Natural earth surface deformation monitoring method considering soil moisture change

Abstract

The invention discloses a natural earth surface deformation monitoring method considering soil moisture change, and relates to the technical field of synthetic aperture radar interferometry. Comprising the following steps: S1, modeling and analyzing a relationship between soil moisture change and an interferometric phase, and obtaining interferometric phase information caused by the soil moisture change; s2, performing multi-temporal SAR data interference processing to obtain initial interference phase information including interference information such as a phase component caused by soil moisture change; s3, optimizing the interferometric phase information, eliminating interferometric phase components caused by soil moisture change, and obtaining the interferometric phase information representing natural surface deformation characteristics; and S4, acquiring natural earth surface deformation information based on the optimized interferometric phase information. According to the method, the interferometric phase component caused by soil moisture change is eliminated, the interferometric phase information is optimized, then the interferometric phase information representing earth surface deformation characteristics reliably is obtained, and the technical effect of natural earth surface high-precision deformation information extraction is achieved.

Description

Technical Field

[0001] The 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 technology to monitor surface deformation has been widely studied. In particular, based on the sensitive response of interferometric phase information to surface deformation, it has been widely used in the fields of ground subsidence monitoring, geological disaster investigation and monitoring, and urban safety monitoring. However, the series of phase components contained in the interferometric phase information have a significant impact on the accuracy of deformation monitoring, including orbit error phase, DEM error phase, atmospheric delay phase, and ionospheric delay phase. Therefore, in order to achieve reliable and accurate acquisition of surface deformation information, it is necessary to effectively remove phase components that are irrelevant to the surface deformation characteristics. That is, whether reliable surface deformation information can be extracted 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 will have a direct impact on deformation monitoring, especially 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. For orbit error phase, DEM error phase, atmospheric delay phase, and ionospheric delay phase, scholars have conducted extensive and in-depth research, such as 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 taking into account soil moisture changes. Based on the characteristics that the interference phase is sensitive to deformation information and the characteristics 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, interference phase information characterizing the natural surface deformation characteristics is obtained, especially effectively suppressing the interference phase information caused by natural surface soil moisture changes, thereby achieving reliable and accurate acquisition of natural surface deformation information.

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

[0005] The present invention is a natural surface deformation monitoring method taking into account soil moisture changes, characterized in that it comprises the following steps:

[0006] S1: Model and analyze the relationship between soil moisture change and interference phase, and obtain the interference phase information caused by soil moisture change; 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 the electromagnetic wave penetration depth information of each pixel based on the soil moisture information at different phases of the application scenario;

[0009] S1.3: Obtain the interference phase component caused by soil moisture changes through pixel-by-pixel penetration depth information in natural scenes;

[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, remove phase components irrelevant to surface deformation, including removing interferometric phase components caused by soil moisture changes, reducing DEM error phase, removing orbit error phase, suppressing atmospheric delay phase and ionospheric delay phase, and obtaining interferometric phase information that characterizes 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 component 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 Combined with the conversion formula between penetration depth change and interference phase, the relationship between the penetration ability of SAR data of a specific radar frequency band on the natural surface and soil moisture is obtained, and the interference phase component information caused by soil moisture change is obtained.

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

[0018]

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

[0020] S2.1 uses the multi-phase SAR data after geometric calibration as input, performs registration, resampling, filtering and interferometric processing to obtain interferometric phase information, which includes terrain, deformation, soil moisture change, orbit error, atmosphere and ionosphere 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 change, obtain the change in electromagnetic wave penetration depth based on soil moisture change information, extract the corresponding interference phase component, and separate the phase component caused by soil moisture change from the interference phase;

[0024] S3.2: Reduce the phase interference of DEM errors, and further reduce the impact of DEM errors on the interference phase through high-precision and high-time external DEM;

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

[0026] S3.4: Reduce atmospheric delay phase interference, use 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 the ionospheric delay phase interference, obtain the ionospheric electron density in the SAR line of sight through the space environment detection system carried by the L-SAR satellite, 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 interference 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 using InSAR technology to monitor natural surface deformation, the present invention fully considers the influence of natural surface soil moisture changes on the interference phase in order to achieve reliable and accurate acquisition of surface deformation information. In view of this problem, a model between electromagnetic wave penetration depth and soil moisture is constructed to effectively obtain the interference phase component caused by soil moisture changes, thereby effectively removing the contribution of natural surface soil moisture changes to the interference phase, and optimizing the interference phase information for surface deformation monitoring. In view of the fact that the phase information of L-band SAR data is significantly affected by the ionosphere, the ionospheric electron density data is combined to obtain the SAR line of sight to the ionosphere delay phase information, eliminate the influence of the ionosphere on the L-band SAR interference phase, thereby obtaining the optimized interference phase information characterizing the natural surface deformation characteristics, and using it for surface deformation information extraction to 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 drawings required for describing the embodiments are briefly introduced below. 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 be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are 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, the change of 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 the change of soil moisture. The patent of this invention first analyzes the characteristics of the electromagnetic wave penetration depth on the change of soil moisture, so as to construct 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, and the phases in the interference phase that are irrelevant to the surface deformation are eliminated item by item, especially the phase components caused by soil moisture changes and the ionospheric delay phase components are effectively removed, so as to obtain reliable interference phase information that characterizes the surface deformation characteristics, 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 change and interference phase, obtaining interference phase information caused by soil moisture change, 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 the electromagnetic wave penetration depth information of each pixel based on the soil moisture information at different phases of the application scenario;

[0044] S1.3: Obtain the interference phase component caused by soil moisture changes through pixel-by-pixel penetration depth information in natural scenes.

