Method for monitoring surface deformation and interference pair optimization method thereof
By performing differential interference processing and optimization of the minimum spanning tree algorithm on SAR images, the selection of programmatic interference pairs is realized, solving the problem of selecting massive SAR image data, improving monitoring efficiency and accuracy, and reducing manpower and material costs.
Patent Information
- Application Number
- CN202410075703.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-18
- Publication Date
- 2025-07-18
AI Technical Summary
In the prior art, in the face of massive SAR image data, manual selection of interference pairs not only consumes a lot of manpower, but also easily introduces measurement errors, resulting in inaccurate monitoring results.
By performing differential interference processing on the SAR image, the unwrapped interference pair is extracted, and the minimum spanning tree algorithm and the root mean square error of the phase closure difference are used as evaluation indicators to achieve the optimization of the programmatic interference pair.
It significantly improves monitoring efficiency and detection accuracy, reduces manpower and material costs, and solves the problem of massive untangling interference in selection.
Smart Images
Figure CN120339342A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of data processing, and in particular to a method for monitoring surface deformation and a method for optimizing interference pairs thereof. Background Art
[0002] With the continuous progress of technology, geodetic techniques have been increasingly widely used in surface deformation monitoring. Through geodetic techniques, the situation of surface deformation can be effectively monitored and analyzed. It is a measurement technique based on mathematical and physical principles. And surface deformation monitoring helps to warn and predict geological disasters, and can provide important references and decision-making bases for engineering projects. At present, geodetic techniques mainly include the Global Positioning System (GPS), Terrestrial Laser Scanning (LiDAR), and Synthetic Aperture Radar Interferometry (InSAR). Among them, the Global Positioning System is one of the most common geodetic techniques, which calculates the position coordinates of the ground by using the distance difference between satellite signals and ground receivers. Terrestrial Laser Scanning measures the shape and contour of the ground by emitting laser beams to the ground and using receivers to receive the reflected laser signals. Synthetic Aperture Radar Interferometry uses the principle of radar measurement to infer the ground deformation situation by measuring the change in the propagation path of the received radar waves.
[0003] With the upgrade of SAR satellites and the development of InSAR technology itself, InSAR technology has been widely used in related research on surface deformation acquisition, such as volcanic activity monitoring, earthquake activity monitoring, geological structure analysis, surface uplift and subsidence analysis, surface water level change analysis, etc. As an important remote sensing technology, InSAR technology has changed the past traditional method of obtaining minute deformations of observed objects, and can measure surface deformation and surface changes with high precision and stability. In the case of an increasing number of on-orbit SAR satellites, in the face of a vast amount of SAR images, the generated interference pairs are also vast. If not selected, it will impose a huge pressure on computing devices and introduce errors, resulting in an impact on the monitoring results and the inability to obtain high-precision detection results. In the prior art, the method of manually selecting interference pairs is mostly adopted, which not only requires a large amount of manpower, but also causes measurement errors due to visual fatigue and different scales of the human eye, and then inaccurate measurement occurs.
[0004] Therefore, in the face of a vast amount of SAR image data, the prior art needs to provide a solution for realizing automatic selection by a program. Summary of the Invention
[0005] The present invention aims to provide a method for optimizing SAR image interference pairs to realize automatic selection of interference pair data of a vast amount of SAR images by a program.
[0006] To solve the above technical problems, an embodiment of the present invention provides a method for optimizing SAR image interferometric pairs, including: obtaining full-time-domain SAR images of a target area; extracting interferometric pairs from the full-time-domain SAR images to obtain differential interferograms, and extracting unwrapped interferometric pairs from the differential interferograms; obtaining necessary interferometric pairs that satisfy the connectivity of the SAR images and have the smallest number of unwrapped interferometric pairs based on the full-time-domain SAR images marked with unwrapped interferometric pairs; dividing the full-time-domain SAR images marked with unwrapped interferometric pairs into multiple image groups, constructing interferometric closed loops in each image group and optimizing the interferometric closed loops with high coherence characteristics, and thus screening out qualified interferometric pairs based on the phase closure differences of the optimized interferometric closed loops; and combining the necessary interferometric pairs and the qualified interferometric pairs into optimized interferometric pairs.
[0007] Preferably, preprocessing operations are performed on the full-time-domain SAR images, including: cropping the full-time-domain SAR images based on the target area, and registering the cropped SAR images according to the precise orbit data and ground digital elevation model data of the target area. The registration includes, but is not limited to: removing Doppler effect correction from the cropped full-time-domain SAR images using the precise orbit data and georegistering the corrected full-time-domain SAR images using the ground digital elevation model data.
