Real-time tide measurement method and system for single Beidou altimetry buoy without base station

Abstract

The present application belongs to the field of ocean observation technology, and specifically relates to a real-time tidal measurement method and system of a single Beidou altimetry buoy without a base station. The method uses a single Beidou navigation satellite to locate the buoy and measure its height, without the need for a shore-based reference station, thereby achieving high-precision real-time tidal monitoring. This technology is widely used in the fields of ocean tidal monitoring, ocean dynamics research, marine environmental monitoring and early warning, marine engineering, etc., and is particularly suitable for sea areas without base stations or far from shore. By reducing costs and improving efficiency, the present invention provides a reliable and low-cost solution for ocean monitoring systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of ocean observation, and in particular relates to a real-time tide measurement method and system of a single Beidou altimetry buoy without a base station. Background Art

[0002] Tidal measurement is an important part of ocean observation. Traditional tidal measurement methods include data collection using buoys, tidal stations, etc. In recent years, altimetry buoys based on the Global Navigation Satellite System (GNSS) have attracted widespread attention because they can be deployed in offshore waters, becoming a unique and effective means of tidal measurement.

[0003] Existing GNSS-based tidal measurement methods mainly include the differential pseudorange correction (PPK) method and the precise point positioning (PPP) method. The PPK method usually relies on shore-based reference stations to correct GNSS signals by differential means to calculate tidal changes. However, the PPK method requires the existence of shore-based reference stations and requires strong communication support to achieve data transmission and real-time calculations. The PPP method does not require shore-based reference stations and uses precise ephemeris for positioning, which can achieve tidal measurement without base stations. However, the PPP method relies on precise ephemeris, cannot perform real-time calculations, and requires high computing power and long post-processing.

[0004] At present, both PPK and PPP methods have the following shortcomings: on the one hand, both PPK and PPP need to rely on shore-based computing platforms and cannot achieve real-time calculations inside the buoy; on the other hand, these methods need to transmit the observation data back to the shore for post-processing, which not only leads to high communication costs, but also makes it difficult to meet the real-time requirements of tidal monitoring. In addition, the computing power inside the buoy is relatively limited and cannot support complex calculation processes. Therefore, it is difficult for existing technical solutions to independently complete the real-time processing of tidal data at the buoy end.

[0005] Therefore, there is an urgent need for a tidal measurement method that does not rely on shore-based reference stations and can perform real-time calculations inside the buoy to overcome the limitations of existing technologies, especially for applications in sea areas far from shore and in complex marine environments. Summary of the invention

[0006] In view of the shortcomings of the existing GNSS-based tidal measurement methods, the present invention proposes a real-time tidal measurement method and system for a single Beidou altimetry buoy without a base station. The core technical innovation of the present invention is to calculate tidal data in real time inside the buoy, reduce dependence on shore-based reference stations, and achieve efficient real-time tidal monitoring. The technical solution is:

[0007] A real-time tidal measurement method of a single Beidou altimetry buoy without a base station comprises the following steps:

[0008] S1. Collect data through Beidou single-frequency receiver;

[0009] S2. Calculate the buoy velocity using TDCP;

[0010] S3. Interpolation of harmonic constants;

[0011] S4. Calculation of disturbed water level;

[0012] S5. Add the tidal background field calculated based on the harmonic constant and the disturbed water level measured by TDCP to obtain the final actual tidal water level.

[0013] Preferably, in step S1, B1 frequency band carrier phase data is used, the data is encoded in RTCM format, and a data file is formed every set time; the collected data includes carrier phase, pseudorange, satellite number and signal quality.

[0014] Preferably, in step S2, the measurement model of the single-frequency TDCP carrier phase is expressed as follows:

[0015] ;

[0016] The wavelength of the frequency signal, Indicates frequency coding, different frequencies of Beidou have different wavelengths;

[0017] :Receiver With satellite between Carrier phase observations on frequency;

[0018] : The geometric distance between the receiver and the satellite;

[0019] :speed of light;

[0020] and : Clock difference between receiver and satellite;

[0021] : The integer ambiguity of the carrier phase is an integer that represents the uncertainty of the carrier phase during signal propagation;

[0022] : ionospheric delay error;

[0023] : Tropospheric delay error, the delay caused by the signal passing through the troposphere of the Earth's atmosphere;

[0024] : Random measurement noise, including multipath effects and other residual errors;

[0025] In the absence of cycle slips, the carrier phase observations of consecutive epochs are differentiated to obtain:

[0026] ;

[0027] : The carrier phase change between two epochs;

[0028] : The geometric distance difference between the receiver and the satellite, indicating the change in the receiver position between two epochs;

