Geological environment displacement surveying system based on GNSS multipath effect

Abstract

The invention relates to the technical field of geodetic surveying instruments and geological disaster monitoring, and discloses a geological environment displacement surveying system based on a GNSS multipath effect, and the system comprises a signal collection unit which is used for receiving a satellite signal and extracting a signal-to-noise ratio sequence; the interference feature separation unit is used for stripping a direct signal power component and generating a residual oscillation sequence; the geometric inversion calculation unit is used for generating a reference interferometric phase template in a height search domain, and generating a height-correlation map to lock the current vertical height by calculating and superposing correlation coefficients between the residual oscillation sequence and the reference interferometric phase template; according to the invention, through a spatial domain geometric matching mechanism, high-precision distance measurement is realized in a complex environment in which a satellite visual segmental arc is broken, dependence of a traditional spectral analysis method on observation duration is broken through, and signal-to-noise ratio data endogenesis is utilized to decouple observation station attitudes and environmental medium attributes. And the stability and the multi-dimensional perception capability are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a geological environment displacement survey system based on GNSS multipath effect, belonging to the field of geodetic surveying instruments and geological disaster monitoring technology. BACKGROUND

[0002] In current precise engineering surveying and geological disaster warning, the geodetic surveying displacement observation technology based on global navigation satellite system is the core mapping means for obtaining the vertical deformation data of geological bodies. The traditional measurement mode mainly suppresses the multipath signal to improve the positioning accuracy. The interferometric reflectometry technology inversely utilizes the interference characteristics of direct signals and surface reflected signals to extract the oscillation frequency of the signal-to-noise ratio observation value and inversely calculate the vertical height of the antenna phase center relative to the reflecting surface. Such technology does not need to lay high-cost measurement-type antennas and reuse the existing monitoring network data, and is preliminarily applied in plain or open water level and settlement monitoring.

[0003] However, when the technical system is applied to complex geological environments such as open-pit mine slopes, deep valleys or densely built-up urban areas, the observation geometry condition is deteriorated, the satellite single transit period is extremely short due to physical shielding by surrounding topography or buildings, and the actual signal-to-noise ratio oscillation sequence is highly fragmented and discontinuous. Under such non-stationary and short-time observation conditions, the data processing method based on classical spectral analysis theory faces the risk of principle failure, the observation arc length is not enough to cover the complete period of the interference oscillation signal, and the frequency estimation using periodogram analysis or fast Fourier transform is limited by the physical constraints of signal length and frequency resolution, resulting in spectral leakage and fence effect, and the frequency solution result appears random jumps of meters or even larger. For example, the Chinese invention patent with publication number CN119851425A discloses a joint GNSS / MEMS collapse geological disaster monitoring and warning method and system. The scheme introduces a MEMS accelerometer to assist GNSS joint warning, uses robust Kalman filtering and ambiguity fixing algorithm to improve positioning accuracy, and the technical core follows the traditional mapping logic of regarding multipath effect as harmful noise and relying on carrier phase continuous locking. In the high shielding environment of deep mines or valleys, the satellite signal is affected by the terrain cutting, the visible time window is short in a single transit period, the observation arc is highly fragmented, and the non-stationary short-time observation condition requires a convergence time for ambiguity fixing far exceeding the satellite visible time, resulting in the inability to obtain effective fixed solutions and further causing the functional failure of the monitoring system. Moreover, stripping the multipath signal discards the geometric feature information of the reflecting surface in complex environments, and cannot break through the bottleneck of high-precision ranging in non-line-of-sight environments.

[0004] Therefore, how to break through the spectral resolution limitation of short-arc observation conditions without increasing external attitude sensors or water level meters, and realize high-precision decoupling monitoring of geological body vertical displacement and environmental state in complex shielding environments using a single-frequency GNSS receiver, has become a technical problem to be solved by the present application. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A geological environment displacement survey system based on GNSS multipath effect, comprising:

[0006] The signal acquisition unit is used to receive satellite navigation signals through an omnidirectional antenna, obtain raw observation data, and extract the signal-to-noise ratio sequence that varies with the satellite elevation angle from the raw observation data;

[0007] The interference feature separation unit is used to perform detrending operations on the signal-to-noise ratio sequence to remove the direct signal power component and generate a residual oscillation sequence.

[0008] The geometric inversion calculation unit performs the following logic to calculate the vertical height of the antenna phase center relative to the effective reflector: It constructs a height search domain containing several discrete hypothetical height values ​​within a preset monitoring height range; for each hypothetical height value within the height search domain, it generates a corresponding reference interferometric phase template based on the geometric relationship between the satellite elevation angle and multipath effects; it calculates the correlation coefficient between the residual oscillation sequence and the reference interferometric phase template, and superimposes the correlation coefficients of all visible satellites at the same time within the height search domain to generate a height-correlation map; it searches for the energy peak of the height-correlation map and locks the hypothetical height value corresponding to the peak as the current vertical height, and separates the incoherent noise components that cannot be matched by the reference interferometric phase template from the residual oscillation sequence.

