Height measurement method and device based on multi-frequency linear combination InSAR and storage medium

Abstract

The invention relates to a height measurement method and device based on a multi-frequency linear combination InSAR and a storage medium, and the method comprises the steps: carrying out the segmentation of a used large-bandwidth signal, so as to extract different center frequencies, carrying out the linear combination of the center frequencies, so as to generate a plurality of synthesized measurement frequencies, measurement is carried out based on all measurement frequencies from small to large, a measurement phase difference of a next measurement result is updated based on a product invariant principle by utilizing a result of a previous measurement frequency, phase unwrapping is guided step by step through hierarchical classification, and the highest precision is achieved. According to the method, the maximum measurement range and the highest measurement precision of the extreme steep terrain (EST) are achieved at the same time, real-time measurement is achieved through single-time large-bandwidth signal collection, no time error exists, and meanwhile the large bandwidth provides excellent distance resolution.

Description

Technical Field

[0001] The invention relates to InSAR height measurement, and in particular to a height measurement method, device and storage medium based on multi-frequency linear combination InSAR. Background Art

[0002] Interferometric Synthetic Aperture Radar (InSAR) is an important remote sensing technology that can reconstruct Digital Elevation Models (DEMs) with high precision. High-precision DEMs are widely used in geological, geomorphological and geophysical analysis.

[0003] However, when measuring extremely steep terrains (EST), including artificial structures such as skyscrapers and steep natural terrain such as cliffs and valleys, traditional InSAR technology cannot measure DEM. This is due to the limitation of the Itoh condition. The Itoh condition states that the phase gradient (PG) between adjacent pixels should not exceed π to avoid phase ambiguity. But for EST, the sharp change in elevation can easily lead to a sudden change in phase, that is, the PG between adjacent pixels exceeds π. This violates the Itoh condition, and therefore, traditional InSAR technology cannot obtain DEM for EST.

[0004] Therefore, multi-baseline InSAR (MB-InSAR) and multi-frequency InSAR (MF-InSAR) were proposed. For extreme terrain (EST), MB-InSAR uses baselines of different lengths to smooth the abrupt phase changes, thereby satisfying the Ito condition. MF-InSAR achieves the same goal by using different frequencies. The former is more difficult in hardware design and implementation, while the latter is easier to implement in hardware.

[0005] MF-InSAR usually needs to obtain information from two or more frequencies, with high frequencies enhancing the measurement accuracy and low frequencies expanding the measurement range. By integrating this multi-frequency information, DEMs with large terrain changes can be measured with high accuracy. Specifically, the signal processing of these multi-frequency information can be divided into three methods. The first method uses maximum likelihood estimation (MLE) to estimate the DEM directly through the wrapped phases of different frequencies, thereby avoiding solving the phase gradient and overcoming the limitations of the Ito condition. The second method uses algorithms such as the Chinese Remainder Theorem (CRT) and cluster analysis (CA) to establish multiple mathematical equations and ultimately obtain a unique solution to the phase gradient, thereby overcoming the limitations of the Ito condition. The third method linearly combines different frequencies to obtain a synthetic frequency that is much lower than any frequency used alone. In theory, when the synthetic frequency is low enough, the phase gradient will not exceed π, thus satisfying the Ito condition.

[0006] However, the above methods still show limitations when measuring EST. First, most methods require information from at least two frequency bands, such as C-band and X-band, to balance the measurement range and accuracy. This results in the radar system having to run at least twice, making it impossible to achieve real-time measurement and introducing time errors. These errors mainly come from inconsistent atmospheric conditions between the two runs and possible time mutations in the terrain, such as earthquakes and mudslides. Second, the low frequency bands (such as C-band) selected by the first two methods determine the measurable range, while the third method produces a synthetic frequency much lower than the low frequency actually used, thus achieving a larger measurement range than the other two methods. For example, Klaus Schmitt and Werner Wiesbeck linearly combined 30 GHz and 37 GHz into a lower frequency of 7 GHz, significantly expanding the measurement range. However, by using two closer frequencies, the synthetic frequency can be further reduced, thereby further expanding the measurement range. But they have not yet studied this aspect in depth. In addition, they ignored the problem of linear superposition of noise caused by linear combination, resulting in reduced measurement accuracy. Summary of the invention