[0029] : The clock error difference between the receiver and the satellite, representing the impact of the clock error change between two epochs on the measurement;

[0030] and : The changes of ionospheric and tropospheric delay errors, which are the changes of the signal passing through the ionosphere and troposphere between two epochs;

[0031] : Random measurement error variation between two epochs, including multipath effects and other residual errors;

[0032] Satellite distance difference:

[0033] ;

[0034] is the unit direction vector between the satellite and the receiver, and is calculated as:

[0035] ;

[0036] in, and Respectively represent the epoch The position coordinate vectors of the satellite and the receiver at time ;

[0037] The position difference is calculated as follows:

[0038] The position information of the receiver in consecutive epochs can be expressed as ,in is the change in position of the receiver between two epochs; the geometric distance difference can be further expanded as:

[0039] ;

[0040] and represent the unit direction vector of the satellite at different epochs, and the error equation for the time-difference carrier phase method is obtained.

[0041] Preferably, in step S2, the TDCP error equation is:

[0042] ;

[0043] in, represents the residual error, is the change in position of the receiver between two epochs, is the change in receiver clock bias;

[0044] Definition:

[0045] ;

[0046] The unknowns in this equation include two:

[0047] : the change in position of the receiver between two epochs;

[0048] : Change of receiver clock bias;

[0049] Calculation of receiver speed:

[0050] By the change in position between two epochs , the instantaneous speed of the receiver can be calculated :

[0051] ;

[0052] in, and are the time points of two epochs, is the change in position of the receiver between these two points in time.

[0053] Preferably, in step S3, the harmonic parameter information of the target position is calculated based on the data of the surrounding known points through an interpolation method, so as to achieve accurate estimation of any longitude and latitude point, and the steps are as follows:

[0054] S31. Determine the grid point position;

[0055] S32. Read the grid data and obtain the tidal amplitude and phase data;

[0056] S33. Interpolation calculation;

[0057] Interpolation of tidal amplitudes:

[0058] ;

[0059] in, It is the target point The tidal amplitude at is the tidal amplitude corresponding to the adjacent grid point, is the interpolation weight coefficient;

[0060] Interpolation of tidal phase:

[0061] ;

[0062] in, It is the target point The tidal phase at is the tidal phase corresponding to the adjacent grid point, is the interpolation weight system;

[0063] S34. Each component corresponds to a specific frequency;

[0064] S35. Prediction of background tides;

[0065] For each tidal component, calculate the positive and negative frequency parts of its complex form, assuming that the amplitude of the tidal component is , the phase is , then the calculation formulas for the positive frequency part and the negative frequency part are as follows:

[0066] Positive frequency part :

[0067] ;

[0068] Negative frequency part :

[0069] ;

[0070] in: is the phase angle, is an imaginary unit;

[0071] Based on the complex representation of tidal components, the predicted values ​​of tides Calculated by the following formula:

[0072] ;

[0073] in:

[0074] For the moment Tidal prediction value at ;

[0075] For the The frequency of the tidal components;

[0076] and Respectively The positive and negative frequency parts of the tidal components;

[0077] For time;

[0078] For long-period tidal components, node correction is required, and the corrected amplitude and phase are as follows:

[0079] Corrected positive frequency part :

[0080] ;

[0081] Corrected negative frequency part :

[0082] ;

[0083] The tidal prediction results after node correction are:

[0084] ;

[0085] in:

[0086] is the node correction factor;

[0087] and are astronomical corrections respectively;

[0088] Is an imaginary unit.

[0089] Preferably, in step S32, from four neighboring points in the grid, including Get tidal amplitude and phase data from:

[0090] Amplitude HC1:

[0091] ;

[0092] Phase :

[0093] ;

[0094] The two-dimensional matrix represents the tidal amplitude and phase at four grid points around the current latitude and longitude point.

[0095] Preferably, when there is invalid data, the processing method is first determined by checking whether there are invalid data points:

[0096] No invalid data: If all points are valid, interpolation calculation is performed directly;

[0097] Partial invalid data: If there is invalid data, the invalid data is replaced by the mean of the remaining valid points, and then interpolation is performed again, and then the interpolation calculation is performed again;

[0098] All invalid data: If all are invalid, expand the grid range and re-interpolate.

