A natural surface deformation monitoring method taking into account soil moisture changes

Abstract

The present invention discloses a natural surface deformation monitoring method that takes into account soil moisture changes, and relates to the field of synthetic aperture radar interferometry technology. The method comprises the following steps: S1: modeling and analyzing the relationship between soil moisture changes and interference phase, and obtaining interference phase information caused by soil moisture changes; S2: multi-phase SAR data interference processing, obtaining initial interference phase information, including interference information such as phase components caused by soil moisture changes; S3: optimizing the interference phase information, eliminating the interference phase components caused by soil moisture changes, and obtaining interference phase information that characterizes the natural surface deformation characteristics; S4: obtaining natural surface deformation information based on the optimized interference phase information. The present invention eliminates the interference phase components caused by soil moisture changes, realizes the optimization processing of the interference phase information, and further obtains reliable interference phase information that characterizes the surface deformation characteristics, achieving the technical effect of extracting high-precision deformation information of the natural surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthetic aperture radar interferometry, and in particular relates to a natural surface deformation monitoring method taking soil moisture changes into consideration. Background Art

[0002] The use of interferometric synthetic aperture radar (ISAR) technology to monitor surface deformation has been extensively studied. In particular, due to the sensitive response of interferometric phase information to surface deformation, it has found important applications in areas such as ground subsidence monitoring, geological disaster investigation and monitoring, and urban safety monitoring. However, the interferometric phase information contains a series of phase components that significantly impact deformation monitoring accuracy, including orbit error phase, DEM error phase, atmospheric delay phase, and ionospheric delay phase. Therefore, to reliably and accurately acquire surface deformation information, it is necessary to effectively remove phase components irrelevant to surface deformation characteristics. In other words, the ability to extract reliable surface deformation information from the interferometric phase directly depends on the degree of compensation for other components in the interferometric phase. The interferometric phase caused by soil moisture changes has a direct impact on deformation monitoring. In particular, for high-precision deformation monitoring of natural surfaces, the interferometric phase corresponding to soil moisture changes needs to be considered in deformation monitoring research and applications. Extensive and in-depth research has been conducted on orbit error phase, DEM error phase, atmospheric delay phase, and ionospheric delay phase, for example, in patent CN118897288A. However, no relevant technical research has been carried out on the interference phase caused by changes in soil moisture on the natural surface. Therefore, it is of great significance to carry out research on deformation monitoring methods that take soil moisture changes into account for high-precision deformation monitoring of the natural surface. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for monitoring natural surface deformation while taking into account soil moisture changes. Based on the characteristics that the interference phase is sensitive to deformation information and that soil moisture changes lead to differences in electromagnetic wave penetration capabilities, an electromagnetic wave penetration depth model is used to obtain the interference phase component caused by soil moisture changes. Combined with ionospheric delay phase correction information, the interference phase information characterizing the natural surface deformation characteristics is obtained, especially the interference phase information caused by natural surface soil moisture changes is effectively suppressed, thereby achieving reliable and accurate acquisition of natural surface deformation information.

[0004] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0005] The present invention is a method for monitoring natural surface deformation taking into account soil moisture changes, characterized by comprising the following steps:

[0006] S1: Model and analyze the relationship between soil moisture changes and interference phase to obtain interference phase information caused by soil moisture changes. The specific steps include:

[0007] S1.1: Based on the content of natural surface soil components, obtain the relationship between the penetration depth of radar electromagnetic waves in the corresponding band and soil moisture;

[0008] S1.2: Obtain pixel-by-pixel electromagnetic wave penetration depth information based on soil moisture information at different time phases of the application scenario;

[0009] S1.3: Obtain the interferometric phase component caused by soil moisture variation by pixel-by-pixel penetration depth information within the natural scene;

[0010] S2: Perform interferometric processing on multi-temporal SAR data to obtain initial interferometric phase information of multiple phase components including terrain phase, deformation phase, interferometric phase caused by soil moisture change, orbit error phase, atmospheric phase, and ionospheric delay phase;

[0011] S3: Optimize the initial interferometric phase information to remove phase components irrelevant to surface deformation, including those caused by soil moisture changes, reduce the DEM error phase, remove the orbit error phase, suppress the atmospheric delay phase and the ionospheric delay phase, and obtain interferometric phase information that characterizes the natural surface deformation characteristics.

