Tomographic SAR three-dimensional point cloud imaging method and device based on holographic model

Abstract

The present invention discloses a tomographic SAR three-dimensional point cloud imaging method and device based on a holographic model, which belongs to the field of multi-polarization multi-band multi-channel tomographic SAR imaging and SAR signal processing. The multi-polarization multi-band tomographic SAR data is preprocessed and two-dimensionally imaged, and the two-dimensional complex image after two-dimensional imaging is registered and amplitude-phase corrected, and then a holographic three-dimensional model is constructed. The holographic model contains the geometric features, multi-polarization and multi-band information of the target. The constructed holographic three-dimensional model is used to reconstruct the three-dimensional point cloud of the two-dimensional tomographic SAR image to obtain high-quality three-dimensional point cloud imaging results and multi-polarization, multi-band scattering characteristic information of the target building. The present invention can obtain high-quality three-dimensional point cloud imaging results and multi-polarization, multi-band scattering characteristic information of the target building.

Description

Technical Field

[0001] The present invention belongs to the field of multi-polarization multi-band multi-channel tomographic SAR imaging and SAR signal processing, and in particular relates to a tomographic SAR three-dimensional point cloud imaging method and device based on a holographic model. Background Art

[0002] With the continuous development of SAR technology and the increasing demand for 3D imaging observation of buildings, SAR technology has been rapidly developed. Traditional tomographic SAR and 3D reconstruction technology of target buildings have also developed in multiple directions, gradually developing multi-band, multi-polarization, and geometrically constrained 3D imaging technologies.

[0003] In view of the development direction of multi-band, many systems have been successfully developed at home and abroad for multi-band imaging of SAR. For example, the Twin-Otter airborne multi-band system developed by the SANDIA laboratory in the United States can work in four bands: Ka, Ku, X and UHF; the E-SAR system developed by the German Space Agency DLR can work in five bands: P, L, C, S and X; the P-3 SAR system developed by the ERIM Institute in the United States can work in four bands: X, C, L and P; the AIRSAR system developed by NASA in the United States can work in three bands: P, L and C. Multi-band information has been widely used in climate monitoring, resource exploration, land classification and other aspects. The information provided by SAR in different bands is redundant, complementary and cooperative. By integrating SAR image information of different frequencies, more complete and accurate target estimation and reconstruction can be obtained than with a single image.

[0004] For multi-polarization SAR, polarization SAR transmits and receives electromagnetic waves through two polarization channels, horizontal and vertical. The four sets of data measured can form a complete polarization basis, and any electromagnetic wave can be represented in this polarization basis. Therefore, polarization SAR can comprehensively obtain the scattering characteristics of the target to any electromagnetic wave in the observation direction, which is usually represented by a polarization scattering matrix. Compared with traditional SAR, polarization SAR greatly improves the ability to obtain scattering information of ground targets. At present, many airborne tomography SARs also have multi-polarization transceiver systems, which can not only achieve three-dimensional resolution of the target area, but also obtain polarization scattering information of the target area, which is called polarization tomography SAR. This further expands the application scope of polarization information.

[0005] Due to the different perspective relationship between SAR images and optical images, it is difficult to directly read SAR images. Therefore, SAR three-dimensional point cloud reconstruction technology can convert the less intuitive SAR two-dimensional images into three-dimensional point clouds that are easy to identify, process and analyze, and has high application value. The geometric structure of the target building, as a priori information that conforms to general cognition, can effectively improve the efficiency and quality of three-dimensional point cloud reconstruction. At present, the drone-mounted MV3DSAR system developed by the Institute of Space Information Innovation of the Chinese Academy of Sciences has also introduced the geometric structure information of the target building as an auxiliary when performing three-dimensional imaging processing of buildings in areas such as Tianjin Lingang.

[0006] Multi-band, multi-polarization and geometric information are important information of the target obtained by tomographic SAR, which can play a key role in the reconstruction of three-dimensional point clouds. However, the current common processing methods can only use one of these information, and the data utilization rate is insufficient. Therefore, it is necessary to build a holographic model for the target building that can contain the above multiple information. By combining tomographic SAR with the holographic model, more accurate, detailed and informative three-dimensional point cloud imaging of buildings can be achieved. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a tomographic SAR three-dimensional point cloud imaging method and device based on a holographic model, which pre-processes and performs two-dimensional imaging on multi-polarization multi-band tomographic SAR data, performs registration and amplitude phase correction on the two-dimensional complex image after two-dimensional imaging, and then constructs a holographic three-dimensional model, which contains the geometric features, multi-polarization and multi-band information of the target. The constructed holographic three-dimensional model is used to reconstruct the three-dimensional point cloud of the two-dimensional tomographic SAR image to obtain high-quality three-dimensional point cloud imaging results and multi-polarization, multi-band scattering characteristic information of the target building.

