A method and system for grading preparation

Abstract

This invention discloses a method and system for de-flattening preprocessing, belonging to the field of radar imaging. The method includes: acquiring a main radar image and a secondary radar image, each containing several main image scattering points and several secondary image scattering points; calculating the secondary image scattering points corresponding to the main image scattering points to form several scattering point pairs; performing a flat-ground phase acquisition action to obtain an ideal flat-ground phase, thereby forming an ideal flat-ground phase map and completing the de-flattening preprocessing process. The flat-ground phase acquisition action includes: calculating the main image Doppler history and the secondary image Doppler history of the scattering point pairs; determining the main image focusing time that meets a preset time threshold to calculate the main image slant range, thereby determining the secondary image focusing time that meets the preset time threshold, and calculating the secondary image slant range based on the secondary image focusing time; and obtaining the ideal flat-ground phase of the scattering point pairs based on the main image slant range and the secondary image slant range. The de-flattening preprocessing method disclosed in this invention can effectively reduce the processing error of de-flattening preprocessing methods.

Description

Technical Field

[0001] This invention belongs to the field of radar imaging, and particularly relates to a method for preprocessing to remove flat terrain. Background Technology

[0002] Tomographic Synthetic Aperture Radar (TomoSAR) is an extension of traditional Synthetic Aperture Radar (SAR) technology, designed to solve the problem of lost elevation resolution in complex scenes. Traditional SAR can only achieve two-dimensional imaging in the azimuth and range directions. When complex terrains such as urban building complexes, mountains, and forests are projected onto a two-dimensional plane, scattering points at different heights overlap within the same pixel, resulting in overlay phenomena that lead to blurred images and difficulties in interpretation. TomoSAR forms a vertical synthetic aperture through multiple flights or multiple antenna arrays, observing the same scene from multiple angles. Then, it performs spectral analysis on the complex numerical sequence of each pixel to infer the distribution of scattering points along the height dimension, thus truly achieving three-dimensional imaging.

[0003] In the TomoSAR 3D reconstruction process, de-flattening phase is a crucial preprocessing step. Due to the geometric characteristics of radar side-looking imaging, a systematic phase term varying with the range direction is introduced into the echo signal. This phase term masks the true elevation signal of vertical structures such as building facades and roofs, leading to blurred interferometric fringes, reduced signal-to-noise ratio, and directly affecting the accuracy of building height extraction. Existing de-flattening methods are geometric methods based on digital elevation models (DEMs): using SAR imaging geometric parameters and a reference DEM to calculate a flat-ground phase compensation factor, thereby canceling it out pixel-by-pixel in the complex image. However, this approximation method has significant limitations under complex TomoSAR systems: firstly, low-order unfolding itself introduces inherent systematic errors, easily leading to uneven ground estimation; secondly, when the terrain is undulating, the vertical baseline is long, or the baseline distribution is uneven, it is difficult to accurately fit the flat-ground phase fringes, resulting in severe phase offset and defocusing phenomena. Therefore, existing TomoSAR-based de-flattening preprocessing methods suffer from significant processing errors. Summary of the Invention

[0004] The present invention aims to provide a method and system for pre-processing de-leveling to solve the above-mentioned technical problems and reduce the processing error of the de-leveling pre-processing method.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for pre-treatment of deflating land, comprising the following steps: Obtain a radar imaging main image and a radar imaging auxiliary image, wherein the radar imaging main image contains a number of main image scattering points and the radar imaging auxiliary image contains a number of auxiliary image scattering points; Calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming several scattering point pairs; For any of the scattering point pairs, perform the flat ground phase acquisition action to obtain the ideal flat ground phase. Based on the ideal flat ground phases corresponding to all the scattering point pairs, form an ideal flat ground phase map to complete the flat ground preprocessing process. The flat-ground phase acquisition operation includes: Calculate the main image Doppler history and the auxiliary image Doppler history of the scattering point pair; Based on the main image Doppler history, the main image focusing time that meets the preset time threshold is determined, and the main image slant distance is calculated based on the main image focusing time. Based on the secondary image Doppler history, the secondary image focusing time that meets the preset time threshold is determined, and the secondary image slant distance is calculated based on the secondary image focusing time. The ideal flat-ground phase of the scattering point pair is obtained based on the slant range of the main image and the slant range of the auxiliary image.

[0006] In the above scheme, the scattering point of the main image is calculated to correspond to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming several scattering point pairs. The flat-ground phase acquisition action is performed on any scattering point pair to obtain the ideal flat-ground phase. The process of forming an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all scattering point pairs advances the time interpolation process to the processing of the main satellite image and the auxiliary satellite image. This avoids the technical problem of systematic error caused by approximating the low-order unfolding of a single image in the existing technology of calculating the flat-ground phase compensation factor through DEM. It also eliminates the residual error introduced by the geometric model approximation, thereby obtaining the image position and phase information of the scattering point pairs, and thus reducing the processing error of the flat-ground preprocessing method.

[0007] Furthermore, the step of acquiring the radar imaging main image and the radar imaging auxiliary image, wherein the radar imaging main image contains a plurality of main image scattering points and the radar imaging auxiliary image contains a plurality of auxiliary image scattering points, includes: acquiring an initial radar imaging main image and an initial radar imaging auxiliary image; establishing image time axes for the initial radar imaging main image and the initial radar imaging auxiliary image respectively, and performing time interpolation on the image time axes based on pre-acquired radar orbit data to obtain the radar imaging main image and the radar imaging auxiliary image.

[0008] It should be noted that the image time axis may include an azimuth image time axis and a range image time axis, the generation of which may depend on imaging geometric parameters such as the initial slant range time, initial azimuth time, azimuth sampling interval, and sampling rate of the input image. Time interpolation specifically refers to the mathematical completion processing of the radar satellite's orbital history and velocity vector along the azimuth image time axis.