[0007] The purpose of the present invention is to provide a method, device and storage medium for height measurement based on multi-frequency linear combination InSAR.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A height measurement method based on multi-frequency linear combination InSAR, comprising:

[0010] Step S1: Initialize the cached wavelength and cached phase difference to be empty;

[0011] Step S2: sort all the measurement frequencies from small to large, and select the measurement frequency with the smallest frequency value among all the measurement frequencies as the current measurement frequency;

[0012] Step S3: Using the current measurement frequency to perform SAR imaging on the target terrain to obtain two phase images;

[0013] Step S4: aligning and subtracting the two phase images to obtain an interference phase image, and obtaining a measurement height corresponding to the current measurement frequency and a measurement phase difference based on the interference phase image, wherein the measurement phase difference is the phase difference between the high point dynamic phase and the low point reference phase;

[0014] Step S5: determine whether the cached phase difference is empty. If so, update the cached phase difference to the measured phase difference of the current measurement frequency, and update the cached wavelength to the wavelength corresponding to the current measurement frequency, and select the next measurement frequency as the current measurement frequency, and return to step S3. Otherwise, execute step S6;

[0015] Step S6: correcting the measured phase difference according to the cached phase difference, the cached wavelength, and the wavelength corresponding to the current measurement frequency, and updating the measurement height of the current measurement frequency based on the corrected measured phase difference;

[0016] Step S7: updating the cached phase difference to the measured phase difference of the current measurement frequency, and updating the cached wavelength to the wavelength corresponding to the current measurement frequency, and judging whether the traversal of all measurement frequencies is completed, if yes, executing step S8, otherwise, selecting the next measurement frequency as the current measurement frequency, and returning to step S3;

[0017] Step S8: taking the measured height of the current frequency as the measurement result.

[0018] The measurement frequency is a synthesized frequency synthesized from two reference frequencies, and at least part of all the reference frequencies are obtained by dividing the same frequency band.

[0019] The frequency of the measurement frequency is the absolute value of the frequency difference between the two reference frequencies.

[0020] The relationship between the wavelengths corresponding to two adjacent measurement frequencies satisfies the following formula:

[0021] Λ i >Λ i-1 / 5

[0022] Where: i is the wavelength of the next measurement frequency, Λ i-1 is the wavelength of the previous measured frequency.

[0023] The process of correcting the phase difference in step S6 is specifically implemented based on the principle that the product of the wavelength corresponding to the measurement frequency and the phase difference of the side face remains unchanged.

[0024] The step S6 specifically includes:

[0025] Step S6-1: Calculating a first phase difference correction value corresponding to the cached phase difference, the cached wavelength and the current measurement frequency;

[0026] Step S6-2: Correct the measured phase difference corresponding to the current measurement frequency according to the quotient of the first phase difference correction amount divided by π:

[0027] △φ i-update =n*π+△φ i MODπ

[0028] Where: △φ i-update is the measured phase difference corresponding to the updated measured frequency i, △φ i is the measured phase difference corresponding to the measured frequency i before updating, and n is the quotient of the first phase difference correction amount divided by π;

[0029] Step S6-3: obtaining the updated measurement height of the current measurement frequency based on the measurement phase difference corresponding to the updated current measurement frequency.

[0030] The first phase difference correction amount is specifically:

[0031] △φ i-re =(Λ cache *△φ cache ) / Λ i

[0032] Where: △φ i-re is the first phase difference, △φ cache is the cache phase difference, Λ cache is the cache wavelength.