[0099] Preferably, in step S4, the calculation process of the disturbed water level is as follows:

[0100] S41. Calculate vertical displacement by integrating vertical velocity:

[0101] Obtaining the vertical velocity of the buoy using the TDCP method , the vertical velocity represents the vertical velocity change of the buoy relative to the reference point, and the vertical displacement is calculated :

[0102] ;

[0103] in, is the time variable, is the variation of vertical velocity with time;

[0104] S42. Identify long-term drift and remove it:

[0105] The high-pass filtering method is used to eliminate the low-frequency component. The formula is as follows:

[0106] ;

[0107] in, represents the vertical displacement signal after low-pass filtering;

[0108] S43. Remove the wave fluctuations:

[0109] Set the time window of low-pass filtering to filter out wave information. The low-pass filtering process is expressed as:

[0110] ;

[0111] Among them, LPF represents the low-pass filtering operation, is the final disturbance water level signal.

[0112] Preferably, the final actual tidal water level is calculated as follows:

[0113] .

[0114] A real-time tidal measurement system of a single Beidou altimetry buoy without a base station, comprising a single Beidou altimetry buoy, a TDCP velocity measurement module, a harmonic constant calculation module, a data processing module, and a communication module;

[0115] Single Beidou altimeter buoy: single-frequency Beidou receiver and antenna, capable of obtaining the buoy's position information and altitude data in real time;

[0116] TDCP speed measurement module: By analyzing the changes in GNSS signals in real time, the dynamic speed changes of the buoy are obtained. The long-period errors can be effectively eliminated through the filtering algorithm, and the actual high-frequency tidal changes can be retained, providing accurate data for subsequent tidal water level recovery;

[0117] Harmonic constant module: responsible for calculating the background field of tides. By introducing the global standard harmonic constants, it provides background values ​​for actual tide measurements. The calculation results of the harmonic constants provide the buoy with standard background values ​​of tides for comparison and synthesis with the actual measured disturbance water level.

[0118] Data processing module: responsible for integrating data from the TDCP speed measurement module and the harmonic constant calculation module;

[0119] Communication module: responsible for transmitting the calculated tidal water level results to the shore-based data center.

[0120] Compared with the prior art, the present invention has the following beneficial effects:

[0121] 1. Low-cost equipment configuration:

[0122] Compared with the traditional submarine pressure gauge measurement method, the device of the present invention only needs a single Beidou receiver system for tidal observation. Conventional submarine pressure gauge measurement methods usually require a temperature and salinity sensor to measure the density of seawater and correct the tidal data. The present invention directly obtains tidal water level data by using a single Beidou receiver system without additional density correction, which significantly reduces the hardware cost of the system. Therefore, the device cost of the present invention is lower and can reduce complex sensor configuration and maintenance requirements.

[0123] 2. Realize real-time tidal measurement in offshore areas:

[0124] Traditional GNSS buoy tide measurement methods, such as PPK and PPP algorithms, usually rely on post-precision ephemeris for data processing and cannot provide real-time observation. The present invention adopts the TDCP algorithm, which can directly realize real-time tide measurement at the buoy end, avoiding the delay of data transmission and post-processing in traditional methods, and can obtain tidal water level information in real time in complex environments such as the open sea. This feature makes the present invention have higher timeliness and application scope in tide monitoring, especially suitable for sea areas far away from shore.

[0125] 3. Low computing power requirements and simplified computing platform:

[0126] The tide measurement method of the present invention uses a single-chip microcomputer to calculate the tide level inside the buoy, which requires low computing power and can be implemented on a low-power, low-cost hardware platform. Unlike traditional PPK and PPP methods, the latter usually require high-performance computers and large memory support for complex calculations and data processing. In contrast, the calculation method of the present invention simplifies the hardware requirements, making the system easier to deploy and maintain, while reducing the power consumption and cost of the equipment.

[0127] 4. Improve system stability and scalability:

[0128] Due to the simple single Beidou receiver and single-chip configuration, the system of the present invention has higher stability and can operate stably in more complex and harsh marine environments. In addition, the low computing power requirement and simplified design of the system make it more scalable and can be flexibly adjusted and optimized according to different application scenarios, making it suitable for a wide range of marine environment monitoring tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] Figure 1 The tidal measurement process of the method of the present invention is as follows:

[0130] Figure 2 To reconcile the tidal background field obtained by analysis,

[0131] Figure 3 is the disturbed water level obtained by TDCP algorithm,

[0132] Figure 4 is the actual water level and error after merging. DETAILED DESCRIPTION

[0133] The technical solution of the present application is described in detail below through specific embodiments and drawings. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application, and the specific technical features may be combined with each other.

[0134] The present invention proposes a real-time tidal measurement method and system for a single Beidou altimetry buoy without a base station. Existing GNSS tidal measurement methods mainly rely on shore-based reference stations, which cannot realize real-time calculations at the buoy end, and usually require the original observation data to be transmitted back to the shore for post-processing, resulting in heavy communication burden, poor real-time performance and high system cost. Therefore, the core technical innovation of the present invention is to calculate tidal data in real time inside the buoy, reduce dependence on shore-based reference stations, and realize efficient real-time tidal monitoring.

