameters are more accurate and reliable. Then, a more accurate and reliable absolute radiation calibration coefficient is obtained according to the acquired backscattering parameters. The required backscattering coefficient is calculated on the basis of inversion, which omits the external calibration test process of placing reference equipment, expands the reference range of distributed target standards, and realizes the normalized monitoring of the calibration coefficient. At the same time, it can reduce the manpower and material resources consumed in the experiment process, reduce the time spent on the layout of a single external calibration experiment equipment, and realize multiple calibrations in a short time to ensure the normalized monitoring of the calibration coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 It is a flow chart of a synthetic aperture radar radiation calibration method in the prior art;

[0047] Figure 2 This is one of the flow charts of the synthetic aperture radar radiation calibration method provided by the present invention;

[0048] Figure 3 It is a specific flow chart of step S200 in the synthetic aperture radar radiation calibration method provided by the present invention;

[0049] Figure 4 It is a specific flow chart of step S300 in the synthetic aperture radar radiation calibration method provided by the present invention;

[0050] Figure 5 It is a specific flow chart of step S400 in the synthetic aperture radar radiation calibration method provided by the present invention;

[0051] Figure 6 It is a specific flow chart of step S500 in the synthetic aperture radar radiation calibration method provided by the present invention;

[0052] Figure 7 This is the second flow chart of the synthetic aperture radar radiation calibration method provided by the present invention;

[0053] Figure 8 It is a specific flow chart of step A200 in the synthetic aperture radar radiation calibration method provided by the present invention;

[0054] Fig. 9 It is a logical schematic diagram of the synthetic aperture radar radiation calibration method provided by the present invention;

[0055] Fig.10 This is one of the structural schematic diagrams of the synthetic aperture radar radiation calibration device provided by the present invention;

[0056] Fig.11 It is a specific structural schematic diagram of a uniform bare ground calibration module in the synthetic aperture radar radiation calibration device provided by the present invention;

[0057] Fig.12 It is a specific structural schematic diagram of the registration module in the synthetic aperture radar radiation calibration device provided by the present invention;

[0058] Fig.13 It is a specific structural schematic diagram of a backscatter coefficient acquisition module in the synthetic aperture radar radiation calibration device provided by the present invention;

[0059] Fig.14 It is a specific structural schematic diagram of a radiation calibration module in the synthetic aperture radar radiation calibration device provided by the present invention;

[0060] Fig.15 This is the second structural schematic diagram of the synthetic aperture radar radiation calibration device provided by the present invention;

[0061] Fig.16 It is a specific structural schematic diagram of a preprocessing module in the synthetic aperture radar radiation calibration device provided by the present invention;

[0062] Fig.17 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Combine the following Figure 2 and Fig. 9 The synthetic aperture radar radiation calibration method of the present invention is described, and the method comprises the following steps:

[0065] S100, selecting a reference image corresponding to the SAR payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the SAR payload image is within a first selected threshold.

[0066] In step S100, the purpose is to select high-precision SAR payload images with similar spatial resolution, illuminating the same imaging scene, and with similar transit time as the SAR payload images to be calibrated as reference images. This set of reference images and the SAR payload images to be calibrated need to be calibrated to the backscatter coefficient.

[0067] In an optional scheme, the reference image is a Radarsat-2 satellite image. Radarsat-2 is a C-band satellite and has a variety of polarization modes to choose from. The resolution of this satellite data can reach up to 1m, and the calibration accuracy is relatively high, which meets the experimental requirements of the present invention. The synthetic aperture radar radiation calibration method of the present invention uses the full polarization data of a uniform and rough bare earth target that is illuminated by the Radarsat-2 satellite and overlaps with the satellite of the SAR payload image to be calibrated. The selected Radarsat-2 image and the SAR payload image to be calibrated have similar spatial resolutions, illuminate the same scene, and have similar transit times.

[0068] It should be noted that, preferably, the reference image is image data that has been calibrated and corrected by satellite-borne or airborne payloads.

[0069] In this embodiment, the first selected threshold value ranges from 0.5 to 2, that is, the spatial resolution ratio of the reference image and the SAR payload image to be calibrated is between 0.5 and 2 times.

[0070] S200, verifying whether the reference image satisfies a first imaging scene condition, and obtaining a verified reference image if the first imaging scene condition is satisfied;

[0071] The synthetic aperture radar radiation calibration method of the present invention uses the Dubois formula to obtain various parameters. At the same time, the application conditions of the Dubois formula are: the product of the radar carrier wave number k and the surface root mean square height s ks <2.5, the radar incident angle θ≥30°, the incident frequency f is between 1.5-11GHz, and the soil moisture content m v The purpose of step S200 is to verify whether the imaging scene of the reference image, that is, the surface parameters of the selected uniform bare land area and the reference image wave number are within the application conditions of the Dubois formula, so as to determine whether the reference image can be used in subsequent steps.