[0008] The tomographic SAR three-dimensional point cloud imaging method based on the holographic model proposed in the present invention can effectively solve the problems of single building structure and polarization information obtained by traditional single-polarization single-band tomographic SAR, poor three-dimensional reconstruction quality, and insufficient point cloud details. It can obtain high-quality three-dimensional point cloud imaging results of the target building and multi-polarization, multi-band scattering characteristic information.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A tomographic SAR three-dimensional point cloud imaging method based on a holographic model, wherein the hologram is polarization, frequency and geometric information obtained for a target, and the holographic model is a physical model constructed by fusing the geometric features, multi-polarization and multi-band information of the target, and comprises the following steps:

[0011] Step 1, performing two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data;

[0012] Step 2, performing registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group;

[0013] Step 3: construct a holographic three-dimensional model, which includes geometric features, multi-polarization and multi-band information of the target; combining the two-dimensional complex image group processed in step 2 and the constructed holographic three-dimensional reconstruction model, a holographic constrained compressed sensing three-dimensional reconstruction algorithm is used to perform three-dimensional point cloud reconstruction to obtain the three-dimensional point cloud imaging result of the target building and the polarization and frequency scattering characteristic information of the target building;

[0014] Step 4: Further post-process the 3D point cloud imaging result in step 3 in combination with the holographic 3D reconstruction model constructed in step 3 to obtain a high-quality 3D point cloud imaging result of tomographic SAR based on the holographic model.

[0015] The present invention also provides a tomographic SAR three-dimensional point cloud imaging device based on a holographic model, comprising the following modules:

[0016] Imaging module, which performs two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data;

[0017] A registration and correction module performs registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group;

[0018] A holographic construction module constructs a holographic three-dimensional model, which usually contains the geometric features, multi-polarization and multi-band information of the target; combines the two-dimensional complex image group and the holographic three-dimensional model, and uses a holographic constrained compressed sensing three-dimensional reconstruction algorithm to reconstruct the three-dimensional point cloud to obtain the three-dimensional point cloud imaging result of the target building as well as the polarization information and frequency scattering characteristic information of the target building;

[0019] The imaging processing module further post-processes the three-dimensional point cloud imaging results in combination with the constructed holographic three-dimensional model to obtain high-quality three-dimensional point cloud imaging results of tomographic SAR based on the holographic model.

[0020] 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 the above-mentioned tomographic SAR three-dimensional point cloud imaging method based on the holographic model are implemented.

[0021] 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 the above-mentioned tomographic SAR three-dimensional point cloud imaging method based on the holographic model are implemented.

[0022] Beneficial effects:

[0023] The present invention constructs a holographic model for a target building, which can include one or more of polarization information, multi-frequency (multi-band) information, and geometric structure information. By combining tomographic SAR with a holographic model, more accurate, detailed, and informative three-dimensional point cloud imaging of buildings can be achieved. The principle is that more SAR imaging information, such as polarization information, frequency information, etc., are introduced into the traditional three-dimensional imaging process, and more prior knowledge of the target building, such as geometric structure information, etc., is introduced, and appropriate constraint methods are used to solve the problem by constructing a joint reconstruction optimization problem. Therefore, it can effectively solve the problems of single building structure and polarization information obtained by traditional single-polarization single-band tomographic SAR, poor three-dimensional reconstruction quality, and insufficient point cloud details, and obtain high-quality three-dimensional point cloud imaging results of the target building. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a tomographic SAR three-dimensional point cloud imaging method based on a holographic model of the present invention;

[0025] Figure 2 This is the result of the three-dimensional point cloud imaging of the target building by traditional tomographic SAR;

[0026] Figure 3 This is the three-dimensional point cloud imaging result of the target building using tomographic SAR with polarization and geometric model. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. used in the present invention to indicate the orientation or position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] The hologram in the present invention refers to the polarization, frequency and geometric information obtained for the target, and the holographic model refers to a physical model constructed by integrating the geometric features, multi-polarization and multi-band information of the target.