[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 component 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 interference phase to obtain the relationship between the penetration ability of SAR data of a specific radar frequency band on the natural surface and soil moisture, and obtain the interference phase component information caused by soil moisture change;

[0049] The specific relevant formula is 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 penetration depth D of SAR in different frequency bands can be obtained through soil parameter information, which is specifically expressed as:

[0051]

[0052] ε'=f(m v ,S,C),ε”=g(m v ,S,C)

[0053] In the formula, 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] From the above formula, we can get that the sensitivity between the radar electromagnetic wave 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 change in the electromagnetic wave penetration depth of L-band SAR signals is more significantly affected by soil moisture changes. That is, when using L-band SAR data to monitor natural surface deformation information, it is necessary to fully consider the interference 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, thus producing corresponding contribution to the interference phase information of SAR data at different time phases. smc .

[0058] φ smc =4π(D 2 -D 1 ) / λ

[0059] Where D 1 and D 2 They are the corresponding penetration depths of electromagnetic waves at different times.

[0060] S2: Perform interferometric processing on the multi-temporal SAR images after geometric calibration to obtain the corresponding interferometric phase information, including terrain phase, deformation phase, interferometric phase caused by soil moisture change, orbit error phase, atmospheric phase, and ionospheric delay phase. Decompose the interferometric phase information and obtain interferometric phase information that characterizes the deformation characteristics of the natural surface by removing the phase components that are irrelevant to deformation monitoring.

[0061] The specific implementation steps are as follows:

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

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

[0064] In the formula, 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 interference phase caused by soil moisture changes, which is also the phase component information that is not fully considered in traditional InSAR surface deformation monitoring. In natural surface deformation monitoring, this component has a direct impact on high-precision surface deformation monitoring. Therefore, the present invention focuses on solving the impact of the interference phase caused by soil moisture changes on deformation monitoring, so as to obtain high-precision and reliable surface deformation information of the natural surface.

[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 external DEM with high timeliness. 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, 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 relationship still includes the interference phase, atmospheric phase and ionospheric delay phase components caused by soil moisture changes. Therefore, the reliable acquisition of natural surface deformation information using the interference phase needs to focus on solving the problems of interference 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, and 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 change 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, thus producing corresponding contribution to the interference phase information of SAR data at different time phases. smc .

[0072] φ smc =4π(D 2 -D 1 ) / λ

[0073] Where D 1 and D 2 are the corresponding penetration depths of electromagnetic waves at different times.

[0074] S3.2 Reducing DEM error phase interference φ topo , the external DEM error will have a certain impact on the interferometric phase. When the interferometric baseline of the image pair is shorter, the phase error caused by the corresponding elevation error is smaller, that is, the shorter the spatial baseline, the less the interferometric phase is affected by the external DEM error. Interferometric SAR satellites use strict regression orbit control, and the heavy orbit interferometric baseline control is better, so the interferometric phase is relatively less affected by the external DEM error. Through high-precision and high-timeliness external DEM, the DEM error phase is further suppressed.

[0075] S3.3 Reduce orbit error phase interference. 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 interference processing uses precise orbit data as input, thereby minimizing the impact of orbit errors in the interference phase.

[0076] S3.4 Atmospheric phase delay φ atm and the ionospheric phase delay φ ion Interference phase optimization processing is performed. First, the atmospheric delay phase is removed. Based on the atmospheric water vapor content and other data obtained by GNSS, the zenith total delay with high spatial resolution is extracted to effectively improve the tropospheric delay. The atmospheric delay information of the same phase is used to correct the interferometric phase information to overcome the influence 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 SAR line of sight to the ionospheric electron density R 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 on 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 ionosphere 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 interference phase to achieve effective optimization of the InSAR phase information. By eliminating the interference 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 interference 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] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0086] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. 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 change and interference phase, and obtain the interference phase information caused by soil moisture change; 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; S1.2: Obtain the electromagnetic wave penetration depth information of each pixel based on the soil moisture information at different phases of the application scenario; S1.3: Obtain the interference phase component caused by soil moisture changes through pixel-by-pixel penetration depth information in natural scenes; 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, remove phase components irrelevant to surface deformation, including removing interferometric phase components caused by soil moisture changes, reducing DEM error phase, removing orbit error phase, suppressing atmospheric delay phase and ionospheric delay phase, and obtaining interferometric phase information that characterizes 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 S1.1 specifically includes: S1.11 Based on the electromagnetic wave penetration depth formula and combined with soil component information, the penetration depth of SAR data in different bands under different soil moisture conditions is analyzed; 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 Combined with the conversion formula between penetration depth change and interference phase, the relationship between the penetration ability of SAR data of a specific radar frequency band on the natural surface and soil moisture is obtained, and the interference phase component information caused by soil moisture change is obtained.

3. A natural surface deformation monitoring method taking into account soil moisture changes according to claim 2, characterized in that: The formula for the penetration depth of electromagnetic waves in S1.11 is:

4. 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 the multi-phase SAR data after geometric calibration as input, performs registration, resampling, filtering and interferometric processing to obtain interferometric phase information, which includes terrain, deformation, soil moisture change, orbit error, atmosphere and ionosphere 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.

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

6. A natural surface deformation monitoring method 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 interference 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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