[0072] S300, registering the verified reference image with the SAR payload image to be calibrated, and converting the geometric relationship and resolution of the verified reference image to be consistent with those of the SAR payload image to be calibrated.

[0073] The purpose of step S300 is to make the horizontal and vertical coordinates of the pixel images of the reference image and the SAR payload image to be calibrated correspond one to one, so as to ensure that the image values ​​Ian of the reference image and the SAR payload image to be calibrated can be directly calculated and compared.

[0074] S400: Invert and obtain surface parameters according to the verified reference image, and obtain backscatter coefficients of the SAR payload image to be calibrated according to the surface parameters and the SAR payload image to be calibrated.

[0075] After the data preparation in step S100 , the uniform bare earth condition check in step S200 , and the image registration in step S300 , the formal calculation of the backscatter coefficient of the SAR payload image to be calibrated begins in step S400 .

[0076] S500: Obtain an absolute radiation calibration coefficient according to the backscattering coefficient, and complete radiation calibration.

[0077] The synthetic aperture radar radiation calibration method of the present invention is an absolute radiation calibration method for SAR real data under realistic conditions. Different from the traditional absolute radiation calibration method, the image data after the calibration of the calibrated satellite-borne or airborne payload is used as the reference data of RCS to solve the absolute radiation calibration coefficient of the SAR payload image to be calibrated, and verify whether the reference image meets the first imaging scene, and obtain the verified reference image, which can effectively screen the reference area and reduce the influence on the subsequent radiation calibration caused by the data not meeting the bare ground requirement. By aligning the reference image with the SAR payload image to be calibrated, the geometric relationship and resolution of the verified reference image are converted to be consistent with the SAR payload image to be calibrated, and the SAR payload image to be calibrated is converted to be consistent with the SAR payload image to be calibrated. Then, it is used as the benchmark image for registration, and the reference image is registered to achieve the registration accuracy at the pixel level, making the matching between images more precise. The traditional absolute radiation calibration method is avoided through inversion, so that the acquired backscattering parameters are more accurate and reliable. Then, a more accurate and reliable absolute radiation calibration coefficient is obtained according to the acquired backscattering parameters, and the required backscattering coefficient is calculated based on the inversion. The external calibration test process of placing reference equipment is omitted, and the reference range of distributed target standards is expanded. The normalized monitoring of the calibration coefficient can be achieved, and at the same time, the manpower and material resources consumed in the experiment process can be reduced, and the time consumed in the layout of a single external calibration experiment equipment can be reduced. Multiple calibrations can be achieved in a short time to ensure the normalized monitoring of the calibration coefficient.

[0078] Combine the following Figure 3 The synthetic aperture radar radiation calibration method of the present invention is described, and step S200 specifically includes the following steps:

[0079] S210. Obtain the surface root mean square height of the imaging scene of the reference image, and determine whether the imaging scene of the reference image satisfies a first imaging scene condition based on scene parameters; wherein the scene parameters include the radar carrier wave number, radar incident angle and incident frequency of the SAR used to generate the SAR payload image to be calibrated, and soil moisture content.

[0080] In step S210, the surface parameters of the reference load image imaging scene are estimated to verify whether the imaging area meets the application conditions of the Dubois formula. Specifically, the OH bare soil empirical model is used to verify whether the imaging area meets the application conditions of the Dubois formula, and the surface root mean square height s is estimated by the OH empirical model, wherein the OH empirical model expression is shown in formula (1), which is:

[0081] σ vh =0.11m v 0.7 (cosθ) 2.2 [1-exp(-0.32(ks)) 1.8 ] (1)

[0082] Therefore, the surface root mean square height S can be derived through the OH empirical model. The calculation formula is shown in formula (2). Formula (2) is:

[0083]

[0084] Among them, σ vh is the backscatter coefficient of the reference image in the vertical transmission and horizontal reception polarization directions, m v is the soil moisture content of the imaging scene, and θ is the incident angle of the reference image on the uniform rough bare soil target, that is, the radar incident angle. In this embodiment, for the soil moisture content m of the imaging scene v It is obtained by querying the Harmonized World Soil Database (HWSD) and the Soil Information System (SIS).

[0085] S220: If the imaging scene of the reference image satisfies the first imaging scene condition, retain the reference image to obtain the verified reference image;

[0086] S230: If the imaging scene of the reference image does not satisfy the first imaging scene condition, delete the reference image, and reselect a reference image, that is, execute step S100 and subsequent steps again.

[0087] If ks is calculated to be less than 2.5, the soil moisture content m v If the value is less than 35%, it is regarded as a valid uniform rough bare ground target, otherwise, the process returns to step S100 to reselect the reference image.