[0031] like Figure 1 As shown, a tomographic SAR three-dimensional point cloud imaging method based on a holographic model of the present invention comprises the following steps:

[0032] Step 1, performing two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data;

[0033] Step 2, performing registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group;

[0034] Step 3: construct a holographic three-dimensional model, which usually includes geometric features, multi-polarization and multi-band information of the target; combining the two-dimensional complex image group processed in step 2 and the constructed holographic three-dimensional model, a holographic constrained compressed sensing three-dimensional reconstruction algorithm is used to reconstruct a three-dimensional point cloud to obtain a three-dimensional point cloud imaging result of the target building and polarization and frequency scattering characteristic information of the target building;

[0035] Step 4: Further post-process the three-dimensional point cloud imaging result in step 3 in combination with the holographic three-dimensional model constructed in step 3 to obtain a high-quality three-dimensional point cloud imaging result of tomographic SAR based on the holographic model.

[0036] Specifically, step 3 includes constructing polarization information and a polarization model of the target building:

[0037] The polarization information and polarization model of the target building can make the 3D point cloud reconstruction result have more details, make the 3D reconstruction result more complete, the information more sufficient, and the scattering characteristics of the target more complete. The holographic 3D model constructed in step 3 contains the geometric characteristics, multi-polarization and multi-band information of the target. First, the polarization information and the construction of the polarization model are introduced.

[0038] Analyzing the polarization response of different structures of the target building is an important part of establishing the polarization model of the building. Multi-polarization SAR usually uses the polarization scattering matrix S to describe the polarization characteristics of the target. The subscript of S represents the polarization mode of transmitting and receiving electromagnetic waves, where H represents horizontal polarization and V represents vertical polarization. For fully polarized SAR, a pair of orthogonal fully polarized waves is transmitted and received, and the polarization scattering matrix corresponding to each pixel can be obtained. By using the multi-polarization scattering characteristics of the target, each observation antenna track can obtain complex image data of four polarization channels. The expression of the polarization scattering matrix S is as follows:

[0039] (1)

[0040] In the above formula, S HH represents the scattering coefficient of horizontal polarization transmission and horizontal polarization reception, S HV S represents the scattering coefficient of horizontal polarization transmission and vertical polarization reception, VH S represents the scattering coefficient of vertically polarized transmission and horizontally polarized reception, VV It represents the scattering coefficient of vertical polarization transmission and vertical polarization reception. Under the condition of reciprocity, we have The polarization scattering matrix S fully expresses the scattering characteristics of the target: energy characteristics, phase characteristics, and polarization characteristics. By decomposing the scattering data of the four polarization channels, the polarization characteristic information of the target can be obtained. In addition, polarization coherence matrices are more often used in the study of polarization scattering processes. First, the Pauli basis is used to convert the scattering matrix S into the Pauli polarization vector k:

[0041] (2)

[0042] in, represents the imaginary unit and the superscript T represents the transpose of the matrix.

[0043] The corresponding polarization coherence matrix T can be obtained from the Pauli polarization vector k, and the formula is as follows:

[0044] (3)

[0045] The superscript in formula (3) Represents the conjugate of the matrix. The polarization coherence matrix T is a 3×3 complex matrix. Like the polarization scattering matrix, it also contains the complete polarization information of the target and is usually used for polarization coherence decomposition of the target.

[0046] By analyzing the common structures in the target building, the following structures can be abstracted: plane structure, dihedral structure, scatterer structure, etc. Taking Freeman decomposition commonly used in polarization decomposition as an example, the corresponding scattering mechanisms are: surface scattering, even scattering and volume scattering.

[0047] The formula for Freeman decomposition is as follows:

[0048] (4)

[0049] Among them, T surface , T double , T volume They represent the polarization coherence matrix corresponding to the surface scattering model, the polarization coherence matrix corresponding to the even-order scattering model, and the polarization coherence matrix corresponding to the volume scattering model. , , They represent the energy of surface scattering, the energy of even scattering, and the energy of volume scattering, respectively. They are all non-negative real numbers, and their sum is equal to the total power , as shown below:

[0050] (5)

[0051] The surface scattering model is a first-order Bragg surface scatterer. The polarization coherence matrix T corresponding to the surface scattering model is surface The expression is as follows:

[0052] (6)

[0053] The model of even-order scattering is similar to that of a dihedral reflector, and the corresponding polarization coherence matrix T for the model of volume scattering is double The expression is as follows:

[0054] (7)

[0055] in, and are all unknown parameters. and are all complex numbers whose absolute values ​​are less than 1.

