Transmission tower deformation monitoring method and SAR image calibration method, device and equipment

Abstract

The invention discloses a power transmission tower deformation monitoring method, an SAR image calibration method, an SAR image calibration device and SAR image calibration equipment, relates to the field of power grid safety, and aims to realize low-cost and high-precision visual position calibration and deformation monitoring. According to the method, the artificial angle inverse array is installed around the power transmission tower as a reference point, and rapid and accurate positioning of the power transmission tower in the SAR image is realized by means of the strong reflectivity of the artificial angle inverse array; and the offset is calculated according to the coordinates of the artificial angle inverse array in the radar coordinate system and the sub-pixel coordinates so as to calibrate the position of the power transmission tower. The elevation phase of the power transmission tower is further simulated through LiDAR point cloud data, the elevation phase is removed from a phase interferogram, and deformation information caused by thermal expansion and stress is isolated. The method has the characteristics of low cost, high efficiency, high accuracy and high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power grid safety, and in particular to a power transmission tower deformation monitoring method, and a power transmission tower deformation monitoring SAR image calibration method, device and equipment. BACKGROUND

[0002] Power transmission towers, especially those used in ultra-high voltage (UHV) and extra-high voltage (EHV) power grids, are key components of national energy infrastructure. These towers operate under harsh environmental conditions, such as icing, strong winds, landslides, seismic activity, or external mechanical forces, which can compromise the structural integrity and reliability of the power transmission system. Given the role of UHV power grids in facilitating long-distance energy transmission, monitoring the safety of power transmission towers is crucial for ensuring national energy security. Early detection of potential structural deformations, including tower bending or foundation settlement, is essential for preventing catastrophic failures that can lead to widespread power outages and severe economic and safety consequences.

[0003] Current methods for monitoring power transmission tower deformation are either through on-site visual inspection or through distributed sensors based on geographic location servers. The visual inspection method requires high labor costs and is limited by the experience of the human inspector and the detection conditions, with poor real-time performance, objectivity, and accuracy. The deformation monitoring method using distributed sensors requires a large amount of labor and material costs in the early stage, and high maintenance costs in the later stage. In addition, the sensor detection method can only reflect the degree of disaster on site from statistical data and cannot achieve visual effects. SUMMARY

[0004] The purpose of the present application is to provide a power transmission tower deformation monitoring method and SAR image calibration method, device and equipment, which can calibrate large-scale power transmission tower deformation monitoring data, and achieve low-cost, visual, and high-precision monitoring.

[0005] The technical solutions adopted by the present application are as follows: A power transmission tower deformation monitoring SAR image calibration method, comprising: installing an artificial corner reflectarray around the power transmission tower, the artificial corner reflectarray comprising at least three artificial corner reflectors (CRs); the artificial corner reflectarray surrounds the power transmission tower; acquiring a synthetic aperture radar (SAR) image covering the power transmission tower and the artificial corner reflectarray; locating the position of the artificial corner reflectarray and the position of the power transmission tower from the SAR image; calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the artificial corner reflectarray in the radar coordinate system in the SAR image. The position of the power transmission tower in the SAR image is calibrated based on the calculated offset.

[0006] In addition, the application further provides a SAR image calibration device for power transmission tower deformation monitoring, which comprises: A first module is configured to acquire a SAR image covering a power transmission tower and an artificial corner reflect array; the artificial corner reflect array is installed around the power transmission tower, and the artificial corner reflect array comprises at least three artificial corner reflectors CR; the artificial corner reflect array surrounds the power transmission tower; A second module is configured to locate the position of the artificial corner reflect array and the position of the power transmission tower from the SAR image; A third module is configured to calculate the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system; A fourth module is configured to calibrate the position of the power transmission tower in the SAR image based on the calculated offset.

[0007] The application further provides a SAR image calibration device for power transmission tower deformation monitoring, which comprises a processor and a storage medium, and the storage medium stores a computer program; when the processor runs the computer program, the following method is executed: A SAR image covering a power transmission tower and an artificial corner reflect array is acquired; the artificial corner reflect array is installed around the power transmission tower, and the artificial corner reflect array comprises at least three artificial corner reflectors CR; the artificial corner reflect array surrounds the power transmission tower; The position of the artificial corner reflect array and the position of the power transmission tower are located from the SAR image; The offset of the power transmission tower in the azimuth direction and the range direction is calculated based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system; The position of the power transmission tower in the SAR image is calibrated based on the calculated offset.

[0008] In another aspect, the application further provides a power transmission tower deformation monitoring method, which comprises: An artificial corner reflect array is installed around a power transmission tower, and the artificial corner reflect array comprises at least three artificial corner reflectors CR; the artificial corner reflect array surrounds the power transmission tower; A SAR image covering the power transmission tower and the artificial corner reflect array, and LiDAR point cloud data of the power transmission tower are acquired; The position of the artificial corner reflect array and the position of the power transmission tower are located from the SAR image; Based on the coordinates and sub-pixel coordinates of the artificial corner reflector array in the SAR image in the radar coordinate system, the offset of the power transmission tower in the azimuth direction and the range direction is calculated; the position of the power transmission tower in the SAR image is calibrated based on the calculated offset; The phase interference diagram of the power transmission tower is generated based on the position of the power transmission tower in the calibrated at least two SAR images; The elevation phase corresponding to the LiDAR point cloud data is subtracted from the phase interference diagram to obtain the deformation information of the power transmission tower.