[0008] Preferably, in the process of extracting unwrapped interferometric pairs from the differential interferograms, it includes: successively performing correlation estimation, filtering and noise reduction processing, minimum cost flow unwrapping processing, atmospheric error removal processing, and trend effect removal processing on the differential interferograms, so as to extract unwrapped interferometric pairs.
[0009] Preferably, in the process of obtaining necessary interferometric pairs, it includes: using the preprocessed full-time-domain SAR images as nodes, and the unwrapped interferometric pairs in the unwrapped interferograms as edges, and constructing a minimum spanning tree that ensures the connectivity of all scenes in the full-time-domain SAR image information through the combination of nodes, edges, and the weights of the unwrapped interferometric pairs. Among them, the weight of the unwrapped interferometric pair is set based on the vertical baseline of the unwrapped interferogram; and taking the unwrapped interferometric pairs corresponding to the edges in the minimum spanning tree as necessary interferometric pairs.
[0010] Preferably, in the process of dividing the full-time-domain SAR images into multiple image groups, it includes: successively taking each scene image of the full-time-domain SAR images as the first scene, and obtaining all images that start from the current first scene and span within the time baseline threshold, so as to form corresponding image groups.
[0011] Preferably, in the step of constructing interference closed loops in each image group and selecting the interference closed loops with high coherence characteristics, it includes: taking the first scene of each image group as the starting point and traversing the remaining scene images in the current image group to form several interference closed loops with the same starting point; calculating the coherence of each interference closed loop in each image group and sorting the coherence of the interference closed loops in the same image group; selecting a preset number of preferred interference closed loops with the top-ranked coherence in each image group.
[0012] Preferably, according to the coherence of each pair of interference pairs within the interference closed loop, the coherence of the corresponding interference closed loop is calculated, where the coherence of the interference closed loop is the sum of the coherence of each interference pair within the current closed loop.
[0013] Preferably, in the step of screening out qualified interference pairs based on the phase closure difference of the preferred interference closed loops, it includes: calculating the phase closure difference and its corresponding root mean square error of each interference closed loop according to the unwrapped phases of the unwrapped interference pairs included in the interference closed loop; according to the root mean square error of each interference closed loop, using a preset error threshold to screen out unqualified interference closed loops, where if the root mean square error of the phase closure difference of the interference closed loop is greater than the error threshold, it is determined that the current interference closed loop is an unqualified interference closed loop; counting the number of times the same unwrapped interference pair appears in all unqualified closed loops, and then according to the number of times each unwrapped interference pair appears, using a preset number threshold to eliminate the unqualified unwrapped interference pairs within the preferred interference closed loops, where if the number of times the unwrapped interference pair appears is greater than the number threshold, it is determined that the current unwrapped interference pair is an unqualified unwrapped interference pair; taking the remaining unwrapped interference pairs after eliminating the unqualified unwrapped interference pairs in the preferred interference closed loops within each image group as qualified interference pairs.
[0014] Preferably, the phase closure difference of each interference closed loop is calculated using the following expression:
[0015]
[0016] Where and respectively represent the unwrapped phases of three unwrapped interference pairs in the current interference closed loop, represents the phase closure difference of the interference closed loop, where the root mean square error of the phase closure difference of each interference closed loop is calculated using the following expression:
[0017]
[0018] Where N represents the total number of pixels in the unwrapped interference pairs, represents the value of the i-th pixel in the phase closure difference of the current interference closed loop, and RMS represents the root mean square error of the phase closure difference of the interference closed loop.
[0019] In addition, an embodiment of the present invention further provides a method for monitoring surface deformation, including: obtaining an original SAR image of a target area; processing the original SAR image according to the method for preferentially selecting an SAR image interference pair as described in the embodiment of the present invention; and obtaining the regional deformation rate by using the processed SAR image.
[0020] Compared with the prior art, one or more embodiments of the above solution may have the following advantages or beneficial effects:
[0021] The present invention proposes a method for monitoring surface deformation and a method for preferentially selecting an interference pair thereof. Based on differential interferometric processing of SAR images, a differential interferogram is obtained and preprocessed such as interference, filtering, unwrapping, and error removal, and then an unwrapped interference pair is obtained. Combining the phase closure error and the minimum spanning tree algorithm, and using the root mean square error of the phase closure error as an evaluation index for interference pair selection, the preferential selection of the interference pair is realized programmatically. The present invention can solve the problem of selecting a large number of unwrapped interference pairs, significantly improve the monitoring efficiency and detection accuracy, and reduce the human and material costs.