[0009] The displacement trend analysis unit is used to calculate the current vertical height and its corresponding calculation weight based on multiple consecutive epochs within different time windows. The change in the current vertical height is calculated by weighting to obtain the vertical displacement of the geological environment.

[0010] Preferably, the system further includes a tilt correction unit, used to acquire the direct signal power component stripped by the interferometric feature separation unit and construct a trend term sequence; identify the measured satellite incident angle corresponding to the power maximum point in the trend term sequence; and calculate the angular deviation between the measured satellite incident angle and the direction of maximum antenna gain.

[0011] The geometric inversion calculation unit is also used to compensate for the satellite elevation angle by using angle deviation before generating the corresponding reference interferometric phase template based on the geometric relationship between the satellite elevation angle and the multipath effect.

[0012] Preferably, the system also includes a data quality control unit, used to calculate the amplitude attenuation rate of the residual oscillation sequence as the amplitude envelope changes with the satellite elevation angle; compare the amplitude attenuation rate with a preset effective reflection threshold; when the amplitude attenuation rate exceeds the effective reflection threshold, generate an invalid data identifier, and control the displacement trend analysis unit to reduce the calculation weight corresponding to the current vertical height or remove it.

[0013] Preferably, the system further includes a dynamic water level correction unit, used to synchronously acquire residual oscillation sequences under at least two different carrier frequency bands; calculate the phase difference between the residual oscillation sequences of the two different carrier frequency bands at the same satellite elevation angle; and, based on a preset dual-frequency interferometry model, use the phase difference to analyze the water level change of the reflector relative to the antenna phase center; the displacement trend analysis unit is also used to perform differential correction of the current vertical height using the water level change.

[0014] Preferably, the system further includes a soil moisture inversion unit, used to obtain incoherent noise components; calculate the root mean square amplitude of the incoherent noise components within a preset time window; and convert the root mean square amplitude into a soil relative humidity value characterizing the dielectric properties of the surface reflective surface based on a preset amplitude-humidity mapping relationship. The displacement trend analysis unit is used to establish a correlation analysis model between the soil relative humidity value and the vertical displacement of the geological environment.

[0015] Preferably, when generating the altitude-correlation map, the geometric inversion calculation unit performs a weighted superposition logic: it obtains the real-time satellite elevation angle of each visible satellite; and according to the preset Fresnel reflectance weight function, it assigns a weight value higher than that of satellites in the high elevation angle range to satellites in the low elevation angle range; it multiplies the weight value as a weighting coefficient with the correlation coefficient of the corresponding visible satellite to obtain the updated correlation coefficient of the visible satellite, and superimposes the correlation coefficients of all visible satellites updated at the same time in the altitude search domain to generate the altitude-correlation map.

[0016] Preferably, in the geometric inversion calculation unit, for each assumed altitude value within the altitude search domain, a corresponding reference interferometric phase template is generated based on the geometric relationship between the satellite elevation angle and the multipath effect. The generation formula is as follows: ,in, For the phase value in the reference interference phase template, Given the current assumed height value in the height search domain, For the corresponding satellite elevation angle, The carrier signal wavelength;

[0017] The geometric inversion computation unit is also used to search different height domains. We construct a series of reference interference phase templates with different oscillation frequencies, and use them as matched filters to perform correlation operations with the measured residual oscillation sequences.

[0018] Preferably, the interference feature separation unit adopts adaptive polynomial fitting logic: monitoring the first derivative of the signal-to-noise ratio sequence; when the change amplitude of the first derivative is lower than the preset stability threshold, a low-order polynomial is selected to fit the trend of the direct signal; when the change amplitude of the first derivative is higher than the preset stability threshold, the order of the fitting polynomial is automatically increased.

[0019] Preferably, the displacement trend analysis unit has a pre-set deformation rate consistency check logic, which is used to calculate the time series variance of the vertical height calculated in multiple consecutive epochs; when the time series variance exceeds the deformation rate threshold set based on the physical characteristics of the geological body, the current vertical height is corrected by using historical state prediction values ​​after Kalman filtering for smoothing.

[0020] Preferably, the signal acquisition unit includes a standard single-frequency GNSS receiver and an omnidirectional antenna connected thereto; the omnidirectional antenna is installed upside down or laterally on the monitoring point bracket at a preset tilt angle.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. In geological environments with GNSS multipath effects, the processor internally constructs a virtual search space containing discrete hypothetical heights, maps the residual oscillation sequences of the entire constellation of satellites to a spatial reference interferometric phase template, and performs global coherent superposition operations. This changes the traditional serial method of relying on single-satellite long-arc data spectrum analysis. It establishes a phase-consistency-based spatial matching filter using the interferometric geometry principle of waves. In complex geological environments where the visible arc of satellites is broken due to deep canyons or open-pit mines, it uses short-time fragmented data and coherent resonance of multi-satellite signals at the real altitude point to cancel out environmental noise incoherently. It locks the vertical distance of the antenna phase center relative to the reflector surface and solves the path based on geometric domain matching. This reduces the system's dependence on continuous observation time while ensuring measurement accuracy, and achieves coverage of obstructed areas.

