Double scattering point separation method and device for array interferometric SAR three-dimensional imaging

Abstract

The present invention discloses a method and device for separating double scattering points for array interferometric SAR three-dimensional imaging, and relates to the field of radar imaging and signal processing technology. The method comprises: estimating the slant height difference of double scattering points according to the amplitude value of the observation vector; estimating the slant height of the low scattering point according to the slant height difference of the double scattering points; accurately searching the positions of the double scattering points, and calculating the backscattering coefficients of the double scattering points. The present invention can accurately separate the overlapping double scattering points, and has super-resolution capability, which is conducive to improving the quality of array interferometric SAR three-dimensional imaging.

Description

Technical Field

[0001] The invention belongs to the technical field of radar imaging and signal processing, and in particular relates to a double scattering point separation method and device for array interferometric SAR three-dimensional imaging. Background Art

[0002] The two-dimensional synthetic aperture radar (SAR) imaging technology realizes range resolution by emitting a large bandwidth signal in the range direction, and realizes azimuth resolution by moving in the azimuth direction to form a synthetic aperture, but it does not have the ability to resolve in the third dimension. The distribution of the backscatter coefficient of the ground object in the third dimension will be integrated into the two-dimensional azimuth-range plane. Tomographic SAR can perform third-dimensional resolution by adding observation positions across the heading and applying inversion algorithms such as spectral analysis and compressed sensing. For urban scenes, due to the presence of buildings, there are a lot of overlapping phenomena in SAR images, among which the overlapping of double scattering points accounts for a large proportion, so it is necessary to separate the overlapping double scattering points to improve the quality of array interferometric SAR three-dimensional imaging.

[0003] The traditional orthogonal matching pursuit (OMP) method has the disadvantage of insufficient super-resolution capability. When the distance between the two scattering points is large, they can be separated to their correct positions, but when the distance between the two scattering points is small, they cannot be separated correctly. Although the traditional multiple signal classification (MUSIC) method has a certain super-resolution capability, it needs to use the covariance matrix of the observation vector. Since the real SAR data does not have multi-snap sampling, multiple observation vectors in the neighborhood are used to estimate the covariance matrix, which will lead to a decrease in image resolution. Moreover, when the distribution of scattering points in the neighborhood is inconsistent, there will be a large separation error. Therefore, it is urgent to find a method that can perform super-resolution without multi-snap data to improve the quality of array interferometric SAR three-dimensional imaging. Summary of the invention

[0004] To solve the above technical problems, the present invention provides a double scattering point separation method and device for array interferometric SAR three-dimensional imaging, so as to obtain the positions and backscattering coefficients of the overlapping double scattering points and improve the quality of array interferometric SAR three-dimensional imaging.

[0005] In order to achieve the above object, the present invention proposes the following technical solutions:

[0006] A double scattering point separation method for array interferometric SAR three-dimensional imaging comprises the following steps:

[0007] Step 1: Using the SLC image of the main channel as the reference image, align the SLC images of each auxiliary channel with the reference image, and then perform amplitude and phase error correction between channels to obtain a preprocessed SLC image stack; SLC stands for single-view complex;

[0008] Step 2: Select pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimate the oblique height difference of the double scattering points according to the amplitude value of the observation vector; construct an observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression;

[0009] Step 3, based on the observation vector, observation matrix, and slant height difference of the double scattering points obtained in step 2, estimate the slant height of the low scattering point;

[0010] Step 4: Calculate the slant height of the high scattering point based on the slant height difference of the double scattering points and the slant height of the low scattering point, accurately search for the position of the double scattering point, and calculate the backscattering coefficient of the double scattering point.

[0011] The present invention also provides a double scattering point separation device for array interferometric SAR three-dimensional imaging, comprising the following modules:

[0012] The image stack acquisition module uses the SLC image of the main channel as the reference image, aligns the SLC images of each auxiliary channel with the reference image, and then performs amplitude and phase error correction between channels to obtain the pre-processed SLC image stack; SLC stands for single-view complex;

[0013] The oblique height difference estimation module selects pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimates the oblique height difference of the double scattering points according to the amplitude value of the observation vector; constructs the observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression;

[0014] The slant height estimation module estimates the slant height of the low scattering point based on the observation vector, observation matrix, and the slant height difference of the double scattering points;

[0015] The backscatter coefficient estimation module calculates the slant height of the high scattering point according to the slant height difference of the double scattering points and the slant height of the low scattering point, accurately searches for the position of the double scattering point, and calculates the backscatter coefficient of the double scattering point.