[0009] In the above scheme, by establishing the image time axis from the initial radar imaging main image and the initial radar imaging auxiliary image, and performing time interpolation based on the radar orbit data, the two-dimensional interpolation calculations that were originally required to be repeatedly performed in image processing are moved forward to the satellite orbit time dimension processing. This ensures the geometric mapping accuracy of the scattering points in the main image and the auxiliary image, while avoiding the computational consumption and accumulated errors caused by the repeated iteration, registration, and two-dimensional interpolation of multiple TomoSAR image scenes in the prior art. This ensures the accuracy of the positional information of the scattering points in the main image and the auxiliary image, thereby reducing the processing error of the de-flattening preprocessing method.

[0010] Further, the step of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, and calculating the main image slant distance based on the main image focusing time; and determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, and calculating the auxiliary image slant distance based on the auxiliary image focusing time, includes: calculating the main image Doppler center frequency based on the main image Doppler history; determining that the main image focusing time is when the main image Doppler center frequency is less than a preset frequency threshold, and calculating the main image slant distance based on the main image focusing time; calculating the auxiliary image Doppler center frequency based on the auxiliary image Doppler history; determining that the auxiliary image focusing time is when the auxiliary image Doppler center frequency is less than a preset frequency threshold, and calculating the auxiliary image slant distance based on the auxiliary image focusing time.

[0011] It should be noted that the Doppler center frequency of the main image and the Doppler center frequency of the auxiliary image are key parameters characterizing the relative motion of the scattering points in the main and auxiliary images during imaging. When the Doppler center frequency of the main image or the auxiliary image is less than a preset frequency threshold, it indicates that the scattering point in the main image or the auxiliary image has reached the focusing condition. The corresponding time is determined as the focusing time of the main image or the auxiliary image, and the slant range of the main image and the auxiliary image can then be calculated based on the focusing time of the main image and the auxiliary image.

[0012] In the above scheme, the Doppler center frequencies of the main image and the auxiliary image are calculated based on the Doppler history of the main image and the auxiliary image, and the focusing time of the main image and the auxiliary image is accurately determined using the preset frequency threshold. This approach uses linear programming to replace the global optimum with a local optimum, thereby reducing space complexity and avoiding the deviation in slant range calculation caused by inaccurate estimation of the focusing time in existing technologies. This ensures the accuracy of the calculation of the slant range of the main image and the auxiliary image, thus providing a basis for obtaining the accurate ideal flat-ground phase and reducing the processing error of the flat-ground preprocessing method.

[0013] Further, obtaining the ideal flat-ground phase of the scattering point pair based on the main image slant range and the auxiliary image slant range includes: calculating the main image slant range propagation time based on the main image slant range and the pre-acquired radar propagation speed; calculating the auxiliary image slant range propagation time based on the auxiliary image slant range and the radar propagation speed; and calculating the ideal flat-ground phase of the scattering point pair based on the main image slant range, the auxiliary image slant range, the main image slant range propagation time, and the auxiliary image slant range propagation time.

[0014] It should be noted that the main image slant range propagation time and the auxiliary image slant range propagation time can be used to characterize the time required for the radar signal to travel along the main image slant range and the auxiliary image slant range paths.

[0015] In the above scheme, the propagation time of the main image slant range and the propagation time of the auxiliary image slant range are calculated based on the radar propagation velocity, and the ideal flat-ground phase is calculated based on this. This ensures that the ideal flat-ground phase is accurately based on the physical difference between the main image slant range and the auxiliary image slant range, thereby avoiding the calculation deviation caused by approximation in existing technologies. This geometric analytical modeling method eliminates the phase offset and defocusing phenomena caused by model simplification, making phase compensation in flat-ground areas more thorough, effectively avoiding the accumulation of residual errors, and thus reducing the processing error of the flat-ground preprocessing method.

[0016] Further, the step of forming an ideal flat-ground phase map based on the ideal flat-ground phase corresponding to all the scattering point pairs includes: obtaining the ideal flat-ground phase of the main image by traversing the ideal flat-ground phase of all the scattering points of the main image based on the radar imaging main image; obtaining the ideal flat-ground phase of the auxiliary image by traversing the ideal flat-ground phase of all the scattering points of the auxiliary image based on the radar imaging auxiliary image; and calculating the ideal flat-ground phase map based on the ideal flat-ground phase of the main image and the ideal flat-ground phase of the auxiliary image.

[0017] It should be noted that obtaining the ideal flat-ground phase of the auxiliary image by traversing all the scattering points of the auxiliary image means ensuring that every pixel position in both the main radar image and the auxiliary radar image is covered.

[0018] In the above scheme, by processing the scattering points of the main image and the scattering points of the auxiliary image separately, a precise mapping relationship between the scene grid and the radar imaging space can be established. This allows the ideal flat-ground phase map to be constructed using the pixels of the main image as an index, thereby achieving pixel-level phase information reconstruction. This yields the ideal flat-ground phase of the main image and the ideal flat-ground phase of the auxiliary image, and the ideal flat-ground phase map is calculated. This ensures that the ideal flat-ground phase map covers all pixel positions, avoiding incomplete phase compensation due to the omission of ground scattering points. It achieves pixel-level ideal flat-ground phase reconstruction, thus providing a foundation for obtaining accurate ideal flat-ground phase and reducing the processing error of the flat-ground preprocessing method.

[0019] The present invention also provides a de-leveling pretreatment system, comprising: A radar imaging acquisition module is used to acquire a radar imaging main image and a radar imaging auxiliary image. The radar imaging main image contains a number of main image scattering points, and the radar imaging auxiliary image contains a number of auxiliary image scattering points. The scattering point pair calculation module is used to calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming a number of scattering point pairs; The flat-ground phase map processing module is used to perform a flat-ground phase acquisition action for any of the scattering point pairs to obtain an ideal flat-ground phase, and to form an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all the scattering point pairs, thus completing the deflating preprocessing process. A flat-ground phase acquisition module, used for the flat-ground phase acquisition action, includes: Calculate the main image Doppler history and the auxiliary image Doppler history of the scattering point pair; Based on the main image Doppler history, the main image focusing time that meets the preset time threshold is determined, and the main image slant distance is calculated based on the main image focusing time. Based on the secondary image Doppler history, the secondary image focusing time that meets the preset time threshold is determined, and the secondary image slant distance is calculated based on the secondary image focusing time. The ideal flat-ground phase of the scattering point pair is obtained based on the slant range of the main image and the slant range of the auxiliary image.

