Urban land subsidence monitoring method integrating Beidou satellite navigation and leveling

Abstract

The invention discloses an urban land subsidence monitoring method integrating Beidou satellite navigation and leveling, which is characterized by comprising the following steps of: 1) performing high-precision positioning calculation on a Beidou base station and peripheral IGS stations to obtain a geodetic height single-day solution and a median error of the Beidou base station under an ITRF (International Telecommunication Radio Frequency) framework; 2) calculating the settlement amount and the median error of the Beidou base station during the two-stage leveling observation; and 3) obtaining two-stage leveling measurement data and carrying out fusion analysis on the settlement amount of the Beidou base station in the same stage, and calculating the settlement amount of all the leveling monitoring points. According to the method, a city continuous operation reference station network is fully utilized, a plurality of Beidou base stations are selected according to a certain principle to be incorporated into a level monitoring network, firstly, the settlement amount of the Beidou base station level field observation in the same period is calculated through a filtering method, and the settlement amount is further fused with two-period level measurement data; the influence of long-distance leveling observation accumulated errors is effectively controlled, and the problem of non-uniform leveling observation precision is obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of land subsidence monitoring, and particularly relates to a method for monitoring urban land subsidence by integrating Beidou satellite navigation and leveling measurement. Background Technique

[0002] Land subsidence is a slow-moving geological disaster with a long formation time, a wide influence range, great governance difficulty, and difficult to repair, which seriously threatens the safety of people's lives and property and the sustainable development of the regional economy. In order to scientifically analyze the causes of subsidence and accurately formulate prevention and control measures, it is necessary to obtain land subsidence information through technical means such as precise leveling measurement, Beidou satellite navigation monitoring, and synthetic aperture radar interferometry (InSAR).

[0003] Currently, urban land subsidence has entered the micro-subsidence stage, which puts forward higher requirements for the monitoring accuracy of land subsidence. The "National Land Subsidence Prevention and Control Plan (2011-2020)" requires that the land subsidence rate in the central urban area and the areas near major engineering areas be controlled within 15 millimeters per year. However, when a single land subsidence monitoring method cannot meet the requirements of such high-precision land subsidence monitoring, the specific situations are as follows:

[0004] (1) The cumulative error of long-distance observation in leveling measurement affects the observation accuracy unevenly. Taking Tianjin area as an example, in the land subsidence leveling monitoring in Binhai New Area, which is far from the monitoring reference point (Baodi bedrock point), the medium error reaches 8.9 mm, and the maximum error reaches 17.8 mm (calculated according to 2 times the medium error), which cannot meet the land subsidence monitoring requirements with an annual settlement of 15 mm.

[0005] (2) Beidou satellite navigation monitoring usually conducts high-precision data processing and analysis on a daily basis. The single-day solution accuracy of geodetic height is ±5 - 10 mm. Although satellite navigation can achieve continuous monitoring, its monitoring point density is very limited due to various factors. Taking Tianjin area as an example, the average medium error of the single-day solution of geodetic height of 27 satellite navigation reference stations is ±7.7 mm, the medium error of geodetic height subsidence is ±10.9 mm, and the maximum error reaches 21.8 mm (calculated according to 2 times the medium error), which cannot meet the land subsidence monitoring requirements with an annual settlement of 15 mm.

[0006] (3) The monitoring accuracy of InSAR is ±5 - 10 mm (in the case of less vegetation). At the same time, the InSAR monitoring result is the change amount relative to the "reference point", and systematic deviation compensation needs to be carried out based on the results of leveling measurement and satellite navigation monitoring. After compensation, the monitoring result is even more unable to meet the land subsidence monitoring requirements with an annual settlement of 15 mm.

[0007] In summary, each of the single ground settlement monitoring methods of leveling, satellite navigation, and InSAR has its own advantages and disadvantages. Integrating multiple technical means to obtain ground settlement monitoring results with higher accuracy and better reliability than single monitoring means has always been a difficult and hot topic in domestic and foreign research and applications. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an urban ground settlement monitoring method that integrates Beidou satellite navigation and leveling, controls the cumulative error effect of long-distance leveling observations, improves the unevenness of leveling observation accuracy, enhances the accuracy of leveling ground settlement monitoring, and meets the ground settlement monitoring requirements with an annual settlement of 15 mm.

