Method and system for measuring sea surface height of deep and far sea based on Beidou PPP-B2b

Abstract

The invention belongs to the technical field of ocean measurement, and discloses a method and a system for measuring the sea surface height of deep and far sea based on Beidou PPP-B2b. The method comprises the following steps: calculating an antenna instantaneous geodetic height of a four-antenna GNSS receiver based on a WGS84 coordinate system; correcting the attitude of the buoy by using a buoy attitude correction algorithm to obtain the height of the buoy in the vertical direction; calculating the buoy draft according to a built-in instantaneous average water depth algorithm; the sea surface instantaneous height is calculated through a sea surface instantaneous height algorithm; carrying out noise reduction processing on the calculated instantaneous height of the sea surface through a filtering calculation unit; and the final result is sent to a monitoring service platform through a data transmission module. The method not only supports ship route planning and navigation safety, helps to avoid risks, but also provides long-term, stable and reliable data support for global climate change monitoring, marine environment protection and deep sea scientific research.

Description

Technical Field

[0001] The present invention belongs to the technical field of ocean measurement, and particularly relates to a method and system for measuring the sea surface height in the deep and far sea based on Beidou PPP-B2b. Background Art

[0002] With the intensification of global climate change and the increasingly serious problem of sea-level rise, the monitoring of ocean height has become increasingly important globally. Especially in the deep and far sea areas, real-time and high-precision sea surface height data is crucial for navigation safety, weather forecasting, early warning of ocean disasters (such as storm surges, tsunamis), and ocean resource development. The accurate measurement of sea surface height directly affects the safety of ship navigation planning, ocean disaster early warning, and deep-sea energy development.

[0003] Traditional ocean height measurement methods face multiple challenges. The ocean measurement system based on RTK (Real-Time Kinematic) technology relies heavily on the differential signal support of ground base stations. In the deep and far sea areas far from land, due to the lack of ground-based signal coverage, it is difficult for RTK technology to achieve high-precision positioning. In addition, in complex sea conditions, the GNSS measurement accuracy of traditional offshore buoys is often affected due to the attitude change of the buoys, resulting in the instability of measurement results. On the other hand, the deficiencies in data transmission also bring difficulties to deep and far sea measurement. Traditional radio communication systems have insufficient coverage in the far sea area and cannot ensure the real-time transmission of measurement data, thus affecting the stability and continuity of the monitoring system. Summary of the Invention

[0004] To overcome the problems existing in the related technologies, the disclosed embodiments of the present invention provide a method and system for measuring the sea surface height in the deep and far sea based on Beidou PPP-B2b.

[0005] The technical solution is as follows: A method for measuring the sea surface height in the deep and far sea based on Beidou PPP-B2b, comprising the following steps: S1, integrating a data acquisition module, a data processing module, and a data transmission module on a buoy, and deploying the buoy to the target deep and far sea area; S2, the four-antenna GNSS receiver, barometer, short message antenna at the top of the buoy, and the pressure gauge at the bottom of the buoy collect data and transmit it in real time to the data processing module in the equipment cabin; S3, the GNSS data processing unit in the data processing module receives the raw data from the four-antenna GNSS receiver and the PPP-B2b correction signal transmitted by the data transmission module, and calculates the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver based on the WGS84 coordinate system; S4. The attitude calculation unit in the data processing module receives the three-dimensional coordinates of the four-antenna GNSS receiver from the GNSS data processing unit, and corrects the buoy attitude using the buoy attitude correction algorithm based on the XYZ coordinate information of the four-antenna GNSS receiver to obtain the buoy height in the vertical direction. S5. The barometer and pressure gauge transmit the measured sea pressure data and the water pressure data at the bottom of the buoy to the environmental pressure data processing unit in the data processing module, and calculate the buoy draft according to the built-in instantaneous average water depth algorithm. S6. Integrate the data from steps S3 to S5, and calculate the instantaneous sea surface height by the instantaneous sea surface height algorithm built in the sea surface height calculation unit of the data processing module. S7. Perform noise reduction processing on the calculated instantaneous sea surface height through the filter calculation unit. S8. Send the result to the monitoring service platform through the data transmission module.

[0006] In step S3, calculate the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver based on the WGS84 coordinate system, including: S301. The PPP-B2b correction signal is broadcast in real time through the GEO satellite of Beidou-3. S302. Match the correction information broadcast by PPP-B2b with the corresponding ephemeris. S303. The buoy receives the orbit and clock error correction information provided by the Beidou PPP-B2b correction signal, and combines the pseudorange and carrier phase observations of the four-antenna GNSS receiver for positioning. S304. Correct the CNAV1 broadcast ephemeris broadcast through the B1C signal using the satellite orbit correction parameters provided by the PPP-B2b correction signal. S305. Correct the ephemeris clock error using the clock error correction information provided by the PPP-B2b correction signal. S306. The buoy adopts a four-antenna GNSS receiver layout, with three sub-GNSS receivers dispersed around the circumference to form a layout of the vertices of a triangle, and the main GNSS receiver is located at the center of the circle. The main GNSS receiver is equipped with a main antenna, and each of the three sub-GNSS receivers is equipped with a sub-antenna; after the correction by PPP-B2b, the pseudorange observation value and the carrier phase observation value Calculate the geometric distance between the main antenna and the satellite , and the expression is: ; In the formula, is the satellite coordinate, is the coordinate of the main antenna of the buoy; The Z coordinate is the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver under the WGS84 coordinate system 。

