Coal mining subsidence monitoring method based on GNSS-IR technology

Abstract

The present invention discloses a coal mining subsidence monitoring method based on GNSS-IR technology. The steps of obtaining the absolute subsidence amount of a surface point in space are as follows: a GNSS receiver and an antenna are installed on the surface of the coal mining subsidence area to be monitored. Before the underground coal seam is mined, the distance between the GNSS antenna and the elevation reference surface is H. 0 After the underground coal seam is mined, the position of the ground surface and the GNSS antenna in space sinks. At this time, the distance between the GNSS antenna and the elevation reference surface is H 1 ; Using GNSS carrier phase differential positioning, we can obtain H 0 and H 1 Then, H 0 Subtract H 1 , obtain the subsidence ΔH at the GNSS antenna abs ; Using GNSS-IR technology, the amount of subsidence of any point P on the surface relative to the GNSS antenna before and after the underground coal seam is mined is obtained as ΔH rel , the settlement amount ΔH abs With the amount of subsidence ΔH rel By adding them together, the absolute subsidence of the surface point P in space can be obtained. A single measuring station can realize high-precision, continuous and real-time monitoring of surface subsidence.

Description

Technical Field

[0001] The invention relates to a method for monitoring surface subsidence caused by underground coal mining using a GNSS-IR technology, and belongs to the field of surface deformation monitoring. Background Art

[0002] After the underground coal seam is mined, the rock layer directly above the goaf moves and bends downward under the action of its own gravity and the overlying rock layer. When the deformation of the rock layer is transmitted to the surface, it will cause the ground to sink, and then form a collapse basin on the surface. Coal mining subsidence will not only lead to a series of ecological and environmental problems, but may even cause major geological disasters, such as cracks and collapse of buildings, subsidence of highway roadbeds, and suspension of railway rails. Monitoring the surface subsidence caused by coal mining can predict, warn, and prevent potential geological disasters, thereby effectively avoiding the occurrence of disasters; the surface subsidence data obtained through monitoring can also provide a reliable and scientific basis for the management of coal mining subsidence areas and the study of the laws of coal mining subsidence.

[0003] The Global Navigation Satellite System (GNSS) refers to all satellite navigation systems, including global, regional and enhanced systems, such as the US GPS, Russia's Glonass, Europe's Galileo, China's BeiDou satellite navigation system and related augmentation systems. A GNSS receiver can measure the distances of four or more GNSS satellites to calculate the spatial position (latitude, longitude, and geodetic height) of the user receiver.

[0004] GNSS-IR is a technology that uses the L-band signal emitted by global navigation satellites as an external radiation source, and uses a ground-based platform as a carrier for the reflected signal receiving device. It receives and processes the interference signal formed by the superposition of the GNSS signal reflected from the ocean, land or other objects and the direct signal to extract the characteristic elements of the measured medium. By receiving and processing the GNSS signal reflected from the surface of the measuring station, the GNSS-IR technology can monitor the surface electromagnetic physical parameters within thousands of square meters around the measuring station.

[0005] Existing coal mining subsidence monitoring technologies can be divided into three categories: ground-based, air-based and satellite-based monitoring technologies. Ground-based coal mining subsidence monitoring technologies include leveling and GNSS positioning technologies; air-based monitoring technologies mainly use drones as carrier platforms, and the technology types include: oblique photogrammetry technology and airborne laser scanning technology (LiDAR); satellite-based monitoring technologies use satellites as carrier platforms, and the technology types are mainly synthetic aperture radar interferometry technology (InSAR).

[0006] The existing technical methods mainly have the following problems:

[0007] Ground monitoring technology: The existing ground mining subsidence monitoring technology can only obtain discrete subsidence data at a few monitoring stations, so the technology has low temporal and spatial resolution and extremely low spatial scale of monitoring. Although the spatial scale of monitoring can be increased by adding more monitoring stations, this method will greatly increase the economic cost and is not feasible in reality.

[0008] Air-based monitoring technology: Air-based monitoring technology is easily affected by weather factors such as clouds and rain, and cannot provide continuous surface subsidence data. In addition, the implementation of this technology is time-consuming, labor-intensive and has high economic costs.

[0009] Satellite-based monitoring technology: Satellite-based monitoring technology is subject to the inherent limitations of spatial sampling, that is, the deformation of adjacent pixels cannot exceed 1 / 4 wavelength (1.4cm / 25m for C-band and 7cm / 2m for L-band); therefore, in practice, this technology cannot be applied to the monitoring of coal mining subsidence in thick coal seams and extra-thick coal seams (especially the monitoring of large-scale surface subsidence during the active period).