[0009] To achieve the technical objectives of the present invention, the technical solution adopted by the present invention is as follows:

[0010] An urban ground settlement monitoring method that integrates Beidou satellite navigation and leveling, comprising the following steps:

[0011] 1) Perform high-precision positioning and solution for the Beidou reference station and surrounding IGS stations to obtain the single-day solution and mean square error of the geodetic height of the Beidou reference station in the ITRF frame.

[0012] 2) Use the single-day solution of the geodetic height as the observation quantity to filter the corresponding simultaneous leveling measurement data of the Beidou reference station to obtain the accurate geodetic height estimation and variance of each Beidou reference station, and calculate the settlement amount and mean square error of the Beidou reference station during two periods of leveling observations.

[0013] 3) Obtain two periods of leveling measurement data and perform fusion analysis with the simultaneous settlement amount of the Beidou reference station to calculate the settlement amount of all leveling monitoring points.

[0014] As one of the preferred solutions, taking the difference between the elevations of the same leveling points in two periods as the observation quantity and the simultaneous settlement amount of the Beidou reference station as the observation quantity, directly solve the settlement amount of all leveling monitoring points through a single adjustment calculation.

[0015] As one of the preferred solutions, the distance between the Beidou reference stations is 70 - 100 km, and the distance from any leveling monitoring point to the nearest Beidou reference station is less than 50 km.

[0016] As one of the preferred solutions, the solution uses internationally authoritative post-processing high-precision data processing software and IGS final orbit and clock products to obtain the single-day solution and mean square error of the geodetic height of the Beidou reference station in the ITRF frame during the same period of leveling field observations.

[0017] As one of the preferred solutions, step 2) includes:

[0018] 2.1 Construct an observation equation, and the observation data uses the single-day solution of the geodetic height as the observation quantity, Uk,t and s k represents the single-day solution and mean square error of the geodetic height of the k-th Beidou reference station at time t, ΔU k,t represents the corresponding observation residual, Δu k,t represents the correction of the single-day solution of the geodetic height, ε k,t represents the observation noise of the single-day solution of the geodetic height. The method for constructing the observation equation is as follows.

[0019] ΔU k,t = Δu k,t + ε k,t

[0020] 2.2 Construct the filtering model. The state model and the observation model are constructed as follows.

[0021] x t = φ t―1 x t―1 + w t―1

[0022] z t = H t x t + v t

[0023] Where

[0024] x t is the state parameter at time t, x t = [Δu k,t T ;

[0025] φ t―1 is the state transition matrix at t - 1 epochs, and its value is the identity matrix;

[0026] x t―1 is the state parameter at t - 1 time;

[0027] w t―1 is the process noise at time t and the previous time, and its variance-covariance matrix is Q t―1 , and its value is the zero matrix;

[0028] z t is the observation vector at time t, z t = [ΔU k,t T ;

[0029] H t is the design matrix at time t, and its value is the identity matrix;

[0030] v t is the observation noise at time t, which is a white noise process with zero mean, and its variance-covariance matrix is R t , R​​t The construction method is

[0031] 2.3 Kalman filter parameter estimation. The superscripts "-" and "+" are used to represent the prediction and correction of relevant parameters respectively.

[0032] (1) Prediction is carried out according to the state model.

[0033]

[0034]

[0035] (2) Correction is carried out according to the observation model.

[0036]

[0037]

[0038] Repeat the above (1) and (2), and output the accurate estimation of the geodetic height of the kth Beidou reference station epoch by epoch and its variance

[0039] 2.4 Calculate the settlement amount of the Beidou reference station during two periods of leveling observations and its mean square error

[0040]

[0041]

[0042] where t1 and t2 are the intermediate times of the first and second periods of leveling field observations respectively.