[0088] It should be noted that the root mean square height calculated for the uniform rough bare land selected by the synthetic aperture radar radiation calibration method of the present invention is in the centimeter level, the moisture content of the selected uniform rough bare soil target is about 15%, and all parameters meet the application conditions of the Dubois formula.

[0089] Combine the following Figure 4 The synthetic aperture radar radiation calibration method of the present invention is described, and step S300 specifically includes the following steps:

[0090] S310: First, the SAR payload image to be calibrated is used as a reference image.

[0091] S320, using the corners and other points in the reference image as control points, and performing a first translation registration on the pixel positions corresponding to the SAR payload image to be calibrated and the verified reference image. The first translation registration is a subjective registration of the verified reference image and the SAR payload image to be calibrated.

[0092] S330, the pixel positions corresponding to the SAR payload image to be calibrated after the first registration and the reference image after verification are translated and registered for the second time through the maximum correlation function method, and the geometric relationship and resolution of the verified reference image are converted to be consistent with the SAR payload image to be calibrated. For example, after processing in step S200, the size of the SAR payload image to be calibrated is 100×100. In step S320, the corners and other points in the SAR payload image to be calibrated are used as control points to subjectively reduce the size of the reference image. The size of the verified reference image is adjusted to 110×110, and a size of 10×10 is reserved as a pre-selected box for the maximum correlation function registration in the subsequent step S330.

[0093] Step S330 uses the maximum correlation function method to perform formal image registration. The correlation function method is a basic method for image registration and the basis of many matching algorithms. The maximum correlation function method calculates the correlation coefficient R between two images at different orientations and distance offsets. At the same time, in this embodiment, the image position when R is maximized is used for image cropping. The expression of the maximum correlation function method is shown in formula (3), which is:

[0094]

[0095] Among them, u' is the frequency shift in the range direction, and v' is the offset in the azimuth direction. The amplitudes of the SAR payload image to be calibrated and the reference image after verification are M1(i, j) and M2(i, j) respectively. Select u' and v' that maximize R as the registration result to complete the pixel-level registration between the verified reference image and the SAR payload image to be calibrated.

[0096] After being processed in step S300 , the verified reference image data is also cropped to a size of 100×100.

[0097] Combine the following Figure 5 The synthetic aperture radar radiation calibration method of the present invention is described, and step S400 specifically includes the following steps:

[0098] S410, gridding the reference image and the verified SAR payload image according to the grid length of the verified SAR payload image, dividing both the reference image and the verified SAR payload image into grids with a side length of l×l; l is the correlation length.

[0099] In step S410, in order to reduce the errors caused by uneven surface, poor registration effect, incident angle influence, and system parameter influence, it is necessary to grid the verified reference image and the SAR payload image to be calibrated. The grid length is determined according to the SAR payload image to be calibrated. First, the range mean of the selected bare ground area is calculated, and the spatial correlation function of the discrete point target is calculated using the range mean. The calculation formula of the spatial correlation function is shown in formula (4). Formula (4) is:

[0100]

[0101] Among them, z i is the mean backscatter coefficient value of the pixels in the i-th column, N is the number of columns of the image, and the maximum integer value when ρ(l)≤1 / e is taken as the statistical correlation length between the backscatter coefficient values ​​of the image pixels. The reference image and the verified SAR payload image are divided into grids with a side length of l×l.

[0102] For example, after calculation, the correlation length l is 10, so the image is divided into grids with a side length of 10 × 10. The backscatter coefficient values ​​under various polarization modes in the grid are averaged, and the selected verified reference image and the SAR payload image data to be calibrated are compressed to a size of 10 × 10.

[0103] S420. Obtain a backscatter coefficient of the reference image according to the divided reference image; wherein the backscatter coefficient of the reference image includes a backscatter coefficient of the reference image in a horizontal transmission and horizontal reception polarization direction and a backscatter coefficient of the reference image in a vertical transmission and vertical reception polarization direction.

[0104] In step S420, the backscatter coefficient values ​​under various polarization modes in the grid are averaged and used as the backscatter coefficient value used for inversion using the Dubois formula.

[0105] S430. Inverting surface parameters according to the backscattering coefficient of the reference image; wherein the surface parameters include the real part of the surface dielectric constant and the surface root mean square height.

[0106] In step S430, the Dubois formula is still used to inversely calculate the real part of the surface dielectric constant ε' and the surface root mean square height s. The specific calculation formulas are shown in formula (5) and formula (6). Formula (5) and formula (6) are respectively:

[0107]

[0108]

[0109] Among them, σ HH is the backscatter coefficient of the horizontal transmit and horizontal receive polarization direction of the verified reference image, σ VV is the backscatter coefficient of the verified reference image in the vertical transmission and vertical reception polarization directions. k is the carrier wave number of the verified reference image, expressed as k = 2π / λ. λ is the carrier wavelength, and θ0 represents the radar incident angle of the verified reference image.