[0009] In summary, due to the adoption of the technical solutions described above, the beneficial effects of the present application are: The present application uses an artificial corner reflector array as a reference point, takes advantage of its high RCS intensity characteristics, and realizes fast and accurate positioning of the power transmission tower in the SAR image. And through the special design of the position of the artificial corner reflector array and the power transmission tower, the SAR image of the power transmission tower is quickly and accurately calibrated according to the oversampling of the artificial corner reflector array region, the random offset is reduced, and the accuracy and reliability of the monitoring of the power transmission tower are improved. On this basis, with the help of the phase interference diagram obtained from the SAR image, and the integration of the LiDAR point cloud data (including the elevation model DEM of the power transmission tower), the elevation phase of the power transmission tower is simulated, and is subtracted from the phase interference diagram, so as to effectively separate the deformation information caused by the structural changes due to thermal expansion and stress, and to provide a more reliable basis for more in-depth understanding of the mechanical behavior of the power transmission tower under different risk factors. BRIEF DESCRIPTION OF DRAWINGS

[0010] The present application will be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a SAR image calibration method flow chart for power transmission tower deformation monitoring provided by the embodiment of the present application.

[0011] Figure 2 is a structure diagram of the artificial corner reflector in the present application.

[0012] Figure 3 is an artificial corner reflector array arrangement diagram in an embodiment of the present application.

[0013] Figure 4 is a SAR image captured in an embodiment of the present application.

[0014] Figure 5 is a SAR image calibration method flow chart for power transmission tower deformation monitoring provided by the embodiment of the present application. Figure 4 is a timing diagram of the CR statistical RCS intensity in the embodiment of the present application.

[0015] Figure 6 is a schematic diagram of the position of the power transmission tower simulated in an embodiment of the present application.

[0016] Figure 7 is a schematic diagram of the position calibration of a simulated power transmission tower in an embodiment of the present application.

[0017] Figure 8 is a flowchart of a power transmission tower deformation monitoring method provided in an embodiment of the present application.

[0018] Figure 9 is a schematic diagram of LiDAR point cloud data obtained in an embodiment of the present application.

[0019] Figure 10 is a sequence of SAR images captured in an embodiment of the present application.

[0020] Figure 11 is a phase interference diagram obtained in an embodiment of the present application in which a DInSAR method is used to calculate the phase interference diagram.

[0021] Figure 12 is a ground surface deformation map obtained in an embodiment of the present application in which a DInSAR method is used to calculate the phase interference diagram.

[0022] Figure 13 is a ground surface deformation degree map obtained in an embodiment of the present application in which a PS-InSAR method is used to calculate the phase interference diagram.

[0023] Figure 14 , Figure 15 are deformation maps obtained by removing the elevation phase from the phase interference diagrams of the power transmission towers of two power transmission lines, respectively. DETAILED DESCRIPTION

[0024] All features disclosed in this specification, and / or all steps of any methods or processes disclosed in this specification, may be combined in any combination, except combinations where at least some of the features and / or steps are mutually exclusive.

[0025] Any feature disclosed in this specification, unless stated otherwise, can be replaced by any equivalent or similar feature, or combination thereof. That is, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0026] In view of the problems of high cost, low efficiency, severe limitations, and inability to visualize in power transmission tower deformation monitoring by manual visual inspection or with the aid of distributed sensors, a power transmission tower deformation monitoring method and intermediate products thereof are provided in an embodiment of the present application, namely a power transmission tower deformation monitoring SAR image calibration method, device, and equipment. The power transmission tower deformation monitoring SAR image calibration method aims to quickly and accurately calibrate large-scale power transmission tower deformation monitoring data to improve the accuracy of deformation monitoring. The power transmission tower deformation monitoring method aims to solve the problem of low-cost, visualized, and high-precision monitoring of power transmission towers.

[0027] like Figure 1 As shown in the embodiments of this application, the SAR image calibration method for power transmission tower deformation monitoring includes the following operations: S1. Install artificial angle counter arrays around the power transmission tower.

[0028] When SAR satellites detect artificial corner reflectors (CRs), due to their structural characteristics, their radar cross section (RCS) intensity is usually more than 20 dB higher than the background. By locating the pixel with the highest intensity in the SAR image, the position (coordinates) of the artificial corner reflector in the SAR image can be clearly identified.

[0029] An artificial corner reflector array consists of three or more artificial corner reflectors (CRs) arranged in an array. The artificial corner reflector array, composed of multiple CRs, surrounds the transmission tower. Thus, by locating the artificial corner reflector array in a SAR image, one can locate the transmission tower surrounded by it.

[0030] Preferably, in order to ensure the intensity of the CR reflection RCS so as to facilitate the rapid identification of the CR in SAR images, the structure of the CR is arranged according to... Figure 2 The design is as shown. The CR is a triangular trihedral structure, composed of three isosceles right-angled aluminum plates connected by a common right-angle vertex, with each pair of plates perpendicular to the others. It is installed on the ground using a mounting bracket. The mounting bracket can use a cement pillar as a base, thereby ensuring the service life and effectiveness of the CR. As an optional implementation, the dimensions of the triangular aluminum plates are 1.2 meters × 1.2 meters × 1.7 meters.