[0007] In step S301, the PPP-B2b correction signal is broadcast in real time through the GEO satellites of Beidou-3, including: continuously observing the GNSS visible satellites by using distributed encrypted high-precision continuous monitoring stations, collecting pseudorange, carrier phase observation data and meteorological data; verifying and evaluating the preprocessed data by the ground master control station, fitting satellite orbits, clock errors, differential code biases and user range accuracy index URAI correction parameters through dynamic smoothing processing, and arranging precise correction parameters according to the protocol; transmitting the correction parameters to the GEO satellites by the uplink station, and broadcasting them by the GEO satellites through the I branch of the PPP-B2b correction signal In step S304, the CNAV1 broadcast ephemeris transmitted through the B1C signal is corrected by the satellite orbit correction parameters provided by the PPP-B2b correction signal, and the expression is ; In the formula, is the satellite position after the orbit correction parameter correction, is the satellite position calculated from the CNAV1 navigation message of the B1C signal, is the satellite position correction vector The calculation formula of ; In the formula, are the unit vectors in the radial, tangential and normal directions respectively, is the orbit correction vector obtained from the PPP-B2b correction signal, and the components are in the order of the radial, tangential and normal directions ; In the formula, are the satellite position vector and velocity vector calculated from the CNAV1 navigation message of the B1C signal respectively In step S305, the clock error of the broadcast ephemeris is corrected by using the clock error correction information provided by the PPP-B2b correction signal, and the expression is ; In the formula, is the satellite clock error obtained after being corrected by the clock error correction parameter of the PPP-B2b correction signal, is the satellite clock error calculated from the CNAV1 navigation message, is the clock error correction parameter, is the speed of light

[0008] In step S4, the attitude of the buoy is corrected using the buoy attitude correction algorithm based on the XYZ coordinate information of the four-antenna GNSS receiver to obtain the buoy height in the vertical direction, including: S401. The four-antenna GNSS receiver on the buoy collects GNSS signals from satellites, and the main antenna and the three sub-antennas respectively obtain independent coordinate data, namely the three-dimensional X, Y, and Z coordinates; S402. The main antenna of the main GNSS receiver of the buoy is located at the center of the circle, and the sub-antennas of the three sub-GNSS receivers are distributed on the circumference to form an equilateral triangle. The baseline vector represents the relative position relationship between the main antenna and the sub-antenna, and the expression is: ; In the formula, are the coordinates of the three sub-antennas, is the coordinate of the main antenna; S403. Calculate the roll angle of the buoy, which represents the rotation angle of the buoy around the X-axis. The calculation formula is: ; In the formula, are the components of the baseline vector on the Y-axis and Z-axis respectively; S404. Calculate the pitch angle of the buoy, which represents the rotation angle of the buoy around the Y-axis. The calculation formula is: ; In the formula, respectively represent the components of the baseline vector on the X-axis and Z-axis; S405. After obtaining the pitch angle and roll angle, calculate the tilt angle of the GNSS main antenna support rod of the buoy body. The expression is: ; Based on the three-dimensional geometric relationship, it reflects the total tilt angle of the buoy body relative to the vertical direction; S406. The height difference between the phase center of the GNSS main antenna at the top of the buoy and the bottom end of the pressure gauge. When the buoy is tilted, the height in the vertical direction is .

[0009] In step S5, it is transmitted to the environmental pressure data processing unit in the data processing module, and the draft depth of the buoy is calculated according to the built-in instantaneous average water depth algorithm, including: S501. Calculate the draft depth according to the atmospheric pressure collected by the barometer at the top of the buoy and the water pressure collected by the pressure gauge at the bottom of the buoy. Each pressure gauge measures the instantaneous water depth is: ; In the formula, is the total pressure measured by the th pressure gauge, is the atmospheric pressure measured by the current barometer, is the seawater density, is the acceleration of gravity; S502, calculate the water depths of the four pressure gauges, and take the average value to obtain the instantaneous average water depth at the bottom of the buoy. The expression is: .

[0010] In step S6, the instantaneous sea surface height is calculated by the instantaneous sea surface height algorithm built in the sea surface height calculation unit of the data processing module, including: Calculate the instantaneous sea surface height of the buoy at present. The expression is: ; In the formula, is the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver, is the height difference from the phase center of the top GNSS antenna to the pressure gauge section, is the angle between the buoy and the vertical direction, is the draft of the buoy.

[0011] In step S7, the calculated instantaneous sea surface height is denoised by the filtering calculation unit, including: For the swell and noise contained in the acquired instantaneous sea surface height data, use the complete ensemble empirical mode decomposition method CEEMD to perform hierarchical extraction of the intrinsic mode function components IMF to complete the denoising of the swell and noise; Furthermore, use the complete ensemble empirical mode decomposition method CEEMD to perform hierarchical extraction of the intrinsic mode function components IMF, including: S701, add Gaussian white noise to the original signal . The expression is: ; In the formula, is the initial signal-to-noise ratio coefficient; Perform times of EMD decomposition, and calculate the average value to obtain the first intrinsic mode function component . The expression is: ; In the formula, is The first intrinsic mode function obtained by decomposition using the EMD method, is Gaussian white noise with a unit variance of 0, ; is the signal-to-noise ratio coefficient obtained by decomposition using the CEEMD method for , and is Gaussian white noise with a unit variance of 0; Subtract the original signal from to obtain the first-order residual , and the expression is: ; S702. Add Gaussian white noise to the obtained first-order residual , and the signal is expressed as: , and perform decomposition again to obtain the second intrinsic mode function . Subtract from to obtain the first-order residual , and the expression is: ; ; S703. By analogy, continue to perform times of decomposition. When the signal is obtained, calculate the th intrinsic mode function component and the th-order residual; ; ; S704. Calculate the intrinsic mode components and residual values through loop calculation until the number of extreme points of the residual is no more than 2, and then the decomposition ends. The final signal is expressed as: ; In the formula, is the number of IMF components obtained by decomposition using the CEEMD method.