[0135] Specifically, the present invention uses harmonic constants to calculate the tidal background field, and this process provides a fixed periodic change trend of the tide. The harmonic constants represent the main periodic components of the tide, can accurately describe the long-term change pattern of the tide, and provide a basic reference for the dynamic changes of the tide. Through this method, the tidal background field can be effectively calculated as a reference framework for subsequent tidal disturbance water level calculations. Combined with the TDCP method, the system can accurately measure the disturbed water level at the location of the buoy in real-time operation. This part of the change reflects the water level fluctuations caused by local ocean dynamic processes and weather and environmental factors such as changes in air pressure and water flow. It can capture the water level changes caused by these factors in real time, thereby providing more accurate tidal monitoring and analysis.

[0136] Finally, the actual tidal level is restored by adding the background field and the disturbed water level. This method avoids the reliance on shore-based reference stations and complex data post-processing in traditional technologies, thus greatly improving the real-time and accuracy of tidal measurement.

[0137] The present invention proposes a high-precision tidal measurement system based on TDCP real-time velocity measurement and error processing. The system calculates the tidal background field by harmonic constants, obtains the disturbed water level by combining the TDCP method, and finally restores the actual tidal water level, avoiding dependence on shore-based reference stations and realizing real-time calculation at the buoy end. The following is a detailed introduction to the technical solution of the present invention.

[0138] This system mainly consists of the following key components:

[0139] (1) Single Beidou altimeter buoy:

[0140] The core component of the system is a single Beidou altimetry buoy. The buoy is equipped with a single-frequency Beidou receiver and antenna, which can obtain the buoy's position information and altitude data in real time. The buoy has autonomous computing capabilities, which can perform data processing and real-time estimation of tidal water levels inside the buoy. The structure of the buoy includes a float, a measurement unit, a data processing module, and a communication module. The measurement unit includes a GNSS receiver, the data processing module uses a low-power microprocessor for real-time calculations, and the communication module is responsible for transmitting the final tidal results to the shore.

[0141] (2) TDCP speed measurement module:

[0142] The TDCP real-time velocity measurement module is a key module for achieving high-precision tidal measurement. The module obtains the dynamic velocity changes of the buoy by analyzing the changes in GNSS signals in real time. The TDCP module can accurately measure the velocity results, but there is a significant systematic long-period drift. The filtering algorithm can effectively eliminate the long-period error, retain the actual high-frequency tidal changes, and provide accurate data for subsequent tidal water level recovery.

[0143] (3) Harmonic constant calculation module:

[0144] The harmonic constant module is responsible for calculating the background field of tides. By introducing the global standard harmonic constants (such as the harmonic constants of the main tidal components such as M2 and S2), this module provides background values ​​for actual tidal measurements. The calculated results of the harmonic constants provide the buoy with a standard background value of tides for comparison and synthesis with the actual measured disturbance water level.

[0145] (4) Data processing module:

[0146] The data processing module is responsible for integrating the data from the TDCP velocity measurement module and the harmonic constant calculation module. First, the data processing module obtains the real-time buoy position information and the measured disturbed water level, and uses the built-in algorithm to process these data in real time, identify and filter the errors in the measurement process, and make necessary accuracy corrections. Then, the data processing module combines the background field calculated by the harmonic constant with the disturbed water level measured by TDCP to restore the final tidal water level.

[0147] (5) Communication module:

[0148] The communication module is responsible for transmitting the calculated tidal level results to the shore-based data center. In order to improve real-time performance and reduce the burden of data transmission, the buoy only needs to upload the tidal level results without transmitting the original data. The communication module supports low-power wireless communication protocols to ensure the stability and reliability of data transmission during long-term operation.

[0149] A real-time tide measurement method of a single Beidou altimetry buoy without a base station, the specific operation steps are as follows:

[0150] S1. Data collection:

[0151] The real-time tidal measurement system of the present invention uses a Beidou single-frequency receiver to collect high-precision data, using B1 band (1559.052 MHz-1591.788 MHz) carrier phase data with a sampling frequency of 2Hz. The data is encoded in RTCM format and a data file is formed every hour to ensure sufficient time resolution to accurately capture tidal changes. The file is stored in the local system for subsequent analysis and processing. The collected data includes information such as carrier phase, pseudorange, satellite number and signal quality.