[0031] Furthermore, to ensure optimal detection by SAR satellites, the installation angle and position of the CRs need to be corrected and calculated based on the SAR satellite's ephemeris information to obtain the best reflection RCS intensity. For example, in the Chongqing area, all CRs are uniformly oriented westward, with an elevation angle of 26.736° and an azimuth angle of 8.56° west of north. This ensures that each CR can be imaged in both right-side ascending orbit and left-side descending orbit observations by SAR satellites. As an optional implementation method, the process of installing artificial angle-reflecting arrays around the transmission towers includes: S11. Calculate the position and attitude of each CR based on the ephemeris information of the SAR satellite, so that the SAR satellite can obtain the optimal scattering cross section (RCS) of each CR in both right-side ascending orbit observation and left-side descending orbit observation, and each CR is not blocked.

[0032] In determining the location of each CR in the above process, to avoid CRs being obstructed during SAR satellite detection, such as... Figure 3As shown, taking an artificial angle counter array consisting of 4 CRs as an example, the 4 CRs (A', B', C' and D' respectively) are respectively set in the outward extension direction of the 4 legs of the transmission tower (corresponding to A, B, C and D respectively). Preferably, they are in the diagonal extension direction of the 4 legs (e.g., CR A' is in the direction of leg CA, CR C' is in the direction of leg AC, and so on), at a position of about 9.89 meters away from the nearest leg. In this way, the spacing between the 4 CRs in the horizontal and vertical directions is about 34 meters.

[0033] In addition, as a preferred implementation, it is important to ensure that the elevation difference of each CR is within a preset value. For example, for the artificial angular inversion array composed of the above four CRs, the elevation difference between two CRs on the same horizontal direction (such as A'D', B'C') or two CRs on the same vertical direction (such as A'B', C'D') does not exceed 0.5 meters, so as to ensure the consistency of RCS intensity and facilitate accurate CR positioning.

[0034] S12. Install each CR according to the calculated position and orientation.

[0035] The location of the transmission tower is determined by the position of the artificial angle inversion array. In some preferred embodiments, in order to reduce the amount of calculation for coordinate conversion and save the time for coordinate calculation, the artificial angle inversion array is installed such that the geometric center of the artificial angle inversion array coincides with the center of the base of the transmission tower.

[0036] S2. Acquire synthetic aperture radar (SAR) images covering power transmission towers and artificial angle-reflecting arrays.

[0037] like Figure 4 As shown, SAR images obtained from the ascent or descent data of SAR satellites can be used for deformation analysis of power transmission towers.

[0038] S3. Locate the position of the artificial angle inverse array and the position of the power transmission tower from the SAR image.

[0039] In some specific embodiments, SAR images are obtained by capturing the study area using SAR satellites. As shown in Table 1, in the embodiments of this application, SAR data captured by the "Fucheng-1" satellite and the S1A SAR dataset are used to study the deformation of power transmission towers.

[0040] Table 1 SAR Dataset Table

[0041] exist Figure 4It can be seen that the intensity of the artificial corner reflect array is particularly prominent in the SAR image. By locating the position of the artificial corner reflect array in the SAR image, and according to the position relationship that the geometric center of the artificial corner reflect array coincides with the center of the tower base of the power transmission tower, the position of the power transmission tower can be located synchronously.

[0042] The above process is specifically implemented as: S31, locating the position of the artificial corner reflect array in the SAR image according to the RCS intensity of the artificial corner reflect array.

[0043] As mentioned above, the RCS intensity of the artificial corner reflect array is about 20 dB higher than the background, and by locating the strongest RCS point, the artificial corner reflect array can be located in the SAR image.

[0044] S32, locating the position of the power transmission tower in the SAR image based on the position relationship between the power transmission tower and the artificial corner reflect array.

[0045] The position of the power transmission tower is located for the consideration that the power transmission tower is the monitoring object. Actually, in the design of the embodiment of the present application, if the center of the tower base of the power transmission tower coincides with the geometric center of the artificial corner reflect array, it is not necessary to locate the position of the power transmission tower for the purpose of SAR image calibration, that is, the step S32 can be understood as that the synchronous positioning of the position of the power transmission tower is realized due to the center coincidence relationship between the power transmission tower and the artificial corner reflect array.

[0046] As shown in FIG. 4, the box part is the position of the power transmission tower located according to the artificial corner reflect array. Figure 4

[0047] S4, calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system.

[0048] The position of the artificial corner reflect array in the SAR image is the position deduced according to the highest RCS intensity principle, and research shows that the accuracy thereof is limited by the pixel resolution of the SAR image. Therefore, this step S4 considers that the positioning accuracy of the artificial corner reflect array is improved through oversampling, and then the position of the power transmission tower is calibrated according to the calculated positioning error, so as to provide accurate original data for subsequent power transmission tower deformation analysis.

[0049] As an optional implementation, the method for calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system comprises: S41, calculating the coordinates in the radar coordinate system according to the real geographical coordinates (i.e. world coordinates) of the artificial corner reflect array . ​

[0050] The real coordinates of the artificial corner reflector are represented by the coordinates of the CR. In some alternative embodiments, the CR employs a real-time kinematic (RTK) tool to accurately measure the coordinates, including longitude, latitude and altitude, of its vertices (i.e. the vertices of the right angle of the three aluminum plates) to a centimeter level.