[0012] Another object of the present invention is to provide a deep-sea sea surface height measurement system based on Beidou PPP-B2b. This system implements the deep-sea sea surface height measurement method based on Beidou PPP-B2b. The system includes: a data acquisition module, a data transmission module, a data processing module, and a monitoring service platform; The data acquisition module includes a four-antenna GNSS receiver, a barometer, and a pressure gauge; The data processing module is located in the equipment compartment below the buoy, and includes a built-in GNSS data processing unit, a filtering calculation unit, an attitude calculation unit, a sea surface height calculation unit, an environmental pressure data processing unit, and an attitude calculation unit; The data transmission module is located in the equipment platform above the buoy, and transmits the measured sea surface height data and the buoy status information to the monitoring service platform in real time. It is also used to transmit the PPP-B2b correction signal broadcast by the four-antenna GNSS receiver; The monitoring service platform is accessed through a browser, and is responsible for receiving the real-time sea surface height data transmitted by the buoy, and providing the display and analysis of real-time monitoring data.

[0013] The hardware of the deep-sea and far-sea sea surface height measurement system based on Beidou PPP-B2b includes: a buoy; The buoy includes an integrated equipment platform located above and an equipment compartment located below; The equipment platform is equipped with a four-antenna GNSS receiver, a short message antenna, a barometer, and a solar panel; The data processing module is installed inside the equipment compartment; the pressure gauge is arranged at the outer lower end of the equipment compartment; An anti-collision fence is installed around the equipment compartment.

[0014] Combining all the above technical solutions, the beneficial effects of the present invention are as follows: The present invention includes a data acquisition module, a data transmission module, and a data processing module integrated in the buoy, as well as a monitoring service platform for data visualization. In the present invention, there are obvious advantages in positioning accuracy and data transmission method. Especially in the context of the intensification of global climate change and the prominent problem of sea level rise, the system fills the gap of traditional technologies in the deep sea and far sea. It not only supports ship route planning and navigation safety, helps to avoid risks, but also provides basic sea surface information for deep-sea oil and gas development, wind farm construction, etc. At the same time, it provides long-term, stable and reliable data support for global climate change monitoring, marine environmental protection and deep-sea scientific research, and promotes the development of global marine science and industry.

[0015] The present invention realizes high-precision sea surface height measurement in deep-sea and far-sea areas through Beidou PPP-B2b technology, solves the limitation of traditional RTK technology relying on ground base stations, and has significant commercial potential. It can be applied to fields such as marine resource development, navigation safety, and climate change monitoring; in addition, the present invention overcomes the traditional technical prejudice, and through the Beidou PPP-B2b correction signal and short message communication technology, proves that high-precision measurement in deep-sea and far-sea areas can be achieved without the support of ground base stations, providing a new technical path for the fields of marine science and engineering. Description of the Drawings

[0016] The accompanying drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure; Figure 1 It is a flowchart of a deep - sea sea - surface height measurement method based on Beidou PPP - B2b provided by an embodiment of the present invention; Figure 2 It is a system diagram of a deep - sea sea - surface height measurement system based on Beidou PPP - B2b provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the hardware of a deep - sea sea - surface height measurement system based on Beidou PPP - B2b provided by an embodiment of the present invention; Figure 4 It is an original sea - surface height result diagram of a deep - sea sea - surface height measurement method based on Beidou PPP - B2b; Figure 5 It is a filtered result diagram of a deep - sea sea - surface height measurement method based on Beidou PPP - B2b.

[0017] In the figure: 1. Four - antenna GNSS receiver; 2. Short - message antenna; 3. Barometer; 4. Solar panel; 5. Equipment cabin; 6. Anti - collision fence; 7. Pressure gauge; 8. Buoy; 9. Equipment platform. Detailed implementation manners

[0018] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the following will give a detailed description of the specific implementation manners of the present invention with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific implementations disclosed below.

[0019] The innovation points of the present invention are as follows: By integrating a four - antenna GNSS receiver, a barometer, and a pressure gauge, and combining with the Beidou PPP - B2b precise correction signal, high - precision sea - surface height measurement is achieved; using a multi - antenna layout and a buoy attitude correction algorithm, the influence of buoy tilt on measurement accuracy is effectively eliminated; the complete ensemble empirical mode decomposition (CEEMD) algorithm is used to denoise the sea - surface height data, significantly improving the data quality. This system does not rely on ground base stations and is applicable to deep - sea areas, providing reliable data support for marine environment monitoring, navigation safety, and climate change research.

[0020] Embodiment 1, as Figure 1 shown, the deep - sea sea - surface height measurement method based on Beidou PPP - B2b includes: S1, integrating a data acquisition module, a data processing module, and a data transmission module on a buoy, and deploying the buoy to the target deep - sea area; S2. The four-antenna GNSS receiver, barometer, short message antenna at the top of the buoy, and the pressure gauge at the bottom of the buoy collect data and transmit it in real time to the data processing module in the equipment cabin; S3. The GNSS data processing unit in the data processing module receives the raw data from the four-antenna GNSS receiver and the PPP-B2b correction signal transmitted by the data transmission module, and calculates the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver based on the WGS84 coordinate system; S4. The attitude calculation unit in the data processing module receives the three-dimensional coordinates of the four-antenna GNSS receiver from the GNSS data processing unit, and corrects the attitude of the buoy using the buoy attitude correction algorithm based on the XYZ coordinate information of the four-antenna GNSS receiver to obtain the buoy height in the vertical direction; S5. The barometer and the pressure gauge transmit the measured sea pressure data and the water pressure data at the bottom of the buoy to the environmental pressure data processing unit in the data processing module, and calculate the draft depth of the buoy according to the built-in instantaneous average water depth algorithm; S6. Integrate the data from step S3 to step S5, and calculate the instantaneous sea surface height by the instantaneous sea surface height algorithm built in the sea surface height calculation unit of the data processing module; S7. Perform noise reduction processing on the calculated instantaneous sea surface height through the filter calculation unit; S8. Send the result to the monitoring service platform through the data transmission module.