[0020] The above-mentioned system architecture is logically clear, with well-defined functional divisions and close collaboration among modules, forming a complete ground-level preprocessing workflow: The radar imaging acquisition module first acquires the initial radar imaging main image and the initial radar imaging auxiliary image. Based on the pre-acquired radar orbit data, it performs time interpolation on the image time axis to obtain the radar imaging main image and the radar imaging auxiliary image containing the scattering points of the main image and the auxiliary image, thus providing a precise spatiotemporal reference for scattering point matching. The scattering point pair calculation module calculates the corresponding auxiliary image scattering points of the main image scattering points in the radar imaging auxiliary image, forming several scattering point pairs, thereby establishing a mapping relationship between the scene grid and the radar imaging space. The ground-level phase acquisition module performs ground-level phase acquisition for any scattering point pair, calculates the Doppler history of the main image and the auxiliary image, determines the main image focusing time and the auxiliary image focusing time that meet the preset time threshold, calculates the slant range of the main image and the auxiliary image, obtains the ideal ground-level phase of the scattering point pair, and extracts pixel-level phase information through geometric derivation. The flat-ground phase map processing module generates an ideal flat-ground phase map based on the ideal flat-ground phase corresponding to all scattering point pairs, thus completing the flat-ground preprocessing process.

[0021] The above-described scheme employs logically synchronized control across all modules for the entire process of data acquisition, point-pair calculation, phase determination, and map construction, ensuring data consistency at each stage and avoiding additional errors caused by mapping deviations. This system achieves de-flattening preprocessing through the collaborative work of its modules. The radar imaging acquisition module advances the interpolation process to the orbital data processing stage via time interpolation, providing fundamental support for subsequent accurate calculations. The scattering point pair calculation module ensures accurate matching of corresponding points from the source by correlating primary and secondary scattering points. The flat-ground phase acquisition module avoids systematic errors caused by approximation through rigorous calculations of Doppler history and focusing time. The flat-ground phase map processing module constructs pixel-level phase maps by traversing all scattering point pairs, avoiding incomplete phase compensation. Furthermore, the logical synchronization of each module ensures consistent data sources at each stage, thereby ensuring stable operation of the entire system. This collaborative mechanism solves the problem of uneven ground estimation caused by systematic errors due to low-order expansion approximation and residual errors in existing TomoSAR deflating technology. It does not rely on simplified geometric model assumptions and can achieve high-precision phase compensation through the orderly linkage of core functional modules. Ultimately, it achieves the technical effect of eliminating residual errors introduced by geometric model approximation and reducing the processing error of deflating preprocessing methods.

[0022] Furthermore, the radar imaging acquisition module is used to acquire a main radar imaging image and a secondary radar imaging image. The main radar imaging image contains a number of main image scattering points, and the secondary radar imaging image contains a number of secondary image scattering points. The module includes: acquiring an initial main radar imaging image and an initial secondary radar imaging image; establishing image time axes for the initial main radar imaging image and the initial secondary radar imaging image respectively; and performing time interpolation on the image time axes based on pre-acquired radar orbit data to obtain the main radar imaging image and the secondary radar imaging image.

[0023] Further, in the flat-ground phase acquisition module, the step of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, and calculating the main image slant range based on the main image focusing time; and determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, and calculating the auxiliary image slant range based on the auxiliary image focusing time, includes: calculating the main image Doppler center frequency based on the main image Doppler history; when the main image Doppler center frequency is less than a preset frequency threshold, determining that time as the main image focusing time, and calculating the main image slant range based on the main image focusing time; calculating the auxiliary image Doppler center frequency based on the auxiliary image Doppler history; when the auxiliary image Doppler center frequency is less than a preset frequency threshold, determining that time as the auxiliary image focusing time, and calculating the auxiliary image slant range based on the auxiliary image focusing time.

[0024] Furthermore, in the flat-ground phase acquisition module, obtaining the ideal flat-ground phase of the scattering point pair based on the main image slant range and the auxiliary image slant range includes: calculating the main image slant range propagation time based on the main image slant range and the pre-acquired radar propagation velocity; calculating the auxiliary image slant range propagation time based on the auxiliary image slant range and the radar propagation velocity; and calculating the ideal flat-ground phase of the scattering point pair based on the main image slant range, the auxiliary image slant range, the main image slant range propagation time, and the auxiliary image slant range propagation time.

[0025] Further, in the flat-ground phase map processing module, a flat-ground phase acquisition action is performed for any pair of scattering points to obtain an ideal flat-ground phase, so as to form an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all pairs of scattering points, thus completing the flat-ground preprocessing process. The step of forming an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all pairs of scattering points includes: obtaining the ideal flat-ground phase of the main image by traversing the ideal flat-ground phases of all scattering points of the main image based on the radar imaging main image; obtaining the ideal flat-ground phase of the auxiliary image by traversing the ideal flat-ground phases of all scattering points of the auxiliary image based on the radar imaging auxiliary image; and calculating the ideal flat-ground phase map based on the ideal flat-ground phases of the main image and the ideal flat-ground phases of the auxiliary image.

[0026] In the above scheme, by acquiring the initial radar imaging main image and the initial radar imaging auxiliary image, and establishing image time axes and performing time interpolation based on radar orbit data, the interpolation process is advanced to the orbit data processing stage. This avoids the cumulative errors caused by the repeated iterations, registration, and two-dimensional interpolation of multiple TomoSAR image scenes in existing technologies, ensuring the accuracy of the positional information of the scattering points in the main image and the auxiliary image. Based on this, the corresponding scattering points in the auxiliary image are calculated to form scattering point pairs. By calculating the Doppler histories of the main image and the auxiliary image for these scattering point pairs, and using preset frequency thresholds, the focusing time of the main image and the auxiliary image is accurately determined. This avoids the slant range calculation deviation caused by inaccurate focusing time estimation in existing technologies, ensuring the accuracy of the slant range calculations for the main image and the auxiliary image. Finally, based on the slant ranges of the main image and the auxiliary image, combined with the radar propagation velocity, the propagation time is calculated to obtain the ideal flat-ground phase. This avoids the calculation deviation caused by approximation in existing technologies, ensuring that the ideal flat-ground phase is accurately based on the true physical difference between the slant ranges of the main image and the auxiliary image. Finally, by traversing all scattering point pairs to form an ideal flat-ground phase map, it is possible to ensure that the ideal flat-ground phase map covers all pixel locations and avoid incomplete phase compensation due to omission of ground scattering points.