[0110] In this embodiment, the real part ε' of the surface dielectric constant and the surface root mean square height s obtained by inversion can be subjected to a secondary test. The real part ε' of the surface dielectric constant is fitted and calculated using the Topp empirical model. The Topp empirical model expression is formula (7). Formula (7) is:

[0111] m v =-5.3×10 -2 +2.92×10 -2 ε'-5.5×10 -4 (ε') 2 +4.3×10 -6 (ε') 3 (7)

[0112] The real part of the surface dielectric constant ε' and the surface root mean square height s obtained by the inversion of the Dubois formula are compared with the real part of the surface dielectric constant ε' estimated by the Topp empirical formula and the surface root mean square height s calculated by the oh model (calculated by formula (1)). The accuracy of the surface parameters inverted by Dubois is determined again. If the accuracy error is large, the data set is reselected. In this embodiment, the error threshold is set to 10%. When the accuracy error exceeds 10%, the data set is reselected, that is, the reference image is reselected, and the corresponding steps are continued.

[0113] S440. Obtain a backscattering coefficient of the verified SAR payload image according to the surface parameters and the self-attitude data of the verified SAR payload image; wherein the self-attitude data includes an incident angle and a wave number, and the backscattering coefficient of the verified SAR payload image includes a backscattering coefficient of the verified SAR payload image in a horizontal transmission and horizontal reception polarization direction and a backscattering coefficient in a vertical transmission and vertical reception polarization direction.

[0114] In step S440, the real part of the surface dielectric constant ε', the surface root mean square height s, and the incident angle θ and wave number k of the attitude data of the payload image to be calibrated obtained by the inversion of the Dubois formula are substituted into the Dubois model for calculation. The backscatter coefficient of the SAR payload image to be calibrated is calculated. is the backscatter coefficient of the SAR payload image to be calibrated in the horizontal transmission and horizontal reception polarization directions, is the backscatter coefficient of the SAR payload image to be calibrated in the vertical transmission and vertical reception polarization directions. Specifically, the calculation formula of the Dubois model is shown in formula (8) and formula (9). Formula (8) and formula (9) are respectively:

[0115]

[0116]

[0117] Combine the following Figure 6 The synthetic aperture radar radiation calibration method of the present invention is described, and step S500 specifically includes the following steps:

[0118] S510, according to the backscatter coefficient of the SAR payload image to be calibrated, and in units of grids, in this embodiment, that is, in units of 10×10 grids, obtain the absolute radiation calibration coefficient of each grid of the AR payload image to be calibrated;

[0119] S520, taking the average of the absolute radiation calibration coefficients of all grids, obtaining the absolute radiation calibration coefficient of the SAR payload image to be calibrated, and completing the radiation calibration. The absolute radiation calibration coefficient calculation formula is shown in formula (10), which is:

[0120]

[0121] Where CF is the absolute radiation calibration factor, is the pixel brightness (digital number, DN) of the remote sensing image in the horizontal transmission and horizontal reception polarization directions of the SAR payload image to be calibrated, is the backscatter coefficient value in the horizontal transmission and horizontal reception polarization directions of the SAR payload image to be calibrated calculated by the Dubois formula.

[0122] Afterwards, the absolute radiation coefficient calculated in step S520 may be compared with the actual absolute radiation coefficient, and the error rate may be calculated to determine the accuracy of the synthetic aperture radar radiation calibration method of the present invention.

[0123] Combine the following Figure 7 The synthetic aperture radar radiation calibration method of the present invention is described. In another embodiment, the method includes the following steps:

[0124] A100. Select a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold.

[0125] A200, preprocess the SAR payload image to be calibrated and the reference image.

[0126] A300. Verify whether the reference image satisfies a first imaging scene condition. If the reference image satisfies the first imaging scene condition, obtain a verified reference image.

[0127] A400, registering the verified reference image with the synthetic aperture radar payload image to be calibrated, and converting the geometric relationship and resolution of the verified reference image to be consistent with those of the synthetic aperture radar payload image to be calibrated.

[0128] A500. Invert and obtain surface parameters according to the verified reference image, and obtain backscatter coefficients of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated.

[0129] A600. Obtain an absolute radiation calibration coefficient according to the backscattering coefficient, and complete radiation calibration.

[0130] Different from the previous embodiment, in this embodiment, step A200 is added between step A100 and step A300. The purpose of step A200 is to perform a series of processing procedures on the image to improve the accuracy of satellite orbit status information, reduce system noise, and eliminate systematic errors caused by external factors.