[0051] According to the calibration parameters of the satellite radar, after obtaining the real geographical coordinates of the CR, the coordinates of the CR in the radar coordinate system can be mapped by using the coordinate system conversion relationship, i.e. to represent the horizontal and vertical coordinates in the radar coordinate system. In some specific embodiments, the CR coordinates in the radar coordinate system are calculated by using a range-Doppler algorithm (RDA) .

[0052] In the SAR image, the RCS intensity of the CR is represented as (in dB): , where DN is the pixel amplitude, is the pixel intensity, and is the calibration value in the lookup table corresponding to .

[0053] S42, oversampling the window region corresponding to the coordinates in the SAR image to obtain the sub-pixel coordinates of the CR in the range direction and the azimuth direction after oversampling.

[0054] The CR coordinates located directly in the SAR image may be offset from the actual coordinates due to coordinate conversion, etc., but the offset is not too large, and the actual position must be near . In the embodiments of the present application, the window region (in the azimuth direction and the range direction) corresponding to the coordinates is oversampled, and the sub-pixel coordinates of the CR in the range direction and the azimuth direction are located according to the RCS intensity (the strongest point) from the oversampled sub-pixels.

[0055] Specifically, in some alternative embodiments, step S42 includes: S421, selecting the pixel point corresponding to the coordinates in the SAR image. The coordinates can be obtained by directly locating the coordinates in the SAR image.

[0056] S422, selecting a window region in the SAR image with the selected pixel point as the center.

[0057] The selected window region is preferably a rectangular window or a circular window, i.e. centered at an n*n window region or a window region with a radius of n is selected in the SAR image as a candidate region for searching the accurate coordinate and as an operation region for oversampling.

[0058] S423, oversampling the window region in the azimuth direction and the range direction according to a set oversampling factor.

[0059] The granularity of the oversampling is determined by the oversampling factor m (representing the oversampling multiple). In some embodiments, a interpolation method based on a sine function is used to perform the oversampling in the azimuth direction and the range direction. The oversampling multiple is set in advance.

[0060] S424, obtaining the sub-pixel coordinates of the CR in the range direction and the azimuth direction in the window region after the oversampling .

[0061] The sub-pixel coordinates of the CR in the window region after the oversampling are the center positions of the RCS intensity peaks.

[0062] Specifically, the sub-pixel coordinates (i.e. the center positions of the peaks) of the CR in the range direction and the azimuth direction in the window region after the oversampling are: wherein the center point coordinates and the average RCS intensity values of each row and each column in the window region after the oversampling are respectively represented as , i represents the row pixel position in the window region, j represents the column pixel position in the window region, m represents the oversampling multiple, and n is the side length of the window region.

[0063] S43, calculating the offset between the coordinate and the coordinate to obtain the offset of the transmission tower in the azimuth direction and the range direction, respectively.

[0064] After obtaining the coordinate of the CR mapped in the SAR image and the accurate coordinate of the CR in the SAR image through the high-precision positioning by the oversampling, the offset of the CR in the range direction and the azimuth direction can be obtained by calculating the offset (pixel difference) between the coordinates. Since the geometric center of the artificial corner reflector array overlaps the center of the tower base of the transmission tower, the offset of the CR position can be equivalent to the offset of the transmission tower position (in the azimuth direction and the range direction).

[0065] ​​​​Specifically, the offset amount of the power transmission tower in the azimuth direction and the distance direction is represented as: , ; In the formula, represents the offset amount in the azimuth direction, represents the offset amount in the distance direction.

[0066] S44, the calculated offset amount is used to calibrate the position of the power transmission tower in the SAR image.

[0067] For example, according to the example of Figure 4 , according to the above method, in the SAR image of the ascending track data, the power transmission tower has an offset amount of 17.7 pixels in the distance direction and 16.5 pixels in the azimuth direction; in the SAR image of the descending track data, the power transmission tower has an offset amount of 8.8 pixels in the distance direction and 14.5 pixels in the azimuth direction.

[0068] S5, the position of the power transmission tower in the SAR image is calibrated based on the calculated offset amount.

[0069] According to the calibration of the position of the power transmission tower in the SAR image based on the offset amount, the corresponding offset amount can be added to the simulated position of the power transmission tower.

[0070] The performance of the method of calibrating the position of the power transmission tower in the single-scene image by relying on the artificial corner reflector array is not sufficient to prove the reliability of the above calibration method. Therefore, as Figure 5 shown, the time sequence statistical analysis is performed on the example (4 CR artificial corner reflector arrays) shown in Figure 4 . Figure 5In the diagram, subplot (a) shows the RCS intensity of CRA' in the SAR image after offset calibration of the ascending orbit data; subplot (b) shows the RCS intensity of CRA' in the SAR image after offset calibration of the descending orbit data; the red dot in the center of the image represents the CR position simulated based on GNSS coordinates, while the dark red dot corresponds to the position of the maximum RCS intensity within that area, i.e., the actual position; subplots (c)-(f) respectively show the time series statistical results of the four CRs (i.e., CRA', B', C', and D'), where subplot (c) shows the time position sequence of the maximum RCS intensity position in the range and azimuth directions of the SAR image of the ascending orbit data; subplot (d) shows the time series of the RCS intensity of the four CRs in the SAR image of the ascending orbit data; subplot (c) shows the time position sequence of the maximum RCS intensity position in the range and azimuth directions of the SAR image of the descending orbit data; subplot (d) shows the time series of the RCS intensity of the four CRs in the SAR image of the descending orbit data.