[0010] The existing GNSS positioning technology can only monitor the surface subsidence at the measuring station (or GNSS antenna), that is, "point monitoring", but cannot monitor the surface subsidence of coal mining in the surrounding area of ​​the measuring station. The present invention uses GNSS-IR technology to fill the gap in the existing technology in the field of high temporal and spatial resolution coal mining subsidence monitoring, and a single measuring station can achieve 7000m 2 High-precision, continuous real-time monitoring of surface subsidence within the scope. Summary of the invention

[0011] The purpose of the present invention is to propose a coal mining subsidence monitoring method based on GNSS-IR technology to solve the problems raised in the above background technology.

[0012] To achieve the above object, the present invention provides the following technical solutions:

[0013] The coal mining subsidence monitoring method based on GNSS-IR technology has the following steps to obtain the absolute subsidence amount of the surface point in space:

[0014] The GNSS receiver and antenna are installed on the ground surface of the coal mining subsidence area to be monitored. Before the underground coal seam is mined, the distance between the GNSS antenna and the elevation reference plane is H0. After the underground coal seam is mined, the position of the ground surface and the GNSS antenna in space sinks. At this time, the distance between the GNSS antenna and the elevation reference plane is H1. GNSS carrier phase differential positioning is used to obtain the values ​​of H0 and H1 respectively. Then, H0 is subtracted from H1 to obtain the subsidence amount ΔHabs at the GNSS antenna.

[0015] Using GNSS-IR technology, the settlement amount of any point P on the surface relative to the GNSS antenna before and after the underground coal seam is mined is obtained as ΔHrel. By adding the settlement amount ΔHabs to the settlement amount ΔHrel, the absolute settlement amount of the surface point P in space can be obtained.

[0016] As a further solution of the present invention: There are four key steps to obtain the amount of subsidence of a surface point relative to a GNSS antenna using GNSS-IR technology: S1 extracting GNSS interference signals, S2 determining feature points of interference signals, S3 calculating phase changes at reference feature points, and S4 calculating surface subsidence at reference feature points.

[0017] As a further solution of the present invention: There are four key steps to obtain the amount of subsidence of a surface point relative to a GNSS antenna using GNSS-IR technology: S1 extracting GNSS interference signals, S2 determining feature points of interference signals, S3 calculating phase changes at reference feature points, and S4 calculating surface subsidence at reference feature points.

[0018] As a further solution of the present invention: the extraction process of GNSS interference signal: S11 takes the GNSS satellite altitude angle as the independent variable and the SNR observation value as the dependent variable to construct the GNSS SNR observation value sequence; S12 intercepts the SNR observation value sequence within the altitude angle range of 5°-25°; S13 uses a high-pass filter to extract high-frequency GNSS interference signals, and the cut-off frequency of the filter is not higher than 10Hz; S14 uses a low-pass filter to remove the observation noise of the GNSS interference signal; the cut-off frequency range of the filter is not less than 80Hz;

[0019] Determine the characteristic points of the interference signal: S21 finds the satellite elevation angle corresponding to when the interference signal sequence value is zero; S22 extracts the interference signal subsequence between two adjacent zero points. S23 Determine the type of characteristic point according to the size of the subsequence observation value; if 2 / 3 of the subsequence SNR observation values ​​are greater than zero, then the type of the characteristic point is the satellite elevation angle corresponding to the peak point; if 2 / 3 of the subsequence SNR observation values ​​are less than zero, then the type of the characteristic point is the satellite elevation angle corresponding to the trough point. S24 Use the satellite elevation angle as the independent variable and the SNR observation value of the subsequence as the dependent variable, and use a second-order polynomial to fit the subsequence;

[0020] Calculate the phase change of the reference feature point: S31 takes the feature point of the GNSS interference signal obtained before the surface subsidence occurs as the reference feature point, and sets the initial phase of the interference signal at the reference feature point to zero or other constants; S32 obtains the phase value of the GNSS interference signal at the reference feature point after the surface subsidence occurs, and subtracts the phase value from the initial phase value to obtain the phase change at the reference feature point;