[0043] As one of the preferred solutions, in step 3), the construction method of the integrated calculation observation equation is as follows:

[0044]

[0045]

[0046] Its matrix form is as follows:

[0047] V = AX - L, weight matrix P

[0048] where

[0049] and represent the height differences between the jth and ith leveling monitoring points in the two periods of t1 and t2 respectively, represents the residual of the difference between the height differences of the two periods of homologous leveling points, and respectively represent the settlement amounts of the \(i\)-th and \(j\)-th leveling monitoring points during two observation periods, represents the observation noise of the height difference between two periods of homologous leveling points, represents the observation noise of the \(k\)-th Beidou reference station, and the mean square error is

[0050] X is the vector of parameters to be estimated, The settlement amount of the leveling monitoring points includes the leveling points that coincide with the Beidou monitoring stations;

[0051] V is the vector of observation residuals, with a length equal to the sum of the number of segments of two-period homologous leveling observations and the number of Beidou reference stations;

[0052] A is the design matrix, constructed according to the relationship between the above observation equations and the settlement amount of the leveling monitoring points ;

[0053] P is the observation weight matrix, The weight of the leveling observation S is the distance of the segment; Beidou base

[0054] The least squares method is used to solve the parameters to be estimated:

[0055] X = (A T PA) ―1 A T PL

[0056]

[0057] where, is the variance of unit weight. Let \(m\) represent the number of observed height differences, \(n\) represent the number of monitoring points, and be the sum of the number of leveling monitoring points and Beidou reference stations, The calculation method is as follows,

[0058]

[0059] The advantages and beneficial effects of the present invention are as follows:

[0060] The present invention makes full use of the urban continuous operation reference station network, selects several Beidou reference stations to be incorporated into the leveling monitoring network according to certain principles. First, a filtering method is used to calculate the settlement amount during the same period of the field leveling observation of the Beidou reference stations, and then it is further fused with the two-period leveling measurement data, effectively controlling the influence of the cumulative error of long-distance leveling observation, significantly improving the problem of uneven leveling observation accuracy, remarkably enhancing the accuracy of leveling ground settlement monitoring, and meeting the ground settlement monitoring requirements with an annual settlement amount of 15 mm. Description of the Drawings

[0061] For those of ordinary skill in the art, other related drawings can be obtained based on the above drawings without creative efforts.

[0062] Figure 1 The implementation process of a method for monitoring urban ground settlement by integrating Beidou satellite navigation and leveling survey according to the present invention.

[0063] Figure 2 It is the layout diagram of monitoring points for the implementation case of the present invention.

[0064] Figure 3 It is the spatial distribution diagram of leveling monitoring errors for the implementation case of the present invention.

[0065] Figure 4 It is the fitting diagram of the normal distribution of leveling monitoring errors for the implementation case of the present invention.

[0066] Figure 5 It is the spatial distribution diagram of leveling monitoring errors for the conventional leveling monitoring scheme.

[0067] Figure 6 It is the fitting diagram of the normal distribution of leveling monitoring errors for the conventional leveling monitoring scheme. Specific implementation manner

[0068] In order to enable those in the technical field to better understand the solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments.

[0069] A method for monitoring urban ground settlement by integrating Beidou satellite navigation and leveling survey according to the present invention includes the following steps:

[0070] 1) Perform high-precision positioning and calculation on the Beidou reference station and surrounding IGS stations to obtain the single-day solution and medium error of the geodetic height of the Beidou reference station under the ITRF framework. Specifically, perform high-precision positioning and calculation on the Beidou reference station and surrounding IGS stations. The calculation uses internationally authoritative post-processing software for high-precision data and IGS final orbit and clock products to obtain the single-day solution and medium error of the geodetic height of the Beidou reference station under the ITRF framework during the same period of the leveling field observation.

[0071] Among them, to implement the monitoring method of the present invention, it is necessary to layout the monitoring points: Beidou reference stations are evenly distributed in the monitoring area, the station spacing is controlled within 70 km - 100 km, and the Beidou reference stations are attached with leveling survey marks, equipped with geodetic satellite navigation receivers and satellite navigation 3D choke ring antennas. The layout position and density of the leveling monitoring points are determined according to the urban ground settlement situation and monitoring requirements, but it must meet the requirement that the distance from any leveling monitoring point to the nearest Beidou reference station is less than 50 km.