[0152] S2.TDCP calculates the buoy speed:

[0153] The measurement model of single-frequency TDCP carrier phase can be expressed as the following formula:

[0154] ;

[0155] The wavelength of the frequency signal, Indicates frequency coding. Different frequencies of Beidou have different wavelengths. This invention only uses ;

[0156] :Receiver With satellite between Carrier phase observations on frequency;

[0157] : The geometric distance between the receiver and the satellite;

[0158] : speed of light;

[0159] and : Clock difference between receiver and satellite;

[0160] : The integer ambiguity of the carrier phase is an integer, which represents the uncertainty of the carrier phase during the signal propagation process;

[0161] : Ionospheric delay error, an error that affects GNSS signal propagation due to refraction of the signal as it passes through the Earth’s ionosphere;

[0162] : Tropospheric delay error, the delay caused by the signal passing through the troposphere of the Earth's atmosphere;

[0163] : Random measurement noise, including multipath effects and other residual errors.

[0164] In the absence of cycle slips, the carrier phase observations of consecutive epochs are differentiated to obtain:

[0165] ;

[0166] : The carrier phase change between two epochs;

[0167] : The geometric distance difference between the receiver and the satellite, indicating the change in the receiver position between two epochs;

[0168] : The clock error difference between the receiver and the satellite, representing the impact of the clock error change between two epochs on the measurement;

[0169] and : The changes of ionospheric and tropospheric delay errors, which are the changes of the signal passing through the ionosphere and troposphere between two epochs;

[0170] : Random measurement error variation between two epochs, including multipath effects and other residual errors.

[0171] Further get the satellite distance difference:

[0172] ;

[0173] is the unit direction vector between the satellite and the receiver, and is calculated as:

[0174] ;

[0175] in, and Respectively represent the epoch The position coordinate vectors of the satellite and receiver at time .

[0176] Position difference:

[0177] The position information of the receiver in consecutive epochs can be expressed as ,in is the change in the position of the receiver between two epochs. Therefore, the geometric distance difference can be further expanded as:

[0178] ;

[0179] here, and They represent the unit direction vector of the satellite at different epochs. Furthermore, the error equation for the time-difference carrier phase method is obtained, which shows how the receiver position change and clock bias change between epochs affect the carrier phase observation. TDCP error equation:

[0180] ;

[0181] in, represents the residual error, is the change in position of the receiver between two epochs, is the change in receiver clock bias.

[0182] Definition:

[0183] ;

[0184] The unknowns in this equation include two:

[0185] : the change in position of the receiver between two epochs,

[0186] : Change in receiver clock bias,

[0187] When the number of observed satellites is greater than 4, the least squares method can be used to solve the receiver position change and clock bias changes .

[0188] Calculation of receiver speed:

[0189] By the change in position between two epochs , the instantaneous speed of the receiver can be calculated :

[0190] ;

[0191] in, and are the time points of two epochs, is the change in position of the receiver between these two points in time.

[0192] When solving the TDCP error equation, the satellite position is calculated using the broadcast ephemeris, while the receiver position is determined using single-point positioning based on pseudorange measurements. These quantities are primarily determined by the direction vector Affects the accuracy of velocity measurement. As long as their error is within 10 meters, the impact on velocity measurement can be controlled at the order of mm / s. The satellite's clock drift rate is also calculated from the broadcast ephemeris. Usually the clock drift rate is less than 0.001 nanoseconds / second, and its impact on velocity measurement is less than 0.3 mm / second. Ionospheric and tropospheric delays generally change slowly. When the sampling frequency reaches 1 Hz or higher, the ionospheric and tropospheric delays between adjacent epochs show a strong correlation. Most atmospheric delays can be eliminated by differential methods, and the residual errors are treated as noise.

[0193] When constructing the TDCP observation equation, it is assumed that no cycle slips occur between epochs. Therefore, in practical applications, cycle slip detection and repair should be performed. The present invention proposes to use a Doppler-assisted method to detect and repair cycle slips in GNSS data. This method uses Doppler shift measurements, which are less sensitive to cycle slips than phase measurements, thereby more effectively detecting and removing cycle slips.

[0194] (3) Interpolation of harmonic constants:

[0195] In the present invention, in order to accurately calculate physical quantities such as tidal amplitude and phase at a given longitude and latitude point, it is necessary to interpolate the internationally disclosed tidal model. Since the tidal model data is usually provided in a gridded manner, the observation data of each grid point has a fixed interval, and the accurate value of certain specific locations cannot be directly obtained. Therefore, through the interpolation method, the harmonic parameter information of the target location can be inferred based on the data of the surrounding known points, thereby achieving accurate estimation of any longitude and latitude point.

[0196] (I) Determine the grid point location:

[0197] When calculating interpolation, we must first determine the current latitude and longitude point ( , ) is located in the grid. This process is completed by the following formula:

[0198] For the calculation of latitude:

[0199] ;

[0200] in, is the grid size in degrees.