[0056] The volume scattering model is obtained by a dipole scatterer with a uniform distribution of azimuth angles from 0 to 2π. The corresponding polarization coherence matrix T volume The expression is as follows:

[0057] (8)

[0058] The specific decomposition process can be done by using traditional Freeman decomposition or Yamaguchi decomposition methods, which will not be described in detail here. is decomposed into surface scattered energy Even-order scattering energy , the volume scattering energy from the purely random scatterer structure Through these decomposition results, a polarization scattering model of the target building can be constructed. Taking a rectangular building as an example, the smooth plane between the top and the ground of the building is usually surface scattering, the angle between the side of the building and the ground forms a dihedral structure, which is usually even scattering, and complex structures such as the window part of the building are usually volume scattering. By making full use of polarization information, polarization tomography SAR can provide richer and more accurate ground object information and improve the application efficiency and value of data.

[0059] Specifically, the step 3 also includes constructing geometric information and a geometric model of the target building:

[0060] Compared with the polarimetric model, which adds more target scattering characteristics to the three-dimensional reconstruction point cloud, the geometric model has more advantages in reducing the number of SAR re-orbit flights and the number of arrays required for array interferometric SAR. In order to reduce the observation channel of tomographic SAR, on the one hand, the radar performance can be improved, but the cost of hardware improvement is relatively large. On the other hand, new information sources can be introduced in the three-dimensional reconstruction process, namely the geometric information of the target building. At present, the mainstream processing method for three-dimensional reconstruction of tomographic SAR is to invert the scattering information and elevation information pixel by pixel for multiple registered two-dimensional tomographic SAR images. In this process, the geometric structure information of the observed target is not fully utilized, and the application of visual semantics is insufficient. By analyzing the microwave scattering mechanism and exploring the visual semantics of the image, the three-dimensional information implicit in the radar echo and the two-dimensional image is extracted, thereby reducing the number of multi-angle observations required and realizing more efficient three-dimensional imaging technology. Among them, in-depth analysis of the geometric structure of the building in the image visual semantics can construct a geometric model based on the geometric information target.

[0061] At present, the three-dimensional reconstruction of buildings based on geometric model constraints mainly consists of the following steps: first, preliminary three-dimensional reconstruction and filtering processing are performed based on the original data; the point, line and surface structure of the building is extracted from the reconstructed point cloud, and a geometric constraint model is formed based on the prior knowledge of the building; combined with the geometric constraint model, the constraint-based three-dimensional reconstruction is completed again. In traditional unconstrained three-dimensional reconstruction, because at the bottom corner of the building, the side and the ground form a scattering structure similar to the dihedral angle, which causes the radar echo to be scattered multiple times here (the constructed polarization model can also confirm this result). The three-dimensional reconstruction result is manifested as a repeated L-shaped structure at the bottom corner, such as Figure 2 As shown in the gray circle. This phenomenon may cause errors in point cloud when it is further clustered, identified and other application scenarios. Therefore, in order to solve the multiple scattering and overlapping problems between buildings generated in the process of building reconstruction and reduce the number of tomographic SAR observation channels, a 3D reconstruction method based on geometric model constraints is proposed.

[0062] The basic model of tomography can be expressed as:

[0063] (9)

[0064] Where y is the observed multi-channel tomographic SAR data vector. A is the tomographic imaging observation matrix, which describes the mapping relationship between the target slant height direction and the two-dimensional projection. x is the slant height vector to be reconstructed. n is the noise vector. The geometric model constraints of tomographic SAR can be implemented through the following optimization problem:

[0065] (10)

[0066] in, It is a data fitting term to ensure the consistency of the reconstruction results with the observed data. is a regularization term that introduces geometric and polarization model constraint information. is a regularization parameter that weighs the effects of the data fitting term and the geometric constraint term. It can usually be selected based on the reconstruction residual and the model similarity. The results of using polarization and geometric model constraints are as follows: Figure 3 As shown in the figure, not only the erroneous point cloud structure is eliminated, but also the point cloud is smoother and has less noise. It can also avoid the occurrence of over-constraint. By introducing geometric model constraints in the 3D reconstruction algorithm, the 3D reconstruction accuracy and robustness of tomographic SAR can be effectively improved, which is particularly suitable for complex scenes and high-resolution imaging requirements.