[0012] S4: Extract natural surface deformation information based on the optimized interferometric phase information.

[0013] As a preferred technical solution of the present invention, S1.1 specifically includes:

[0014] S1.11 Based on the electromagnetic wave penetration depth formula and combined with soil composition information, the penetration depth of SAR data in different bands under different soil moisture conditions is analyzed;

[0015] S1.12 By calculating the partial derivative of the electromagnetic wave penetration depth formula, the sensitivity of electromagnetic wave penetration depth in different bands to soil moisture changes is obtained;

[0016] S1.13 combines the conversion formula between penetration depth change and interference phase to obtain the relationship between the penetration ability of SAR data of a specific radar frequency band into the natural surface and soil moisture, and obtains the interference phase component information caused by soil moisture change.

[0017] As a preferred technical solution of the present invention, the formula for the electromagnetic wave penetration depth in S1.11 is:

[0018]

[0019] As a preferred technical solution of the present invention, the S2 specifically includes the following processing steps:

[0020] S2.1 uses geometrically calibrated multi-temporal SAR data as input and performs registration, resampling, filtering, and interferometric processing to obtain interferometric phase information. This interferometric phase includes terrain, deformation, soil moisture changes, orbit error, atmosphere, and ionospheric phase components.

[0021] S2.2 uses satellite precise orbit data to reduce the impact of the phase component of orbit error, and combines it with a highly timely and high-precision external DEM to effectively remove terrain phase information.

[0022] As a preferred technical solution of the present invention, S3 specifically includes the following steps:

[0023] S3.1: Suppress the interference phase component caused by soil moisture changes. Based on the soil moisture change information, obtain the change in electromagnetic wave penetration depth, extract the corresponding interference phase component, and separate the phase component caused by soil moisture changes from the interference phase.

[0024] S3.2: Reduce the phase interference of DEM errors. Use a high-precision and timely external DEM to further reduce the impact of DEM errors on the interferometric phase.

[0025] S3.3: Reduce orbit error phase interference. L-SAR satellites use dual-frequency differential GNSS to achieve precise orbit determination. Precise orbit data is uniformly used in the InSAR processing process to reduce the impact of orbit error on the interferometric phase.

[0026] S3.4: Reduce atmospheric delay phase interference by using atmospheric water vapor content data obtained by GNSS to extract high-resolution zenith total delay information and perform atmospheric delay correction on the interferometric phase;

[0027] S3.5: Reduce ionospheric delay phase interference. Use the space environment detection system carried by the L-SAR satellite to obtain the ionospheric electron density in the SAR line of sight, extract the ionospheric phase delay component of the SAR propagation path, separate the ionospheric phase delay component from the interference phase, and obtain the interference phase information that characterizes the natural surface deformation characteristics.

[0028] As a preferred technical solution of the present invention, in step S4, the method for extracting natural surface deformation information based on the optimized interferometric phase information includes:

[0029] Perform phase unwrapping and Doppler center correction on the interferometric phase information that characterizes natural surface deformation characteristics;

[0030] The relationship model between phase information and deformation is used to calculate high-precision surface deformation information.