[0072] 2) Using the single-day solution of the geodetic height as the observation quantity, filter the corresponding simultaneous leveling measurement data of the Beidou reference station to obtain the accurate geodetic height estimation and variance of each Beidou reference station.

[0073] 3) Calculate the settlement amount and mean square error of the Beidou reference station during two periods of leveling observations.

[0074] 4) Obtain and conduct a fusion analysis on the simultaneous two-period leveling measurement data and the settlement amount of the simultaneous Beidou reference station, and calculate the settlement amount of the leveling monitoring points.

[0075] Among them, for the above-mentioned monitoring data collection: The leveling data collection conducts 2 periods of field observations. In each period, all leveling monitoring points and the Beidou reference station leveling measurement marks are simultaneously connected for measurement. The time of the leveling field observations is controlled within 1 month, and the maximum does not exceed 2 months. The quality of the leveling field observation results must meet the specification requirements of the "National First- and Second-Class Leveling Surveying Specification" (GB / T 12897-2006); For the Beidou data collection, the Beidou multi-frequency code-phase and carrier-phase raw observation data are collected, and continuous observations are maintained. The data sampling rate is 30 s. The data can be transmitted to the data center for storage through a wireless network, or can be stored in an offline storage medium and collected regularly.

[0076] The present invention jointly solves the single-day solution of the geodetic height of the Beidou reference station in the ITRF framework by combining the Beidou reference station with the surrounding IGS (International GNSS Service, IGS) stations, calculates the settlement amount during the simultaneous leveling field observations of the Beidou reference station through a filtering method, and further conducts a fusion process with the two-period leveling measurement data to calculate the high-precision settlement amounts of all leveling monitoring points.

[0077] Among them, for the calculation of the settlement amount of the Beidou reference station during the simultaneous leveling field observations in step 2), the method is as follows:

[0078] 2.1 Construct an observation equation. The observation data uses the single-day solution of the geodetic height as the observation quantity. For the convenience of expression, use U k,t and s k to represent the single-day solution of the geodetic height and the mean square error of the k-th Beidou reference station at time t, use ΔU k,t to represent the corresponding observation residual (the difference between the observed value U k,t at time t and the single-day solution of the geodetic height ΔU k,t0 at the first observation time t0), use Δu k,t to represent the correction of the single-day solution of the geodetic height, and use ε k,t to represent the observation noise of the single-day solution of the geodetic height. The method for constructing the observation equation is as follows:

[0079] ΔU k,t =Δu k,t +ε k,t

[0080] 2.2 Construct a filtering model. The state model and the observation model are constructed as follows:

[0081] x t = φ t―1 x t―1 + w t―1 (State model)

[0082] z t = H t x t + v t (Observation model)

[0083] Among them,

[0084] x t is the state parameter at time t, x t = [Δu k,t T ;

[0085] φ t―1 is the state transition matrix at t - 1 epochs, and its value is the identity matrix;

[0086] x t―1 is the state parameter at time t - 1;

[0087] w t―1 is the process noise at time t and the previous time, and its variance - covariance matrix is Q t―1 , and its value is the zero matrix;

[0088] z t is the observation vector at time t, z t = [ΔU k,t T ;

[0089] H t is the design matrix at time t, and its value is the identity matrix;

[0090] v t is the observation noise at time t, which is a white noise process with zero mean, and its variance - covariance matrix is R t , and using diag to represent constructing a diagonal matrix, then the construction method of R t can be expressed as

[0091] 2.3 Kalman filter parameter estimation. Use superscripts "-" and "+" to represent the time update (prediction) and observation update (correction) of relevant parameters respectively. The calculation process is as follows:

[0092] (1) According to the state model, perform "prediction":

[0093] ​​

[0094]

[0095] (2) According to the observation model, perform "correction":

[0096]

[0097]

[0098] Repeat the above processes of (1) "prediction" and (2) "correction", and output the accurate estimated value of the geodetic height of the k-th Beidou reference station epoch by epoch (day) and variance The superscript T is the matrix transpose.

[0099] 2.4 Calculate the settlement amount of the Beidou reference station during two periods of leveling observations and the mean square error

[0100]

[0101]

[0102] where t1 and t2 are the intermediate times of the first and second periods of leveling field observations, respectively.