[0016] 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 double scattering point separation method for array interferometric SAR three-dimensional imaging are implemented.

[0017] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned double scattering point separation method for array interferometric SAR three-dimensional imaging.

[0018] Beneficial effects of the present invention:

[0019] The present invention converts the problem of separating double scattering points into estimating the slant height difference of double scattering points by modeling the overlapping situation of double scattering points, and can still accurately separate the double scattering points when the interval between the two scattering points is very small. When the method is used for array interferometric SAR three-dimensional imaging, the density of the imaging point cloud can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of a double scattering point separation method for array interferometric SAR three-dimensional imaging according to the present invention;

[0021] Figure 2a , Figure 2b The double scattering point separation experiment results in the embodiment of the present invention; wherein, Figure 2a is the processing result of the OMP method, Figure 2b It is the processing result of the method proposed by the present invention. DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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.

[0025] According to an embodiment of the present invention, Figure 1 As shown, a double scattering point separation method for array interferometric SAR three-dimensional imaging of the present invention comprises the following steps:

[0026] Step 1: Using the single look complex (SLC) image of the main channel as the reference image, align the SLC images of each auxiliary channel with the reference image, and then perform amplitude and phase error correction between channels to obtain a preprocessed SLC image stack.

[0027] Step 2: Select pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimate the oblique height difference of the double scattering points according to the amplitude value of the observation vector; construct an observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression; specifically include:

[0028] Step 2.1: Use the cosine theorem of the triangle to construct the relationship between the amplitude value of the observation vector, the amplitude value of the double scattering point, the slant height difference of the double scattering points, and the phase difference of the double scattering points;

[0029] First, establish the relationship between the observation vector and the backscattering coefficient and slant height of the two scattering points:

[0030] (1)

[0031] in, is the mth element of the observation vector, is the observation vector The magnitude of the elements, The value range is 1 to , meaning is The amplitude of the SLC image pixels obtained by the antennas is Antennas; For index operation, is an imaginary unit, is the observation vector The phase of an element, It is The distance from the antenna to the reference terrain, is the wavelength of the radar carrier, is the backscatter coefficient of the low scattering point, is the magnitude of the backscatter coefficient at the low scattering point, is the phase of the backscatter coefficient at the low scattering point, It is The vertical baseline component of the antenna, is the slant height of the low scattering point, is the backscattering coefficient of the high scattering point, is the magnitude of the backscatter coefficient at the high scattering point, is the phase of the backscatter coefficient at the high scattering point, is the slant height of the high scattering point.

[0032] According to the cosine theorem of a triangle, we can get:

[0033] (2)

[0034] in, is the angle between the sides represented by the double scattering points in the triangle, and is expressed as follows:

[0035] (3)

[0036] make , represents the slant height difference of the double scattering points; let , represents the phase difference of the backscattering coefficients of the double scattering points; let the intermediate parameter , which is convenient for subsequent representation. We can get:

[0037] (4)

[0038] Special, order represents the main antenna. The vertical baseline component corresponding to the main antenna is 0, so , then we get:

[0039] (5)

[0040] Further we can get:

[0041] (6)

[0042] The following three intermediate variables are defined: , , .

[0043] Let the intermediate variable (7)

[0044] (8)

[0045] Here c1, The intermediate parameter The formula can be deduced by analogy.

[0046] (9)

[0047] Construct the relationship between the amplitude value of the observation vector, the amplitude value of the double scattering point, the slant height difference of the double scattering point, and the phase difference of the double scattering point:

[0048] (10)

[0049] Step 2.2: Use the optimization method combining coarse grid search and gradient descent to solve equation (10) obtained in step 2.1 and estimate the slant height difference of the double scattering points. :

[0050] (11)

[0051] Among them, the superscript Indicates matrix transpose, superscript represents the matrix inversion, The meaning is to minimize the objective function , It means to calculate the 2-norm of a vector.