[0031] The present invention has the following beneficial effects:

[0032] In the process of monitoring natural surface deformation using InSAR technology, the present invention fully considers the impact of natural surface soil moisture changes on the interferometric phase to achieve reliable and accurate acquisition of surface deformation information. To address this issue, a model is constructed between electromagnetic wave penetration depth and soil moisture, effectively obtaining the interferometric phase component caused by soil moisture changes, thereby effectively removing the contribution of natural surface soil moisture changes to the interferometric phase and optimizing the interferometric phase information for surface deformation monitoring. Furthermore, considering that the phase information of L-band SAR data is significantly affected by the ionosphere, the present invention combines ionospheric electron density data to obtain the SAR line of sight to the ionosphere delay phase information, eliminating the influence of the ionosphere on the L-band SAR interferometric phase, thereby obtaining optimized interferometric phase information that characterizes the characteristics of natural surface deformation. This interferometric phase information is then used to extract surface deformation information and achieve accurate monitoring of natural surface deformation characteristics.

[0033] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 Schematic diagram of the process of the present invention;

[0036] Figure 2 Schematic diagram of the process of step S1 in the present invention;

[0037] Figure 3 Schematic diagram of the relationship between radar electromagnetic wave penetration ability and soil moisture. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] For natural surface deformation monitoring, due to the difference in the penetration ability of electromagnetic waves in soils with different humidity, changes in soil moisture on the natural surface will directly contribute to the interference phase. Therefore, to obtain high-precision deformation information of the natural surface, it is necessary to effectively remove the phase component caused by soil moisture changes. The patent of this invention first analyzes the characteristics of the electromagnetic wave penetration depth on soil moisture changes, thereby constructing an interference phase component model caused by soil moisture. On this basis, the corresponding interference phase component is extracted through the soil moisture change information. By eliminating the phases in the interference phase that are irrelevant to the surface deformation one by one, especially effectively removing the phase components caused by soil moisture changes and the ionospheric delay phase components, reliable interference phase information that characterizes the surface deformation characteristics is obtained, thereby realizing high-precision deformation monitoring of the natural surface.

[0040] See also Figure 1-3 As shown, the present invention is a natural surface deformation monitoring method taking into account soil moisture changes. A specific application of the present invention is:

[0041] S1: Modeling and analyzing the relationship between soil moisture changes and interference phase, obtaining interference phase information caused by soil moisture changes, further including:

[0042] S1.1: Based on the content of natural surface soil components, obtain the relationship between the penetration depth of radar electromagnetic waves in the corresponding band and soil moisture;

[0043] S1.2: Obtain pixel-by-pixel electromagnetic wave penetration depth information based on soil moisture information at different time phases of the application scenario;

[0044] S1.3: Obtain the interferometric phase component caused by soil moisture variation by pixel-by-pixel penetration depth information within the natural scene.

[0045] S1.1 obtains the relationship between radar electromagnetic wave penetration depth and soil moisture based on the natural surface soil component content, including:

[0046] S1.11 Based on the electromagnetic wave penetration depth formula and combined with soil composition information, the penetration depth of SAR data in different bands under different soil moisture conditions is analyzed;

[0047] S1.12 By calculating the partial derivative of the electromagnetic wave penetration depth formula, the sensitivity of electromagnetic wave penetration depth in different bands to soil moisture changes is obtained;

[0048] S1.13 Combine the conversion formula between penetration depth change and interferometric phase to obtain the relationship between the penetration ability of SAR data of a specific radar frequency band into the natural surface and soil moisture, and obtain the interferometric phase component information caused by soil moisture change;

[0049] The specific relevant formulas are as follows:

[0050] The penetration depth of electromagnetic waves can be characterized as a function of parameters such as radar frequency band, soil composition, and soil moisture content. Therefore, the SAR penetration depth D of different frequency bands can be obtained based on soil parameter information. Specifically, it can be expressed as:

[0051]

[0052] ε'=f(m v ,S,C),ε”=g(m v ,S,C)

[0053] Where ε' and ε" are the real and imaginary parts of the soil dielectric constant, respectively, expressed as soil moisture content m v , soil clay content C and sand content S. m v Indicates soil moisture content in cm 3 / cm 3 , S and C represent the proportion of sand and clay in the soil respectively, D is the penetration depth of electromagnetic waves, and λ is the radar wavelength.