[0103] In step 3) above, fuse and analyze the two-period leveling measurement data and the settlement amount of the Beidou reference station during the same period to calculate the settlement amount of the leveling monitoring point.

[0104] For the sake of convenient expression, use and to represent the elevation differences between the j-th and i-th leveling monitoring points in the two periods of t1 and t2, respectively, and use to represent the residual of the difference between the elevation differences of the same-named leveling points in the two periods, use and to represent the settlement amounts of the i-th and j-th leveling monitoring points during the two periods of observations, respectively, use to represent the observation noise of the difference between the elevation differences of the same-named leveling points in the two periods, and use to represent the observation noise of the k-th Beidou reference station. The mean square error is The construction method of the fusion calculation observation equation is as follows:

[0105]

[0106]

[0107] Its matrix form is as follows:

[0108] V = AX - L, weight matrix P

[0109] where,

[0110] X is the vector of parameters to be estimated, The settlement of the leveling monitoring points (including the leveling points coinciding with the Beidou monitoring stations);

[0111] V is the vector of observation residuals, The length is the sum of the number of leveling observation segments of two periods and the number of Beidou reference stations;

[0112] A is the design matrix, constructed according to the above observation equation and the relationship of the settlement of the leveling monitoring points of.

[0113] P is the observation weight matrix, The weight of the leveling observation S is the distance of the survey segment; Beidou base

[0114] The least squares method is used to solve the parameters to be estimated:

[0115] X = (A T PA) ―1 A T PL

[0116]

[0117] Among them, is the variance of unit weight, m represents the number of observed height differences, and n represents the number of monitoring points (the sum of the number of leveling monitoring points and Beidou reference stations), The calculation method is as follows:

[0118]

[0119] The present invention optimizes the layout scheme of Beidou reference stations and leveling monitoring points, provides a filtering method to calculate the settlement during the field observation of Beidou reference station leveling, improves the mean square error of geodetic height settlement from ±10.9 mm (calculation method based on single-day solution) to 2.9 mm, provides a fusion calculation method for two-period leveling measurement data and the settlement of Beidou reference stations during the same period, controls the cumulative error of long-distance leveling observation through the precise relative positioning results of Beidou satellite navigation, and improves the monitoring accuracy of ground settlement by leveling.

[0120] Specific embodiments are described below, taking the plain area of Tianjin as an example for the monitoring area, with a monitoring area of 11,000 square kilometers. Twenty-three stations in the continuously operating reference network of Tianjin are selected as Beidou reference stations, which are evenly distributed in the monitoring area, and the station spacing is controlled within 70 km to 100 km. The Beidou reference stations are attached with leveling measurement marks and are equipped with geodetic satellite navigation receivers and satellite navigation 3D choke ring antennas. The layout positions and densities of the leveling monitoring points are determined according to the urban land subsidence situation and monitoring requirements. There are a total of 1,614 points, meeting the requirement that the distance from any leveling monitoring point to the nearest Beidou reference station is less than 50 km. The layout of the points is shown in Figure 2 .

[0121] Monitoring data acquisition: For the leveling data acquisition, two-phase field observations are carried out. The first-phase observation time is from August 15 to October 15, 2023, and the second-phase observation time is from August 15 to October 15, 2024. In each phase, all leveling monitoring points and the leveling measurement marks of the Beidou reference stations are continuously measured at the same time. The field observation time for leveling does not exceed 2 months, and the quality of the field observation results for leveling meets the requirements of the "National First and Second-Class Leveling Survey Specification" (GB / T 12897-2006); for Beidou data acquisition, Beidou multi-frequency code-phase and carrier-phase raw observation data are collected, and continuous observations are maintained. The data sampling rate is 30 s, and the data can be transmitted to the data center for storage through a wireless network.

[0122] Step 1) Jointly solve the single-day solution of the geodetic height of the Beidou reference station in the ITRF framework by combining the Beidou reference station with the surrounding IGS stations (10 stations), and calculate the single-day solution of the geodetic height of the Beidou reference station. High-precision positioning and solution are carried out for the Beidou reference station and the surrounding IGS stations. The solution uses internationally authoritative post-processing high-precision data processing software and IGS final orbit and clock products to obtain the single-day solution of the geodetic height of the Beidou reference station in the ITRF framework and the mean square error during the same period of the leveling field observation. The average mean square error of the single-day solution of the geodetic height of the selected Beidou reference station is ±7.7 mm.