[0021] Exemplarily, in S3, the GNSS data processing unit in the data processing module receives the raw data from the four-antenna GNSS receiver and the PPP-B2b correction signal transmitted by the data transmission module, and calculates the instantaneous geodetic height of the four-antenna GNSS receiver based on the WGS84 coordinate system, specifically including: S301. The PPP-B2b correction signal is broadcast in real time through the GEO satellites of BDS-3. Its generation process is as follows: First, continuous observations are made on the visible GNSS satellites using distributed encrypted high-precision continuous monitoring stations to collect pseudorange, carrier phase observation data, and meteorological data. Subsequently, the ground master control station verifies and evaluates the preprocessed data, fits correction parameters such as satellite orbits, clock biases, differential code biases, and user range accuracy indices (URAIs) through dynamic smoothing processing, and arranges the precise correction parameters according to the BDS protocol. The PPP-B2b information is encoded in binary format. After 64-ary low-density parity-check channel coding, the navigation message data frame of the PPP-B2b signal is concatenated with a synchronization header of 16 symbols, a satellite PRN number of 6 symbols, and a reserved identification bit of 6 symbols, totaling 1000 symbols. The broadcast time of each frame is 1 s. Finally, the uplink station transmits the correction parameters to the GEO satellite, and the GEO satellite broadcasts them through the I branch of the PPP-B2b correction signal. After the four-antenna GNSS receiver obtains the PPP-B2b correction signal, real-time precise point positioning can be achieved. Compared with traditional PPP that relies on the Internet to transmit correction information, the PPP-B2b correction signal can achieve high-precision positioning without an external network, which is especially suitable for areas difficult to cover by base stations such as the deep sea and remote regions.

[0022] S302. To ensure that the correction information broadcast by PPP-B2b can correctly match the corresponding ephemeris, each information type contains an IOD parameter for determining the matching strategy. It includes the IOD of the state space description data version (IOD SSR), the IOD of the mask data version (IODP), and the IODN and IOD Corr of the satellite orbit and clock bias correction information.

[0023] The matching of the corresponding ephemeris includes: IODSSR serves as the version identifier for the state space description data and is used to mark the update status of the current data generation configuration. In the broadcast information, IODSSR is an essential component. In practical applications, data matching and usage can only be achieved when the IODSSRs of various types of information received by the user are consistent; if the IODSSRs are inconsistent, matching cannot be completed. IODP is the version identifier for the masked data and is used to distinguish different versions of satellite mask information. This parameter is encoded in both the mask information and the clock offset parameter and is transmitted synchronously during broadcast. Matching usage can only be achieved when the IODPs of both are consistent. IODN is the version identifier for the satellite orbit and clock offset correction information. If the IOD of GNSS is inconsistent with the IODN broadcast by the PPP-B2b signal, it indicates that the navigation message has been updated. At this time, the system will preferentially use the old PPP-B2b signal and match it with the new signal after it is updated. The specific matching rules are as follows: the IODN of GPS matches the IODC of the LNAV navigation message, and the IODN of BDS-3 matches the IODC of the CNAV1 navigation message. IODCorr is the version identifier for the satellite orbit and clock offset correction information. When the IODCorrs of the orbit and clock offset are consistent, they can be combined for use; if they are inconsistent, matching cannot be achieved.

[0024] S303. In the present invention, the buoy realizes high-precision positioning by receiving the orbit and clock offset correction information provided by the Beidou PPP-B2b correction signal and combining the pseudorange and carrier phase observations of the four-antenna GNSS receiver. Pseudorange and carrier phase are the core observables for GNSS precise positioning, and their original observation value expressions are the commonly used PPP positioning models. The formulas are as follows: ; ; In the formula, the superscript represents the satellite system, and the subscripts and represent the receiver and the frequency respectively; and are the original pseudorange measurement value and the original carrier phase measurement value respectively; represents the geometric distance between the satellite and the site; is the speed of light; and represent the receiver clock offset at the signal reception time and the satellite clock offset at the signal transmission time respectively; and represent the time delays of the pseudorange observations caused by the receiver and satellite hardware respectively; and represent the ionospheric delay and the tropospheric delay during the propagation of the signal of frequency j from the satellite to the receiver respectively; and are the carrier wavelength and the integer ambiguity of the carrier phase, respectively; and represent the phase time delays caused by satellite and receiver hardware delays, respectively; represents the error term independent of frequency; and represent the multipath effects and other unmodeled noises of the pseudorange observation and the carrier observation, respectively.

[0025] S304. The satellite orbit correction parameters provided by the PPP-B2b correction signal include the correction values of three components: radial (R), tangential (A), and normal (C), with the unit of meter. These correction parameters are used to correct the CNAV1 broadcast ephemeris broadcast through the B1C signal. According to the document issued by Beidou, the specific formula is as follows: ; In the formula, is the satellite position after correction by the orbit correction parameters, is the satellite position calculated from the CNAV1 navigation message of the B1C signal, is the satellite position correction vector; The calculation formula of ; In the formula, are the unit vectors in the radial, tangential, and normal directions, respectively, is the orbit correction vector obtained from the PPP-B2b correction signal, and the components are in the order of the radial, tangential, and normal directions; ; In the formula, are the satellite position vector and velocity vector calculated from the CNAV1 navigation message of the B1C signal, respectively; S305. The clock offset correction information provided by the PPP-B2b correction signal is the correction of the clock offset of the broadcast ephemeris. According to the document issued by Beidou, the correction method is as follows: ; In the formula, is the satellite clock offset after correction by the clock offset correction parameters of the PPP-B2b correction signal, is the satellite clock offset calculated from the CNAV1 navigation message, is the clock offset correction parameter, is the speed of light.