[0201] For the calculation of longitude:

[0202] ;

[0203] Using these two formulas, the code is able to determine the current latitude and longitude position in a two-dimensional grid.

[0204] (II) Reading grid data:

[0205] From four neighboring points in the grid (including Get tidal amplitude and phase data from:

[0206] Amplitude (HC1):

[0207] ;

[0208] Phase (HS1):

[0209] ;

[0210] The above two-dimensional matrix represents the tidal amplitude and phase at four grid points around the current longitude and latitude point.

[0211] (III) Interpolation calculation:

[0212] For four valid grid points, the tidal amplitude and phase at a given longitude and latitude point are calculated by two-dimensional spline interpolation.

[0213] Interpolation of tidal amplitudes:

[0214] For four valid grid points, the interpolation process can be written as:

[0215] ;

[0216] in, It is the target point The tidal amplitude at is the tidal amplitude corresponding to four adjacent grid points, is the interpolation weight coefficient, which is calculated by two-dimensional spline interpolation.

[0217] Interpolation of tidal phase:

[0218] Similarly, the interpolation formula for tidal phase is:

[0219] ;

[0220] in, It is the target point The tidal phase at is the tidal phase corresponding to four adjacent grid points, is the interpolation weight coefficient, which is also calculated by two-dimensional spline interpolation. (IV) Handling invalid data (NaN):

[0221] If all four points are valid, interpolation is performed directly. When there is invalid data (NaN), the processing method is first determined by checking whether there are invalid data points:

[0222] Partial invalid data: If there is invalid data among the four points, the invalid data is replaced by the mean of the remaining valid points, and then interpolation is performed again, and then the interpolation calculation is performed again.

[0223] All invalid data: If all four points are invalid, expand the grid range to 16 points or more and re-interpolate.

[0224] The extended interpolation method increases the data validity by increasing the size of the surrounding grid. For example, expanding to 16 points ( grid) or 36 points ( grid) until valid data is found.

[0225] 16 points Grid):

[0226] ;

[0227] 36 points (6 6 grids):

[0228] ;

[0229] These are done by gradually enlarging the grid to cope with the situation where all data points are invalid. Finally, when the data at one grid point is valid, a two-dimensional interpolation is performed and the final result is obtained.

[0230] (V) Harmony parameters:

[0231] The harmonic parameters used in the present invention include 29 components, such as 2N2, J1, K1, K2, etc., each of which corresponds to a specific frequency. Its period is as follows:

[0232]

[0233] (VI) Prediction of background tides:

[0234] For each tidal component, calculate the positive and negative frequency parts of its complex form. Assume that the amplitude of the tidal component is , the phase is , then the calculation formulas for the positive frequency part and the negative frequency part are as follows:

[0235] Positive frequency part :

[0236] ;

[0237] Negative frequency part :

[0238] ;

[0239] in: is the phase angle, in degrees; Is an imaginary unit.

[0240] Based on the complex representation of tidal components, the predicted values ​​of tides It can be calculated by the following formula:

[0241] ;

[0242] in:

[0243] For the moment Tidal prediction value at ;

[0244] For the The frequency of the tidal components;

[0245] and Respectively The positive and negative frequency parts of the tidal components;

[0246] The time is in days.

[0247] For long-period tidal components, node correction is required, and the corrected amplitude and phase are as follows:

[0248] Corrected positive frequency part :

[0249] ;

[0250] Corrected negative frequency part :

[0251] ;

[0252] in:

[0253] is the node correction factor;

[0254] and are astronomical corrections respectively;

[0255] Is an imaginary unit.

[0256] The tidal prediction results after node correction are:

[0257] ;

[0258] (4) Calculation of disturbed water level:

[0259] In the present invention, the calculation process of the disturbed water level is divided into the following steps, which ensures that the system error is removed and the real-time water level change is accurately calculated:

[0260] (I) Calculate vertical displacement by integrating vertical velocity:

[0261] First, the vertical velocity of the buoy is obtained by the TDCP method. , the vertical velocity represents the vertical velocity change of the buoy relative to the reference point, and the vertical displacement is calculated :

[0262] ;

[0263] in, is the time variable, is the variation of vertical velocity with time.

[0264] (II) Identify long-term drift and remove it:

[0265] Due to the inherent systematic error of the TDCP algorithm, vertical displacement usually has long-term drift. In order to remove this drift, a high-pass filter method is used to eliminate the low-frequency component. High-pass filtering can be achieved by the following formula:

[0266] ;

[0267] in, It represents the vertical displacement signal after low-pass filtering, removing the long-term drift and low-frequency trend items. After a large amount of data testing, the time window of the filter is set to 4 hours (14400 seconds), which can filter out the drift error signal.