[0054] The above equation is differentiated to obtain the sensitivity of electromagnetic wave penetration depth in different bands to soil moisture changes.

[0055]

[0056] The above equation shows that the sensitivity between radar electromagnetic penetration depth and soil moisture changes directly depends on the radar wavelength, λ. That is, the longer the wavelength, the higher the sensitivity. Therefore, compared with X-band and C-band SAR signals, the electromagnetic penetration depth of L-band SAR signals is more significantly affected by soil moisture changes. Therefore, when using L-band SAR data to monitor natural surface deformation, it is necessary to fully consider the interferometric phase component caused by changes in surface soil moisture.

[0057] By formula The penetration depth of SAR signals of different frequency bands to different soil components and different soil moisture contents can be obtained, and then it can be found that the change of soil moisture will cause the change of electromagnetic wave penetration depth, thereby producing corresponding contributions to the interferometric phase information of SAR data at different time phases. smc .

[0058] φ smc =4π(D2-D1) / λ

[0059] Where D1 and D2 are the corresponding penetration depths of electromagnetic waves at different times.

[0060] S2: Interferometrically process the geometrically calibrated multi-temporal SAR imagery to obtain interferometric phase information, including terrain phase, deformation phase, interferometric phase due to soil moisture changes, orbit error phase, atmospheric phase, and ionospheric delay phase. This interferometric phase information is decomposed, removing phase components irrelevant to deformation monitoring to obtain interferometric phase information that characterizes natural surface deformation.

[0061] The specific implementation steps are as follows:

[0062] S2.1 uses geometrically calibrated multi-temporal SAR data as input and performs registration, resampling, filtering, and interferometric processing to obtain interferometric phase information. This interferometric phase includes terrain, deformation, soil moisture change, orbit error, atmosphere, and ionospheric phase components, as shown in the formula:

[0063] φ int =φ topo +φ def +φ smc +φ orb +φ atm +φ ion

[0064] Where, φ int is the interference phase, φ topo is the terrain phase, φ def is the deformation phase, φ orb is the orbit error, φ atm is the atmospheric phase, φ ion is the ionospheric delay phase. Compared with the traditional interference phase expression formula, the above formula focuses on adding the interference phase component φ smc , represents the interferometric phase caused by soil moisture changes. This phase component is not fully considered in traditional InSAR surface deformation monitoring. However, this component has a direct impact on high-precision surface deformation monitoring in natural surface deformation monitoring. Therefore, this invention focuses on addressing the impact of the interferometric phase caused by soil moisture changes on deformation monitoring, thereby obtaining high-precision and reliable surface deformation information on natural surfaces.

[0065] S2.2 Using satellite precise orbit data to reduce the orbit error phase component φ orb The influence of terrain phase information φ is effectively removed by combining the high-precision and timely external DEM. topo .

[0066] The interference phase is thus expressed as the superposition of the deformation phase, the phase caused by soil moisture change, the atmospheric delay phase, and the ionospheric delay phase, which can be expressed as:

[0067] φ int =φ def +φ smc +φatm +φ ion

[0068] Aiming at natural surface deformation monitoring, the focus is on extracting the interferometric phase information φ that characterizes the surface deformation characteristics. def , but the expression still includes the interferometric phase caused by soil moisture changes, atmospheric phase, and ionospheric delay phase components. Therefore, reliable acquisition of natural surface deformation information using interferometric phase requires focusing on solving the problems of interferometric phase components, atmospheric delay, and ionospheric delay caused by soil moisture changes.

[0069] S3 interferometric phase optimization processing uses satellite precise orbit data to remove the impact of orbit error phase on several phase components contained in the interferometric phase. It effectively reduces terrain phase interference through high-precision and high-timeliness external DEM, focusing on removing phase components caused by soil moisture changes, atmospheric delay phase, and ionospheric delay phase.