[0023] 2. When separating multipath interference signals, the power trend term of the direct signal, which is regarded as background interference, is extracted and utilized. Based on the physical anisotropy of the antenna gain pattern, the phase drift of the peak power trend envelope is tracked and inverted into the equivalent tilt angle parameter of the station. The parameter is fed back to the geometric inversion calculation unit, and the incident angle parameter vector compensation of the reference interference phase template is performed. The attitude perception function is internalized into the displacement measurement signal stream without introducing an additional inertial measurement unit. This eliminates the geometric projection error caused by the accompanying tilt of the geological body, ensuring that the output displacement data represents the true vertical settlement, rather than false readings caused by equipment attitude changes.

[0024] 3. For special working conditions where there are dynamic fluctuations in the reflective surface of reservoir banks or tailings dams, a dual-frequency differential geometric model is constructed by utilizing the difference in interference phase response generated when different carrier frequency signals face the same dynamic interface changes. By analyzing the time-varying rate of the instantaneous phase difference of the dual-frequency signals, the dynamic fluctuation of the reflective surface and the static displacement of the station base are mathematically separated. This solves the inherent defect of the single-frequency model in being unable to distinguish between geological settlement and water level rise, enabling the system to directly eliminate common-mode interference from water level changes and restore the net displacement trend of the geological structure in a dynamic hydrological environment. Attached Figure Description

[0025] Figure 1 This is a flowchart of the signal processing and displacement calculation logic of the system of the present invention;

[0026] Figure 2 This is a comparison diagram of the influence of environmental media effects and the phase correction effect of the present invention;

[0027] Figure 3 This is a geometric inversion height search and energy peak locking spectrum diagram of the present invention;

[0028] Figure 4 This is a schematic diagram of the interaction of system functional modules and the multi-maintenance correction architecture of the present invention. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a geological displacement survey system based on GNSS multipath effect, comprising a signal acquisition unit, an interferometric feature separation unit, a geometric inversion calculation unit, and a displacement trend analysis unit. These units work collaboratively, utilizing the signal-to-noise ratio data acquired by a single-frequency GNSS receiver, and employing a spatial domain geometric matching mechanism to calculate the vertical height change of the antenna phase center relative to the surface reflection surface, thereby achieving geological displacement monitoring. The signal acquisition unit captures satellite signals and outputs raw observation data. This unit includes a standard single-frequency GNSS receiver and a right-hand circularly polarized omnidirectional antenna (hereinafter referred to as the omnidirectional antenna) connected to it. In actual engineering deployment, the omnidirectional antenna is installed upside down or laterally at a preset tilt angle on the monitoring point support so that the antenna beam main lobe points to the surface reflection area to be measured. The receiver continuously records satellite observation data according to a preset sampling frequency, such as 1Hz, and outputs the raw data from the original signal. The initial observation file, such as a RINEX format file, extracts the signal-to-noise ratio (SNR) sequence that varies with the satellite elevation angle, along with the corresponding satellite elevation angle data. This SNR sequence contains the interferometric oscillation characteristics generated by the superposition of direct signals and surface reflected signals. The interferometric feature separation unit is used to remove the background trend term from the original SNR sequence to generate a residual oscillation sequence. This unit performs adaptive polynomial fitting logic: calculates the first derivative of the input SNR sequence; compares the magnitude of the change of the first derivative with a preset stationarity threshold, such as 0.05 dB / deg; when the magnitude of the change is lower than the stationarity threshold, a second-order polynomial is used to fit the power trend of the direct signal; when the magnitude of the change is higher than the stationarity threshold, the order of the fitting polynomial is automatically increased to the fourth order or higher to track and subtract complex background trends. The original SNR sequence is subtracted from the fitted trend term, thus generating a residual oscillation sequence containing multipath interferometric information.

[0031] The system utilizes tilt correction logic to calibrate the station's attitude. The tilt correction unit acquires the direct signal power component, representing the direct signal power variation, extracted by the interferometric feature separation unit, and constructs a trend term sequence. This sequence physically corresponds to the antenna's actual gain pattern. The system identifies the measured satellite incidence angle corresponding to the point of maximum power in this trend term sequence and calculates the angular deviation between this measured satellite incidence angle and the antenna's nominal gain direction (e.g., 90 degrees towards the zenith). This angular deviation is the station's equivalent tilt angle. The geometric inversion calculation unit uses this equivalent tilt angle to perform vector rotation compensation on the satellite elevation angle data in subsequent processing to eliminate the geometric projection error introduced by the antenna's physical tilt. The geometric inversion calculation unit calculates the current vertical altitude within a preset monitoring altitude range, such as the antenna's nominal altitude. Meters, constructing a height value containing several discrete hypothetical values. The height search domain is defined with a search step size in millimeters, for example, 0.001 meters. For each assumed height value within the height search domain... A corresponding reference interferometric phase template is generated based on the geometric relationship between the satellite elevation angle and the multipath effect. The generation of this reference interferometric phase template follows the formula: ,in, The phase values ​​in the generated reference interference phase template, Given the current assumed height value in the height search domain, The satellite elevation angle after tilt correction. The wavelength is the carrier signal wavelength.