[0026] S306. In the present invention, the buoy adopts a four-antenna GNSS receiver layout, where three secondary GNSS receivers are roughly scattered around the circumference, forming a layout of the vertices of a triangle, and the primary GNSS receiver is located at the center of the circle. The primary GNSS receiver is equipped with a primary antenna, and each of the three secondary GNSS receivers is equipped with a secondary antenna. After being corrected by PPP-B2b, the pseudorange observation value and the carrier phase observation value are used to calculate the geometric distance between the primary antenna and the satellite ,

[0027] where is the satellite coordinate, is the coordinate of the primary antenna of the buoy, and the Z coordinate is the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver under the WGS84 coordinate system .

[0028] Exemplarily, in step S4, the attitude of the buoy is corrected using the buoy attitude correction algorithm to obtain the height of the buoy in the vertical direction, including: S401. The four-antenna GNSS receiver on the buoy collects GNSS signals from satellites, and the primary antenna and the three secondary antennas respectively obtain independent coordinate data, usually three-dimensional X, Y, and Z coordinates; S402. The primary antenna (labeled 4) of the primary GNSS receiver of the buoy is located at the center of the circle, and the secondary antennas (labeled 1, 2, and 3 respectively) of the remaining three secondary GNSS receivers are distributed around the circumference, forming an equilateral triangle. The baseline vector represents the relative position relationship between the primary antenna and the secondary antenna: ; In the formula, are the coordinates of the three secondary antennas, is the coordinate of the primary antenna; S403. Calculate the roll angle of the buoy, which represents the rotation angle of the buoy around the X-axis. The calculation formula is: ; In the formula, are the components of the baseline vector on the Y-axis and Z-axis respectively; S404. Calculate the pitch angle of the buoy, which represents the rotation angle of the buoy around the Y-axis. The calculation formula is: ; In the formula, respectively represent the components of the baseline vector on the X-axis and Z-axis; S405. After obtaining the pitch angle and roll angle, calculate the tilt angle of the GNSS main antenna support rod of the buoy body. , the expression is: ; Based on the three-dimensional geometric relationship, it reflects the total tilt angle of the buoy body relative to the vertical direction; S406. The height difference between the phase center of the GNSS main antenna at the top of the buoy and the bottom end of the pressure gauge , when the buoy is tilted, the height in the vertical direction is .

[0029] Exemplarily, the environmental pressure data processing unit in the data processing module to which the step S5 is transmitted calculates the draft depth of the buoy according to the built-in instantaneous average water depth algorithm, including: S501. Calculate the draft depth according to the atmospheric pressure collected by the barometer at the top of the buoy and the water pressure collected by the pressure gauge at the bottom of the buoy. The instantaneous water depth measured by each pressure gauge is: ; In the formula, is the total pressure measured by the th pressure gauge, is the atmospheric pressure measured by the current barometer, is the seawater density, usually taken as 1025 kg / m 3 ; is the acceleration due to gravity, approximately 9.81 m / s 2 ; There are four pressure gauges; S502. Calculate the water depths of the four pressure gauges , and take the average value to obtain the instantaneous average water depth at the bottom of the buoy, and the expression is: ; Exemplarily, in step S6, the instantaneous sea surface height is calculated by the instantaneous sea surface height algorithm built in the sea surface height calculation unit of the data processing module, including: Calculate the instantaneous sea surface height of the buoy at present, and the expression is: ; In the formula, is the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver, is the height difference between the phase center of the top GNSS antenna and the bottom of the pressure gauge, is the angle between the buoy and the vertical direction, is the draft depth of the buoy.

[0030] Exemplarily, in step S7, the calculated instantaneous sea surface height is denoised by a filtering calculation unit, including: For the swell and noise contained in the acquired instantaneous sea surface height data, the complete ensemble empirical mode decomposition method (CEEMD) is used to hierarchically extract the intrinsic mode function components (IMFs) to complete the denoising of the swell and noise.

[0031] Among them, the complete ensemble empirical mode decomposition method (CEEMD), an improved recursive denoising algorithm based on EMD and EMMD, reduces the number of screening iterations and further weakens the mode mixing phenomenon. It has great advantages for filtering the sea tide height time series. The IMF hierarchical extraction is completed through the following steps; specifically including: S701, in the original signal Add Gaussian white noise , and the expression is: ; In the formula, is the initial signal-to-noise ratio coefficient; Perform times of EMD decomposition, and calculate the average to obtain the first intrinsic mode function component , and the expression is: ; In the formula, is the first intrinsic mode function obtained by decomposing through the EMD method, is Gaussian white noise with a unit variance of 0, ; is the signal-to-noise ratio coefficient decomposed by the CEEMD method for , is Gaussian white noise with a unit variance of 0; Subtract the original signal from to obtain the first-order residual , and the expression is: ; S702, add Gaussian white noise to the obtained first-order residual , and the signal is expressed as: , decompose again to obtain the second intrinsic mode function , and subtract from to obtain the first-order residual , and the expression is: ; ; S703, and so on, continue to perform times of decomposition. When obtaining the signal , calculate the th intrinsic mode function component and order residual; ; ; S704. Cyclically calculate to obtain the intrinsic mode components and residual values until the number of extreme points of the residual is no more than 2, then the decomposition ends. The final signal is expressed as: ; In the formula, is the number of IMF components obtained by decomposing using the CEEMD method.