[0022] Other features and advantages of the present invention will be described in the subsequent description, and some of them will be obvious from the description, or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the description, the claims, and the drawings. Description of the Drawings
[0023] The drawings are used to provide a further understanding of the present invention, and constitute a part of the description. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:
[0024] Figure 1 It is a schematic diagram of the steps of the method for preferentially selecting an SAR image interference pair according to an embodiment of the present application.
[0025] Figure 2 It is a schematic diagram of the specific process of the method for preferentially selecting an SAR image interference pair according to an embodiment of the present application.
[0026] Figure 3 It is an example diagram of the minimum spanning tree in the method for preferentially selecting an SAR image interference pair according to an embodiment of the present application.
[0027] Figure 4 It is an example diagram of the recognition result of the preferential interference closed loop in the method for preferentially selecting an SAR image interference pair according to an embodiment of the present application.
[0028] Figure 5It is a result statistical example diagram of root mean square error in the method for optimizing SAR image interference pairs according to the embodiments of the present application.
[0029] Figure 6 It is an example diagram of the recognition result of unqualified interference closed loops in the method for optimizing SAR image interference pairs according to the embodiments of the present application.
[0030] Figure 7 It is an example diagram of the recognition result of unqualified interference pairs in the method for optimizing SAR image interference pairs according to the embodiments of the present application.
[0031] Figure 8 It is an example diagram of the recognition result of optimized interference pairs in the method for optimizing SAR image interference pairs according to the embodiments of the present application.
[0032] Figure 9 It is a standard deviation comparison example diagram in the method for optimizing SAR image interference pairs according to the embodiments of the present application.
[0033] Figure 10 It is a schematic diagram of the steps of the method for monitoring ground deformation according to the embodiments of the present application.
[0034] Figure 11 It is an example diagram of the regional ground deformation rate of the method for monitoring ground deformation according to the embodiments of the present application. Detailed implementation manners
[0035] The following will describe in detail the implementation manners of the present invention in combination with the accompanying drawings and embodiments, so as to fully understand how the present invention uses technical means to solve technical problems and achieve the implementation process of technical effects and implement accordingly. It should be noted that as long as there is no conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.
[0036] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.
[0037] The terms used here are only for describing specific embodiments and do not intend to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a" and "an" used here also intend to include the plural. It should also be understood that the terms "comprises" and / or "comprising" used here specify the presence of the stated features, integers, steps, operations, units and / or components, and do not exclude the presence or addition of one or more other features, integers, steps, operations, units, components and / or their combinations.
[0038] With the continuous progress of technology, geodetic techniques are increasingly widely used in surface deformation monitoring. Through geodetic techniques, the situation of surface deformation can be effectively monitored and analyzed. It is a measurement technique based on mathematical and physical principles. And surface deformation monitoring helps to warn and predict geological disasters, and can provide important references and decision-making bases for engineering projects.
[0039] With the upgrade of SAR satellites and the development of InSAR technology itself, InSAR technology has been widely used in related research on obtaining surface deformation, such as: volcanic activity monitoring, earthquake activity monitoring, geological structure analysis, surface uplift and subsidence analysis, surface water level change analysis, etc. As an important remote sensing technology, InSAR technology has changed the past traditional method of obtaining small deformations of observation objects, and can measure surface deformation and surface changes with high precision and stability. In the case of more and more on-orbit SAR satellites, in the face of a large number of SAR images, the number of generated interferometric pairs is also huge. If they are not selected, it will cause great pressure on computing devices and introduce errors, resulting in an impact on the monitoring results and unable to obtain high-precision detection results. In the existing technology, most of them adopt the method of manually selecting interferometric pairs, which not only requires a large amount of manpower, but also causes measurement errors due to visual fatigue and different human eye scales, and then leads to inaccurate measurement.
[0040] To solve the above problems, the present invention proposes a method for monitoring surface deformation and a method for optimizing interferometric pairs. The present invention is based on differential interferometric processing of SAR images, obtaining a differential interferogram and performing preprocessing such as interference, filtering, phase unwrapping, and error removal on it, and then obtaining an unwrapped interferometric pair. Combining the phase closure error and the minimum spanning tree algorithm, using the root mean square error of the phase closure error as the evaluation index for interferometric pair selection, realizing the optimization of interferometric pairs in a programmed manner. The present invention can solve the problem of selecting a large number of unwrapped interferometric pairs, significantly improve the monitoring efficiency and detection accuracy, and reduce the cost of manpower and material resources.