[0071] Depend on Figure 5 Statistical data shows that the positions of the maximum radar cross section (RCS) of all four CRs are very stable, with variations in azimuth and range over time remaining within one pixel. Furthermore, the scattering intensity variations from CRA' to CRC' are all less than 1 dB, and the RCS intensity is more than 20 dB higher than the background (CRD' may have experienced a sharp drop in RCS intensity due to environmental obstruction). A careful comparison of Figures 5(e) and 5(f) reveals that the scattering intensity during orbit ascent consistently remains between 22.2 dB and 22.8 dB, while the scattering intensity during orbit descent remains between 23.8 dB and 25.3 dB. These findings indicate that the CR positions are highly stable, with minimal deformation detected in the region during observation. This demonstrates the accuracy and reliability of the aforementioned calibration method.

[0072] like Figure 6 As shown, the red dots represent... Figure 4 Before calibrating the transmission tower positions in the SAR images from the up-orbit data in the example, the transmission tower positions in the SAR images are simulated based on LiDAR point cloud data and the range-Doppler equation. The four CR positions marked with orange circles are the precise locations (i.e., the locations after oversampling) of the SAR images. After calibrating the transmission tower positions using the above calibration method, the simulated transmission tower positions in the SAR images are as follows: Figure 7 As shown. By Figure 7 It can be seen that after position calibration, the center of the transmission tower base coincides with the geometric center of the artificial angle inversion array again, proving the accuracy and reliability of the high-precision position calibration based on the artificial angle inversion array in this application.

[0073] According to the idea of the present application, the present application also provides a power transmission tower deformation monitoring SAR image calibration device, which comprises: The first module is configured to acquire a SAR image covering a power transmission tower and an artificial corner reflect array. The artificial corner reflect array is installed around the power transmission tower, and the artificial corner reflect array comprises at least three artificial corner reflectors CR. The artificial corner reflect array surrounds the power transmission tower.

[0074] The second module is configured to locate the positions of the artificial corner reflect array and the power transmission tower in the SAR image.

[0075] The third module is configured to calculate the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system.

[0076] The fourth module is configured to calibrate the position of the power transmission tower in the SAR image based on the calculated offset.

[0077] The first module, the second module, the third module and the fourth module can be configured with optional data in different feasible embodiments, which can refer to the features configured for the corresponding steps in the foregoing calibration method embodiments.

[0078] In addition, the present application also provides a power transmission tower deformation monitoring SAR image calibration device, which comprises a processor and a storage medium, and the storage medium stores a computer program. When the processor runs the computer program, the following method is executed: A SAR image covering a power transmission tower and an artificial corner reflect array is acquired. The artificial corner reflect array is installed around the power transmission tower, and the artificial corner reflect array comprises at least three artificial corner reflectors CR. The artificial corner reflect array surrounds the power transmission tower.

[0079] The positions of the artificial corner reflect array and the power transmission tower in the SAR image are located.

[0080] The offset of the power transmission tower in the azimuth direction and the range direction is calculated based on the coordinates and sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system.

[0081] The position of the power transmission tower in the SAR image is calibrated based on the calculated offset.

[0082] According to the design idea of another aspect of the present application, in the optional embodiments of the present application, a power transmission tower deformation monitoring method is provided, as shown in Figure 8 The method comprises the following steps: S1, an artificial corner reflect array is installed around a power transmission tower.

[0083] The artificial corner reflect array includes at least three artificial corner reflectors CR, and the artificial corner reflect array surrounds the power transmission tower. The specific optional implementation of this step can refer to S1 in the foregoing calibration method embodiment, and details are not described herein again.

[0084] S2, acquiring a SAR image covering the power transmission tower and the artificial corner reflect array; in addition, acquiring LiDAR point cloud data of the power transmission tower.

[0085] In step S2, the operation of acquiring the SAR image covering the power transmission tower and the artificial corner reflect array is the same as step S2 in the foregoing calibration method embodiment. The LiDAR point cloud data of the power transmission tower is acquired to simulate the DEM of the power transmission tower. The LiDAR point cloud data integrates three technologies of laser point cloud, GNSS and INS, and is used to obtain point cloud data of a measured object and generate an accurate digital three-dimensional model. In the embodiment of the present application, the LiDAR point cloud data includes the DEM of the ground of the power transmission tower. According to the LiDAR point cloud data and the range-Doppler equation, the position (not calibrated) of the power transmission tower in the SAR image can be simulated, as shown in FIG. 2. Figure 9

[0086] S3, locating the position of the artificial corner reflect array and the position of the power transmission tower from the SAR image.

[0087] Step S3 is the same as step S3 in the foregoing calibration method embodiment.

[0088] S4, calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and the sub-pixel coordinates of the artificial corner reflect array in the SAR image in the radar coordinate system; and calibrating the position of the power transmission tower in the SAR image based on the calculated offset.

[0089] Step S4 is the same as step S4 and step S5 in the foregoing calibration method embodiment.

[0090] S5, generating a phase interference graph of the power transmission tower based on the calibrated positions of the power transmission tower in at least two SAR images.