[0027] The above scheme achieves de-flattening preprocessing through the coordinated work of each step. The acquisition step provides a foundation for subsequent accurate calculations through time interpolation; the scattering point pair calculation step ensures the accuracy of matching corresponding points from the source; the flat-ground phase acquisition step avoids systematic errors caused by approximation through rigorous calculation of Doppler history and focusing time; and the flat-ground phase map processing step avoids incomplete phase compensation by constructing a pixel-level phase map by traversing all scattering point pairs. This collaborative mechanism specifically solves the problems of systematic errors caused by low-order expansion approximation and uneven ground estimation due to residual errors in existing TomoSAR de-flattening techniques. It does not rely on simplified geometric model assumptions and can achieve high-precision phase compensation through the orderly linkage of core steps, ultimately achieving the technical effect of eliminating residual errors introduced by geometric model approximation and reducing the processing error of de-flattening preprocessing methods. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a pre-treatment method for leveling land provided in an embodiment of the present invention; Figure 2 A schematic diagram of the geometric model of TomoSAR satellite imaging provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating a real-world process of removing flat bottoms, as provided in an embodiment of the present invention. Figure 4 A phase color map of the flattened result is obtained using an existing technical method; Figure 5This is a phase color map of the flattening result provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of a deflating preprocessing system architecture provided in an embodiment of the present invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see Figure 1 This embodiment provides a method for pre-treatment of de-leveling land, including the following steps: Step S1: Obtain the radar imaging main image and the radar imaging auxiliary image. The radar imaging main image contains several main image scattering points, and the radar imaging auxiliary image contains several auxiliary image scattering points. Step S2: Calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming several scattering point pairs; Step S3: Perform a flat-ground phase acquisition operation for any of the scattering point pairs, including: calculating the main image Doppler history and the auxiliary image Doppler history of the scattering point pairs; determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, calculating the main image slant range based on the main image focusing time; determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, calculating the auxiliary image slant range based on the auxiliary image focusing time; obtaining the ideal flat-ground phase of the scattering point pairs based on the main image slant range and the auxiliary image slant range; Step S4: Based on the ideal flat-ground phase corresponding to all the scattering point pairs, form an ideal flat-ground phase map to complete the flat-ground preprocessing process.

[0031] In this embodiment, the scattering points of the main image are calculated to correspond to the scattering points of the auxiliary image in the radar imaging auxiliary image, forming several scattering point pairs. A flat-ground phase acquisition operation is performed on any of the scattering point pairs to obtain the ideal flat-ground phase. The process of forming an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all the scattering point pairs advances the time interpolation process to the processing of the main satellite image and the auxiliary satellite image. This avoids the technical problem of systematic errors caused by approximating the low-order unfolding of a single image in the existing technology of calculating the flat-ground phase compensation factor through DEM. It also eliminates the residual errors introduced by the geometric model approximation, thereby obtaining the image position and phase information of the scattering point pairs, and thus reducing the processing error of the flat-ground preprocessing method.

[0032] Figure 2This is a schematic diagram of a geometric model for TomoSAR satellite imaging according to an embodiment of the present invention. , These are the main radar imaging image transmitting satellite and the auxiliary radar imaging image transmitting satellite, respectively. , These are the main radar imaging image receiving satellite and the auxiliary radar imaging image receiving satellite, respectively. For any scattering point in either the main or auxiliary radar image, it corresponds to the same point P on the ground. By correlating the scattering points in the main and auxiliary images representing the same point, a scattering point pair O is obtained. The orange and blue dashed arrows in the figure represent the transmission and reception paths of the signals during the echo acquisition process of the two images, respectively. V S0 V S1 V S2 and V S3 This represents the velocity vector of the radar imaging satellite in the ground coordinate system.

[0033] Furthermore, the step of acquiring the radar imaging main image and the radar imaging auxiliary image, wherein the radar imaging main image contains a plurality of main image scattering points and the radar imaging auxiliary image contains a plurality of auxiliary image scattering points, includes: acquiring an initial radar imaging main image and an initial radar imaging auxiliary image; establishing image time axes for the initial radar imaging main image and the initial radar imaging auxiliary image respectively, and performing time interpolation on the image time axes based on pre-acquired radar orbit data to obtain the radar imaging main image and the radar imaging auxiliary image.

[0034] It should be noted that the image time axis may include an azimuth image time axis and a range image time axis, the generation of which may depend on imaging geometric parameters such as the initial slant range time, initial azimuth time, azimuth sampling interval, and sampling rate of the input image. Time interpolation specifically refers to the mathematical completion processing of the radar satellite's orbital history and velocity vector along the azimuth image time axis.

[0035] In one embodiment, for a size of The initial radar image, assuming its initial slant range time and direction and time The sampling interval is obtained from the radar data. and sampling rate Generate a two-dimensional timeline of the image. ; In the formula, For the azimuth image time axis, This represents the distance-oriented time axis of the image.

[0036] In this embodiment, by establishing the image time axis from the initial radar imaging main image and the initial radar imaging auxiliary image, and performing time interpolation based on the radar orbit data, the two-dimensional interpolation calculations that were originally required to be repeatedly performed in image processing are moved forward to the satellite orbit time dimension processing. This ensures the geometric mapping accuracy of the scattering points in the main image and the auxiliary image, while avoiding the computational consumption and accumulated errors caused by the repeated iteration, registration, and two-dimensional interpolation of multiple TomoSAR image scenes in the prior art. This ensures the accuracy of the positional information of the scattering points in the main image and the auxiliary image, thereby reducing the processing error of the de-flattening preprocessing method.