[0041] Example 1
[0042] Figure 1 It is a schematic diagram of the steps of the method for optimizing SAR image interferometric pairs according to an embodiment of the present application. Figure 2 It is a specific process schematic diagram of the method for optimizing SAR image interferometric pairs according to an embodiment of the present application. The following combines Figure 1 and Figure 2 to describe the method of this embodiment in detail.
[0043] Step S110: Obtain full-time domain SAR images of the target area.
[0044] In an embodiment of the present invention, the radar remote sensing image of the target area collected is used as the full-time-domain SAR image. In order to eliminate the position and attitude differences between different images, preprocessing operations need to be performed on the obtained full-time-domain SAR image. First, based on the target area, the full-time-domain SAR image is cropped, and the cropped SAR image is registered according to the precise orbit data and ground digital elevation model data of the target area, including but not limited to: removing Doppler effect correction from the cropped full-time-domain SAR image using the precise orbit data and georegistering the corrected full-time-domain SAR image using the ground digital elevation model data.
[0045] In one embodiment, first, based on the target area, the full-time-domain SAR image is cropped, and then a clearest image is selected from the cropped full-time-domain SAR image as the main image, and the remaining images are auxiliary images. The auxiliary images at different acquisition times are registered based on the main image. During the registration process, first, referring to the precise orbit data of the target area, Doppler effect removal correction is performed on the cropped image; then, in combination with the ground digital elevation model data, the radar remote sensing images collected at different times are registered under the radar coordinates of the main image, and resampling is performed on the images under the same reference coordinates through a registration offset polynomial according to the range direction and azimuth direction; then, registration in the overlapping area is performed based on spectral diversity to eliminate satellite orbit errors (phase discontinuities), thereby eliminating the position and attitude differences between different images, and thus completing the preprocessing of the full-time-domain SAR image. After preprocessing, the full-time-domain SAR images have higher coherence, providing a more accurate data basis for step S120.
[0046] Step S120: Extract the interferometric pairs from the preprocessed full-time-domain SAR image obtained in step S110 to obtain a differential interferogram, and extract the unwrapped interferometric pairs from the differential interferogram.
[0047] In an embodiment of the present invention, differential interferometry is performed on the preprocessed full-time-domain SAR image to form a differential interferogram representing the phase difference between two different-scene images. These interferograms contain surface deformation information and other interference noises, so optimization processing needs to be performed on them. In an embodiment of the present invention, the optimization processing includes but not limited to: successively performing correlation estimation, filtering and noise reduction processing, minimum cost flow unwrapping processing, removing atmospheric error processing, and removing trend effect processing on the differential interferogram. After optimization processing, the noise can be reduced, and then unwrapped interferometric pairs can be obtained in the full-time-domain SAR image.
[0048] Step S130: Obtain the necessary interferometric pairs that satisfy the connectivity of the SAR image and have the smallest number of unwrapped interferometric pairs according to the full-time-domain SAR image marked with unwrapped interferometric pairs.
[0049] In step S130, first, the preprocessed full-time-domain SAR image is used as a node, and the unwrapped interference pairs in the unwrapped interferogram are used as edges. By combining the nodes, edges, and weights of the unwrapped interference pairs, a minimum spanning tree that ensures the connectivity of all scenes in the full-time-domain SAR image information is constructed. Among them, the weight of the unwrapped interference pair is set based on the vertical baseline of the unwrapped interferogram. The unwrapped interference pair corresponding to the edge in the minimum spanning tree is the necessary interference pair.
[0050] Figure 3 This is an example diagram of the minimum spanning tree in the method for preferentially selecting SAR image interference pairs according to the embodiment of the present application. As Figure 3 shown, points 1 to 28 represent the preprocessed full-time-domain SAR images obtained through steps S110 and S120, and the edges connecting two of these points represent the unwrapped interference pairs in the unwrapped interferogram. First, all points are connected using the fewest unwrapped interference pairs. Among all cases where the points are connected, the Prim algorithm is used to calculate the weight of the connected graph in each case, and the case with the smallest weight of the connected graph is selected as the minimum spanning tree. Among them, the weight of the connected graph is the sum of the weights of each unwrapped interference pair within the current connected graph, and the weight of each unwrapped interference pair is set according to the vertical baseline of the unwrapped interferogram. The unwrapped interference pair corresponding to the edge in the minimum spanning tree is the necessary interference pair.