[0091] The SAR satellite can capture multiple SAR images covering the power transmission tower and the artificial corner reflect array in chronological order. Each SAR image can obtain a SAR image sequence according to the time sequence. Figure 10 As shown in FIG. 3, the SAR images captured at five observation times are shown, wherein each row refers to the same power transmission tower, and each column represents a different observation time (the observation time is marked at the top of each column). ​

[0092] In some alternative embodiments, the phase interferogram can be acquired using the Differential Interferometric SAR (DInSAR) method. DInSAR measures small displacements in the transmission tower by comparing the phase difference of two calibrated SAR images, where the phase difference of the transmission tower in the two SAR images is may be expressed as: , where, φ1and φ2represent the phase of the transmission tower in the two SAR images, respectively, represents the phase contribution due to the ground surface deformation in the direction parallel to the radar Line-Of-Sight (LOS); represents the topographic phase contribution due to the ground surface elevation variation; is the phase contribution due to the flat earth effect, is the phase contribution due to the noise. The number of phase cycles containing the wrapped phase difference is denoted by n1.

[0093] SAR images containing complex features and may be expressed as: , , and represent the signal intensity in the respective SAR images, and represent the phase of the SAR images and respectively.

[0094] The conjugate multiplication of the two SAR images results in the following equation u: .

[0095] Accordingly, the interferometric phase may be expressed as: , represent the imaginary and real parts of the equation u, respectively.

[0096] The phase interferogram of the two SAR images can be calculated according to the above equation.

[0097] Furthermore, the LOS displacement (i.e., deformation) can be expressed as: , represents the radar wavelength.

[0098] Figure 11 The ground deformation map shown is generated by the DInSAR method based on SAR images captured of the study area during a two-month period (September 5, 2024 - October 19, 2024).

[0099] Figure 12 The phase observations of the power transmission towers in the ascending (sub-plot (a)) and descending (sub-plot (b)) data of the SAR images under investigation are shown. The phase of several power transmission towers is clearly visible within the wide experimental area. In addition to the phase of the power transmission towers, the phase of several visible power transmission lines can be detected in the descending data. Figure 12 The magnified images in correspond to Figure 6-7 The power transmission towers equipped with artificial corner reflectarrays described in the embodiments. These CRs exhibit highly stable phases in both ascending and descending data, as shown in Figure 12 The four highlighted circles in sub-plot (a) and sub-plot (b) in correspond to

[0100] In contrast, the shape and phase of the power transmission towers differ significantly between the orbits. In the descending data, the number of distance pixels occupied by the power transmission towers is inconsistent with that in the ascending data. Specifically, the power transmission towers occupy fewer distance pixels in the ascending data, while in the descending data, the number of distance pixels occupied increases by 150% compared to the ascending data. These observations highlight the changes in SAR image imaging geometry and the potential of SAR images to provide key features for power transmission tower deformation and structural behavior analysis.

[0101] In other alternative embodiments, it is possible to select the use of the Permanent Scatterer InSAR (PS-InSAR) method to obtain the phase interferograms.

[0102] PS-InSAR is a multi-temporal (MT-InSAR) technique that enables the high-precision monitoring of ground deformation over time. Unlike conventional InSAR and DInSAR techniques, which are often limited by temporal and spatial decorrelation and atmospheric disturbances, PS-InSAR exploits a set of radar targets known as permanent scatterers (PS). PSs are stable reflectors, i.e., artificial corner reflectarrays in the embodiments of the present application, that maintain consistent backscattering properties over long periods of time, making them ideal for long-term deformation analysis. This method uses complex statistical models to mitigate atmospheric disturbances and other noise factors and provides robust millimeter-level deformation pattern measurements, enabling high-precision measurements even in densely urbanized or geologically active areas. PS-InSAR requires a significant number of SAR images, typically more than 20, to perform the temporal and spatial analysis of each phase contribution.

[0103] The PS-InSAR method focuses on the discrete distribution of PS points. Assuming is the reference point (i.e. CR), is the target point (i.e. transmission tower), in the interferogram composed of the i-th SAR image and the k-th SAR image, the interferometric phase can be expressed as The interferometric phase includes the phase difference of elevation, deformation, atmospheric disturbance and noise between the target point and the reference point . The phase difference between the two targets due to the difference in elevation and surface deformation can be expressed as: , , In the formula, and respectively represent the phase difference between SAR image i and SAR image k due to the difference in elevation and the phase difference due to the difference in surface deformation; and respectively represent the difference in elevation and deformation rate between the target point and the reference point ; and respectively represent the spatial and temporal baselines between SAR image i and SAR image k perpendicular to the radar LOS direction; R represents the slant range between the target point and the SAR satellite; Here represents the radar incidence angle.

[0104] The phase interferogram of the transmission tower in the SAR image can be obtained by the above formula.

[0105] Generally, the PS-InSAR method estimates the target point elevation and its deformation rate by maximizing the temporal coherence, that is: , , In the formula, and respectively represent the target point elevation and its deformation rate to be solved, M represents the number of phase interferograms, represents the difference interferometric phase (which has removed the flat ground phase and the rough terrain phase) between the acquired SAR image i and SAR image k, and respectively represent the phase difference between SAR image i and SAR image k due to the difference in elevation and the phase difference due to the difference in surface deformation, which are the same as and in the previous formula. The phase difference due to the difference in surface deformation includes the linear deformation phase and the nonlinear deformation phase: , In the formula, and respectively represent linear deformation phase and nonlinear deformation phase, and have the same meaning, represent nonlinear offset.