[0067] Specifically, the step 3 also includes constructing a frequency information application model in multi-band tomographic SAR:

[0068] Multi-band tomographic SAR uses SAR data of different frequencies (bands) for three-dimensional reconstruction. These data of different frequencies can provide complementary information, thereby improving the reconstruction accuracy and the richness of information extraction. For example, different objects have different scattering characteristics at different frequencies. Low-frequency (such as P-band, L-band) signals can penetrate vegetation and soil to obtain information below the surface; high-frequency (such as C-band, X-band) signals provide higher spatial resolution, which is suitable for detail capture and surface feature extraction. When using multi-band tomographic SAR data to perform three-dimensional modeling of building targets in urban areas, low-frequency data provides the overall outline of the building, such as segmentation and extraction of multiple buildings; high-frequency data captures the details of the building, such as the structure of the roof and walls.

[0069] The basic model of multi-band tomographic SAR can be expressed as:

[0070] (11)

[0071] in, is the observation vector of the mth frequency band tomographic SAR. is the observation matrix of the mth frequency band tomography. is the slant height vector to be reconstructed in the mth frequency band. is the noise vector of the mth frequency band, and N is the number of frequency bands. Multi-band tomographic SAR can achieve complementarity in space and information dimensions by combining data of different frequencies, thereby improving the accuracy and information richness of 3D reconstruction. In practical applications, the key to successfully achieving high-quality reconstruction is to reasonably select and process tomographic SAR data of different frequencies.

[0072] Specifically, in step 4, the holographic model and tomographic SAR combined three-dimensional reconstruction and point cloud post-processing include:

[0073] By combining the polarization and frequency information received by the tomographic SAR with the geometric structure information of the target building itself, a holographic model of the target building can be constructed. The holographic model contains one or more of the above-mentioned information, and then the constructed holographic model is used for joint 3D reconstruction, which is solved by the joint reconstruction optimization problem:

[0074] (12)

[0075] in, is the data fitting term for the mth frequency band. is the regularization term of the mth frequency band, which is used to introduce geometric and polarization model constraint information. is the regularization parameter, which weighs the influence of data fitting term and polarization and geometric constraint term. min represents the minimization of the optimization problem. is the slant height vector to be reconstructed in the Nth frequency band. The specific reconstruction algorithm is completed by using a modified compressed sensing algorithm, such as a modified OMP algorithm, etc., which will not be described in detail here.

[0076] In step 3, the point cloud after 3D reconstruction using the holographic model has high reconstruction accuracy and polarization frequency information. However, since the data received by SAR usually contains noise, the reconstructed original 3D point cloud will inevitably have problems such as redundant points, noise points, and irregular distribution. Therefore, it is very important to post-process the reconstructed point cloud, which can effectively improve the accuracy and practicality of the data, that is, step 4.

[0077] First, point cloud denoising. Scattering intensity filtering and reconstruction confidence filtering can eliminate some erroneous point clouds caused by overlapping or irregular distribution. Statistical filtering or mean filtering can eliminate discrete noise points and improve the quality and smoothness of point clouds. Secondly, point cloud downsampling can be performed, such as voxel grid downsampling algorithms, to reduce the amount of point cloud data, improve processing efficiency, and maintain the geometric features of point clouds. Point cloud surface reconstruction, point cloud classification and instance segmentation, point cloud clustering and other processing methods can also be performed to improve data quality and make the number of point clouds suitable for various application environments, preparing for the next step of target recognition, target classification, urban modeling, etc.

[0078] The present invention also provides a tomographic SAR three-dimensional point cloud imaging device based on a holographic model, comprising the following modules:

[0079] Imaging module, which performs two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data;

[0080] A registration and correction module performs registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group;

[0081] A holographic construction module constructs a holographic three-dimensional model, which usually contains the geometric features, multi-polarization and multi-band information of the target; combines the two-dimensional complex image group and the holographic three-dimensional model, and uses a holographic constrained compressed sensing three-dimensional reconstruction algorithm to reconstruct the three-dimensional point cloud to obtain the three-dimensional point cloud imaging result of the target building and the polarization and frequency scattering characteristic information of the target building;

[0082] The imaging processing module further post-processes the three-dimensional point cloud imaging results in combination with the constructed holographic three-dimensional model to obtain high-quality three-dimensional point cloud imaging results of tomographic SAR based on the holographic model.