[0021] After the surface subsidence, the phase value at the reference feature point of the interference signal is calculated using the linear interpolation method, that is, find the feature points closest to the left and right sides of the reference feature point. If the feature point on the left is a wave crest point and the feature point on the right is a wave trough point, the phase value at the reference feature point after the surface subsidence is calculated using formula (1); if the feature point on the left is a wave trough point and the feature point on the right is a wave crest point, the phase value at the reference feature point after the surface subsidence is calculated using formula (2);

[0022]

[0023]

[0024] Calculate the surface subsidence at the benchmark feature point: S41 takes the observation date of the GNSS interference signal as the independent variable and the phase change at the benchmark feature point as the dependent variable to construct a time series of the phase change at the benchmark feature point; S42 takes the difference between the phase changes of two adjacent observation dates. If the difference is greater than π / 2, all phase changes on and after that date are added with 2π; if the difference is less than -π / 2, all phase changes on and after that date are subtracted with 2π; use formula 3 to convert the unwrapped phase change into the surface subsidence at the benchmark feature point;

[0025]

[0026] As a further solution of the present invention: based on the surface subsidence at the reference feature points, a coal mining surface subsidence curve and a curve of inclination and curvature deformation in a certain direction are generated.

[0027] As a further solution of the present invention: The specific steps for generating the surface subsidence surface are as follows: Taking the GNSS antenna phase center as the coordinate zero point, use Formula 4 to calculate the plane position coordinates (x, y) of the surface mirror reflection point corresponding to the reference feature point. Combine the plane coordinates of the surface reflection point and the subsidence amount at the corresponding reference feature point to construct the three-dimensional subsidence coordinates of the surface reflection point. Finally, based on the constructed three-dimensional subsidence coordinate discrete point sequence, use the Kriging interpolation method to generate the surface subsidence surface around the measuring station.

[0028] As a further solution of the present invention: the specific steps of generating the tilt and curvature deformation curve are:

[0029] On the generated surface subsidence surface, specify the required direction vector curve. Extract the surface subsidence value on the curve; take the distance from any point on the curve to the starting point as the independent variable, and the subsidence value of the point as the dependent variable, and use the B-spline function to fit the surface subsidence value on the curve. The order of the spline function should be greater than or equal to 3. The first-order derivative of the fitted spline function can be obtained to obtain the tilt deformation curve in the specified direction; the second-order derivative of the fitted spline function can be obtained to obtain the curvature deformation curve in the specified direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention uses this technology to obtain a model diagram of surface subsidence caused by coal mining;

[0031] Figure 2 This is a flow chart of a method for obtaining the amount of subsidence of a surface point relative to a GNSS antenna according to the present invention;

[0032] Figure 3 This is a flow chart of extracting GNSS interference signals of the present invention;

[0033] Figure 4 A schematic diagram of phase unwrapping of the phase variation at the reference feature point in the present invention;

[0034] Figure 5 This is a generated diagram of the ground subsidence surface and the inclination and curvature deformation curves in the present invention. DETAILED DESCRIPTION

[0035] 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.

[0036] See also Figure 1 In the embodiment of the present invention, in the implementation of this scheme, the GNSS receiving equipment (including the GNSS receiver and the antenna) is installed on the ground surface of the coal mining subsidence area that needs to be monitored. Since the spatial range monitored by this technology is proportional to the height of the GNSS antenna, the height of the GNSS antenna should be at least greater than 5m during the actual installation process. Before the underground coal seam is mined, the distance between the GNSS antenna and the elevation reference plane is H0; after the underground coal seam is mined, the position of the ground surface and the GNSS antenna in space sinks, and at this time the distance between the GNSS antenna and the elevation reference plane is H1. Using GNSS carrier phase differential positioning, the values ​​of H0 and H1 are obtained respectively; then, H0 is subtracted from H1 to obtain the settlement amount ΔH at the GNSS antenna (or measuring station) absBefore and after the underground coal seam is mined, the amount of subsidence of any point P on the surface relative to the GNSS antenna is ΔH rel By using GNSS-IR technology, after obtaining the settlement of the surface point P relative to the GNSS antenna, the settlement is added to the settlement at the GNSS antenna to obtain the settlement of the surface point P relative to the elevation reference plane (or the absolute settlement of the surface point in space).

[0037] See also Figures 2 to 4 In this embodiment, the present invention uses GNSS-IR technology to obtain the amount of subsidence of the surface point relative to the GNSS antenna. There are four key steps: extracting the GNSS interference signal, determining the feature points of the interference signal, calculating the phase change at the reference feature points, and calculating the surface subsidence at the reference feature points.