[0106] As Figure 13 shows the deformation analysis result obtained by the PS-InSAR method for surface deformation analysis. Figure 13 In the figure, subgraph (a) is a wide-area view of the entire observation area (Chongqing City) (the part enclosed by the larger rectangular frame), the blue square frame (smaller rectangular frame) marks the main research area, and the red circular frame marks the risk area. As can be seen from subgraph (a), the deformation amount in the observation area basically remains stable, and subgraph (b) is a local enlarged view of the maximum deformation area. The risk area is marked with a white circular frame, and the highest deformation rate of 8 mm / year is monitored in this area.

[0107] The elevation phase of the power transmission tower can be obtained by the above method.

[0108] S6, subtract the elevation phase corresponding to the LiDAR point cloud data from the phase interference diagram to obtain the deformation information of the power transmission tower.

[0109] Subtracting the elevation phase corresponding to the LiDAR point cloud data from the phase interference diagram isolates the deformation information caused by structural changes due to thermal expansion and stress.

[0110] Figure 12 In the figure, the phase of the power transmission tower shows obvious changes from the base to the top, wherein the observed phase change contains an elevation phase component, so the true deformation phase of the power transmission tower cannot be directly separated from the SAR image. Therefore, in the embodiments of the present application, the LiDAR point cloud data and the position offset of the power transmission tower calculated based on the artificial corner reflect array are combined to simulate the elevation phase change of the power transmission tower.

[0111] Table 2 shows the calculated values of the vertical baseline and elevation phase change of the base point in the time series image of the selected power transmission tower. The cells in the 1st, 3rd, 5th, and 7th rows are ascending track data, and the remaining cells represent descending track data. The vertical baseline refers to the vertical baseline between the primary and secondary images. Significant differences are observed between the data sets of 2024-09-07 and 2024-10-10. As can be seen from the data shown in Table 2 and the images shown in Figure 12 In the figure, the elevation phase change of the power transmission tower is closely related to the vertical baseline, which highlights its influence on the imaging results. Therefore, Figure 14 shows the deformation information of the power transmission tower obtained by subtracting the elevation phase change from the phase interference diagram. Figure 12interferometric phase after removing the elevation phase. This way of removing the phase effectively isolates the elevation phase, allowing a detailed analysis of the deformation of the transmission tower. By removing the phase component related to the elevation, Figure 14 allowing a more accurate assessment of the structural deformation of the transmission tower, contributing to a clearer understanding of its mechanical behavior under different environmental and operating conditions. Figure 14 In FIG. 2, sub-plot (a) shows the deformation phase of transmission tower 1 in ascending track SAR images between September 18, 2024 and October 21, 2024, and in descending track SAR images between September 16, 2024 and October 19, 2024 (ascending track master image: September 7, 2024; descending track master image: September 5, 2024). Sub-plot (b) shows the deformation phase of transmission tower 2 in ascending track SAR images between September 18, 2024 and October 21, 2024, and in descending track SAR images between September 16, 2024 and October 19, 2024 (ascending track master image: September 7, 2024; descending track master image: September 5, 2024).

[0112] Table 2. Temporal and spatial baseline parameters of SAR image phase interferograms

[0113] To further verify the effectiveness of the proposed method, Figure 15 The analysis results of another transmission line in the same area are shown. Similarly, transmission tower 3 and transmission tower 4 are connected to each other, and their stress responses are similar. In the ascending track SAR image on September 29, 2024, both transmission towers show good phase consistency, indicating that the current phase is highly consistent with the master image. In contrast, the results on September 18, 2024 show uneven stress distribution, with greater stress on one side of transmission tower 3 and transmission tower 4, and the phase difference between the upper and lower parts exceeds 1π.

[0114] In descending track SAR images, the phase of the transmission tower remained essentially consistent on September 16, 2024, September 27, 2024, and October 19, 2024. However, in the image on October 8, 2024, the upper end of the transmission tower showed a clear stress effect. It is important to note that, as shown in Table 2, the vertical baseline of the SAR image pair in the ascending track on October 10, 2024 was significantly longer than the master image. Therefore, in data processing, careful selection of the master image is crucial to consider the extended vertical baseline. In Figure 15In particular, sub-plot (a) shows the deformation phase of transmission tower 3 in ascending track SAR images between September 18, 2024 and October 21, 2024, and in descending track SAR images between September 16, 2024 and October 19, 2024 (ascending track master image: September 7, 2024; descending track master image: September 5, 2024). Sub-plot (b) shows the deformation phase of tower 4 in ascending track SAR images between September 18, 2024 and October 21, 2024, and in descending track SAR images between September 16, 2024 and October 19, 2024 (ascending track master image: September 7, 2024; descending track master image: September 5, 2024).

[0115] Overall, the present application achieves the first successful application of SAR images in extracting the intrinsic phase information directly from transmission towers, which highlights the potential of SAR technology in monitoring subtle changes in large-scale measured objects.

[0116] The application is not restricted to the described specific embodiments. The application extends to any novel one, or any new combination, of the characteristics disclosed in this specification, and to any novel method or process disclosed in this specification, or any new combination of the steps of the disclosed methods or processes.