[0051] Step S140: Divide the full-time-domain SAR image marked with unwrapped interference pairs into multiple image groups, construct interference closed loops in each image group, and preferentially select the interference closed loops with high coherence characteristics, so as to screen out qualified interference pairs based on the phase closure difference of the preferentially selected interference closed loops.
[0052] In step S140, first, the full-time-domain SAR image marked with unwrapped interference pairs is grouped. Each scene image of the full-time-domain SAR image is sequentially used as the first scene, and all images within the time baseline threshold starting from the current first scene are obtained, thereby forming the corresponding image group.
[0053] In this embodiment, a time baseline threshold of 60 days and a spatial baseline threshold of 200 m are set. Images 1, 2, 3... 28 are obtained in chronological order. Then, starting from the first time node, the full-time-domain SAR images marked with unwrapped interferometric pairs are grouped by time. Starting from the first SAR image, a first image group is formed based on the current starting point and spanning 60 days. The images included in the first image group are Images 1, 2, 3, 4, and 5 respectively. Next, starting from the second SAR image, a second image group is formed based on the current starting point and spanning 60 days. The images included in the second image group are Images 2, 3, 4, 5, 6, and 7 respectively. In this way, corresponding image groups are formed using the full-time-domain SAR images marked with unwrapped interferometric pairs. It should be noted that the number of SAR images included in each image group may vary, which depends on the number of images captured by the radar within the time baseline threshold.
[0054] Further, in each image group, an interferometric closure loop is constructed and the interferometric closure loops with high coherence characteristics are selected. First, starting from the first image of each image group and traversing the remaining images in the current image group (the remaining images refer to all images in the subsequent sequence of the starting point), several interferometric closure loops with the same starting point are formed. Then, the coherence of each interferometric closure loop in each image group is calculated, and the coherence of the interferometric closure loops in the same image group is sorted. Among them, the coherence of an interferometric closure loop is the sum of the coherences of each interferometric pair within the current closure loop. Finally, a preset number of preferred interferometric closure loops with the top coherence in each image group are selected.
[0055] In this embodiment, Images 1 to 28 are represented by numbers 1 to 28 respectively. In each image group, starting from the first image of the current image group, a closed loop is formed by connecting it with other images in the group. Among them, each closed loop includes at least three images. Traverse all the images in the current image group to form several interferometric closure loops starting from the first image of the current image group.
[0056] In one embodiment, each interferometric closure loop consists of three images. In the first image group, it includes Images 1, 2, 3, 4, and 5, and the corresponding numbers are 1, 2, 3, 4, and 5 respectively. Starting from Image 1, in ascending order of the numbers, traverse the remaining images in the first group (Images 2 - 5) to form interferometric closure loops with the same starting point (Image 1). Enumerate the interferometric closure loops and represent them with numbers as: 123, 124, 125, 134, 135, and 145.
[0057] In the second image group, it includes Image 2, Image 3, Image 4, Image 5, Image 6, and Image 7, with corresponding numbers 2, 3, 4, 5, 6, and 7 respectively. Starting from Image 2, in ascending order of the numbers, traverse the remaining images in the second group (Images 3 - 7) to form an interference closed loop with the same starting point (Image 2). Enumerate the interference closed loops and represent them with numbers as: 234, 235, 236, 237, 245, 246, 247, 256, 257, and 267. According to this method, interference closed loops are constructed in each image group.
[0058] Furthermore, according to the coherence of each interference pair within the interference closed loop, calculate the coherence of the corresponding interference closed loop. Among them, the coherence of the interference closed loop is the sum of the coherences of each interference pair within the current closed loop. Then, perform coherence sorting on the interference closed loops in the same image group, and select a preset number of preferred interference closed loops with higher coherence in each image group.
[0059] Figure 4 This is an example diagram of the recognition result of the preferred interference closed loop in the method for preferentially selecting SAR image interference pairs according to the embodiments of the present application. In this embodiment, select 4 closed loops with higher coherence in each image group as the preferred interference closed loops. If there are less than four closed loops in a certain image group, then all the closed loops within this group are selected as the preferred interference closed loops.