[0032] Calculate the correlation coefficient between the measured residual oscillation sequence and each reference interferometric phase template, and apply this correlation to all visible satellites at the same assumed altitude value at the same time epoch. The calculated correlation coefficients are superimposed. During the superposition process, based on a preset Fresnel reflectance weighting function, satellites with elevation angles between 5 and 30 degrees are assigned weight values ​​higher than those in the high elevation angle range. After full-domain scanning and superposition, an elevation-correlation map is generated. The energy peak in this elevation-correlation map is searched, and the hypothetical elevation value corresponding to this peak is the locked current vertical elevation. The weighting function construction and discretization coherent superposition procedure are as follows: Define the elevation angle weighting function. This is used to normalize the contribution of satellite signals under different geometric observation conditions. The calculation formula is: ,against The interval is based on nonlinear gain, and the other intervals are set to zero; a normalized cross-correlation accumulation equation is constructed. The equation is defined as a global coherent accumulation function of multiple stars in space, and its numerical value characterizes the state at a certain assumed altitude. Below, the average cross-correlation strength (i.e., matching degree) between all visible satellite measured residual sequences and the reference phase template, where The total number of visible satellites. The measured instantaneous value of the signal-to-noise ratio residual oscillation sequence is given. Set the real-time satellite elevation angle of the k-th visible satellite; set the search step size. In the domain Convolution operations are performed internally in parallel, where Antenna nominal height; extraction function Global maximum coordinates Calculate the peak-to-sidelobe ratio ,in The amplitude of the main energy peak. This is the maximum sidelobe amplitude; if This is then determined to be multipath aliasing, triggering the historical trend extrapolation logic.

[0033] The data quality control unit verifies the physical validity of the reflected signal. This unit uses Hilbert transform to construct the amplitude envelope of the residual oscillation sequence and calculates the amplitude attenuation rate of the envelope as the satellite elevation angle changes. It compares this attenuation rate with a preset effective reflection threshold. If the attenuation rate exceeds this threshold, it determines that the reflecting surface is covered by vegetation or experiences non-specular scattering interference, generates an invalid data identifier, and controls the displacement trend analysis unit to remove the current vertical height of the current epoch. The dynamic water level correction unit separates water level changes from geological displacement in aquatic environments. This unit synchronously acquires the residual oscillation sequences from the signal acquisition unit at at least two different carrier frequency bands, such as GPS L1 and L2. It calculates the instantaneous phase difference between the residual oscillation sequences of these two frequency bands at the same satellite elevation angle. Based on a preset dual-frequency interferometric geometric model, it uses this instantaneous phase difference to resolve the dynamic fluctuation of the reflecting surface relative to the antenna phase center. The displacement trend analysis unit uses this dynamic fluctuation to differentially correct the calculated current vertical height, thereby obtaining the net displacement of the geological body after removing the influence of water level.

[0034] The soil moisture inversion unit is used to monitor environmental media properties. This unit acquires the incoherent noise components that remain after processing by the geometric inversion calculation unit and cannot be matched by the reference interferometric phase template. It calculates the root mean square amplitude of this incoherent noise component within a preset time window. Based on a preset amplitude-humidity mapping relationship, the root mean square amplitude is converted into a soil relative humidity value characterizing the dielectric properties of the surface reflector, and outputs it synchronously with the vertical displacement of the geological environment. The in-situ calibration of the dielectric constant and the construction procedure of the inversion model are as follows: Perform on-site leaching control tests and simultaneously collect soil volumetric water content measured by time domain reflectometer (TDR). and root mean square amplitude of incoherent noise Construct a binary regression dataset and fit a nonlinear mapping model. The coefficient matrix is ​​solved iteratively using the Levenberg-Marquardt algorithm. Set the model convergence threshold. The calibration parameters are stored in the lookup table unit of the DSP (Digital Signal Processor); the real-time calculation process is based on the Topp formula. The real part of the inverted permittivity is given by, where, The relative permittivity of the reflecting medium is the real part, and its magnitude directly determines the phase shift of the electromagnetic wave during interface reflection. Based on this, the phase angle of the Fresnel reflection coefficient is dynamically compensated. The displacement trend analysis unit is used to output the final vertical displacement of the geological environment. This unit has built-in deformation rate consistency check logic, calculates the time series variance of the vertical height for multiple consecutive epochs, such as 10 sampling points. When the time series variance exceeds the deformation rate threshold set based on the physical characteristics of the geological body, Kalman filtering smoothing is initiated, and the current vertical height is corrected using historical state prediction values. Finally, this unit calculates and outputs the determined vertical displacement of the geological environment based on the change in the current vertical height within different time windows.