[0037] Further, the step of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, and calculating the main image slant distance based on the main image focusing time; and determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, and calculating the auxiliary image slant distance based on the auxiliary image focusing time, includes: calculating the main image Doppler center frequency based on the main image Doppler history; determining that the main image focusing time is when the main image Doppler center frequency is less than a preset frequency threshold, and calculating the main image slant distance based on the main image focusing time; calculating the auxiliary image Doppler center frequency based on the auxiliary image Doppler history; determining that the auxiliary image focusing time is when the auxiliary image Doppler center frequency is less than a preset frequency threshold, and calculating the auxiliary image slant distance based on the auxiliary image focusing time.

[0038] It should be noted that the Doppler center frequency of the main image and the Doppler center frequency of the auxiliary image are key parameters characterizing the relative motion of the scattering points in the main and auxiliary images during imaging. When the Doppler center frequency of the main image or the auxiliary image is less than a preset frequency threshold, it indicates that the scattering point in the main image or the auxiliary image has reached the focusing condition. The corresponding time is determined as the focusing time of the main image or the auxiliary image, and the slant range of the main image and the auxiliary image can then be calculated based on the focusing time of the main image and the auxiliary image.

[0039] In this embodiment, for Figure 2 The radar imaging main image receiving satellite The Doppler equations are: ; In the above equation, These are the radar imaging main image transmitting satellites. Radar imaging auxiliary image launch satellite Radar imaging main image receiving satellite Radar imaging auxiliary image receiving satellite And the position vector of the scattering point P in the geocentric coordinate system; The geometric center of the radar imaging main image transmitting star and the radar imaging auxiliary image transmitting star and the position vector of the scattering point P; The velocity vector of the transmitting star in the main radar imaging image. The velocity vector of the receiving star in the main radar imaging image; This is the Earth's rotational angular velocity vector. These are the Doppler center frequencies used during the initial radar imaging main image and the initial radar imaging auxiliary image, respectively. Where is the wavelength of light. Similarly, the above equation can also be used to construct radar imaging auxiliary image receiving satellites. The Doppler equations.

[0040] By analyzing the orbital history of the aforementioned satellites , , , Interpolation is performed along the azimuth time axis to obtain... , , , This yields multiple sets of Doppler equations for time interpolation, which are the main-map Doppler history and the auxiliary-map Doppler history. For the main-map Doppler center frequency in the main-map Doppler history... and take satisfy , believes that the first Moment The moment the main image focuses is determined. The slant distance of the main image at that moment is then calculated as follows: ; In the formula, The slant distance of the main image; These are the radar imaging main image transmitting satellites. Radar imaging main image receiving satellite And the position vector of the scattering point P in the geocentric coordinate system.

[0041] In this embodiment, the Doppler center frequencies of the main image and the auxiliary image are calculated based on the Doppler history of the main image and the auxiliary image, and the focusing time of the main image and the auxiliary image is accurately determined using the preset frequency threshold. This approach uses linear programming to replace the global optimum with a local optimum, thereby reducing space complexity and avoiding the deviation in slant range calculation caused by inaccurate estimation of the focusing time in the prior art. This ensures the accuracy of the calculation of the slant range of the main image and the auxiliary image, thus providing a basis for obtaining the accurate ideal flat-ground phase and reducing the processing error of the flat-ground preprocessing method.

[0042] Further, obtaining the ideal flat-ground phase of the scattering point pair based on the main image slant range and the auxiliary image slant range includes: calculating the main image slant range propagation time based on the main image slant range and the pre-acquired radar propagation speed; calculating the auxiliary image slant range propagation time based on the auxiliary image slant range and the radar propagation speed; and calculating the ideal flat-ground phase of the scattering point pair based on the main image slant range, the auxiliary image slant range, the main image slant range propagation time, and the auxiliary image slant range propagation time.

[0043] It should be noted that the main image slant range propagation time and the auxiliary image slant range propagation time can be used to characterize the time required for the radar signal to travel along the main image slant range and the auxiliary image slant range paths.

[0044] In the above embodiment, the specific calculation method for the main image slant range propagation time is as follows: ; In the formula, when i=0, The slant distance propagation time of the main image. The slant distance of the main graph; when i=1, The slant range propagation time of the auxiliary graph. is the slant range of the auxiliary diagram; c is the pre-acquired radar propagation speed, which is the speed of light in this embodiment.

[0045] In this embodiment, the propagation time of the main image slant range and the propagation time of the auxiliary image slant range are calculated based on the radar propagation velocity, and the ideal flat-ground phase is calculated based on this. This ensures that the ideal flat-ground phase is accurately based on the physical difference between the main image slant range and the auxiliary image slant range, thereby avoiding the calculation deviation caused by approximation in the prior art. This geometric analytical modeling method eliminates the phase offset and defocusing phenomena caused by model simplification, making phase compensation in flat-ground areas more thorough, effectively avoiding the accumulation of residual errors, and thus reducing the processing error of the flat-ground preprocessing method.

[0046] Further, the step of forming an ideal flat-ground phase map based on the ideal flat-ground phase corresponding to all the scattering point pairs includes: obtaining the ideal flat-ground phase of the main image by traversing the ideal flat-ground phase of all the scattering points of the main image based on the radar imaging main image; obtaining the ideal flat-ground phase of the auxiliary image by traversing the ideal flat-ground phase of all the scattering points of the auxiliary image based on the radar imaging auxiliary image; and calculating the ideal flat-ground phase map based on the ideal flat-ground phase of the main image and the ideal flat-ground phase of the auxiliary image.

[0047] In the above embodiments, the ideal flat-ground phase is obtained as follows: ; In the formula, These are the radar imaging main image transmitting satellites. Radar imaging main image receiving satellite The ideal flat-ground phase map can be calculated by traversing all pairs of scattering points, along with the position vector of the scattering point P in the geocentric coordinate system.

[0048] It should be noted that obtaining the ideal flat-ground phase of the auxiliary image by traversing all the scattering points of the auxiliary image means ensuring that every pixel position in both the main radar image and the auxiliary radar image is covered.