[0131] Combine the following Figure 8 The synthetic aperture radar radiation calibration method of the present invention is described, and step A200 specifically includes the following steps:

[0132] A210, determining a target scene area, selecting the SAR payload image to be calibrated and the data of the reference image located in the target scene area, and obtaining a cropped data set.

[0133] In step A210, since different SAR satellite images have different widths and different uniform rough bare soil areas, it is necessary to roughly crop the reference image and the SAR payload image to be calibrated, and crop the data in the target scene area to make a cropped data set.

[0134] For example, the size of the reference image after cropping is 200×200, and the size of the SAR payload image to be calibrated is 100×100. The reference image captures a larger area in order to reserve a certain range for subsequent image registration.

[0135] A220. Perform orbit correction on the cropped data set to obtain a first corrected data set.

[0136] The purpose of step A220 is that the satellite orbit state information in the original satellite data file is not accurate, and subsequent image registration and other processes require accurate orbit information data, so it is necessary to perform the first correction processing on the cropped data set through the orbit.

[0137] A230. Perform speckle filtering on the first correction data set to obtain a filtered data set.

[0138] Coherent speckle noise is a type of system noise. Coherent speckle can reduce the image signal-to-noise ratio, blur the image, or even make the image features disappear. Coherent speckle is an inherent defect of polarimetric SAR. Coherent speckle exists in any polarization mode, so it is necessary to filter the coherent speckle in step A230.

[0139] A240, performing relative radiation correction on the filtered data set, in particular, performing relative radiation correction on the SAR payload image to be calibrated, and after processing from step A210 to step A240, obtaining a second correction data set, i.e., the preprocessed SAR payload image to be calibrated and the reference image.

[0140] Step A240 performs relative radiation correction on the SAR payload image to be calibrated to eliminate the systematic and random radiation distortion or distortion generated by the system during data acquisition and transmission due to external factors. In this embodiment, the relative radiation correction method includes but is not limited to a series of processing procedures such as antenna pattern correction, distance correction, and in-device calibration. In step A240, the error of the satellite device itself is compensated by relative correction.

[0141] In the synthetic aperture radar radiation calibration method of the present invention, steps A210 to A240 perform a series of processing procedures such as orbit correction, coherent speckle filtering, antenna pattern correction, distance correction, and in-device calibration on the image through SNAP software to improve the accuracy of satellite orbit status information, reduce system noise, and eliminate systematic errors caused by external factors.

[0142] The synthetic aperture radar radiation calibration device provided by the present invention is described below. The synthetic aperture radar radiation calibration device described below and the synthetic aperture radar radiation calibration method described above can be referred to each other.

[0143] Combine the following Fig.10 The synthetic aperture radar radiation calibration device of the present invention is described, and the device comprises:

[0144] The reference image selection module 100 is used to select a reference image corresponding to the SAR payload image to be calibrated; wherein the spatial resolution ratio of the reference image to the SAR payload image is within a first selection threshold.

[0145] The uniform bare ground verification module 200 is used to verify whether the reference image satisfies the first imaging scene condition, and if the first imaging scene condition is satisfied, obtain the verified reference image;

[0146] The registration module 300 is used to register the verified reference image with the SAR payload image to be calibrated, and convert the geometric relationship and resolution of the verified reference image to be consistent with those of the SAR payload image to be calibrated.

[0147] The backscatter coefficient acquisition module 400 is used to invert the surface parameters according to the verified reference image, and obtain the backscatter coefficient of the SAR payload image to be calibrated according to the surface parameters and the SAR payload image to be calibrated.

[0148] The radiation calibration module 500 is used to obtain an absolute radiation calibration coefficient according to the backscatter coefficient to complete the radiation calibration.

[0149] Combine the following Fig.11 The synthetic aperture radar radiation calibration device of the present invention is described, and the uniform bare ground calibration module 200 specifically includes:

[0150] The first verification unit 210 is used to obtain the surface root mean square height of the imaging scene of the reference image, and determine whether the imaging scene of the reference image meets the first imaging scene condition based on scene parameters; wherein the scene parameters include the radar carrier wave number, radar incident angle and incident frequency of the SAR used to generate the SAR payload image to be calibrated, and soil moisture content.

[0151] In the first verification unit 210, surface parameters of the reference payload image imaging scene are estimated to verify whether the imaging area meets the application conditions of the Dubois formula.

[0152] A second verification unit 220, configured to retain the reference image to obtain the verified reference image if the imaging scene of the reference image satisfies the first imaging scene condition;

[0153] The third verification unit 230 is used to delete the reference image if the imaging scene of the reference image does not meet the first imaging scene condition, and reselect the reference image, that is, re-execute the reference image selection module 100 and subsequent steps.

[0154] Combine the following Fig.12 The synthetic aperture radar radiation calibration device of the present invention is described, and the registration module 300 specifically includes:

[0155] The first registration unit 310 is used to use the SAR payload image to be calibrated as a reference image.