[0035] Example 1: In a slope displacement monitoring scenario at the bottom of a high-depth-to-width open-pit mine, the monitoring point faces extreme geometrically constrained conditions. Due to the physical obstruction of the steep slope at the mine edge, the continuous visible time window of a single satellite is compressed to less than 20 minutes, resulting in a highly fragmented signal-to-noise ratio (SNR) observation sequence. Under these conditions, conventional methods based on spectrum analysis face the physical limit of reduced frequency resolution due to insufficient data length to cover the complete interferometric oscillation period, and cannot calculate effective altitude values. The system of this invention utilizes a standard single-frequency GNSS receiver and an inverted right-hand circularly polarized omnidirectional antenna in the signal acquisition unit to capture satellite signals. The interferometric feature separation unit performs detrending operations on the fragmented SNR sequence, stripping the direct signal power component and retaining the residual oscillation sequence. The geometric inversion calculation unit initiates spatial domain geometric matching logic to construct a series of discrete hypothetical altitude values ​​within a preset altitude search domain. And for each assumed height value, according to the formula Generate the corresponding reference interference phase template, where For the satellite elevation angle, For the carrier signal wavelength, the system calculates the correlation coefficient between the measured residual oscillation sequence and the template. Utilizing a multi-satellite global coherent superposition mechanism, the correlation coefficients of all visible satellites at the same moment are accumulated within the altitude search domain. This mechanism enables the originally discrete and weak single-satellite signal energy to achieve coherent focusing at the actual vertical altitude. Environmental noise cancels out due to phase randomness, resulting in an energy peak on the altitude-correlation spectrum. Addressing the station tilt problem associated with slope creep, the system uses the direct signal power trend term extracted by the interferometric feature separation unit to invert the station's equivalent tilt angle. The system identifies the measured satellite incident angle corresponding to the point of maximum power in the trend term, calculates the deviation of this angle from the direction of maximum nominal gain of the antenna line of sight, and uses this deviation as a tilt correction factor for the satellite elevation angle when generating the reference interferometric phase template. Vector compensation is performed, and the displacement trend analysis unit outputs the net displacement of the geological body based on the current vertical height change corresponding to the energy peak in the height-correlation spectrum.

[0036] Example 2: The monitoring performance of the system of the present invention was verified in a landslide monitoring scenario on the left bank of a reservoir with dynamic hydrological environmental characteristics. The surface vegetation in the monitoring area was sparse, but the reservoir water level fluctuated irregularly by an average of 0.2 meters to 0.5 meters per day due to rainfall and dam regulation. The test platform consisted of the survey system of the present invention deployed at the feature points of the landslide, a high-precision hydrostatic level (as a true reference) installed at the same site, and a radar water level gauge. The signal acquisition unit of the system of the present invention was equipped with a standard single-frequency GNSS receiver connected to an inverted right-hand circularly polarized omnidirectional antenna. The antenna was erected at a height of about 5 meters above the initial water surface. During the test, the receiver simultaneously acquired signal-to-noise ratio data of two frequency bands, GPS L1 (1575.42MHz) and L2 (1227.60MHz), at a frequency of 1Hz for 30 days. During this period, the reservoir experienced a rapid water storage process, and the water level rose by about 3 meters cumulatively.

[0037] After the experiment started, the interferometric feature separation unit performed detrending operations on the signal-to-noise ratio sequences of the L1 and L2 frequency bands to generate residual oscillation sequences. The dynamic water level correction unit calculated the instantaneous phase difference between the two frequency band residual sequences at the same satellite elevation angle. Since the interferometric phase responses of different frequency carriers facing the same reflector with varying elevations have a definite dispersion relationship, the time-varying rate of this phase difference directly reflects the dynamic fluctuation of the water surface relative to the antenna. The system uses a preset dual-frequency interferometric geometric model to invert the water level change from the phase difference data. At the same time, the geometric inversion calculation unit uses the residual oscillation sequence of the L1 frequency band... The oscillation sequence, combined with geometric matching filtering and multi-star superposition mechanism, calculates the total vertical height change including the influence of water level. The displacement trend analysis unit uses the water level change output by the dynamic water level correction unit to differentially correct the total vertical height, thereby extracting the net displacement of the geological body. The table below shows the monitoring data at three times on the 5th, 15th and 25th days of the water storage process. The displacement calculated by this invention is the vertical displacement of the geological body after dynamic water level correction. The true value of the hydrostatic level is the measured value of the geological settlement during the same period. The uncorrected displacement is the result calculated using only single-frequency data without removing the influence of water level.

[0038] Table 1: Comparison of Displacement Monitoring Data under Dynamic Water Level Environment

[0039]

[0040] As can be seen from the data in Table 1, under the background of a significant rise in water level (accumulated to nearly 3 meters), the uncorrected single-frequency solution result (uncorrected displacement) shows a false displacement that is highly correlated with the water level change, with values ​​reaching the meter level, which masks the real geological micro-movements. In contrast, the displacement calculated by the system of this invention (the displacement calculated by this invention) is stable at the millimeter level and highly consistent with the real settlement value measured by the hydrostatic level (the true value of the hydrostatic level), with a maximum deviation of 0.3 mm. Through the dual-frequency phase difference mechanism, the system decouples the large-scale water level fluctuation interference from the small geological displacement signal at the signal processing level.