[0049] like Figure 3 The image shown is a schematic diagram of a real-world scene of the flattening process provided in this embodiment. The real-world scene is the Bird's Nest. Echo simulation and two-dimensional imaging were performed using traditional methods to obtain the following results: Figure 4 The phase color map of the flattened surface shown is shown. The phase color map of the flattened surface obtained by performing the flattening process using the method provided in this embodiment is shown below. Figure 5 As shown, the horizontal axis represents the pixel index along the x-axis, and the vertical axis represents the pixel index along the y-axis. Through... Figure 4 and Figure 5 The comparison shows that as the baseline distance between the image and the main image increases, Figure 4 In traditional methods, the residual phase components in flat areas become increasingly apparent, with the phase color map in flat areas transitioning from green (representing 0) to a slightly undulating blue (greater than 0). Furthermore, phase compensation in shadow areas causes interference fringes to appear even in unrelated regions. In contrast, the complex image processed by this technique, after deflating, exhibits characteristics of a clean background, unrelated shadow areas, and clearly defined fringes in the building target area. This is highly consistent with the expected deflating interference results. The interference fringes in the building area are captured without introducing additional or residual errors, which is more beneficial for subsequent 3D modeling.

[0050] In this embodiment, by processing the scattering points of the main image and the scattering points of the auxiliary image separately, a precise mapping relationship between the scene grid and the radar imaging space can be established. This allows the ideal flat-ground phase map to be constructed using the main image pixels as an index, thereby achieving pixel-level phase information reconstruction. This yields the ideal flat-ground phase of the main image and the ideal flat-ground phase of the auxiliary image, and the calculated ideal flat-ground phase map ensures that the ideal flat-ground phase map covers all pixel locations, avoiding incomplete phase compensation due to the omission of ground scattering points. This achieves pixel-level ideal flat-ground phase reconstruction, providing a foundation for obtaining accurate ideal flat-ground phase and reducing the processing error of the flat-ground preprocessing method.

[0051] like Figure 6 As shown, this embodiment also provides a de-leveling pretreatment system, including: A radar imaging acquisition module is used to acquire a radar imaging main image and a radar imaging auxiliary image. The radar imaging main image contains a number of main image scattering points, and the radar imaging auxiliary image contains a number of auxiliary image scattering points. The scattering point pair calculation module is used to calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming a number of scattering point pairs; The flat-ground phase map processing module is used to perform a flat-ground phase acquisition action for any of the scattering point pairs to obtain an ideal flat-ground phase, and to form an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all the scattering point pairs, thus completing the deflating preprocessing process. A flat-ground phase acquisition module, used for the flat-ground phase acquisition action, includes: Calculate the main image Doppler history and the auxiliary image Doppler history of the scattering point pair; Based on the main image Doppler history, the main image focusing time that meets the preset time threshold is determined, and the main image slant distance is calculated based on the main image focusing time. Based on the secondary image Doppler history, the secondary image focusing time that meets the preset time threshold is determined, and the secondary image slant distance is calculated based on the secondary image focusing time. The ideal flat-ground phase of the scattering point pair is obtained based on the slant range of the main image and the slant range of the auxiliary image.

[0052] The system architecture provided by the above embodiments is logically clear, with well-defined functional divisions and close collaboration among modules, forming a complete ground-level preprocessing flow: The radar imaging acquisition module first acquires the initial radar imaging main image and the initial radar imaging auxiliary image. Based on the pre-acquired radar orbit data, it performs time interpolation on the image time axis to obtain the radar imaging main image and the radar imaging auxiliary image containing the scattering points of the main image and the auxiliary image, thus providing a precise spatiotemporal reference for scattering point matching. The scattering point pair calculation module calculates the auxiliary image scattering point corresponding to the scattering point of the main image in the radar imaging auxiliary image, forming several scattering point pairs, thereby establishing a mapping relationship between the scene grid and the radar imaging space. The ground-level phase acquisition module performs ground-level phase acquisition for any scattering point pair, calculates the Doppler history of the main image and the auxiliary image, determines the main image focusing time and the auxiliary image focusing time that meet the preset time threshold, calculates the slant range of the main image and the slant range of the auxiliary image, obtains the ideal ground-level phase of the scattering point pair, and extracts pixel-level phase information through geometric derivation. The flat-ground phase map processing module generates an ideal flat-ground phase map based on the ideal flat-ground phase corresponding to all scattering point pairs, thus completing the flat-ground preprocessing process.

[0053] The modules in the above embodiments implement logical synchronization control over the entire process of data acquisition, point pair calculation, phase solving, and map construction, ensuring data consistency at each stage and avoiding additional errors caused by mapping deviations. This system achieves de-flattening preprocessing through the collaborative work of its modules. The radar imaging acquisition module advances the interpolation process to the orbital data processing stage through time interpolation, providing a foundation for subsequent accurate calculations. The scattering point pair calculation module ensures accurate matching of corresponding points from the source by corresponding primary and secondary scattering points. The flat-ground phase acquisition module avoids system errors caused by approximation through rigorous calculation of Doppler history and focusing time. The flat-ground phase map processing module constructs a pixel-level phase map by traversing all scattering point pairs, avoiding incomplete phase compensation. The logical synchronization of each module ensures consistent data sources at each stage, thereby ensuring stable operation of the entire system. This collaborative mechanism solves the problem of uneven ground estimation caused by systematic errors due to low-order expansion approximation and residual errors in existing TomoSAR deflating technology. It does not rely on simplified geometric model assumptions and can achieve high-precision phase compensation through the orderly linkage of core functional modules. Ultimately, it achieves the technical effect of eliminating residual errors introduced by geometric model approximation and reducing the processing error of deflating preprocessing methods.

[0054] Furthermore, the radar imaging acquisition module is used to acquire a main radar imaging image and a secondary radar imaging image. The main radar imaging image contains a number of main image scattering points, and the secondary radar imaging image contains a number of secondary image scattering points. The module includes: acquiring an initial main radar imaging image and an initial secondary radar imaging image; establishing image time axes for the initial main radar imaging image and the initial secondary radar imaging image respectively; and performing time interpolation on the image time axes based on pre-acquired radar orbit data to obtain the main radar imaging image and the secondary radar imaging image.