[0038] In this embodiment, the GNSS interference signal is extracted. This technology uses GNSS SNR (Signal-to-Noise) observations to extract GNSS interference signals. The extraction process of GNSS interference signals is as follows: S11: Use the GNSS satellite elevation angle as the independent variable and the SNR observation value as the dependent variable to construct a GNSS SNR observation value sequence. S12: Intercept the SNR observation value sequence within the elevation angle range of 5°-25°. S13: Use a high-pass filter to extract high-frequency GNSS interference signals; the cutoff frequency of the filter is not higher than 10Hz. S14 Use a low-pass filter to remove the observation noise of the GNSS interference signal; the cutoff frequency range of the filter is not less than 80Hz. Figure 3 As an embodiment of extracting GNSS interference signals, the GNSS interference signals extracted by this process have an obvious periodic oscillation trend and no significant interference noise, and the normalized main frequency power spectrum density is greater than 0.6.

[0039] Determine the characteristic points of the interference signal: In the present invention, the characteristic points of the interference signal refer to the satellite altitude angles corresponding to the peaks and troughs of the GNSS interference signal sequence (or, the satellite altitude angles corresponding to the maximum SNR value and the minimum SNR value points). The process of determining the characteristic points of the GNSS interference signal is as follows: S21 finds the satellite altitude angle corresponding to the interference signal sequence value when it is zero. S22 extracts the interference signal subsequence between two adjacent zero points. S23 determines the type of characteristic point according to the size of the observed value of the subsequence; if 2 / 3 of the subsequence SNR observed values ​​are greater than zero, the type of the characteristic point is the satellite altitude angle corresponding to the peak point; if 2 / 3 of the subsequence SNR observed values ​​are less than zero, the type of the characteristic point is the satellite altitude angle corresponding to the trough point. S24 takes the satellite altitude angle as the independent variable and the SNR observed value of the subsequence as the dependent variable, and uses a second-order polynomial (or, parabola) to fit the subsequence. The satellite altitude angle corresponding to the peak point of the parabolic function obtained by fitting is the characteristic point value of the interference signal subsequence (that is, the satellite altitude angle corresponding to the peak or trough).

[0040] Calculate the phase change at the reference feature point:

[0041] In the present invention, the phase change of the GNSS interference signal at the reference feature point is a key parameter for calculating the surface subsidence. The process of calculating the phase change of the reference feature point is as follows: S31 takes the feature point of the GNSS interference signal obtained before the surface subsidence occurs as the reference feature point, and sets the initial phase of the interference signal at the reference feature point to zero or other constants. S32 obtains the phase value of the GNSS interference signal at the reference feature point after the surface subsidence occurs, and subtracts the phase value from the initial phase value to obtain the phase change at the reference feature point.

[0042] After the surface subsidence, the phase value at the reference feature point of the interference signal is calculated using the linear interpolation method, that is, find the feature points closest to the left and right sides of the reference feature point. If the feature point on the left is a crest point and the feature point on the right is a trough point, the phase value at the reference feature point after the surface subsidence is calculated using formula (1); if the feature point on the left is a trough point and the feature point on the right is a crest point, the phase value at the reference feature point after the surface subsidence is calculated using formula (2).

[0043]

[0044]

[0045] Calculate the surface subsidence at the benchmark feature points.

[0046] After obtaining the phase change of the GNSS interference signal at the reference feature point, the phase change needs to be converted into the surface subsidence. Before converting the phase change into the surface subsidence, the phase change at the obtained reference feature point needs to be phase unwrapped to solve the problem of whole-cycle phase jump. The unwrapping process of this scheme is as follows: S41 uses the observation date of the GNSS interference signal as the independent variable and the phase change at the reference feature point as the dependent variable to construct a time series of the phase change at the reference feature point; S42 takes the difference between the phase changes of two adjacent observation dates. If the difference is greater than π / 2, all phase changes on and after that date are added by 2π; if the difference is less than -π / 2, all phase changes on and after that date are subtracted by 2π. An implementation example of this scheme is as follows: Figure 4 As shown, after the phase variation at the reference feature point is unwrapped by this scheme, the absolute value of the difference between any two adjacent date phase variables in the phase variation sequence is less than π / 2.

[0047] Finally, the unwrapped phase change is converted into the surface subsidence at the benchmark feature point using Formula 3.