[0033] The relationship between the measured height and the measured phase difference is:

[0034]

[0035] Where: △h is the measurement height, c is the speed of light, R is the slant distance, f is the frequency value of the measurement frequency, θ is the lower viewing angle, and △φ is the measurement frequency difference.

[0036] A height measurement device based on multi-frequency linear combination InSAR comprises a memory, a processor, and a program stored in the memory. When the processor executes the program, the above method is implemented.

[0037] A storage medium stores a program, which implements the above method when executed.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. By measuring the frequency from small to large, the hierarchical classification gradually guides the phase unwrapping to achieve the highest accuracy. The method of this application achieves the maximum measurement range and the highest measurement accuracy of EST at the same time.

[0040] 2. The measurement frequency is a composite frequency synthesized by two reference frequencies, and at least part of all reference frequencies are obtained by dividing the same frequency band, so that a sufficiently small minimum frequency can be obtained to ensure that the phase difference of the first measurement does not exceed π, while reducing costs and ensuring measurement accuracy.

[0041] 3. Using the quotient of the first phase difference and the remainder of its own phase difference as the updated measured phase difference can ensure that the result is sufficiently accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram illustrating the failure of single-frequency InSAR in EST measurement;

[0043] Figure 2 This is a schematic diagram of the principle of this application;

[0044] Figure 3 Schematic diagram of the process of obtaining synthetic wavelength;

[0045] Figure 4 This is a schematic diagram of a darkroom;

[0046] Figure 5 is the SAR intensity map;

[0047] Figure 6 The parameter range required by a certain prior art 3 and the method of this application;

[0048] Figure 7 It is a schematic flow chart of the main steps of the method of the present invention; DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0050] The existing failure problems of single-frequency InSAR in EST measurement are as follows: Figure 1 The three-dimensional scene simulated in the Cartesian coordinate system is shown in Figure 1 As shown in part (a), S 1 (x 1 ,y 1 ,z1 ) is the main antenna, S 2 (x 2 ,y 2 ,z 2 ) is the auxiliary antenna. The baseline length and antenna working height are d=x 2 -x 1 =5m,H=z 1 =z 2 =10000m. 1 and S 2 All move along the y-axis, and at any time there is y 1 =y 2 The downward viewing angle of the antenna is θ = 60°, and the center frequency of the radar system is f = 9CHz. The target is a mountain, and its left foot is located at point A (x A ,y A ,z A ), the top of the mountain is located at point B(x B ,y B ,z B ). The height difference dh between points A and B is

[0051] S 1 and S 2 At the same time, SAR imaging is performed on the target and phase Figure 1 After the two phase images are aligned and subtracted, the interference phase image is generated as shown in Figure 1 The corresponding height h can be calculated as:

[0052]

[0053] Where c is the speed of light, R is the slant distance corresponding to h and Figure 1 (b), (c) and (d). By taking the derivative of φ with respect to h, we can obtain the relationship between dh and the phase difference dφ, which is expressed as:

[0054]

[0055] exist Figure 1 In (d), point A(R A1 ,y A ,φ A ) and point B(R B1 ,y B ,φ B ) is dφ AB =φ A -φ B .

[0056] According to formula (2), we know that in dh ABWhen R, d, and θ remain constant, the larger f is, the larger dφ is. AB Under single-frequency InSAR measurement conditions, a larger f means a larger dφ AB .exist Figure 1 In part (d) of A1 and R B1 , this larger dφ AB This will cause phase ambiguity. Therefore, for elevation change terrain (EST), it is difficult to reconstruct its digital elevation model (DEM) using single-frequency InSAR.

[0057] In order to solve the above problems, this application proposes a method that can simultaneously expand the measurement range and improve the measurement accuracy.