[0055] Further, in the flat-ground phase acquisition module, the step of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, and calculating the main image slant range based on the main image focusing time; and determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, and calculating the auxiliary image slant range based on the auxiliary image focusing time, includes: calculating the main image Doppler center frequency based on the main image Doppler history; when the main image Doppler center frequency is less than a preset frequency threshold, determining that time as the main image focusing time, and calculating the main image slant range based on the main image focusing time; calculating the auxiliary image Doppler center frequency based on the auxiliary image Doppler history; when the auxiliary image Doppler center frequency is less than a preset frequency threshold, determining that time as the auxiliary image focusing time, and calculating the auxiliary image slant range based on the auxiliary image focusing time.

[0056] Furthermore, in the flat-ground phase acquisition module, obtaining the ideal flat-ground phase of the scattering point pair based on the main image slant range and the auxiliary image slant range includes: calculating the main image slant range propagation time based on the main image slant range and the pre-acquired radar propagation velocity; calculating the auxiliary image slant range propagation time based on the auxiliary image slant range and the radar propagation velocity; and calculating the ideal flat-ground phase of the scattering point pair based on the main image slant range, the auxiliary image slant range, the main image slant range propagation time, and the auxiliary image slant range propagation time.

[0057] Further, in the flat-ground phase map processing module, a flat-ground phase acquisition action is performed for any pair of scattering points to obtain an ideal flat-ground phase, so as to form an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all pairs of scattering points, thus completing the flat-ground preprocessing process. The step of forming an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all pairs of scattering points includes: obtaining the ideal flat-ground phase of the main image by traversing the ideal flat-ground phases of all scattering points of the main image based on the radar imaging main image; obtaining the ideal flat-ground phase of the auxiliary image by traversing the ideal flat-ground phases of all scattering points of the auxiliary image based on the radar imaging auxiliary image; and calculating the ideal flat-ground phase map based on the ideal flat-ground phases of the main image and the ideal flat-ground phases of the auxiliary image.

[0058] In this embodiment, by acquiring the initial radar imaging main image and the initial radar imaging auxiliary image, and establishing image time axes and performing time interpolation based on radar orbit data, the interpolation process is advanced to the orbit data processing stage. This avoids the accumulated errors caused by the repeated iterations, registration, and two-dimensional interpolation of multiple TomoSAR image scenes in existing technologies, ensuring the accuracy of the positional information of the scattering points in the main image and the auxiliary image. Based on this, the corresponding scattering points in the auxiliary image are calculated to form scattering point pairs. By calculating the Doppler histories of the main image and the auxiliary image for these scattering point pairs, and using preset frequency thresholds, the focusing time of the main image and the auxiliary image is accurately determined. This avoids the slant range calculation deviation caused by inaccurate focusing time estimation in existing technologies, ensuring the accuracy of the slant range calculations for the main image and the auxiliary image. Furthermore, the propagation time is calculated based on the slant range of the main image and the auxiliary image, combined with the radar propagation velocity, to obtain the ideal flat-ground phase. This avoids the calculation deviation caused by approximation in existing technologies, ensuring that the ideal flat-ground phase is accurately based on the true physical difference between the slant ranges of the main image and the auxiliary image. Finally, by traversing all scattering point pairs to form an ideal flat-ground phase map, it is possible to ensure that the ideal flat-ground phase map covers all pixel locations and avoid incomplete phase compensation due to omission of ground scattering points.

[0059] The above embodiments achieve de-flattening preprocessing through the coordinated work of each step. The acquisition step provides a foundation for subsequent accurate calculations through time interpolation; the scattering point pair calculation step ensures the accuracy of matching corresponding points from the source; the flat-ground phase acquisition step avoids systematic errors caused by approximation through rigorous calculation of Doppler history and focusing time; the flat-ground phase map processing step avoids incomplete phase compensation by constructing a pixel-level phase map by traversing all scattering point pairs. This collaborative mechanism specifically solves the problems of systematic errors caused by low-order expansion approximation and uneven ground estimation due to residual errors in existing TomoSAR de-flattening techniques. It does not rely on simplified geometric model assumptions, and can achieve high-precision phase compensation through the orderly linkage of core steps. Ultimately, it achieves the technical effect of eliminating residual errors introduced by geometric model approximation and reducing the processing error of the de-flattening preprocessing method.

[0060] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for pre-treatment of de-leveling land, characterized in that, include: Obtain a radar imaging main image and a radar imaging auxiliary image, wherein the radar imaging main image contains a number of main image scattering points and the radar imaging auxiliary image contains a number of auxiliary image scattering points; Calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming several scattering point pairs; For any of the scattering point pairs, perform the flat ground phase acquisition action to obtain the ideal flat ground phase. Based on the ideal flat ground phases corresponding to all the scattering point pairs, form an ideal flat ground phase map to complete the flat ground preprocessing process. The flat-ground phase acquisition operation includes: Calculate the main image Doppler history and the auxiliary image Doppler history of the scattering point pair; Based on the main image Doppler history, the main image focusing time that meets the preset time threshold is determined, and the main image slant distance is calculated based on the main image focusing time. Based on the secondary image Doppler history, the secondary image focusing time that meets the preset time threshold is determined, and the secondary image slant distance is calculated based on the secondary image focusing time. The ideal flat-ground phase of the scattering point pair is obtained based on the slant range of the main image and the slant range of the auxiliary image.

2. The method for pre-treatment of de-leveling land according to claim 1, characterized in that, The process of acquiring a main radar image and a secondary radar image, wherein the main radar image contains a plurality of main image scattering points, and the secondary radar image contains a plurality of secondary image scattering points, including: Obtain the initial radar imaging main image and the initial radar imaging auxiliary image; Image time axes are established for the initial radar imaging main image and the initial radar imaging auxiliary image, respectively. Based on the pre-acquired radar orbit data, time interpolation is performed on the image time axes to obtain the radar imaging main image and the radar imaging auxiliary image.