[0123] Step 2) Calculate the settlement amount of the Beidou reference station during the same period of the leveling field observation, and the method is as follows:

[0124] 2.1 Construct the observation equation. The observation data uses the single-day solution of the geodetic height as the observed quantity. For the convenience of expression, use U k,t and s k to represent the single-day solution of the geodetic height and the mean square error of the kth Beidou reference station at time t, use ΔU k,t to represent the corresponding observation residual (the difference between the observed value U k,t at time t and the single-day solution of the geodetic height ΔU k,t0 at the first observation time t0), use Δu k,t to represent the correction of the single-day solution of the geodetic height, and use ε k,t to represent the observation noise of the single-day solution of the geodetic height. The method for constructing the observation equation is as follows:

[0125] ΔU k,t = Δu t,t + ε k,t

[0126] 2.2 Construct the filtering model. The state model and the observation model are constructed as follows:

[0127] x t = φ t―1 x t―1 + w t―1 (State model)

[0128] z t = H t x t + v t (Observation model)

[0129] Among them,

[0130] x t is the state parameter at time t, x t = [Δu k,t T ;

[0131] φ t―1 is the state transition matrix at the (t - 1)th epoch, and its value is the identity matrix;

[0132] x t―1 is the state parameter at time (t - 1);

[0133] w t―1 is the process noise at time t and the previous time, and its variance - covariance matrix is Q t―1 , and its value is the zero matrix;

[0134] z t is the observation vector at time t, z t = [ΔU k,t T ;

[0135] H t is the design matrix at time t, and its value is the identity matrix;

[0136] v t is the observation noise at time t, which is a white noise process with zero mean, and its variance - covariance matrix is R t , and using diag to represent constructing a diagonal matrix, then R t The construction method can be expressed as

[0137] 2.3 Kalman filter parameter estimation. Use superscripts "-" and "+" to represent the time update (prediction) and the observation update (correction) of relevant parameters respectively. The calculation process is as follows: ​​

[0138] (1) Based on the state model, perform "prediction":

[0139]

[0140]

[0141] (2) Based on the observation model, perform "correction":

[0142]

[0143]

[0144] Repeat the above processes of (1) "prediction" and (2) "correction", and output the precise estimated value of the geodetic height of the k-th BeiDou reference station epoch by epoch (day). and its variance

[0145] 2.4 Calculate the settlement amount of the BeiDou reference station during two periods of leveling observations and its mean square error

[0146]

[0147]

[0148] Among them, t1 and t2 are the intermediate times of the first and second periods of field leveling observations respectively.

[0149] The average value of the mean square error of the settlement amount of the selected BeiDou reference station during two periods of leveling observations is ±0.98 mm, and the maximum value is ±2.81 mm.

[0150] Step 3) Integrate and analyze the two-period leveling measurement data and the settlement amount of the BeiDou reference station during the same period, and calculate the settlement amount of the leveling monitoring points.

[0151] For the convenience of expression, use and to represent the height differences between the j-th and i-th leveling monitoring points in the two periods respectively, use to represent the residual of the difference between the height differences of the same-name leveling points in the two periods, use and to represent the settlement amounts of the i-th and j-th leveling monitoring points during the two periods of observations respectively, use to represent the observation noise of the difference between the height differences of the same-name leveling points in the two periods, use to represent the observation noise of the k-th BeiDou reference station, and the mean square error is The construction method of the integrated calculation observation equation is as follows:

[0152]

[0153]

[0154] Its matrix form is as follows:

[0155] V = AX - L, weight matrix P

[0156] Wherein,

[0157] X is the vector of parameters to be estimated, The settlement amount of the leveling monitoring points (including the leveling points coinciding with the Beidou monitoring stations);

[0158] V is the residual vector of the observed quantity, The length is the sum of the number of leveling observation segments of two periods and the number of Beidou reference stations;

[0159] A is the design matrix, constructed according to the relationship between the above-mentioned observation equation and the settlement amount of the leveling monitoring points The relationship is constructed.