[0058] Specifically, it is a height measurement method based on multi-frequency linear combination InSAR, such as Figure 2 and Figure 7 As shown, including:

[0059] Step S1: Initialize the cached wavelength and cached phase difference to be empty;

[0060] Before starting each measurement, the cached wavelength and cached phase difference need to be initialized to empty;

[0061] Step S2: sort all the measurement frequencies from small to large, and select the measurement frequency with the smallest frequency value among all the measurement frequencies as the current measurement frequency;

[0062] The measurement frequency is a synthesized frequency synthesized from two reference frequencies, and at least some of all the reference frequencies are obtained by dividing the same frequency band. Specifically, the frequency of the measurement frequency is the absolute value of the frequency difference between the two reference frequencies.

[0063] Specifically, according to formula (2), in order to use a smaller dφ AB Measuring larger dh AB , a smaller f can be used. For terrain with sudden elevation changes (EST) that cannot be measured, a smaller f can make dφ AB When dφ AB When it is reduced to a certain extent, for the R caused by EST A1 and R B1 If the reference frequencies are close, there will be no phase ambiguity, thus solving the above problem. Based on this concept, by combining two close reference frequencies f 1 and f 2 To generate the measurement frequency f min , that is, f min =|f 1 -f 2 ∣, and design fmin The value of f should be set to ensure that it does not cause phase ambiguity. min The theoretical design of is as follows. Figure 1 For points A and B in (a), we first need to estimate the approximate dh AB . Requires the use of f min When dφ nB <π to satisfy the Ito condition. AB <πCombined with formula (2), f min The following conditions should be met:

[0064]

[0065] Specifically, in order to solve the above problem, a signal with a center frequency of 9 GHz and a bandwidth of 2 GHz is used. 1 =8.5GHz and f 2 =9.1GHz to form f min =9.1-8.5=0.6GHz <Q=1.5GHz。f 1 and f 2 The interference phase diagram is Figure 2 In parts (e) and (f), there is phase ambiguity on the left side, while f min The interference phase diagram is Figure 2 The phase ambiguity is avoided by using the (g) part. Therefore, f min To reconstruct a digital elevation model (DEM), such as Figure 2 As shown in part (h) of Figure 1 The real DEM in part (a) is roughly consistent. However, due to the expansion of the measurement range, it inevitably has a large measurement error. min The measured peak dh AB is 630m, while the real is 600m. In addition, using f min The measured DEM is generally rough.

[0066] In order to expand the measurement range and improve the measurement accuracy at the same time, we cannot rely solely on f 1 and f 2 The single f min A series of reference frequencies f 1 <f 2 <f 3 … <f n To generate a series of synthetic frequencies, that is, the measurement frequency f sy1 <f sy2 <f sy3 … <f syn , where fsy1 =f min The synthetic frequency can be expressed in terms of synthetic wavelength, and the relationship between them is:

[0067]

[0068] Therefore, a series of synthetic frequencies arranged from smallest to largest can be expressed as a series of synthetic wavelengths, namely Λ 1 >Λ 2 >Λ 3 …>Λ n , where Λ 1 =c / f min According to formula (2), for the same dφ AB , the larger the wavelength (i.e. the smaller the frequency), the corresponding dh AB The larger the measuring range, the lower the measuring accuracy, and vice versa. 1 ,Λ 2 ,Λ 3 , the relationship between the measurement range and accuracy of λ is as follows Figure 2 As shown in part (j), where λ = c / f 1 .exist Figure 2 In part (i), by using a gradually decreasing wavelength Λ 1 ,Λ 2 ,Λ 3 ,λ to gradually guide the phase unwrapping process, the measurement accuracy is gradually improved, which is manifested in the measured dh AB Changing from 630, 621, 609, 602m, gradually approaching the real This proves that the method proposed in this application can achieve the largest measurement range and the highest measurement accuracy at the same time.