[0083] 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 the above-mentioned tomographic SAR three-dimensional point cloud imaging method based on the holographic model are implemented.

[0084] 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 the above-mentioned tomographic SAR three-dimensional point cloud imaging method based on the holographic model are implemented.

[0085] It should be understood by those skilled in the art that the embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The solutions in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and interpreted scripting language JavaScript, etc.

[0086] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0087] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0088] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0089] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0090] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A tomographic SAR three-dimensional point cloud imaging method based on a holographic model, characterized in that: The steps include: Step 1, performing two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data; Step 2, performing registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group; Step 3: construct a holographic three-dimensional model, which includes geometric features, multi-polarization and multi-band information of the target; combining the two-dimensional complex image group obtained in step 2 and the constructed holographic three-dimensional model, a holographic constrained compressed sensing three-dimensional reconstruction algorithm is used to reconstruct a three-dimensional point cloud to obtain a three-dimensional point cloud imaging result of the target building as well as polarization information and frequency scattering characteristic information of the target building; It also includes constructing the polarization information and polarization model of the target building, constructing the geometric information and geometric model of the target building, and constructing the frequency information application model in multi-band tomographic SAR; Step 4: further post-process the three-dimensional point cloud imaging result in step 3 in combination with the holographic three-dimensional model constructed in step 3 to obtain a high-quality three-dimensional point cloud imaging result of tomographic SAR based on the holographic model; The post-processing includes point cloud denoising, using scattering intensity filtering and reconstruction confidence filtering, and using statistical filtering or mean filtering to eliminate discrete noise points; performing point cloud downsampling to maintain the geometric features of the point cloud; Perform point cloud surface reconstruction, point cloud classification and instance segmentation, and point cloud clustering.

2. The method for tomographic SAR three-dimensional point cloud imaging based on a holographic model according to claim 1, characterized in that: In step 3, the geometric features include the position, size, and structure of the target building in the three-dimensional Euclidean space or the radar oblique height space.

3. The method for tomographic SAR three-dimensional point cloud imaging based on a holographic model according to claim 1, characterized in that: In step 3, the polarization information includes the scattering characteristics and polarization type of the target building, which are described by the polarization scattering matrix S and the Pauli scattering vector K.

4. The method for tomographic SAR three-dimensional point cloud imaging based on a holographic model according to claim 1, characterized in that: In step 3, the frequency scattering characteristic information includes multi-band tomographic SAR imaging results, and the influence of different SAR frequencies on polarization scattering characteristics and geometric features.

5. A tomographic SAR three-dimensional point cloud imaging device based on a holographic model, characterized in that: Includes the following modules: Imaging module, which performs two-dimensional imaging on multi-polarization multi-band tomographic SAR echo data; A registration and correction module performs registration and amplitude phase correction on the two-dimensional complex image obtained by two-dimensional imaging to obtain a registered and corrected two-dimensional complex image group; A holographic construction module constructs a holographic three-dimensional model, which includes the geometric features, multi-polarization and multi-band information of the target; combines the two-dimensional complex image group and the constructed holographic three-dimensional model, and uses a holographic constrained compressed sensing three-dimensional reconstruction algorithm to reconstruct a three-dimensional point cloud to obtain the three-dimensional point cloud imaging result of the target building and the polarization information and frequency scattering characteristic information of the target building; constructs the polarization information and polarization model of the target building, constructs the geometric information and geometric model of the target building, and constructs a frequency information application model in multi-band tomographic SAR; The imaging processing module further post-processes the three-dimensional point cloud imaging results in combination with the holographic three-dimensional model to obtain a high-quality three-dimensional point cloud imaging result of the tomographic SAR based on the holographic model; the post-processing includes point cloud denoising, using scattering intensity filtering and reconstruction confidence filtering, and using statistical filtering or mean filtering to eliminate discrete noise points; performing point cloud downsampling to maintain the geometric features of the point cloud; Perform point cloud surface reconstruction, point cloud classification and instance segmentation, and point cloud clustering.

6. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the tomographic SAR three-dimensional point cloud imaging method based on a holographic model are implemented as described in any one of claims 1 to 4.

7. 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 tomographic SAR three-dimensional point cloud imaging method based on a holographic model as described in any one of claims 1 to 4 are implemented.

Images