[0041] Example 3: This example combines Figures 1 to 4 This section describes a geological environment displacement survey system based on GNSS multipath effects, such as... Figure 1 As shown in the flowchart, this flowchart illustrates the closed-loop data processing logic of the system. It begins at the satellite signal input stage, where the system receives raw observation data formed by satellite navigation signals from the entire constellation. The signal acquisition unit performs satellite signal reception operations and extracts the signal-to-noise ratio sequence, transferring the data to the interferometric feature separation unit. This unit is used to remove the direct signal power component and generate a residual oscillation sequence. The processed residual oscillation sequence enters the geometric inversion calculation unit. In this step, the system constructs a reference interferometric phase template, performs correlation coefficient calculation and multi-satellite superposition operation, thereby generating an altitude-correlation map and locking the current vertical altitude, achieving the goal of locking the current vertical altitude. Finally, the displacement trend analysis unit calculates the vertical displacement of the geological environment based on the current vertical altitude change, and outputs the displacement to generate geological displacement monitoring results that include the vertical displacement of the geological environment.

[0042] like Figure 2 As shown, the horizontal axis represents time in hours, with a scale range of 0 to 69; the left vertical axis represents phase / displacement, with a scale range of -10 to 50; and the right vertical axis represents soil moisture / RMS amplitude, with a value range of 0 to 1.0. The figure contains four main curves: the soil relative moisture curve and the RMS amplitude curve show a correlated fluctuation trend; the uncorrected phase curve with medium effect shows a spike in the 30-60 hour interval as the above parameters increase; while the corrected phase true displacement curve remains stable throughout the time period, showing the displacement trend after removing the influence of the environmental medium. Figure 3 As shown, this graph displays the peak search results in the geometric inversion calculation unit, with the horizontal axis representing the assumed height. The values ​​range from 4.50 to 5.10. The vertical axis represents the superposition correlation coefficient, which ranges from 0 to 1.0. The solid line in the figure is the multi-star superposition correlation coefficient curve, which forms a bulge at a specific height. The apex is marked as the energy peak point corresponding to the actual vertical height. The system uses this energy peak to lock the current vertical height. In this example, the locked height value corresponds to a horizontal axis reading of approximately 4.82.

[0043] like Figure 4 As shown, the monitoring personnel are located on the left, and their operating permissions include viewing soil moisture inversion and geological displacement reports. The right side of the system connects to the GNSS satellite constellation to acquire signals. The internal core processing path begins with extracting the signal-to-noise ratio oscillation sequence, and branches to perform adaptive trend separation and calculate the current vertical height. In the process of calculating the current vertical height, the three auxiliary correction modules at the bottom are logically linked, namely dynamic water level difference correction, data quality control, and station tilt correction, which together support the accuracy of the core calculation.

[0044] Example 4: To address the potential abrupt changes in the properties of reflective surfaces during monitoring of complex geological environments, such as sudden heavy rainfall causing drastic fluctuations in soil dielectric constant or rapid melting of snow and ice altering the reflection coefficient, this invention's system, based on the fundamental displacement calculation architecture, further integrates a medium property sensing and adaptive compensation mechanism. This solves the non-geometric phase drift error that may arise when relying solely on geometric matching during drastic changes in medium properties. The system continuously acquires the signal-to-noise ratio sequence through the signal acquisition unit, and the direct signal trend term is stripped away by the interferometric feature separation unit to obtain the residual oscillation sequence. Based on this, the medium property inversion logic is initiated. The system utilizes the incoherent noise components in the residual oscillation sequence that cannot be completely fitted by the reference interferometric phase template to calculate their root mean square amplitude (RMS) within a preset time window, such as 30 minutes. This RMS value is directly related to the roughness and dielectric loss characteristics of the reflective surface.

[0045] The system establishes and executes a medium state determination logic based on an RMS threshold. When the real-time calculated RMS value is lower than the preset stable reflection threshold, the system determines that the reflecting surface is in a relatively stable geometric reflection state and continues to use the standard geometric inversion calculation unit for displacement calculation. When the RMS value rises sharply and exceeds the threshold, it indicates that the medium properties of the reflecting surface have changed, such as soil moisture saturation or surface roughening. At this time, the system automatically triggers an adaptive compensation process and calls a preset medium-phase response correction model. This model quantifies the nonlinear pulling effect of the dielectric change of the reflecting surface on the interference phase under different RMS levels. Based on the real-time RMS value, the system retrieves the corresponding phase compensation factor from the model and injects it into the displacement trend analysis unit. After receiving the phase compensation factor, the displacement trend analysis unit performs a secondary correction on the preliminary vertical height output by the geometric inversion calculation unit. Mathematically, this correction process is represented by subtracting the non-geometric phase component caused by the change in medium properties from the total phase change, thereby restoring the geometric phase change caused purely by the physical displacement of the geological body.