[0160] P is the observation weight matrix, The weight of the leveling observation S is the distance of the survey segment; Beidou base

[0161] The least squares method is used to solve the parameters to be estimated:

[0162] X = (A T PA) ―1 A T PL

[0163]

[0164] Wherein, is the unit weight variance, m represents the number of observed height differences, n represents the number of monitoring points (the sum of the number of leveling monitoring points and Beidou reference stations), The calculation method is as follows:

[0165]

[0166] The spatial distribution diagram of the leveling monitoring error and the normal distribution fitting diagram of the leveling monitoring error in the embodiment of the present invention are respectively shown in Figure 3 and Figure 4 . The average value of the mean square error of the settlement amount of the leveling monitoring points is 3.3 mm, the maximum value is 7.3 mm, and the maximum error of the ground settlement is 14.6 mm (calculated according to 2 times the mean square error), which can meet the accuracy requirements of the ground settlement monitoring with an annual settlement amount of 15 mm.

[0167] For the two - period leveling monitoring data of the present invention case, the elevations of the two - period leveling monitoring points are calculated respectively according to the conventional static adjustment method, and further the settlement amounts of the leveling monitoring points are calculated by taking the difference. The spatial distribution of errors and the fitting situation of the normal distribution of errors are shown respectively in Figure 5 and Figure 6 . The average error is 6.4 mm, the maximum value is 8.9 mm, and the maximum ground settlement error is 17.8 mm (calculated according to 2 times the mean square error), which cannot meet the ground settlement monitoring accuracy requirement of an annual settlement of 15 mm.

[0168] In summary, for the ground settlement leveling monitoring of the technical solution of the present invention, the average mean square error is 3.3 mm and the maximum value is 7.3 mm. Compared with the conventional method, the mean square errors are reduced by 3.1 mm and 1.6 mm respectively, and the spatial distribution of the mean square error is relatively uniform.

[0169] For conventional leveling monitoring, the adjustment calculations are carried out on the two - period leveling data respectively. In each period of calculation, the elevation of the leveling monitoring point is calculated with the height difference of the leveling measurement as the observed quantity. By taking the difference between the elevations of the two - period leveling monitoring points, the corresponding settlement amount is calculated. Affected by the cumulative error of long - distance observations, the monitoring accuracy is limited and the calculation is complex.

[0170] Compared with the prior art, the present invention has the following advantages and effects:

[0171] (1) The monitoring errors are uniform and the monitoring accuracy is high. The urban ground settlement monitoring method that combines Beidou satellite navigation and leveling measurement provided by the present invention can effectively control the influence of the cumulative error of long - distance leveling observations, significantly improve the problem of uneven leveling observation accuracy, and remarkably improve the ground settlement monitoring accuracy of leveling, meeting the ground settlement monitoring requirements of an annual settlement of 15 mm.

[0172] (2) The application cost is low and the application scope is wide. The present invention can make full use of the continuously operating reference stations and the first - and second - class leveling networks that are generally built in cities. Only by selecting some Beidou reference stations according to the present invention's scheme for simultaneous connection measurement with leveling, and only adding a small amount of field observations, can the problem that a single monitoring method cannot meet the ground settlement monitoring requirements of an annual settlement of 15 mm be solved. The application cost is low and the applicable range is wide.

[0173] The above is an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification, or equivalent replacement that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. A method for monitoring urban land subsidence by integrating Beidou satellite navigation and leveling, characterized in that: The following steps are included: 1) Perform high-precision positioning calculations on the BeiDou base station and the surrounding IGS stations to obtain the geodetic height single-sky solution and mean error of the BeiDou base station under the ITRF framework. 2) Using the single-day solution of geodetic height as the observation quantity, the leveling data corresponding to the Beidou reference station in the same period are filtered to obtain the geodetic height accurate estimation and variance of each Beidou reference station, and the settlement and mean error of the Beidou reference station during the two-period leveling observation period are calculated. 3) Obtain the two-phase leveling data and integrate them with the Beidou base station settlement data of the same period to calculate the settlement of all leveling monitoring points.