[0048]

[0049] The subsidence surface of the subsidence area or the deformation curve along a certain direction is the basic data required for the application of mines and related unit projects. This part uses the surface subsidence at the benchmark feature points derived in Scheme 2 to generate the surface subsidence surface of coal mining and the inclination and curvature deformation curve in a certain direction; the steps are as follows Figure 5 As shown, the process is described as follows:

[0050] (1) Generation of surface subsidence surface.

[0051] Taking the GNSS antenna phase center as the coordinate zero point, use Formula 4 and Formula 5 to calculate the plane position coordinates (x, y) of the surface mirror reflection point corresponding to the benchmark feature point. Combine the plane coordinates of the surface reflection point and the settlement amount at the corresponding benchmark feature point to construct the three-dimensional settlement coordinates of the surface reflection point. Finally, based on the constructed three-dimensional settlement coordinate discrete point sequence, the Kriging interpolation method is used to generate the settlement surface of the surface around the measuring station.

[0052]

[0053] (2) Generation of tilt and curvature deformation curves

[0054] On the generated surface subsidence surface, specify the required direction vector curve. Extract the surface subsidence value on the curve; take the distance from any point on the curve to the starting point as the independent variable, and the subsidence value of the point as the dependent variable, and use the B-spline function to fit the surface subsidence value on the curve. The order of the spline function should be greater than or equal to 3. The first-order derivative of the fitted spline function can be obtained to obtain the tilt deformation curve in the specified direction; the second-order derivative of the fitted spline function can be obtained to obtain the curvature deformation curve in the specified direction.

[0055] The improvement of this patent compared to the prior art is to use the phase of the GNSS interference signal collected before the surface subsidence as the reference phase, and subtract the phase of the GNSS interference signal collected after the surface subsidence from it to obtain the change in the phase of the GNSS interference signal. The relationship between the change in the phase of the GNSS interference signal and the GNSS wavelength, satellite altitude angle, and surface subsidence (i.e., Formula 3) is used to reversely calculate the amount of subsidence of the surface relative to the GNSS antenna. GNSS positioning is used to obtain the absolute amount of subsidence of the GNSS antenna in space, and GNSS-IR is used to obtain the amount of subsidence of the surface relative to the GNSS antenna. The absolute amount of subsidence of the surface is calculated based on the absolute amount of subsidence of the surface in space and the geometric relationship between the two.

[0056] The surface subsidence at the benchmark feature points is used to generate the coal mining surface subsidence surface and the inclination and curvature deformation curve in a certain direction, which are the basic data required for mines and related unit engineering applications.

[0057] The beneficial effects of the present invention are:

[0058] 1. The present invention uses GNSS positioning data and GNSS interferometric data to monitor surface subsidence caused by coal mining. It can obtain both subsidence monitoring data of the surface points at the measuring station and surface subsidence monitoring data within thousands of square meters around the measuring station. This achieves high temporal resolution and mesoscale "surface monitoring" effects of surface subsidence caused by underground coal mining.

[0059] 2. The phase change of the GNSS interference signal is used to calculate the subsidence of the surface point relative to the GNSS antenna. Since the phase of the interference signal has a high sensitivity and accuracy in response to the surface subsidence, the present invention can accurately monitor the surface subsidence (the monitoring error is better than 6cm). This achieves the effect of high spatial resolution and high-precision monitoring of coal mining surface subsidence.

[0060] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A coal mining subsidence monitoring method based on GNSS-IR technology, characterized by: The steps to obtain the absolute subsidence of a surface point in space are: The GNSS receiver and antenna are installed on the ground surface of the coal mining subsidence area to be monitored. Before the underground coal seam is mined, the distance between the GNSS antenna and the elevation reference plane is H0. After the underground coal seam is mined, the position of the ground surface and the GNSS antenna in space sinks. At this time, the distance between the GNSS antenna and the elevation reference plane is H1. GNSS carrier phase differential positioning is used to obtain the values ​​of H0 and H1 respectively. Then, H0 is subtracted from H1 to obtain the subsidence amount ΔH at the GNSS antenna. abs ; Using GNSS-IR technology, the amount of subsidence of any point P on the surface relative to the GNSS antenna before and after the underground coal seam is mined is obtained as ΔH rel , the settlement amount ΔH abs With the amount of subsidence ΔH rel By adding them together, we can obtain the absolute subsidence of the surface point P in space; There are four steps to obtain the amount of ground point subsidence relative to the GNSS antenna using GNSS-IR technology: S1 extracts the GNSS interference signal, S2 determines the feature points of the interference signal, S3 calculates the phase change at the reference feature points, and S4 calculates the ground subsidence at the reference feature points.