[0268] (III) Removing ocean wave fluctuations:

[0269] In order to further remove the short-term fluctuations caused by ocean waves, low-pass filtering is also required. Ocean waves usually have a short period, so the low-pass filter is designed to remove high-frequency noise and retain longer-period disturbances such as changes in air pressure and water flow.

[0270] The low-pass filter time window is set to 300 seconds to filter out wave information and achieve data smoothing. The specific low-pass filter process can be expressed as:

[0271] ;

[0272] Among them, LPF represents the low-pass filtering operation, is the final disturbance water level signal.

[0273] (5) Data fusion and tidal water level restoration:

[0274] The data processing module calculates the tidal background field based on the harmonic constant and the disturbed water level measured by TDCP, and adds the two together to obtain the final actual tidal water level. The calculation formula is:

[0275] .

[0276] (6) Result transmission and real-time monitoring:

[0277] The tide monitoring system of the present invention uploads the tide level result calculated inside the buoy to the shore-based data center through the communication module to realize real-time tide level monitoring. In this system, the buoy end only needs to transmit the tide level result without transmitting a large amount of raw data, which significantly reduces the bandwidth requirement for data transmission and improves the real-time response speed of the system. In the present invention, TDCP has the ability of real-time calculation, and the harmonic analysis can also be calculated through the model without time processing. Specifically, the tide level data includes the tide level value at each time point and the corresponding timestamp information.

[0278] Compared with the prior art, the system of the present invention can independently complete the real-time calculation of tidal data inside the buoy, without relying on the shore-based reference station for data correction and calculation processing. In addition, the buoy only needs to transmit the tidal results after real-time calculation to the shore, without transmitting a large amount of original observation data, which greatly reduces the burden of data transmission, reduces communication costs and improves the operating efficiency of the system. Therefore, the present invention not only significantly improves the real-time performance of the system while reducing costs, but also enhances the applicability of the system in complex marine environments.

[0279] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A real-time tidal measurement method using a single Beidou altimeter buoy without a base station, characterized in that: The following steps are involved: S1. Collect data through Beidou single-frequency receiver; S2. Calculate the buoy velocity using TDCP; S3. Interpolation of harmonic constants: Through the interpolation method, the harmonic parameter information of the target position is calculated based on the data of the surrounding known points, so as to achieve accurate estimation of any longitude and latitude point. The steps are as follows: S31. Determine the grid point position; S32. Read the grid data and obtain the tidal amplitude and phase data; S33. Interpolation calculation: Calculate the interpolation of tidal amplitude and tidal phase: S34. Each component corresponds to a specific frequency; S35. Prediction of background tides; For each tidal component, calculate the positive and negative frequency parts of its complex form, that is, the positive frequency part and negative frequency part ; Based on the complex representation of tidal components, the predicted values ​​of tides Calculated by the following formula: ; in: For the moment Tidal prediction value at ; For the The frequency of the tidal components; and Respectively The positive and negative frequency parts of the tidal components; For time; For long-period tidal components, node correction is required, and the corrected amplitude and phase are as follows: Corrected positive frequency part : ; Corrected negative frequency part : ; The tidal prediction results after node correction are: ; in: and are astronomical corrections respectively; is an imaginary unit; S4. Calculation of disturbed water level; S5. Add the tidal background field calculated based on the harmonic constant and the disturbed water level measured by TDCP to obtain the final actual tidal water level.

2. The real-time tidal measurement method of a single Beidou altimeter buoy without a base station according to claim 1, characterized in that: In step S1, the B1 band carrier phase data is used, the data is encoded in RTCM format, and a data file is formed every set time; the collected data includes carrier phase, pseudorange, satellite number and signal quality.

3. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 1, characterized in that: In step S2, the measurement model of the single-frequency TDCP carrier phase is expressed as follows: ; The wavelength of the frequency signal, Indicates frequency coding, different frequencies of Beidou have different wavelengths; :Receiver With satellite between Carrier phase observations on frequency; : The geometric distance between the receiver and the satellite; :speed of light; and : Clock difference between receiver and satellite; : Integer ambiguity of carrier phase; : ionospheric delay error; : Tropospheric delay error, the delay caused by the signal passing through the troposphere of the Earth's atmosphere; : Random measurement noise, including multipath effects and other residual errors; In the absence of cycle slips, the carrier phase observations of consecutive epochs are differentiated to obtain: ; : The carrier phase change between two epochs; : The geometric distance difference between the receiver and the satellite, indicating the change in the receiver position between two epochs; : The clock error difference between the receiver and the satellite, representing the impact of the clock error change between two epochs on the measurement; and : The changes of ionospheric and tropospheric delay errors, which are the changes of the signal passing through the ionosphere and troposphere between two epochs; : Random measurement error variation between two epochs, including multipath effects and other residual errors; Satellite distance difference: ； is the unit direction vector between the satellite and the receiver, and is calculated as: ； in, and Respectively represent the epoch The position coordinate vectors of the satellite and the receiver at time ; The position difference is calculated as follows: The position information of the receiver in consecutive epochs can be expressed as ,in is the change in position of the receiver between two epochs; the geometric distance difference can be further expanded as: ; and represent the unit direction vector of the satellite at different epochs, and the error equation for the time-difference carrier phase method is obtained.