[0156] The second registration unit 320 is used to use the corners and other points in the reference image as control points to perform a first translation registration on the pixel positions corresponding to the SAR payload image to be calibrated and the verified reference image.

[0157] The third registration unit 330 is used to perform a second translation registration on the pixel positions corresponding to the SAR payload image to be calibrated after the first registration and the verified reference image through the maximum correlation function method, and convert the geometric relationship and resolution of the verified reference image to be consistent with the SAR payload image to be calibrated.

[0158] Combine the following Fig.13 The synthetic aperture radar radiation calibration device of the present invention is described, and the backscatter coefficient acquisition module 400 specifically includes:

[0159] The first acquisition unit 410 is used to perform grid division on the reference image and the verified SAR payload image according to the grid length of the verified SAR payload image, and divide both the reference image and the verified SAR payload image into grids with a side length of l×l; l is the correlation length.

[0160] The second acquisition unit 420 is used to obtain the backscatter coefficient of the reference image according to the divided reference image; wherein the backscatter coefficient of the reference image includes the backscatter coefficient of the reference image in the horizontal transmission and horizontal reception polarization direction and the backscatter coefficient of the reference image in the vertical transmission and vertical reception polarization direction.

[0161] The second acquisition unit 420 uses the backscatter coefficient values ​​under various polarization modes in the grid to obtain an average value as the backscatter coefficient value used when the Dubois formula is inverted.

[0162] The third acquisition unit 430 is used to invert the surface parameters according to the backscatter coefficient of the reference image; wherein the surface parameters include the real part of the surface dielectric constant and the surface root mean square height.

[0163] The fourth acquisition unit 440 is used to obtain the backscattering coefficient of the verified SAR payload image according to the surface parameters and the self-attitude data of the verified SAR payload image; wherein the self-attitude data includes the incident angle and the wave number, and the backscattering coefficient of the verified SAR payload image includes the backscattering coefficient of the verified SAR payload image in the horizontal transmission and horizontal reception polarization direction and the backscattering coefficient in the vertical transmission and vertical reception polarization direction.

[0164] Combine the following Fig.14 The synthetic aperture radar radiation calibration device of the present invention is described, and the radiation calibration module 500 specifically includes:

[0165] The first calibration unit 510 is used to obtain the absolute radiation calibration coefficient of each grid of the AR payload image to be calibrated according to the backscatter coefficient of the SAR payload image to be calibrated and in units of grids, that is, in this embodiment, in units of 10×10 grids;

[0166] The second calibration unit 520 is used to take the average of the absolute radiation calibration coefficients of all grids to obtain the absolute radiation calibration coefficient of the SAR payload image to be calibrated, and complete the radiation calibration.

[0167] Combine the following Fig.15 The synthetic aperture radar radiation calibration device of the present invention is described. In another embodiment, different from the previous embodiment, a pre-processing module 600 is added between the reference image selection module 100 and the uniform bare ground verification module 200.

[0168] Combine the following Fig.16Describing the synthetic aperture radar radiation calibration device of the present invention, the preprocessing module 600 specifically includes:

[0169] The first processing unit 610 is used to determine the target scene area, select the SAR payload image to be calibrated and the data of the reference image located in the target scene area, and obtain a cropped data set.

[0170] The second processing unit 620 is used to perform orbit correction on the cropped data set to obtain a first corrected data set.

[0171] The purpose of the second processing unit 620 is that the satellite orbit state information in the original satellite data file is not accurate, and subsequent image registration and other processes require accurate orbit information data, so it is necessary to perform the first correction processing on the cropped data set through the orbit.

[0172] The third processing unit 630 is configured to perform speckle filtering on the first corrected data set to obtain a filtered data set.

[0173] The fourth processing unit 640 is used to perform relative radiation correction on the filtered data set, in particular, to perform relative radiation correction on the SAR payload image to be calibrated. After being processed by the first processing unit 610 to the fourth processing unit 640, a second correction data set, i.e., the preprocessed SAR payload image to be calibrated and the reference image, is obtained.

[0174] The fourth processing unit 640 performs relative radiation correction on the SAR payload image to be calibrated to eliminate systematic and random radiation distortion or aberration generated by the system during data acquisition and transmission due to external factors.

[0175] Fig.17 An example of a physical structure diagram of an electronic device is shown in FIG. Fig.17 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830 and a communication bus 840, wherein the processor 810, the communication interface 820 and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute the synthetic aperture radar radiation calibration method, and the synthetic aperture radar radiation calibration method includes:

[0176] S100, selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold;

[0177] S200, verifying whether the reference image satisfies a first imaging scene condition, and obtaining a verified reference image if the first imaging scene condition is satisfied;

[0178] S300, registering the verified reference image with the synthetic aperture radar payload image to be calibrated, and converting the geometric relationship and resolution of the verified reference image to be consistent with those of the synthetic aperture radar payload image to be calibrated;

[0179] S400, inverting to obtain surface parameters according to the verified reference image, and obtaining a backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated;

[0180] S500: Obtain an absolute radiation calibration coefficient according to the backscattering coefficient, and complete radiation calibration.