[0060] In step S140, the steps of screening out qualified interference pairs based on the phase closure difference of the preferred interference closed loop include: First, according to the unwrapped phases of each unwrapped interference pair included in the interference closed loop, calculate the phase closure difference of each interference closed loop and its corresponding root mean square error. Then, in combination with the root mean square error of each interference closed loop and a preset error threshold, screen out the unqualified interference closed loops. Among them, if the root mean square error is greater than the error threshold, it is determined that the current interference closed loop is an unqualified interference closed loop.
[0061] After that, count the number of times the same unwrapped interference pair appears in all unqualified closed loops, and in combination with a preset number threshold, eliminate the unqualified unwrapped interference pairs within the preferred interference closed loop. Among them, if the number of appearances of the unwrapped interference pair is greater than the number threshold, it is determined that the current unwrapped interference pair is an unqualified unwrapped interference pair. Finally, take the remaining unwrapped interference pairs after eliminating the unqualified unwrapped interference pairs within the preferred interference closed loop in each image group as the qualified interference pairs.
[0062] In the embodiments of the present application, according to the unwrapped phases of each unwrapped interference pair included in the interference closed loop, calculate the phase closure difference of each interference closed loop. Among them, the phase closure difference of the interference closed loop is calculated using the following expression:
[0063]
[0064] Among them, and respectively represent the unwrapped phases of three unwrapped interference pairs in the current interference closed loop, represents the phase closure difference of the interference closed loop. In the embodiments of the present invention, each pixel of the SAR image contains phase value information related to the radar slant range. Differential interferometry is an operation of subtracting two SAR images, thereby obtaining an interference pair. The interference pair is in the form of a matrix, and the numerical value of the matrix represents the unwrapped phase of the pixels at the corresponding positions of the two SAR images of the current interference. Further, three interference pairs are connected end to end to form an interference closed loop, and the interference closed loop characterizes the phase closure relationship between the corresponding three SAR images. Since the interference pair is a matrix representing the phase difference of the SAR image, the phase closure difference of the interference closed loop is also a matrix, and the numerical value in the matrix is the sum of the numerical values of the three interference pairs forming the closed loop at the corresponding positions, characterizing the phase closure relationship of the three SAR images at the pixels corresponding to the numerical value. In an ideal case, the phase closure difference of the interference closed loop is 0, but due to errors and noises introduced during the unwrapping process of the interference pair, the phase closure difference is too large. Therefore, it is necessary to calculate the root mean square error of the phase closure difference of the interference closed loop to screen out unqualified interference closed loops. Among them, the root mean square error of the phase closure difference of the interference closed loop is calculated using the following expression:
[0065]
[0066] Among them, N represents the total number of pixels in the unwrapped interference pair, represents the value of the i-th pixel in the phase closure difference of the current interference closed loop, and RMS represents the root mean square error of the phase closure difference of the interference closed loop.
[0067] Figure 5 is an example diagram of the result statistics of the root mean square error in the method for optimizing the SAR image interference pair according to the embodiments of the present application. Figure 5 The distribution of the root mean square error of the phase closure difference of the interference closed loop is counted. Based on the root mean square error of the phase closure difference of each interference closed loop and in combination with a preset error threshold, unqualified interference closed loops are screened out. In this embodiment, the preset error is 1.5 rad, and unqualified interference loops with a root mean square error greater than 1.5 rad are screened out. Figure 6 is an example diagram of the identification result of the unqualified interference closed loop in the method for optimizing the SAR image interference pair according to the embodiments of the present application. As Figure 6As shown, most of the interferometric closure loops are unqualified interferometric closure loops. However, this does not mean that all the unwrapped interferometric pairs included in the unqualified interferometric closure loops are unqualified interferometric pairs. There is a situation where an unqualified interferometric closure loop is caused by an unqualified unwrapped interferometric pair. Therefore, count the number of times the same unwrapped interferometric pair appears in all unqualified closure loops, and combine it with a preset number threshold to eliminate the unqualified unwrapped interferometric pairs.
[0068] Figure 7 This is an example diagram of the identification result of unqualified interferometric pairs in the method for optimizing interferometric pairs of SAR images according to an embodiment of the present application. As Figure 7 shown, the preset number threshold is 3 times. By counting the frequency of unwrapped interferometric pairs in unqualified closure loops, eliminate the unqualified interferometric pairs that appear more than 3 times in unqualified closure loops. And in the optimized interferometric closure loops within each image group, the remaining unwrapped interferometric pairs are used as qualified interferometric pairs.