[0032] Example 2, as Figure 2 shown, the embodiment of the present invention provides a deep - sea and far - sea sea surface height measurement system based on Beidou PPP - B2b, which includes a data acquisition module, a data transmission module, a data processing module integrated in the buoy 8, and a monitoring service platform for data visualization; The design of the modules of the deep - sea and far - sea sea surface height measurement system based on Beidou PPP - B2b of the present invention ensures that high - precision and stable data acquisition can be provided in the deep - sea and far - sea areas, without relying on the support of ground base stations, and overcomes the limitations of traditional ocean measurement methods; The data acquisition module includes a four - antenna GNSS receiver 1, a barometer 3, and a pressure gauge 7, as Figure 3 ; The layout of the four - antenna GNSS receiver is as follows: three sub - GNSS receivers are roughly dispersed around the circumference, forming a layout of the vertices of a triangle, and the main GNSS receiver is located at the center of the circle. The main GNSS receiver is equipped with a main antenna, and each of the three sub - GNSS receivers is equipped with a sub - antenna; The barometer 3, like the receiver, is connected to the circular bracket below; The pressure gauge 7 is installed in the bottom area of the buoy, and the four pressure gauges are distributed in a cross shape to measure the pressure of the surrounding water body.

[0033] The data processing module is located in the equipment compartment 5 below the buoy 8, and includes a built - in GNSS data processing unit, a filtering calculation unit, an attitude calculation unit, a sea surface height calculation unit (sea surface instantaneous height calculation unit), an environmental pressure data processing unit (draft depth calculation unit), and an attitude calculation unit; The data transmission module is located in the equipment platform 9 above the buoy 1. It has the function of Beidou short message service, and can transmit the measured sea surface height data and buoy status information to the monitoring service platform in real time. In addition, it also has the function of broadcasting PPP-B2b correction signals to the four-antenna GNSS receiver 1; The monitoring service platform can be accessed through a browser, and is responsible for receiving the real-time sea surface height data transmitted by the buoy, and providing the functions of displaying and analyzing real-time monitoring data; Exemplarily, the four-antenna GNSS receiver 1 transmits the received data to the GNSS data processing unit, and the GNSS data processing unit simultaneously receives the PPP-B2b correction signal data transmitted by the data transmission module; The GNSS data processing unit transmits the processed data to the attitude calculation unit, and the attitude calculation unit transmits the processed data to the sea surface height calculation unit. At the same time, the environmental pressure data processing unit sends the processed data of the barometer 3 and the pressure gauge 7 to the sea surface height calculation unit; The sea surface height calculation unit transmits the calculated instantaneous height and buoy status information, etc. to the filtering calculation unit, and the filtering calculation unit sends the processed data through the filtering algorithm to the data transmission module, and sends it to the monitoring service platform through the short message service data.

[0034] Another example is as Figure 3 As shown, the hardware of a deep-sea and far-sea sea surface height measurement system based on Beidou PPP-B2b provided by an embodiment of the present invention includes: a four-antenna GNSS receiver 1, a short message antenna 2, a barometer 3, a solar panel 4, an equipment cabin 5, a collision prevention fence 6, a pressure gauge 7, a buoy 8, and an equipment platform 9; The buoy 8 includes an integrated equipment platform 9 located above and an equipment cabin 5 located below; The four-antenna GNSS receiver 1, the short message antenna 2, the barometer 3, and the solar panel 4 are installed on the equipment platform 9; The solar panel 4 provides energy for the four-antenna GNSS receiver 1, the short message antenna 2, the barometer 3, and the pressure gauge 7; the short message antenna 2 can be used as a data transmission module.

[0035] The equipment cabin 5 is internally equipped with a data processing module; the pressure gauges 7 are arranged at the outer lower end of the equipment cabin 5, and there can be multiple; The collision prevention fence 6 is installed on the periphery of the equipment cabin 5.

[0036] The deep-sea and far-sea sea surface height measurement device based on Beidou PPP-B2b is signal-connected to an external monitoring service platform through the short message antenna 2.

[0037] This experiment was conducted in a certain test sea area in Qing. The water depth in this area is moderate and the sea conditions are complex, which can better simulate the environmental conditions of the deep and far - sea areas. After the buoy was assembled, it was deployed at sea. During the test period, the buoy performed stably without phenomena such as tipping, capsizing or violent fluctuations, verifying the reliability of the buoy structure and its ability to resist wind and waves. At the same time, a radar and a tide gauge were deployed in the test area as reference devices to verify the accuracy of the measurement results by comparison.

[0038] The four - antenna GNSS receiver at the top of the buoy receives the pseudorange and carrier - phase observations from multiple GNSS satellites in real - time. At the same time, it collects atmospheric pressure and water pressure data through a barometer and a pressure gauge. Using the precise orbit and clock - bias information provided by the Beidou PPP - B2b correction signal, the errors of the pseudorange and carrier - phase observations are corrected to ensure the positioning accuracy. Through the buoy attitude correction algorithm, based on the coordinate data of the four - antenna GNSS receiver, the tilt angle of the buoy is calculated, and the draft is calculated in combination with the data of the water pressure gauge and the barometer. After integrating the above data, a tidal chart is generated by the sea - surface height calculation unit (as shown in Figure 4 ). This chart clearly reflects the changing trend of the sea - surface height and is compared with the measurement results of the radar and the tide gauge, verifying the high - precision measurement ability of the present invention in the deep and far - sea areas.

[0039] To further improve the data quality, the Complete Ensemble Empirical Mode Decomposition (CEEMD) algorithm is used to denoise the sea - surface height data to eliminate the influence of swell and noise on the measurement results. As shown in Figure 5 the tidal chart after CEEMD filtering shows that the data noise is significantly reduced, and the changing trend of the sea - surface height is smoother and clearer. This result further verifies the data stability and reliability of the present invention under complex sea conditions and is consistent with the reference data of the radar and the tide gauge, demonstrating the measurement accuracy and practicality of the present invention.