[0052] Step 3: Based on the observation vector, observation matrix, and the slant height difference of the double scattering points obtained in step 2 , estimate the slope height of low scattering points, including:

[0053] Step 3.1: Based on the array interferometric SAR three-dimensional imaging model, the relationship between the observation vector, the slant height difference of the double scattering points, and the slant height of the low scattering point is constructed;

[0054] The relationship between the observation vector, the slant height difference of the double scattering points, and the slant height of the low scattering point is as follows:

[0055] (12)

[0056] The following three intermediate variables are defined: , , .

[0057] Let the intermediate variable (13)

[0058] (14)

[0059] (15)

[0060] Construct the relationship between the observation vector in matrix form, the slant height difference of the double scattering points, and the slant height of the low scattering point:

[0061] (16)

[0062] Step 3.2: Use the optimization method combining coarse grid search and gradient descent to solve the formula (16) obtained in step 3.1 to estimate the slope height of the low scattering point. :

[0063] (17)

[0064] Step 4: Calculate the slant height of the high scattering point according to the slant height difference of the double scattering points and the slant height of the low scattering point, accurately search for the position of the double scattering point, and calculate the backscattering coefficient of the double scattering point, including:

[0065] Step 4.1: Calculate the slant height of the high scattering point, and then convert the slant height of the double scattering point into a downward viewing angle according to the spherical wave model;

[0066] Slope height of high scattering point The calculation formula is as follows:

[0067] (18)

[0068] The formula for calculating the viewing angle is as follows:

[0069] (18)

[0070] in, Number the scatter points, represents the low scattering point, represents a high scattering point, It is The lower viewing angle of the scattering point, represents the overall baseline inclination, It is The slope height of the scattering point is is the slant distance of the main antenna, The bottom perspective of the reference terrain.

[0071] Step 4.2: Taking the current double scattering point position as the initial value, use the gradient descent optimization method to further accurately search the lower viewing angle of the double scattering point and calculate the backscattering coefficient of the double scattering point;

[0072] The following three intermediate variables are defined: , , .

[0073] Let the intermediate variable (13)

[0074] (14)

[0075] (15)

[0076] in, Indicates Antenna to The slope distance of a scattering point is expressed as follows:

[0077] (15)

[0078] in It is The baseline tilt of the antenna, It is The baseline length of the antenna.

[0079] The lower viewing angle of the double scattering point is accurately searched by solving the following optimization equation:

[0080] (17)

[0081] Get accurate , substitute into the matrix , then solve :

[0082] (15)

[0083] The backscattering coefficients of the double scattering points are , , For vector The first element of For vector The second element of .

[0084] Step 4.3: Convert the downward viewing angle of the double scattering point to ground distance and altitude:

[0085] The formula for converting the downward viewing angle to ground distance and height is as follows:

[0086] (19)

[0087] (20)

[0088] in, , They are The ground distance of the scattering point, The height of the scattering point, , They are the ground distance of the main antenna and the height of the main antenna respectively.

[0089] Example:

[0090] In order to verify the effectiveness of the method proposed in the present invention, the overlapping of double scattering points with different spacings was simulated. The traditional OMP method and the method proposed in the present invention were used respectively. The splitting results are shown in the figure below. Figure 2a , Figure 2b As shown, it can be seen that the method proposed in the present invention effectively separates the double scattering points and has super-resolution capability.

[0091] A double scattering point separation device for array interferometric SAR three-dimensional imaging, comprising the following modules:

[0092] The image stack acquisition module uses the SLC image of the main channel as the reference image, aligns the SLC images of each auxiliary channel with the reference image, and then performs amplitude and phase error correction between channels to obtain the pre-processed SLC image stack; SLC stands for single-view complex;

[0093] The oblique height difference estimation module selects pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimates the oblique height difference of the double scattering points according to the amplitude value of the observation vector; constructs the observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression;

[0094] The slant height estimation module estimates the slant height of the low scattering point based on the observation vector, observation matrix, and the slant height difference of the double scattering points;

[0095] The backscatter coefficient estimation module calculates the slant height of the high scattering point according to the slant height difference of the double scattering points and the slant height of the low scattering point, accurately searches for the position of the double scattering point, and calculates the backscatter coefficient of the double scattering point.