[0070] When doing specific operations:

[0071] S3.1 Interference phase component φ caused by soil moisture changes smc , to optimize the overall interference phase information. The penetration depth of SAR signals of different frequency bands to different soil components and different soil moisture contents can be obtained, and then it can be found that the change of soil moisture will cause the change of electromagnetic wave penetration depth, thereby producing corresponding contributions to the interferometric phase information of SAR data at different time phases. smc .

[0072] φ smc =4π(D2-D1) / λ

[0073] Where D1 and D2 are the corresponding penetration depths of electromagnetic waves at different times.

[0074] S3.2 Reducing DEM error phase interference φ topo External DEM errors will have a certain impact on the interferometric phase. When the interferometric baseline is short, the phase error caused by elevation errors is correspondingly smaller. In other words, the shorter the spatial baseline, the less the interferometric phase is affected by external DEM errors. Interferometric SAR satellites use strict re-orbit control, and the re-orbit interferometric baseline is well controlled. Therefore, the interferometric phase is relatively less affected by external DEM errors. Using a high-precision, timely external DEM can further suppress DEM error phase.

[0075] S3.3 Reduce orbit error phase interference. The L-SAR satellite uses dual-frequency differential GNSS to achieve precise orbit determination. The satellite's precise orbit determination accuracy is better than 10cm. Multi-phase SAR data interferometric processing uses precise orbit data as input, thereby minimizing the impact of orbit error in the interferometric phase.

[0076] S3.4 Atmospheric phase delay φ atm and the ionospheric phase delay φ ion Interferometric phase optimization is performed. First, atmospheric delay phase is removed. Based on GNSS data such as atmospheric water vapor content, high-spatial-resolution zenithal total delay is extracted, effectively improving tropospheric delay. Interferometric phase information is corrected using atmospheric delay information of the same phase, overcoming the impact of tropospheric atmospheric delay on high-precision deformation monitoring of natural surfaces.

[0077] S3.5 for the ionospheric delay component φ in the interferometric phase ion , through the space environment detection system carried by the SAR satellite, the ionospheric electron density R in the SAR line of sight is obtained e (l), and then extract the ionospheric delay phase component φ ion .

[0078] The total content of free electrons in the SAR signal propagation path is expressed as the integral of the ionospheric electron density along the propagation path, that is:

[0079] TEC SAR =∫ L R e (l)dl

[0080] Where L is the propagation path of the SAR signal in the ionosphere. The ionospheric phase delay of the SAR signal propagation path is:

[0081]

[0082] Among them, n p is the phase refractive index, and f is the radar electromagnetic wave frequency. The ionospheric delay phase component of the SAR propagation path is obtained through the ionospheric density information obtained by the space environment monitoring system. The ionospheric phase delay component is separated from the interferometric phase to achieve effective optimization of the InSAR phase information. By eliminating the interferometric phase components irrelevant to the natural surface deformation characteristics, including the phase caused by soil moisture changes, atmospheric delay phase and ionospheric delay phase, the interferometric phase information φ that characterizes the surface deformation characteristics is obtained. def .

[0083] φ def =φ int -φ smc -φ atm -φ ion

[0084] S4: Using the optimized interferometric phase φ to characterize natural surface deformation def High-precision surface deformation information is calculated. The specific method can be to perform phase unwrapping and Doppler center correction on the interference phase information that characterizes the natural surface deformation characteristics; and to calculate high-precision surface deformation information using a relationship model between phase information and deformation.