[0069] Step S150: Combine the necessary interferometric pairs and the qualified interferometric pairs into optimized interferometric pairs.
[0070] Figure 8 This is an example diagram of the identification result of optimized interferometric pairs in the method for optimizing interferometric pairs of SAR images according to an embodiment of the present application. As Figure 8 shown, the optimized interferometric pairs include: necessary interferometric pairs and qualified interferometric pairs.
[0071] Figure 9 This is an example diagram of standard deviation comparison in the method for optimizing interferometric pairs of SAR images according to an embodiment of the present application. In this embodiment, respectively based on the optimized interferometric pairs and the unoptimized interferometric pairs, use GAMMA software to generate a standard deviation result diagram representing the ground surface deformation rate. As Figure 9 shown, the standard deviation of the optimized interferometric pairs is closer to 0 than that of the unoptimized interferometric pairs. Thus, it can be seen that the deformation standard deviation of the interferometric pairs after optimization is smaller and the accuracy is higher.
[0072] Example 2
[0073] Based on the method for optimizing interferometric pairs of SAR images described in the above Embodiment 1, the present invention also provides a method for monitoring ground surface deformation. Figure 10 This is a schematic diagram of the steps of the method for monitoring ground surface deformation according to an embodiment of the present application. Next, Figure 10 the method of this embodiment will be described in detail.
[0074] Step S1001: Obtain the original SAR images of the target area.
[0075] In the embodiment of the present invention, the radar remote sensing images of the target area collected are used as full-time domain SAR images.
[0076] Step S1002: Process the original SAR image obtained in step S1001. Specifically, perform registration and differential interferometry processing on the original SAR image, extract the unwrapped interference pairs from the generated differential interferogram, and then screen out the preferred interference pairs.
[0077] In the embodiment of the present invention, based on the method for preferentially selecting SAR image interference pairs described in Embodiment 1, process the original SAR image, obtain the preferred interference pairs, and enter step S1003.
[0078] Step S1003: Use the processed SAR image to obtain the regional deformation rate.
[0079] Figure 11 This is an example diagram of the regional deformation rate of the method for monitoring surface deformation in the embodiments of this application. As Figure 11 shown, based on the obtained preferred interference pairs, use the Stacking-InSAR technology to obtain the high-precision deformation rate of the target area, which verifies the reliability of the method for monitoring surface deformation in the embodiments of this application.
[0080] The present invention proposes a method for monitoring surface deformation and a method for preferentially selecting interference pairs thereof. The present invention is based on performing differential interferometry processing on SAR images, obtaining a differential interferogram and performing preprocessing such as interference, filtering, unwrapping, and error removal on it, and then obtaining unwrapped interference pairs. Combining the phase closure error and the minimum spanning tree algorithm, using the root mean square error of the phase closure error as the evaluation index for selecting interference pairs, realizing the programmed preference of interference pairs. The present invention can solve the problem of selecting a large number of unwrapped interference pairs, significantly improve the monitoring efficiency and detection accuracy, and reduce the human and material costs.
[0081] As mentioned above, only the specific preferred embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
[0082] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "backend", "head", "tail", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are 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 thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.
[0083] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" 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 directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.
[0084] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not imply limitation.
[0085] The phrase "an embodiment" or "embodiments" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiments are included in at least one embodiment of the present invention. Therefore, the phrases "an embodiment" or "embodiments" that appear throughout the specification do not necessarily all refer to the same embodiment.
[0086] Although the embodiments disclosed in the present invention are as above, the content described above is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains, without departing from the spirit and scope disclosed by the present invention, can make any modifications and changes in the form of implementation and details, but the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.
Claims
1. A method for optimizing SAR image interferometric pairs, characterized in that, Including: Obtain the full-time-domain SAR image of the target area; Extract the interferometric pairs from the full-time-domain SAR image to obtain a differential interferogram, and extract the unwrapped interferometric pairs from the differential interferogram; Based on the full-time-domain SAR image marked with the unwrapped interferometric pairs, obtain the necessary interferometric pairs that satisfy the connectivity of the SAR image and have the minimum number of unwrapped interferometric pairs; Divide the full-time-domain SAR image marked with the unwrapped interferometric pairs into multiple image groups, construct interferometric closed loops in each image group and select the interferometric closed loops with high coherence characteristics, and then screen out the qualified interferometric pairs based on the phase closure difference of the selected interferometric closed loops; Merge the necessary interferometric pairs and the qualified interferometric pairs into the selected interferometric pairs.