[0069] In order to correctly implement Figure 2 For the step-by-step cascade phase unwrapping shown in part (j), these wavelengths need to satisfy Λ i The measurement range is greater than Λ i-1 The measurement accuracy of Λ i The measurement accuracy can be roughly estimated based on experience. i One fifth of i Therefore, in order to perform cascading, the wavelength needs to meet the following conditions:

[0070] Λ i >Λ i-1 / 5 (5)

[0071] Where: i is the wavelength of the next measurement frequency, Λ i-1 is the wavelength of the previous measured frequency.

[0072] In the simulation, a series of synthetic wavelengths are designed, namely Λ 1 =0.5m,Λ 2 =0.3m,Λ 3 =0.16m,λ=0.034m,where Λ 1 Satisfies formula (3), and the relationship between them satisfies formula (5). These wavelengths are obtained by a series of combinations separated from the broadband signal, such as Figure 3 As shown. The center frequency of the split is f 1 =8.1GHz,f 2 =8.5GHz,f 3 =9.1GHz,f 4 =9.9GHz.

[0073] In summary, the method of this application achieves the largest elevation measurement range and the highest elevation measurement accuracy at the same time. The simulation results verify the effectiveness of the method proposed in this application.

[0074] Step S3: Using the current measurement frequency to perform SAR imaging on the target terrain to obtain two phase images;

[0075] Step S4: aligning and subtracting the two phase images to obtain an interference phase image, and obtaining a measurement height corresponding to the current measurement frequency and a measurement phase difference based on the interference phase image, wherein the measurement phase difference is the phase difference between the high point dynamic phase and the low point reference phase;

[0076] Step S5: determine whether the cached phase difference is empty. If so, update the cached phase difference to the measured phase difference of the current measurement frequency, and update the cached wavelength to the wavelength corresponding to the current measurement frequency, and select the next measurement frequency as the current measurement frequency, and return to step S3. Otherwise, execute step S6;

[0077] Step S6: Correct the measured phase difference according to the cached phase difference, the cached wavelength, and the wavelength corresponding to the current measurement frequency, and update the measurement height of the current measurement frequency based on the corrected measured phase difference, wherein the process of correcting the phase difference is specifically implemented based on the principle that the product of the wavelength corresponding to the measurement frequency and the side face phase difference remains unchanged.

[0078] Step S6 specifically includes:

[0079] Step S6-1: A first phase difference correction value corresponding to the cached phase difference, the cached wavelength and the current measurement frequency, wherein the first phase difference correction value is specifically:

[0080] △φ i-re =(Λ cache *△φ cache ) / Λ i

[0081] Where: △φ i-re is the first phase difference, △φ cache is the cache phase difference, Λ cache is the cache wavelength.

[0082] Step S6-2: Correct the measured phase difference corresponding to the current measurement frequency according to the quotient of the first phase difference correction amount divided by π:

[0083] △φ i-update =n*π+△φ i MODπ

[0084] Where: △φ i-update is the measured phase difference corresponding to the updated measured frequency i, △φ i is the measured phase difference corresponding to the measured frequency i before updating, and n is the quotient of the first phase difference correction amount divided by π;

[0085] Step S6-3: obtaining the updated measurement height of the current measurement frequency based on the measurement phase difference corresponding to the updated current measurement frequency.

[0086] Step S7: updating the cached phase difference to the measured phase difference of the current measurement frequency, and updating the cached wavelength to the wavelength corresponding to the current measurement frequency, and judging whether the traversal of all measurement frequencies is completed, if yes, executing step S8, otherwise, selecting the next measurement frequency as the current measurement frequency, and returning to step S3;

[0087] Step S8: Taking the measured height of the current frequency as the measurement result, as shown in Formula 5, the relationship between the measured height and the measured phase difference is:

[0088]

[0089] Where: △h is the measurement height, c is the speed of light, R is the slant distance, f is the frequency value of the measurement frequency, θ is the lower viewing angle, and △φ is the measurement frequency difference.