[0181] In addition, the logic instructions in the above-mentioned memory 830 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0182] On the other hand, the present invention further provides a computer program product, the computer program product comprising a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, when the program instructions are executed by a computer, the computer can execute the synthetic aperture radar radiation calibration method provided by the above methods, the synthetic aperture radar radiation calibration method comprising:

[0183] S100, selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold;

[0184] S200, verifying whether the reference image satisfies a first imaging scene condition, and obtaining a verified reference image if the first imaging scene condition is satisfied;

[0185] S300, registering the verified reference image with the synthetic aperture radar payload image to be calibrated, and converting the geometric relationship and resolution of the verified reference image to be consistent with those of the synthetic aperture radar payload image to be calibrated;

[0186] S400, inverting to obtain surface parameters according to the verified reference image, and obtaining a backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated;

[0187] S500: Obtain an absolute radiation calibration coefficient according to the backscattering coefficient, and complete radiation calibration.

[0188] In another aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the synthetic aperture radar radiation calibration method provided above, and the synthetic aperture radar radiation calibration method comprises:

[0189] S100, selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold;

[0190] S200, verifying whether the reference image satisfies a first imaging scene condition, and obtaining a verified reference image if the first imaging scene condition is satisfied;

[0191] S300, registering the verified reference image with the synthetic aperture radar payload image to be calibrated, and converting the geometric relationship and resolution of the verified reference image to be consistent with those of the synthetic aperture radar payload image to be calibrated;

[0192] S400, inverting to obtain surface parameters according to the verified reference image, and obtaining a backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated;

[0193] S500: Obtain an absolute radiation calibration coefficient according to the backscattering coefficient, and complete radiation calibration.

[0194] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0195] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A synthetic aperture radar radiation calibration method, characterized in that: The following steps are involved: Selecting a reference image corresponding to the synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selected threshold; Verify whether the reference image satisfies the first imaging scene, and if so, obtain a verified reference image; The verified reference image is registered with the synthetic aperture radar payload image to be calibrated, and the geometric relationship and resolution of the verified reference image are converted to be consistent with those of the synthetic aperture radar payload image to be calibrated; Inverting the surface parameters according to the verified reference image, and obtaining the backscattering coefficient of the synthetic aperture radar payload image to be calibrated according to the surface parameters and the synthetic aperture radar payload image to be calibrated; According to the backscattering coefficient, an absolute radiation calibration coefficient is obtained to complete radiation calibration; Verifying whether the reference image satisfies the first imaging scene, and if the first imaging scene condition is satisfied, obtaining a verified reference image; specifically comprising the following steps: Acquire the surface root mean square height of the imaging scene of the reference image, and determine whether the imaging scene of the reference image meets the first imaging scene condition according to scene parameters; wherein the scene parameters include the radar carrier wave number, radar incident angle and incident frequency of the synthetic aperture radar used to generate the synthetic aperture radar payload image to be calibrated, and soil moisture content; If the imaging scene of the reference image satisfies the first imaging scene condition, retaining the reference image to obtain the verified reference image; If the imaging scene of the reference image does not meet the first imaging scene condition, the reference image is deleted and a new reference image is selected.

2. The synthetic aperture radar radiation calibration method according to claim 1, characterized in that: The verified reference image is registered with the synthetic aperture radar payload image to be calibrated, and the geometric relationship and resolution of the verified reference image are converted to be consistent with the synthetic aperture radar payload image to be calibrated, specifically including the following steps: Taking the synthetic aperture radar payload image to be calibrated as the reference image; Using the corners and other points in the reference image as control points, a first translation registration is performed on the pixel positions corresponding to the synthetic aperture radar payload image to be calibrated and the verified reference image; The pixel positions corresponding to the synthetic aperture radar payload image to be calibrated and the verified reference image after the first translation and registration are subjected to a second translation and registration through a maximum correlation function method, and the geometric relationship and resolution of the verified reference image are converted to be consistent with those of the synthetic aperture radar payload image to be calibrated.