[0046] Example 5: To ensure the consistency of monitoring by the system of the present invention under different geographical latitudes, altitudes, and ionospheric activity levels, a standardized offline calibration and data filling procedure was constructed. An environment-parameter mapping database covering typical geological monitoring scenarios worldwide was established. A group of representative benchmark test sites were selected, covering diverse environmental characteristics from polar permafrost to tropical rainforests, and from sea level to high-altitude mountainous areas. At each test site, the system of the present invention was deployed and a high-precision total station was run synchronously as a true reference for continuous observation for at least one complete solar activity cycle. By comparing the system's calculated values ​​with the true values, different environmental factors, such as the total electron content of the ionosphere and the tropospheric delayed wet component, were extracted. For the systematic deviations in interference phase and signal-to-noise ratio attenuation, a multivariate regression analysis method was used to establish quantitative functional relationships between each environmental factor and key system calculated parameters, such as the signal-to-noise ratio detrending fitting order and phase template correction coefficient. These relationships were solidified into lookup tables or parameterized models and pre-stored in the non-volatile memory of the system processor.

[0047] To address the potential micro-environmental differences that the surveying system may face during the initial deployment of actual engineering projects, such as micro-topographical undulations around the antenna and local electromagnetic interference, a set of pre-deployment calibration procedures were developed. Before the system is officially put into operation, a standardized zero-state calibration process is executed, including: setting up a temporary high-precision geodetic benchmark station near the monitoring point and continuously collecting static observation data for at least 24 hours to determine the precise three-dimensional coordinates and initial attitude angle of the antenna at the monitoring point. Using the observation data during this period, the system automatically runs an environmental fingerprint extraction algorithm to identify and record the multipath background noise feature spectrum in the current environment, such as constant reflection signals caused by fixed buildings or terrain. Based on the extracted background feature spectrum, the system automatically fine-tunes the filtering parameters of the interferometric feature separation unit and the judgment threshold of the data quality control unit to generate a dedicated configuration file for the monitoring point. This configuration file serves as the initial benchmark for the system's subsequent long-term monitoring and operation, ensuring the optimal performance of the system under specific micro-environments.

[0048] Example 6: To eliminate potential performance fluctuations in different mining areas under varying latitudes and electromagnetic environments, and to address the lack of initialization parameter calibration procedures, this example establishes a standardized pre-deployment calibration and model building procedure. This procedure is executed before the system is officially put into monitoring operation. The aim is to establish a reference parameter matrix for specific monitoring points. Reference points with open views and stable geological structures are selected within the target monitoring area. The signal acquisition unit of this invention is deployed at these points, and a high-precision measurement-type GNSS receiver is simultaneously set up as a reference. Static observation data is continuously collected for at least 24 hours, covering the complete satellite constellation operation cycle. Using observation data from a high-precision receiver, the precise three-dimensional coordinates of the reference point and the true altitude of the antenna phase center are calculated. The system reads its own signal-to-noise ratio (SNR) sequence and, combined with the known true altitude and satellite elevation angle, reverse-engineers the SNR attenuation model parameters under the current electromagnetic environment. For each satellite elevation angle interval (e.g., every 5 degrees), the deviation between the measured SNR and the predicted value of the theoretical geometric model is calculated, generating a set of environmental-SNR correction factors. This set of correction factors is fixed into a lookup table and stored in the non-volatile memory of the system processor for preprocessing of real-time SNR data during subsequent long-term monitoring.

[0049] In addition, to address potential sensor drift or abnormal states that may occur during long-term unattended operation, an online self-checking and fault-tolerant logic is constructed. The system has a built-in confidence assessment algorithm to monitor the maxima of the height-correlation spectrum output by the geometric inversion calculation unit in real time. The specific quantitative indicator is the ratio of the main peak energy to the secondary peak energy in the spectrum, i.e., the peak-to-sidelobe ratio. When this ratio is lower than a preset confidence threshold, such as 1.5, it indicates that the current satellite observation geometry is poor or the environmental noise is too high, resulting in low confidence of the solution. At this time, the system automatically triggers the historical trend constraint mechanism, calls the high-confidence displacement data of the past 72 hours, and generates the predicted displacement interval for the current moment through the prediction step of the Kalman filter. If the current solution value falls outside this interval, it is marked as an outlier and removed. At the same time, the filter's predicted value is directly output as the displacement result of the current epoch.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A GNSS multi-path effect based geologic environmental displacement surveying system, characterized in that, The system comprises: a signal acquisition unit configured to receive satellite navigation signals through an omnidirectional antenna, obtain raw observation data, and extract a signal-to-noise ratio sequence varying with a satellite elevation angle from the raw observation data; an interference feature separation unit configured to perform a detrending operation on the signal-to-noise ratio sequence to strip a direct signal power component, and generate a residual oscillation sequence; a geometric inversion calculation unit configured to perform the following logic to solve a vertical height of an antenna phase center relative to an effective reflecting surface: constructing a height search domain containing a plurality of discrete assumed height values within a preset monitoring height range; for each assumed height value in the height search domain, generating a corresponding reference interference phase template according to a geometric relationship between the satellite elevation angle and a multipath effect; calculating a correlation coefficient between the residual oscillation sequence and the reference interference phase template, and superimposing correlation coefficients of all visible satellites at the same time in the height search domain to generate a height-correlation graph; searching for an energy peak value of the height-correlation graph and locking an assumed height value corresponding to the peak value as a current vertical height, and separating a non-coherent noise component from the residual oscillation sequence, which fails to be matched with the reference interference phase template; a displacement trend analysis unit configured to solve the current vertical height and a corresponding calculation weight in different time windows, and obtain a geological environment vertical displacement by weighted calculation of a change amount of the current vertical height.

2. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The system further comprises a tilt correction unit configured to obtain the direct signal power component stripped by the interference feature separation unit, and construct a trend item sequence; identify a measured satellite incident angle corresponding to a power maximum value point in the trend item sequence; calculate an angular deviation between the measured satellite incident angle and a maximum gain direction of the antenna; the geometric inversion calculation unit is further configured to perform angular compensation on the satellite elevation angle by using the angular deviation before generating the corresponding reference interference phase template according to the geometric relationship between the satellite elevation angle and the multipath effect.

3. The GNSS multi-path effect based geologic environment displacement surveying system according to claim 1, wherein, The system further comprises a data quality control unit configured to calculate an amplitude decay rate of an amplitude envelope of the residual oscillation sequence varying with the satellite elevation angle; compare the amplitude decay rate with a preset effective reflection threshold value; when the amplitude decay rate exceeds the effective reflection threshold value, generate an invalid data identifier, and control the displacement trend analysis unit to reduce the calculation weight corresponding to the current vertical height or remove it.

4. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The system further comprises a dynamic water level correction unit configured to synchronously obtain residual oscillation sequences at at least two different carrier frequency bands; calculate a phase difference of the residual oscillation sequences at the same satellite elevation angle at the two different carrier frequency bands; based on a preset dual-frequency interference model, analyze a water level change amount of the reflecting surface relative to the antenna phase center by using the phase difference; and the displacement trend analysis unit is further configured to differentially correct the current vertical height by using the water level change amount.

5. The GNSS multipath-based geologic environmental displacement surveying system according to claim 1, wherein, The system further comprises a soil moisture inversion unit configured to obtain the non-coherent noise component; calculate a root mean square amplitude of the non-coherent noise component within a preset time window; based on a preset amplitude-moisture mapping relationship, convert the root mean square amplitude into a soil relative humidity value representing dielectric properties of the ground reflecting surface; and the displacement trend analysis unit is configured to establish an association analysis model of the soil relative humidity value and the geological environment vertical displacement.

6. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The geometric inversion calculation unit performs a weighted superposition logic when generating the height-correlation map: obtaining the real-time satellite elevation angle of each visible satellite; and according to the preset Fresnel reflection zone weight function, assigning a higher weight value to the satellite in the low elevation angle interval than to the satellite in the high elevation angle interval; multiplying the weight value as a weighted coefficient with the correlation coefficient of the corresponding visible satellite to obtain the updated correlation coefficient of the visible satellite, and superimposing the updated correlation coefficients of all visible satellites at the same time in the height search domain to generate the height-correlation map.

7. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The geometric inversion calculation unit generates a corresponding reference interference phase template according to the geometric relationship between the satellite elevation angle and the multipath effect for each assumed height value in the height search domain, and the generation formula is: wherein, is a phase value in the reference interference phase template, is a current assumed height value in the height search domain, is a corresponding satellite elevation angle, is a carrier signal wavelength; The geometric inversion calculating unit is further configured to construct a series of reference interference phase templates with different oscillation frequencies by traversing different values in the height search domain and correlating them with the measured residual oscillation sequence as a matched filter. The geometric inversion calculating unit is further configured to construct a series of reference interference phase templates with different oscillation frequencies by traversing different values in the height search domain and correlating them with the measured residual oscillation sequence as a matched filter.

8. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The interference feature separation unit adopts an adaptive polynomial fitting logic: monitoring the first derivative of the signal-to-noise ratio sequence; when the change amplitude of the first derivative is lower than the preset stationary threshold, a low-order polynomial is selected to fit the direct signal trend; when the change amplitude of the first derivative is higher than the preset stationary threshold, the order of the fitting polynomial is automatically increased.

9. The GNSS multi-path based geologic environmental displacement surveying system according to claim 1, wherein, The displacement trend analysis unit is preinstalled with a deformation rate consistency checking logic for calculating the time series variance of the vertical height calculated at a plurality of continuous epochs; when the time series variance exceeds the deformation rate threshold set based on the physical properties of the geological body, the current vertical height is corrected by Kalman filtering smoothing processing using the historical state prediction value.

10. The GNSS multipath-based geoenvironmental displacement surveying system according to claim 1, wherein, The signal acquisition unit includes a standard single-frequency GNSS receiver and an omnidirectional antenna connected thereto; the omnidirectional antenna is installed upside down or laterally at a preset inclination angle on the monitoring point support.

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