[0090] The verification was carried out in a darkroom, and a complete set of radar interferometric imaging experimental links was established. Figure 4 shown.

[0091] The radar system adopts a one-transmit-two-receive working mode, and the baseline length is d = 0.4m. The system runs a total of one acquisition. A corner reflector is used as a measurement target to simulate a steep terrain with a sharp height change. Here, two corner reflectors A and B are used, and the height difference between them is The signal with center frequency f=10GHz and bandwidth of 2GHz is used. The SAR intensity image obtained by one antenna is as follows: Figure 5As shown, where A and B are magnified on the right. A and B represent discontinuous phases, corresponding to a sudden change in elevation.

[0092] When measuring using traditional single - frequency InSAR, the dφ calculated by formula (2) AB = 7.4 > π, which violates the Itoh condition, so dh cannot be obtained AB .

[0093] To solve this problem, a lower f is obtained to expand the measurement range. f is selected by splitting from the broadband signal 1 = 9.1 GHz and f 2 = 9.3 GHz to form f min = 9.3 - 9.1 = 0.2 GHz < Q = 3 GHz, which satisfies formula (3). In this case, dφ AB does not exceed π, so dh can be obtained AB = 0.62 m.

[0094] However, compared with , this value still has a relatively large error. Therefore, the measurement accuracy is improved by performing the cascaded step - by - step phase unwrapping method. A series of signals with synthetic wavelengths are designed, namely Λ 1 = 1.5 m, Λ 2 = 0.75 m, Λ 3 = 0.15 m, and λ = c / f 1 = 0.034 m, where Λ 1 = c / f min satisfies formula (3), and the relationship between them satisfies formula (5). These wavelengths are obtained by splitting a combination of a series of bands from the broadband signal, as Figure 3 shown. The center frequencies of the splits are f 1 = 9.1 GHz, f 2 = 9.3 GHz, f 3 = 9.7 GHz, f 4 = 10.9 GHz. The results recovered from this series of wavelengths are shown in Table 1.

[0095] Table 1 Experimental Results

[0096]

[0097]

[0098] In Table 1, as the wavelength decreases, the measurement accuracy gradually improves, and the error changes from 0.28, 0.06, 0.05 to 0.02 m, and dh AB gradually approaches the true value By f min The measurement range is extended and the 1 ,Λ 2 ,Λ 3 ,λ improves the measurement accuracy. Finally, large-scale and high-precision measurement are achieved at the same time. The experimental results prove the effectiveness of the method proposed in this application.

[0099] In order to solve the problem that single-frequency InSAR cannot measure EST, a linear combination multi-frequency InSAR (MF-InSAR) method is proposed. This method can not only expand the measurement range, but also improve the measurement accuracy, while eliminating the error superposition caused by linear combination. Both simulation and experiments have proved the effectiveness of the proposed method.

[0100] In addition, the performance of the method of the present application is compared with some previous prior art, and the results are shown in Table 2, under the same set of hardware condition parameters, the parameters are the same as those used in the simulation. The method of the present application not only needs to be run only once, but also can achieve a larger measurement range while maintaining high accuracy.

[0101] Table 2 Comparison of theoretical performance of the proposed method with three existing methods

[0102]

[0103] In other words, when measuring the same height, the method of the present application has fewer hardware constraints on the radar system parameters d, H, and θ. Figure 6 Green means that the method can measure within the range of the set of parameters, while red means that it cannot measure. Obviously, for the measurement of EST, the method of this application covers a wider range of parameters.