2. The urban land subsidence monitoring method integrating Beidou satellite navigation and leveling as claimed in claim 1, characterized in that: The difference between the height differences of the two same-name leveling points and the settlement of the Beidou reference station during the same period are taken as the observation quantity, and the settlement of all leveling monitoring points is directly solved through one adjustment calculation.

3. The urban land subsidence monitoring method integrating Beidou satellite navigation and leveling as claimed in claim 1, characterized in that: The distance between the Beidou reference stations is 70-100km, and the distance between any leveling monitoring point and the nearest Beidou reference station is less than 50km.

4. The urban land subsidence monitoring method integrating Beidou satellite navigation and leveling as claimed in claim 1, characterized in that: The solution described above adopts internationally authoritative post-event high-precision data processing software and the final orbit and clock products of the IGS to obtain the single-day solution and mean error of the geodetic height of the Beidou reference station under the ITRF framework during the same period of leveling field observations.

5. The urban land subsidence monitoring method integrating Beidou satellite navigation and leveling as claimed in claim 1, characterized in that: The step 2) comprises: 2.1 Construct the observation equation. The observation data uses the single sky solution of the geodetic height as the observation quantity, U k,t and k represents the mean error of the single sky solution of the geodetic height at the kth BeiDou reference station at time t, ΔU k,t Denotes the corresponding observation residual, Δu k,t represents the correction number of the single sky solution of the geodetic height, ε k,t represents the observation noise of the single sky solution of the Earth's height. The observation equation is constructed as follows: D.U. k,t =Δu k,t +e k,t 2.2 Construct the filter model, the state model and the observation model as follows: x t =φ t―1 x t―1 +w t―1 z t =H t x t +v t in, x t is the state parameter at time t, x t =[Δu k,t ] T ; φ t―1 is the state transfer matrix of the t-1 epoch, which is the unit matrix; x t―1 is the state parameter at time t-1; w t―1 is the process noise at time t and the previous time, and its variance covariance matrix is ​​Q t―1 , the value is 0 matrix; z t is the observation vector at time t, z t =[ΔU k,t ] T ; H t Design the matrix for time t, which takes the value as the unit matrix; v t is the observation noise at time t, which is a zero-mean white noise process, and its variance-covariance matrix R t ,R t The construction method is 2.3 Kalman filter parameter estimation, the superscripts "-" and "+" are used to indicate the prediction and correction of the relevant parameters, respectively. (1) Make predictions based on the state model, (2) Make corrections based on the observation model. Repeat (1) and (2) above, and output the high-precision geodetic estimate of the kth Beidou reference station per epoch. and variance 2.4 Calculation of the settlement of the Beidou reference station during the two-phase leveling observation Mean error in, t1 and t2 are the middle moments between the first and second phases of leveling field observations respectively.

6. The urban land subsidence monitoring method integrating Beidou satellite navigation and leveling as claimed in claim 1, characterized in that: In step 3, the method for constructing the fusion calculation observation equation is as follows: Its matrix form is as follows: V = AX-L, weight matrix P in, and They represent the height difference between the jth level monitoring point and the ith level monitoring point in periods t1 and t2 respectively. The residual represents the difference between the height differences of the same level points in two periods. and Respectively represent the settlement of the ith and jth leveling monitoring points during the two observation periods, represents the observation noise of the difference between the height differences of the same-named level points in two periods, represents the observation noise of the kth BeiDou reference station, and the mean error is X is the parameter vector to be estimated, Settlement of leveling monitoring points, including leveling points that coincide with Beidou monitoring stations; V is the observed residual vector, The length is the sum of the number of leveling observation sections with the same name in two phases and the number of Beidou reference stations; A is the design matrix, based on the above observation equation and the settlement of the level monitoring point relationship building; P is the observation weight matrix, The right of level observation S is the measuring distance; Beidou base The least square method is used to solve the parameters to be estimated: X=(A T PA) ―1 A T PL in, is the unit weight variance, m represents the number of observed height differences, n represents the number of monitoring points, and is the sum of the number of leveling monitoring points and Beidou reference stations. The calculation method is as follows,

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