2. The method for monitoring coal mining subsidence based on GNSS-IR technology according to claim 1 is characterized in that: The specific steps for obtaining the amount of subsidence of a surface point relative to a GNSS antenna using GNSS-IR technology are as follows: GNSS interference signal extraction process: S11 takes the GNSS satellite altitude angle as the independent variable and the SNR observation value as the dependent variable to construct the GNSS SNR observation value sequence; S12 intercepts the SNR observation value sequence within the altitude angle range of 5°-25°; S13 uses a high-pass filter to extract high-frequency GNSS interference signals, and the cut-off frequency of the filter is not higher than 10Hz; S14 uses a low-pass filter to remove the observation noise of the GNSS interference signal; the cut-off frequency range of the filter is not less than 80Hz; Determine the characteristic points of the interference signal: S21 finds the satellite elevation angle corresponding to the interference signal sequence value of zero; S22 extracts the interference signal subsequence between two adjacent zero points; S23 determines the type of the characteristic point according to the size of the subsequence observation value; if 2 / 3 of the subsequence SNR observation values ​​are greater than zero, the type of the characteristic point is the satellite elevation angle corresponding to the peak point; if 2 / 3 of the subsequence SNR observation values ​​are less than zero, the type of the characteristic point is the satellite elevation angle corresponding to the trough point; S24 uses the satellite elevation angle as the independent variable and the SNR observation value of the subsequence as the dependent variable, and uses a second-order polynomial to fit the subsequence; Calculate the phase change of the reference feature point: S31 takes the feature point of the GNSS interference signal obtained before the surface subsidence occurs as the reference feature point, and sets the initial phase of the interference signal at the reference feature point to zero or other constants; S32 obtains the phase value of the GNSS interference signal at the reference feature point after the surface subsidence occurs, and subtracts the phase value from the initial phase value to obtain the phase change at the reference feature point; After the surface subsidence, the phase value at the reference feature point of the interference signal is calculated using the linear interpolation method, that is, find the nearest feature points on the left and right sides of the reference feature point. If the feature point on the left is a crest point and the feature point on the right is a trough point, the phase value at the reference feature point after the surface subsidence is calculated using formula (1); if the feature point on the left is a trough point and the feature point on the right is a crest point, the phase value at the reference feature point after the surface subsidence is calculated using formula (2): Calculate the surface subsidence at the benchmark feature point: S41 takes the observation date of the GNSS interference signal as the independent variable and the phase change at the benchmark feature point as the dependent variable to construct a time series of the phase change at the benchmark feature point; S42 takes the difference between the phase changes of two adjacent observation dates. If the difference is greater than π / 2, all phase changes on and after that date are added with 2π; if the difference is less than -π / 2, all phase changes on and after that date are subtracted with 2π; use formula 3 to convert the unwrapped phase change into the surface subsidence at the benchmark feature point; 3. The method for monitoring coal mining subsidence based on GNSS-IR technology according to claim 2 is characterized in that: According to the surface subsidence at the reference feature points, a surface subsidence curve of coal mining and a curve of inclination and curvature deformation in a certain direction are generated.

4. The method for monitoring coal mining subsidence based on GNSS-IR technology according to claim 3 is characterized in that: The specific steps for generating the surface subsidence surface are as follows: taking the GNSS antenna phase center as the coordinate zero point, using formula 4, calculate the plane position coordinates (x, y) of the surface mirror reflection point corresponding to the benchmark feature point, combining the plane coordinates of the surface reflection point and the subsidence amount at the corresponding benchmark feature point to construct the three-dimensional subsidence coordinates of the surface reflection point; finally, based on the constructed three-dimensional subsidence coordinate discrete point sequence, the Kriging interpolation method is used to generate the surface subsidence surface around the measuring station.

5. The method for monitoring coal mining subsidence based on GNSS-IR technology according to claim 4 is characterized in that: The specific steps for generating the tilt and curvature deformation curves are: On the generated surface subsidence surface, specify the required direction vector curve, extract the surface subsidence value on the curve, take the distance from any point on the curve to the starting point as the independent variable, and the subsidence value of the point as the dependent variable. Use the B-spline function to fit the surface subsidence value on the curve, and the order of the spline function should be greater than or equal to 3; by taking the first-order derivative of the fitted spline function, the inclination deformation curve in the specified direction can be obtained, and by taking the second-order derivative of the fitted spline function, the curvature deformation curve in the specified direction can be obtained.

Images