[0104] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

Claims

1. A height measurement method based on multi-frequency linear combination InSAR, characterized in that: include: Step S1: Initialize the cached wavelength and cached phase difference to be empty; Step S2: sort all the measurement frequencies from small to large, and select the measurement frequency with the smallest frequency value among all the measurement frequencies as the current measurement frequency; Step S3: Using the current measurement frequency to perform SAR imaging on the target terrain to obtain two phase images; Step S4: aligning and subtracting the two phase images to obtain an interference phase image, and obtaining a measurement height corresponding to the current measurement frequency and a measurement phase difference based on the interference phase image, wherein the measurement phase difference is the phase difference between the high point dynamic phase and the low point reference phase; Step S5: determine whether the cached phase difference is empty. If so, update the cached phase difference to the measured phase difference of the current measurement frequency, and update the cached wavelength to the wavelength corresponding to the current measurement frequency, and select the next measurement frequency as the current measurement frequency, and return to step S3. Otherwise, execute step S6; Step S6: correcting the measured phase difference according to the cached phase difference, the cached wavelength, and the wavelength corresponding to the current measurement frequency, and updating the measurement height of the current measurement frequency based on the corrected measured phase difference; Step S7: updating the cached phase difference to the measured phase difference of the current measurement frequency, and updating the cached wavelength to the wavelength corresponding to the current measurement frequency, and judging whether the traversal of all measurement frequencies is completed, if yes, executing step S8, otherwise, selecting the next measurement frequency as the current measurement frequency, and returning to step S3; Step S8: taking the measured height of the current frequency as the measurement result.

2. The method for measuring height based on multi-frequency linear combination InSAR according to claim 1, characterized in that: The measurement frequency is a synthesized frequency synthesized from two reference frequencies, and at least part of all the reference frequencies are obtained by dividing the same frequency band.

3. The method for measuring height based on multi-frequency linear combination InSAR according to claim 2, characterized in that: The frequency of the measurement frequency is the absolute value of the frequency difference between the two reference frequencies.

4. The method for measuring height based on multi-frequency linear combination InSAR according to claim 1, characterized in that: The relationship between the wavelengths corresponding to two adjacent measurement frequencies satisfies the following formula: L i >L i-1 / 5 Where: i is the wavelength of the next measurement frequency, Λ i-1 is the wavelength of the previous measured frequency.

5. The method for measuring height based on multi-frequency linear combination InSAR according to claim 1, characterized in that: The process of correcting the phase difference in step S6 is specifically implemented based on the principle that the product of the wavelength corresponding to the measurement frequency and the phase difference of the side face remains unchanged.

6. The method for measuring height based on multi-frequency linear combination InSAR according to claim 5, characterized in that: The step S6 specifically includes: Step S6-1: Calculating a first phase difference correction value corresponding to the cached phase difference, the cached wavelength and the current measurement frequency; Step S6-2: Correct the measured phase difference corresponding to the current measurement frequency according to the quotient of the first phase difference correction amount divided by π: △φ i-update =n*π+△φ i MODπ Where: △φ i-update is the measured phase difference corresponding to the updated measured frequency i, △φ i is the measured phase difference corresponding to the measured frequency i before updating, and n is the quotient of the first phase difference correction amount divided by π; Step S6-3: obtaining the updated measurement height of the current measurement frequency based on the measurement phase difference corresponding to the updated current measurement frequency.

7. The method for measuring height based on multi-frequency linear combination InSAR according to claim 6, characterized in that: The first phase difference correction amount is specifically: △φ i-re =(Λ cache *△φ cache ) / L i Where: △φ i-re is the first phase difference, △φ cache is the cache phase difference, Λ cache is the cache wavelength.

8. The method for measuring height based on multi-frequency linear combination InSAR according to claim 6, characterized in that: The relationship between the measured height and the measured phase difference is: Where: △h is the measurement height, c is the speed of light, R is the slant distance, f is the frequency value of the measurement frequency, θ is the lower viewing angle, and △φ is the measurement frequency difference.

9. A height measurement device based on multi-frequency linear combination InSAR, comprising a memory, a processor, and a program stored in the memory, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 8 is implemented.

10. A storage medium having a program stored thereon, characterized in that: When the program is executed, the method according to any one of claims 1 to 8 is implemented.

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