2. The method according to claim 1, wherein The method further includes: preprocessing the full-time-domain SAR image, which includes: Based on the target area, crop the full-time-domain SAR image, and register the cropped SAR image according to the precise orbit data and ground digital elevation model data of the target area. The registration includes, but is not limited to: removing the Doppler effect correction of the cropped full-time-domain SAR image using the precise orbit data and georegistering the corrected full-time-domain SAR image using the ground digital elevation model data.
3. The method according to claim 1 or 2, characterized in that, In the process of extracting the unwrapped interferometric pairs from the differential interferogram, it includes: Successively perform correlation estimation, filtering and noise reduction processing, minimum cost flow unwrapping processing, atmospheric error removal processing and trend effect removal processing on the differential interferogram, so as to extract the unwrapped interferometric pairs.
4. The method according to any one of claims 1 to 3, characterized in that In the process of obtaining the necessary interferometric pairs, it includes: Use the preprocessed full-time-domain SAR image as nodes, and the unwrapped interferometric pairs in the unwrapped interferogram as edges. By combining the nodes, the edges and the weights of the unwrapped interferometric pairs, construct a minimum spanning tree that ensures the connectivity of all scenes in the full-time-domain SAR image information. Among them, the weight of the unwrapped interferometric pair is set based on the vertical baseline of the unwrapped interferogram; Use the unwrapped interferometric pairs corresponding to the edges in the minimum spanning tree as the necessary interferometric pairs.
5. The method according to any one of claims 1 to 4, characterized in that In the process of dividing the full-time-domain SAR image into multiple image groups, it includes: Successively use each scene image of the full-time-domain SAR image as the first scene, and obtain all the images within the time baseline threshold starting from the current first scene, so as to form the corresponding image group.
6. The method according to claim 5, wherein In the step of constructing interferometric closed loops in each image group and selecting the interferometric closed loops with high coherence characteristics, it includes: Starting from the first scene of each image group and traversing the remaining scene images in the current image group, form several interferometric closed loops with the same starting point; Calculate the coherence of each interferometric closed loop in each image group, and sort the coherence of the interferometric closed loops in the same image group; Select a preset number of selected interferometric closed loops with the top coherence in each image group.
7. The method according to claim 6, characterized in that, According to the coherence of each pair of interferometric pairs within the interferometric closed loop, calculate the coherence of the corresponding interferometric closed loop. Among them, the coherence of the interferometric closed loop is the sum of the coherences of each interferometric pair within the current closed loop.
8. The method according to any one of claims 1 to 7, characterized in that In the step of screening qualified interference pairs based on the phase closure difference of the preferred interference closure loop, it includes: According to the unwrapped phases of each unwrapped interference pair included in the interference closure loop, calculate the phase closure difference of each interference closure loop and its corresponding root mean square error; According to the root mean square error of each interference closure loop, use a preset error threshold to screen out unqualified interference closure loops. Among them, if the root mean square error of the phase closure difference of the interference closure loop is greater than the error threshold, it is determined that the current interference closure loop is an unqualified interference closure loop; Count the number of times the same unwrapped interference pair appears in all unqualified closure loops, and then according to the number of times each unwrapped interference pair appears, use a preset number threshold to eliminate the unqualified unwrapped interference pairs within the preferred interference closure loop. Among them, if the number of times the unwrapped interference pair appears is greater than the number threshold, it is determined that the current unwrapped interference pair is an unqualified unwrapped interference pair; Take the remaining unwrapped interference pairs after eliminating the unqualified unwrapped interference pairs in the preferred interference closure loop within each image group as the qualified interference pairs.
9. The method according to claim 8, wherein The phase closure difference of each interference closure loop is calculated using the following expression: Among them, and respectively represent the unwrapped phases of three unwrapped interferometric pairs in the current interferometric closed loop, represents the phase closure difference of the interferometric closed loop. Among them, the root mean square error of the phase closure difference of each interferometric closed loop is calculated using the following expression: where N represents the total number of pixels in the unwrapped interference pair, represents the value of the i-th pixel in the phase closure error of the current interference closed loop, and RMS represents the root mean square error of the phase closure error of the interference closed loop.
10. A method for monitoring surface deformation, characterized in that, It includes: Obtain the original SAR image of the target area; Process the original SAR image according to the method described in any one of claims 1 to 9; Use the processed SAR image to obtain the regional deformation rate.