Claims

1. A method for calibrating a transmission tower deformation monitoring SAR image, characterized in that, Comprising: installing a corner reflector array around a power transmission tower, the corner reflector array comprising at least three corner reflectors CR; the corner reflector array surrounds the power transmission tower; acquiring a synthetic aperture radar (SAR) image covering the power transmission tower and the corner reflector array; locating the positions of the corner reflector array and the power transmission tower from the SAR image; calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the corner reflector array in the radar coordinate system in the SAR image; calibrating the position of the power transmission tower in the SAR image based on the calculated offset. 2.The power transmission tower deformation monitoring SAR image calibration method of claim 1, wherein, installing a corner reflector array around a power transmission tower, comprising: installing the corner reflector array in such a way that the geometric center of the corner reflector array coincides with the tower base center of the power transmission tower. 3.The power transmission tower deformation monitoring SAR image calibration method of claim 2, wherein, installing a corner reflector array around a power transmission tower, comprising: calculating the position and attitude of each CR based on the ephemeris information of the SAR satellite, so that the SAR satellite can obtain the best scattering cross section (RCS) of each CR in right side view ascending orbit observation and left side view descending orbit observation, and each CR is not blocked; installing each CR according to the calculated position and attitude. 4.The power transmission tower deformation monitoring SAR image calibration method of claim 2, wherein, locating the positions of the corner reflector array and the power transmission tower from the SAR image, comprising: locating the position of the corner reflector array from the SAR image according to the RCS intensity of the corner reflector array; locating the position of the power transmission tower from the SAR image based on the positional relationship between the power transmission tower and the corner reflector array. 5.The power transmission tower deformation monitoring SAR image calibration method of claim 1, wherein, calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the corner reflector array in the radar coordinate system in the SAR image, comprising: Coordinates in the radar coordinate system are calculated from real geographical coordinates of the artificial corner reflector ; For the corresponding coordinates in the SAR image Oversample the window region and obtain the sub-pixel coordinates of CR in the range and azimuth directions within the oversampled window region. ; Calculate coordinates and coordinates The offset between the two sides is used to obtain the offset of the transmission tower in the azimuth and distance directions, respectively. 6.The power transmission tower deformation monitoring SAR image calibration method of claim 5, wherein, For the corresponding coordinates in the SAR image Oversample the window region and obtain the sub-pixel coordinates of CR in the range and azimuth directions within the oversampled window region. ,include: Selecting coordinates in a SAR image Corresponding pixel points; selecting a window region in the SAR image with a selected pixel point as the center; oversampling the window region in the azimuth direction and the range direction according to the set oversampling factor; Obtaining sub-pixel coordinates of CR in the distance direction and the azimuth direction in the window region after oversampling .

7. The power transmission tower deformation monitoring SAR image calibration method according to claim 5 or 6, characterized in that, The sub-pixel coordinates is the center position of the RCS intensity peak in the post-sampling window region.

8. A power transmission tower deformation monitoring SAR image calibration device, characterized in that, Comprising: a first module for acquiring a SAR image covering a power transmission tower and a corner reflector array; the corner reflector array is installed around the power transmission tower, the corner reflector array comprises at least three corner reflectors CR; the corner reflector array surrounds the power transmission tower; a second module for locating the positions of the corner reflector array and the power transmission tower from the SAR image; a third module for calculating the offset of the power transmission tower in the azimuth direction and the range direction based on the coordinates and sub-pixel coordinates of the corner reflector array in the radar coordinate system in the SAR image; a fourth module for calibrating the position of the power transmission tower in the SAR image based on the calculated offset.

9. A power transmission tower deformation monitoring SAR image calibration device, characterized in that, Comprising a processor and a storage medium, the storage medium storing a computer program, the processor executing the computer program to perform the following method: acquiring a SAR image covering a power transmission tower and a corner reflector array; the corner reflector array is installed around the power transmission tower, the corner reflector array comprises at least three corner reflectors CR; the corner reflector array surrounds the power transmission tower; locating the positions of the corner reflector array and the power transmission tower from the SAR image; Based on the coordinates and sub-pixel coordinates of the artificial corner reflector array in the SAR image in the radar coordinate system, the offset of the power transmission tower in the azimuth direction and the range direction is calculated; The position of the power transmission tower in the SAR image is calibrated based on the calculated offset.

10. A method for monitoring the deformation of power transmission towers, characterized in that, It comprises: An artificial corner reflector array is installed around the power transmission tower, and the artificial corner reflector array comprises at least three artificial corner reflectors CR; The artificial corner reflector array surrounds the power transmission tower; A SAR image covering the power transmission tower and the artificial corner reflector array is obtained, and LiDAR point cloud data of the power transmission tower is obtained; The position of the artificial corner reflector array and the position of the power transmission tower are located from the SAR image; Based on the coordinates and sub-pixel coordinates of the artificial corner reflector array in the SAR image in the radar coordinate system, the offset of the power transmission tower in the azimuth direction and the range direction is calculated; the position of the power transmission tower in the SAR image is calibrated based on the calculated offset; The phase interference diagram of the power transmission tower is generated based on the position of the power transmission tower in the calibrated at least two SAR images; The elevation phase corresponding to the LiDAR point cloud data is subtracted from the phase interference diagram to obtain the deformation information of the power transmission tower.

Images