4. The real-time tidal measurement method of a single Beidou altimeter buoy without a base station according to claim 3 is characterized in that: In step S2, the TDCP error equation is: ; in, represents the residual error, is the change in position of the receiver between two epochs, is the change in receiver clock bias; Definition: ; The unknowns in this equation include two: : the change in position of the receiver between two epochs; : Change of receiver clock bias; Calculation of receiver speed: By the change in position between two epochs , the instantaneous speed of the receiver can be calculated : ； in, and are the time points of two epochs, is the change in position of the receiver between these two points in time.

5. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 3 is characterized in that: In step S3: Interpolation of tidal amplitudes: ; in, It is the target point The tidal amplitude at is the tidal amplitude corresponding to the adjacent grid point, is the interpolation weight coefficient; Interpolation of tidal phase: ; in, It is the target point The tidal phase at is the tidal phase corresponding to the adjacent grid point, is the interpolation weight system; Assume that the amplitude of the tidal component is , the phase is , then the calculation formulas for the positive frequency part and the negative frequency part are as follows: Positive frequency part : ; Negative frequency part : ; in: is the phase angle, Is an imaginary unit.

6. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 5 is characterized in that: In step S32, four neighboring points in the grid are selected, including Get tidal amplitude and phase data from: Amplitude HC1: ; Phase : ; The two-dimensional matrix represents the tidal amplitude and phase at four grid points around the current latitude and longitude point.

7. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 5, characterized in that: When there is invalid data, first decide how to handle it by checking whether there are invalid data points: No invalid data: If all points are valid, interpolation calculation is performed directly; Partial invalid data: If there is invalid data, the invalid data is replaced by the mean of the remaining valid points, and then interpolation is performed again, and then the interpolation calculation is performed again; All invalid data: If all are invalid, expand the grid range and re-interpolate.

8. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 1, characterized in that: In step S4, the calculation process of the disturbance water level is as follows: S41. Calculate vertical displacement by integrating vertical velocity: Obtaining the vertical velocity of the buoy using the TDCP method , the vertical velocity represents the vertical velocity change of the buoy relative to the reference point, and the vertical displacement is calculated : ; in, is the time variable, is the variation of vertical velocity with time; S42. Identify long-term drift and remove it: The high-pass filtering method is used to eliminate the low-frequency component. The formula is as follows: ; in, represents the vertical displacement signal after low-pass filtering; S43. Remove the wave fluctuations: Set the time window of low-pass filtering to filter out wave information. The low-pass filtering process is expressed as: ; Among them, LPF represents the low-pass filtering operation, is the final disturbance water level signal.

9. The real-time tide measurement method of a single Beidou altimeter buoy without a base station according to claim 1, characterized in that: The final actual tidal water level is calculated as follows: 。 10. A real-time tide measurement system of a single Beidou altimeter buoy without a base station, using the real-time tide measurement method of a single Beidou altimeter buoy without a base station as claimed in any one of claims 1 to 9, characterized in that: It includes single Beidou altimeter buoy, TDCP speed measurement module, harmonic constant calculation module, data processing module and communication module; Single Beidou altimeter buoy: single-frequency Beidou receiver and antenna, capable of obtaining the buoy's position information and altitude data in real time; TDCP speed measurement module: By analyzing the changes in GNSS signals in real time, the dynamic speed changes of the buoy are obtained. The long-period errors can be effectively eliminated through the filtering algorithm, and the actual high-frequency tidal changes can be retained, providing accurate data for subsequent tidal water level recovery; Harmonic constant module: responsible for calculating the background field of tides. By introducing the global standard harmonic constants, it provides background values ​​for actual tide measurements. The calculation results of the harmonic constants provide the buoy with standard background values ​​of tides for comparison and synthesis with the actual measured disturbance water level. Data processing module: responsible for integrating data from the TDCP speed measurement module and the harmonic constant calculation module; Communication module: responsible for transmitting the calculated tidal water level results to the shore-based data center.

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