3. The method for pre-treatment of de-leveling land according to claim 2, characterized in that, The process of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, calculating the main image slant distance based on the main image focusing time, and determining the secondary image focusing time that meets a preset time threshold based on the secondary image Doppler history, and calculating the secondary image slant distance based on the secondary image focusing time, includes: Based on the main image Doppler history, the main image Doppler center frequency is calculated; When the Doppler center frequency of the main image is less than a preset frequency threshold, the moment is determined to be the main image focusing moment, and the main image slant distance is calculated based on the main image focusing moment. Based on the auxiliary Doppler history, the auxiliary Doppler center frequency is calculated. When the center frequency of the auxiliary image Doppler is less than a preset frequency threshold, the moment is determined to be the moment of auxiliary image focusing, and the slant range of the auxiliary image is calculated based on the moment of auxiliary image focusing.

4. The method for pre-treatment of de-leveling land according to claim 3, characterized in that, The process of obtaining the ideal flat-ground phase of the scattering point pair based on the slant range of the main image and the slant range of the auxiliary image includes: Based on the slant range of the main image and the pre-acquired radar propagation speed, calculate the slant range propagation time of the main image; Based on the auxiliary map slant range and the radar propagation speed, the propagation time of the auxiliary map slant range is calculated; Based on the slant range of the main image, the slant range of the auxiliary image, the propagation time of the slant range of the main image, and the propagation time of the slant range of the auxiliary image, the ideal flat-ground phase of the scattering point pair is calculated.

5. The method for pre-treatment of de-leveling land according to claim 1, characterized in that, The process of forming an ideal flat-ground phase map based on the corresponding ideal flat-ground phase of all the scattering point pairs includes: Based on the radar imaging master image, the ideal flat-ground phase of the master image is obtained by traversing all the scattering points of the master image; Based on the radar imaging auxiliary map, the ideal flat-ground phase of the auxiliary map is obtained by traversing all the scattering points of the auxiliary map; An ideal flat-ground phase map is calculated based on the ideal flat-ground phase of the main map and the ideal flat-ground phase of the auxiliary map.

6. A de-leveling pretreatment system, characterized in that, include: A radar imaging acquisition module is used to acquire a radar imaging main image and a radar imaging auxiliary image. The radar imaging main image contains a number of main image scattering points, and the radar imaging auxiliary image contains a number of auxiliary image scattering points. The scattering point pair calculation module is used to calculate the scattering point of the main image corresponding to the scattering point of the auxiliary image in the radar imaging auxiliary image, forming a number of scattering point pairs; The flat-ground phase map processing module is used to perform a flat-ground phase acquisition action for any of the scattering point pairs to obtain an ideal flat-ground phase, and to form an ideal flat-ground phase map based on the ideal flat-ground phases corresponding to all the scattering point pairs, thus completing the deflating preprocessing process. A flat-ground phase acquisition module, used for the flat-ground phase acquisition action, includes: Calculate the main image Doppler history and the auxiliary image Doppler history of the scattering point pair; Based on the main image Doppler history, the main image focusing time that meets the preset time threshold is determined, and the main image slant distance is calculated based on the main image focusing time. Based on the secondary image Doppler history, the secondary image focusing time that meets the preset time threshold is determined, and the secondary image slant distance is calculated based on the secondary image focusing time. The ideal flat-ground phase of the scattering point pair is obtained based on the slant range of the main image and the slant range of the auxiliary image.

7. The de-leveling pretreatment system according to claim 6, characterized in that, The radar imaging acquisition module is used to acquire a main radar image and a secondary radar image. The main radar image contains several main image scattering points, and the secondary radar image contains several secondary image scattering points, including: Obtain the initial radar imaging main image and the initial radar imaging auxiliary image; Image time axes are established for the initial radar imaging main image and the initial radar imaging auxiliary image, respectively. Based on the pre-acquired radar orbit data, time interpolation is performed on the image time axes to obtain the radar imaging main image and the radar imaging auxiliary image.

8. The de-leveling pretreatment system according to claim 7, characterized in that, In the flat-ground phase acquisition module, the step of determining the main image focusing time that meets a preset time threshold based on the main image Doppler history, calculating the main image slant range based on the main image focusing time, and determining the auxiliary image focusing time that meets a preset time threshold based on the auxiliary image Doppler history, calculating the auxiliary image slant range based on the auxiliary image focusing time, includes: Based on the main image Doppler history, the main image Doppler center frequency is calculated; When the Doppler center frequency of the main image is less than a preset frequency threshold, the moment is determined to be the main image focusing moment, and the main image slant distance is calculated based on the main image focusing moment. Based on the auxiliary Doppler history, the auxiliary Doppler center frequency is calculated. When the center frequency of the auxiliary image Doppler is less than a preset frequency threshold, the moment is determined to be the moment of auxiliary image focusing, and the slant range of the auxiliary image is calculated based on the moment of auxiliary image focusing.

9. A de-leveling pretreatment system according to claim 8, characterized in that, In the flat-ground phase acquisition module, obtaining the ideal flat-ground phase of the scattering point pair based on the main map slant range and the auxiliary map slant range includes: Based on the slant range of the main image and the pre-acquired radar propagation speed, calculate the slant range propagation time of the main image; Based on the auxiliary map slant range and the radar propagation speed, the propagation time of the auxiliary map slant range is calculated; Based on the slant range of the main image, the slant range of the auxiliary image, the propagation time of the slant range of the main image, and the propagation time of the slant range of the auxiliary image, the ideal flat-ground phase of the scattering point pair is calculated.

10. A de-leveling pretreatment system according to claim 6, characterized in that, In the flatland phase map processing module, a flatland phase acquisition action is performed for any pair of scattering points to obtain an ideal flatland phase, so as to form an ideal flatland phase map based on the ideal flatland phases corresponding to all pairs of scattering points, thus completing the flatland preprocessing process. The step of forming an ideal flatland phase map based on the ideal flatland phases corresponding to all pairs of scattering points includes: Based on the radar imaging master image, the ideal flat-ground phase of the master image is obtained by traversing all the scattering points of the master image; Based on the radar imaging auxiliary map, the ideal flat-ground phase of the auxiliary map is obtained by traversing all the scattering points of the auxiliary map; An ideal flat-ground phase map is calculated based on the ideal flat-ground phase of the main map and the ideal flat-ground phase of the auxiliary map.

Images