[0085] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0086] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for monitoring natural surface deformation taking into account soil moisture changes, characterized in that: The following steps are involved: S1: Model and analyze the relationship between soil moisture changes and interference phase to obtain interference phase information caused by soil moisture changes; The specific steps include: S1.1: Based on the content of natural surface soil components, obtain the relationship between the penetration depth of radar electromagnetic waves in the corresponding band and soil moisture; S1.11 analyzes the penetration depth of SAR data in different bands under different soil moisture conditions based on the electromagnetic wave penetration depth formula and soil composition information. The electromagnetic wave penetration depth formula is: ε'=f(m v ,S,C),ε”=g(m v ,S,C) Where ε' and ε" are the real and imaginary parts of the soil dielectric constant, respectively, expressed as soil moisture content m v , function of soil clay content C and sand content S, m v Indicates soil moisture content in cm 3 / cm 3 , S and C represent the proportion of sand and clay in the soil respectively, D is the penetration depth of electromagnetic waves, and λ is the radar wavelength; S1.12 By calculating the partial derivative of the electromagnetic wave penetration depth formula, the sensitivity of electromagnetic wave penetration depth in different bands to soil moisture changes is obtained; S1.13 Combine the conversion formula between penetration depth change and interferometric phase to obtain the relationship between the penetration ability of SAR data of a specific radar frequency band into the natural surface and soil moisture, and obtain the interferometric phase component information caused by soil moisture change; S1.2: Obtain pixel-by-pixel electromagnetic wave penetration depth information based on soil moisture information at different time phases of the application scenario; S1.3: Obtain the interferometric phase component caused by soil moisture variation by pixel-by-pixel penetration depth information within the natural scene; S2: Perform interferometric processing on multi-temporal SAR data to obtain initial interferometric phase information of multiple phase components including terrain phase, interferometric phase caused by soil moisture change, deformation phase, orbit error phase, atmospheric phase, and ionospheric delay phase; S3: Optimize the initial interferometric phase information to remove phase components irrelevant to surface deformation, including those caused by soil moisture changes, reduce the DEM error phase, remove the orbit error phase, suppress the atmospheric delay phase and the ionospheric delay phase, and obtain interferometric phase information that characterizes the natural surface deformation characteristics. S4: Extract natural surface deformation information based on the optimized interferometric phase information.

2. A natural surface deformation monitoring method taking into account soil moisture changes according to claim 1, characterized in that: The S2 specifically includes the following processing steps: S2.1 uses geometrically calibrated multi-temporal SAR data as input and performs registration, resampling, filtering, and interferometric processing to obtain interferometric phase information. This interferometric phase includes terrain, deformation, soil moisture changes, orbit error, atmosphere, and ionospheric phase components. S2.2 uses satellite precise orbit data to reduce the impact of the phase component of orbit error, and combines it with a highly timely and high-precision external DEM to effectively remove terrain phase information.

3. A natural surface deformation monitoring method taking into account soil moisture changes according to claim 2, characterized in that: The S3 specifically includes the following steps: S3.1: Suppress the interference phase component caused by soil moisture changes. Based on the soil moisture change information, obtain the change in electromagnetic wave penetration depth, extract the corresponding interference phase component, and separate the phase component caused by soil moisture changes from the interference phase. S3.2: Reduce the phase interference of DEM errors. Use a high-precision and timely external DEM to further reduce the impact of DEM errors on the interferometric phase. S3.3: Reduce orbit error phase interference. L-SAR satellites use dual-frequency differential GNSS to achieve precise orbit determination. Precise orbit data is uniformly used in the InSAR processing process to reduce the impact of orbit error on the interferometric phase. S3.4: Reduce atmospheric delay phase interference by using atmospheric water vapor content data obtained by GNSS to extract high-resolution zenith total delay information and perform atmospheric delay correction on the interferometric phase; S3.5: Reduce ionospheric delay phase interference. Use the space environment detection system carried by the L-SAR satellite to obtain the ionospheric electron density in the SAR line of sight, extract the ionospheric phase delay component of the SAR propagation path, separate the ionospheric phase delay component from the interference phase, and obtain the interference phase information that characterizes the natural surface deformation characteristics.

4. The method for monitoring natural surface deformation taking into account soil moisture changes according to claim 1, characterized in that: In step S4, the method for extracting natural surface deformation information based on the optimized interferometric phase information includes: Perform phase unwrapping and Doppler center correction on the interferometric phase information that characterizes natural surface deformation characteristics; The relationship model between phase information and deformation is used to calculate high-precision surface deformation information.

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