[0040] The present invention has obvious advantages in positioning accuracy and data transmission mode. Especially in the open sea area without ground-based signal coverage, high-precision sea surface height measurement is achieved through the PPP-B2b precise point positioning technology of Beidou-3. The system realizes two-way communication through the Beidou short message function, ensuring the continuous operation and real-time data transmission of the measurement equipment in the deep and far sea environment, improving the intelligence and automation level of the system, and having important significance in the fields of ocean monitoring, ocean resource development, navigation safety, weather forecasting and environmental protection. Especially against the background of the intensification of global climate change and the prominent problem of sea level rise, accurate sea surface height measurement is crucial for ocean environmental monitoring, ocean disaster early warning (such as storm surges, tsunamis) and the protection of coastal infrastructure. This system fills the gap of traditional technologies in the deep and far sea. It not only supports ship route planning and navigation safety, helps to avoid risks, but also provides basic sea surface information for deep-sea oil and gas development, wind farm construction, etc. At the same time, it provides long-term, stable and reliable data support for global climate change monitoring, ocean environmental protection and deep-sea scientific research, promoting the development of global ocean science and industry.

[0041] As described above, only the relatively optimal specific implementation mode of the present invention is provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for measuring deep sea surface height based on Beidou PPP-B2b, characterized in that: The method comprises the following steps: S1, integrating the data acquisition module, data processing module and data transmission module on the buoy, and deploying the buoy to the target deep sea area; S2, the four-antenna GNSS receiver, barometer, short message antenna on the top of the buoy and the pressure gauge at the bottom of the buoy collect data and transmit it in real time to the data processing module in the equipment cabin; S3, the GNSS data processing unit in the data processing module receives the raw data from the four-antenna GNSS receiver and the PPP-B2b correction signal transmitted by the data transmission module, and calculates the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver based on the WGS84 coordinate system; S4, the attitude calculation unit in the data processing module receives the three-dimensional coordinates of the four-antenna GNSS receiver from the GNSS data processing unit, and corrects the buoy attitude using the buoy attitude correction algorithm based on the XYZ coordinate information of the four-antenna GNSS receiver to obtain the buoy height in the vertical direction; S5, the barometer and the pressure gauge transmit the measured sea pressure data and the water pressure data at the bottom of the buoy to the environmental pressure data processing unit in the data processing module, and calculate the draft depth of the buoy according to the built-in instantaneous average water depth algorithm; S6, integrating the data from step S3 to step S5, and calculating the instantaneous sea surface height by the sea surface instantaneous height algorithm built into the sea surface height calculation unit of the data processing module; S7, performing noise reduction processing on the calculated instantaneous sea surface height through a filtering calculation unit; S8, sending the results to the monitoring service platform through the data transmission module.

2. The deep sea surface height measurement method based on Beidou PPP-B2b according to claim 1 is characterized in that: In step S3, the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver based on the WGS84 coordinate system is calculated, including: S301, PPP-B2b correction signal is broadcast in real time via BeiDou-3’s GEO satellite; S302, the correction information broadcast by PPP-B2b matches the corresponding ephemeris; S303, the buoy performs positioning by receiving the orbit and clock correction information provided by the Beidou PPP-B2b correction signal, combined with the pseudorange and carrier phase observation values ​​of the four-antenna GNSS receiver; S304, correcting the CNAV1 broadcast ephemeris broadcasted via the B1C signal using the satellite orbit correction parameters provided by the PPP-B2b correction signal; S305, using the clock correction information provided by the PPP-B2b correction signal to correct the broadcast ephemeris clock error; S306, the buoy adopts a four-antenna GNSS receiver layout, and the three secondary GNSS receivers are scattered around the circumference to form a triangle vertex layout. The main GNSS receiver is located at the center of the circle. The main GNSS receiver is equipped with a main antenna, and the three secondary GNSS receivers are equipped with a secondary antenna respectively. After the correction of PPP-B2b, the pseudorange observation value and carrier phase observations Calculate the geometric distance between the main antenna and the satellite , the expression is: ； In the formula, are the satellite coordinates, is the coordinates of the buoy main antenna; The Z coordinate is the instantaneous geodetic height of the antenna of the four-antenna GNSS receiver in the WGS84 coordinate system. .

3. The deep sea surface height measurement method based on Beidou PPP-B2b according to claim 2 is characterized in that: In step S301, the PPP-B2b correction signal is broadcasted in real time through the GEO satellite of BeiDou-3, including: using distributed encrypted high-precision continuous monitoring stations to continuously observe GNSS visible satellites, collect pseudorange, carrier phase observation data and meteorological data; the ground master control station verifies and evaluates the pre-processed data, fits the satellite orbit, clock error, differential code deviation and user ranging accuracy index URAI correction parameters through dynamic smoothing processing, and arranges the precise correction parameters according to the protocol; the uplink station transmits the correction parameters to the GEO satellite, which is broadcast by the GEO satellite through the I branch of the PPP-B2b correction signal; In step S304, the CNAV1 broadcast ephemeris broadcasted via the B1C signal is corrected using the satellite orbit correction parameters provided by the PPP-B2b correction signal, as expressed by: ； In the formula, is the satellite position after the orbit correction parameters are corrected, The satellite position calculated from the CNAV1 navigation message of the B1C signal, is the satellite position correction vector; The calculation formula is: ； In the formula, are the unit vectors of radial, tangential and normal directions respectively, is the orbit correction vector obtained from the PPP-B2b correction signal, in the order of radial, tangential and normal components; ； In the formula, are the satellite position vector and velocity vector calculated from the B1C signal CNAV1 navigation message; In step S305, the broadcast ephemeris clock error is corrected using the clock error correction information provided by the PPP-B2b correction signal, and the expression is: ； In the formula, is the satellite clock error obtained after correction by the clock error correction parameters of the PPP-B2b correction signal, is the satellite clock error calculated from the CNAV1 navigation message, is the clock correction parameter, The speed of light.