3. The synthetic aperture radar radiation calibration method according to claim 1, characterized in that: According to the verified reference image, the surface parameters are inverted, and according to the surface parameters and the synthetic aperture radar payload image to be calibrated, the backscatter coefficient of the synthetic aperture radar payload image to be calibrated is obtained, which specifically includes the following steps: According to the grid length of the synthetic aperture radar payload image to be calibrated, the verified reference image and the synthetic aperture radar payload image to be calibrated are grid-divided, and the verified reference image and the synthetic aperture radar payload image to be calibrated are both divided into grids with side lengths of l × l A grid; wherein the l is the correlation length; According to the divided verified reference image, a backscatter coefficient of the verified reference image is obtained; wherein the backscatter coefficient of the verified reference image includes a backscatter coefficient of the verified reference image in a horizontal transmission and horizontal reception polarization direction and a backscatter coefficient of the verified reference image in a vertical transmission and vertical reception polarization direction; Inverting the surface parameters according to the backscatter coefficient of the verified reference image; wherein the surface parameters include the real part of the surface dielectric constant and the surface root mean square height; According to the surface parameters and the self-attitude data of the synthetic aperture radar payload image to be calibrated, the backscattering coefficient of the synthetic aperture radar payload image to be calibrated is obtained; wherein the self-attitude data includes the incident angle and the wave number, and the backscattering coefficient of the synthetic aperture radar payload image to be calibrated includes the backscattering coefficient of the synthetic aperture radar payload image to be calibrated in the horizontal transmission and horizontal reception polarization direction and the backscattering coefficient of the synthetic aperture radar payload image to be calibrated in the vertical transmission and vertical reception polarization direction.

4. The synthetic aperture radar radiation calibration method according to claim 3, characterized in that: According to the backscattering coefficient, an absolute radiation calibration coefficient is obtained to complete the radiation calibration, which specifically includes the following steps: According to the backscattering coefficient of the synthetic aperture radar payload image to be calibrated, and taking the grid as the unit, the absolute radiation calibration coefficient of each grid of the synthetic aperture radar payload image to be calibrated is obtained; The average of the absolute radiation calibration coefficients of all grids is taken to obtain the absolute radiation calibration coefficient of the synthetic aperture radar payload image to be calibrated, and the radiation calibration is completed.

5. The synthetic aperture radar radiation calibration method according to claim 1, characterized in that: Verifying whether the reference image satisfies the first imaging scene, and if the first imaging scene condition is satisfied, obtaining a verified reference image; the above also includes the following steps: The synthetic aperture radar payload image to be calibrated and the reference image are preprocessed.

6. The synthetic aperture radar radiation calibration method according to claim 5, characterized in that: Preprocessing the synthetic aperture radar payload image to be calibrated and the reference image specifically includes the following steps: Determine a target scene area, select data of a synthetic aperture radar payload image to be calibrated and a reference image located in the target scene area, and obtain a cropped data set; Performing orbit correction on the cropped data set to obtain a first corrected data set; performing speckle filtering on the first corrected data set to obtain a filtered data set; Relative radiation correction is performed on the filtered data set to obtain a second corrected data set, namely, the preprocessed synthetic aperture radar payload image to be calibrated and the reference image.

7. A synthetic aperture radar radiation calibration device, characterized in that: The following steps are involved: A reference image selection module (100) is used to select a reference image corresponding to a synthetic aperture radar payload image to be calibrated; wherein a spatial resolution ratio between the reference image and the synthetic aperture radar payload image is within a first selection threshold; A uniform bare ground verification module (200) is used to verify whether the reference image satisfies a first imaging scene condition, and if the first imaging scene condition is satisfied, obtain a verified reference image; A registration module (300) is used to register the verified reference image with the synthetic aperture radar payload image to be calibrated, and convert the geometric relationship and resolution of the verified reference image to be consistent with the synthetic aperture radar payload image to be calibrated; A backscatter coefficient acquisition module (400) is used to invert and obtain surface parameters based on the verified reference image, and obtain the backscatter coefficient of the synthetic aperture radar payload image to be calibrated based on the surface parameters and the synthetic aperture radar payload image to be calibrated; A radiation calibration module (500), used to obtain an absolute radiation calibration coefficient according to the backscatter coefficient, and complete radiation calibration; Verifying whether the reference image satisfies the first imaging scene, and if the first imaging scene condition is satisfied, obtaining a verified reference image; specifically comprising the following steps: Acquire the surface root mean square height of the imaging scene of the reference image, and determine whether the imaging scene of the reference image meets the first imaging scene condition according to scene parameters; wherein the scene parameters include the radar carrier wave number, radar incident angle and incident frequency of the synthetic aperture radar used to generate the synthetic aperture radar payload image to be calibrated, and soil moisture content; If the imaging scene of the reference image satisfies the first imaging scene condition, retaining the reference image to obtain the verified reference image; If the imaging scene of the reference image does not meet the first imaging scene condition, the reference image is deleted and a new reference image is selected.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the synthetic aperture radar radiation calibration method according to any one of claims 1 to 6 are implemented.

9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the synthetic aperture radar radiation calibration method according to any one of claims 1 to 6 are implemented.

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