[0096] 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 double scattering point separation method for array interferometric SAR three-dimensional imaging are implemented.

[0097] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned double scattering point separation method for array interferometric SAR three-dimensional imaging.

[0098] 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.

[0099] 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.

[0100] 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 including 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.

[0101] 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 in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0102] 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.

[0103] 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 double scattering point separation method for array interferometric SAR three-dimensional imaging, characterized in that: The steps include: Step 1: Using the SLC image of the main channel as the reference image, align the SLC images of each auxiliary channel with the reference image, and then perform amplitude and phase error correction between channels to obtain a preprocessed SLC image stack; SLC stands for single-view complex; Step 2: Select pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimate the oblique height difference of the double scattering points according to the amplitude value of the observation vector; construct an observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression; Step 3, based on the observation vector, observation matrix, and slant height difference of the double scattering points obtained in step 2, estimate the slant height of the low scattering point; Step 4: Calculate the slant height of the high scattering point based on the slant height difference of the double scattering points and the slant height of the low scattering point, accurately search for the position of the double scattering point, and calculate the backscattering coefficient of the double scattering point.

2. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 1, characterized in that: The step 2 comprises: Step 2.1: Use the cosine theorem of the triangle to construct the relationship between the amplitude value of the observation vector, the amplitude value of the double scattering point, the slant height difference of the double scattering points, and the phase difference of the double scattering points; Step 2.2: Use the optimization method combining coarse grid search and gradient descent to solve the relationship obtained in step 2.1 and estimate the slant height difference of the double scattering points.

3. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 1, characterized in that: The step 3 comprises: Step 3.1: Based on the array interferometric SAR three-dimensional imaging model, construct the relationship between the observation vector, the slant height difference of the double scattering points, and the slant height of the low scattering point.

4. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 3, characterized in that: The step 3 also includes: Step 3.2: Use a combination of coarse grid search and gradient descent optimization to solve the relationship obtained in step 3.1 and estimate the slope height of the low scattering point.

5. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 1, characterized in that: The step 4 comprises: Step 4.1: Calculate the slant height of the high scattering point and convert the slant height of the double scattering point into a downward viewing angle according to the spherical wave model.

6. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 5, characterized in that: The step 4 also includes: Step 4.2: Taking the current double scattering point position as the initial value, use the gradient descent optimization method to further accurately search the lower viewing angle of the double scattering point and calculate the backscattering coefficient of the double scattering point.

7. The double scattering point separation method for array interferometric SAR three-dimensional imaging according to claim 6, characterized in that: The step 4 also includes: Step 4.3: Convert the downward viewing angle of the double scattering points to ground distance and altitude.

8. A double scattering point separation device for array interferometric SAR three-dimensional imaging, characterized in that: Includes the following modules: The image stack acquisition module uses the SLC image of the main channel as the reference image, aligns the SLC images of each auxiliary channel with the reference image, and then performs amplitude and phase error correction between channels to obtain the pre-processed SLC image stack; SLC stands for single-view complex; The oblique height difference estimation module selects pixels of each image at the same azimuth sampling index and the same distance sampling index of the SLC image stack to form an observation vector, and estimates the oblique height difference of the double scattering points according to the amplitude value of the observation vector; constructs the observation matrix based on the imaging geometric relationship of the SLC images of the main channel and each auxiliary channel and the SLC image pixel expression; The slant height estimation module estimates the slant height of the low scattering point based on the observation vector, observation matrix, and the slant height difference of the double scattering points; The backscatter coefficient estimation module calculates the slant height of the high scattering point according to the slant height difference of the double scattering points and the slant height of the low scattering point, accurately searches for the position of the double scattering point, and calculates the backscatter coefficient of the double scattering point.

9. 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 a double scattering point separation method for array interferometric SAR three-dimensional imaging are implemented as described in any one of claims 1 to 7.

10. 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 a double scattering point separation method for array interferometric SAR three-dimensional imaging as claimed in any one of claims 1 to 7 are implemented.

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