4. The method for measuring deep sea surface height based on Beidou PPP-B2b according to claim 1, characterized in that: In step S4, the buoy attitude is corrected using a buoy attitude correction algorithm based on the XYZ coordinate information of the four-antenna GNSS receiver to obtain the buoy height in the vertical direction, including: S401, the four-antenna GNSS receiver on the buoy collects GNSS signals from the satellite, and the main antenna and three sub-antennas obtain independent coordinate data, three-dimensional X, Y, and Z coordinates; S402, the main antenna of the main GNSS receiver of the buoy is located at the center of the circle, and the auxiliary antennas of the three auxiliary GNSS receivers are distributed around the circumference to form an equilateral triangle. The baseline vector It represents the relative position relationship between the main antenna and the secondary antenna, and the expression is: ； In the formula, are the coordinates of the three sub-antennas, is the main antenna coordinates; S403, calculate the rolling angle of the buoy , represents the rotation angle of the buoy around the X-axis, and the calculation formula is: ； In the formula, The baseline vector Components on the Y and Z axes; S404, calculate the pitch angle of the buoy , represents the rotation angle of the buoy around the Y axis, and the calculation formula is: ； In the formula, Represents the baseline vector Components in the X and Z axes; S405, after obtaining the pitch angle and the roll angle, calculate the inclination angle of the buoy body GNSS main antenna support rod , the expression is: ； Based on the three-dimensional geometric relationship, it reflects the total inclination angle of the buoy body relative to the vertical direction; S406, height difference from the phase center of the GNSS main antenna on the top of the buoy to the bottom of the water pressure gauge , when the buoy is tilted, the vertical height is .

5. The method for measuring deep sea surface height based on Beidou PPP-B2b according to claim 1, characterized in that: In step S5, the ambient pressure data processing unit in the data processing module calculates the draft of the buoy according to the built-in instantaneous average water depth algorithm, including: S501, calculate the draft depth based on the atmospheric pressure collected by the barometer on the top of the buoy and the water pressure collected by the pressure gauge on the bottom of the buoy. Each pressure gauge measures the instantaneous water depth. for: ； In the formula, For the The total pressure measured by the manometers is is the atmospheric pressure measured by the current barometer, is the density of seawater, is the acceleration due to gravity; S502, calculate the water depth of four pressure gauges , take the average value to get the instantaneous average water depth at the bottom of the buoy , the expression is: 。 6. The method for measuring deep sea surface height based on Beidou PPP-B2b according to claim 1, characterized in that: In step S6, the instantaneous sea surface height is calculated by the instantaneous sea surface height algorithm built into the sea surface height calculation unit of the data processing module, including: Calculate the current instantaneous sea surface height of the buoy , the expression is: ； In the formula, is the instantaneous geodetic height of the antennas of the four-antenna GNSS receiver, is the height difference from the phase center of the top GNSS antenna to the pressure gauge section, is the angle between the buoy and the vertical direction, is the draft depth of the buoy.

7. The method for measuring deep sea surface height based on Beidou PPP-B2b according to claim 1, characterized in that: In step S7, the calculated instantaneous sea surface height is subjected to noise reduction processing by a filtering calculation unit, including: For the surge and noise contained in the acquired instantaneous sea surface height data, the complete ensemble empirical mode decomposition method (CEEMD) is used to perform hierarchical extraction of intrinsic mode function components (IMF) to achieve denoising of surge and noise.

8. The method for measuring deep sea surface height based on Beidou PPP-B2b according to claim 7 is characterized in that: The complete ensemble empirical mode decomposition method CEEMD is used to perform hierarchical extraction of intrinsic mode function components IMF, including: S701, in the original signal Add Gaussian white noise , the expression is: ； In the formula, is the initial signal-to-noise ratio coefficient; conduct Second EMD decomposition, average calculation to obtain the first intrinsic mode function component , the expression is: ； In the formula, for The first intrinsic mode function obtained by EMD decomposition is: is Gaussian white noise with unit variance of 0, ; Decomposed by CEEMD method indivual The signal-to-noise ratio coefficient under is Gaussian white noise with unit variance of 0; The original signal and Subtract to get the first-order residual , the expression is: ； S702, the first-order residual obtained Adding Gaussian white noise, the signal is expressed as: , decompose again to obtain the second intrinsic eigenmode function ,Will and Subtract to get the first-order residual , the expression is: ； ； S703, and so on, continue Decomposition, after getting the signal , calculate the IMF components and order residual; ； ； S704, loop calculation to obtain the intrinsic mode components and residual values, until the number of residual extreme value points is no more than 2, the decomposition is completed, and the final signal is expressed as: ； In the formula, is the number of IMF components decomposed by the CEEMD method.

9. A deep sea surface height measurement system based on Beidou PPP-B2b, characterized in that: The system implements the deep-sea sea surface height measurement method based on Beidou PPP-B2b as described in any one of claims 1 to 8, and the system includes: a data acquisition module, a data transmission module, a data processing module and a monitoring service platform; The data acquisition module includes a four-antenna GNSS receiver, a barometer and a pressure gauge; The data processing module is located in the equipment compartment below the buoy, and has built-in GNSS data processing unit, filter calculation unit, attitude calculation unit, sea level height calculation unit, environmental pressure data processing unit and attitude calculation unit; The data transmission module is located in the equipment platform above the buoy, and transmits the measured sea surface height data and buoy status information to the monitoring service platform in real time. It is also used to transmit the PPP-B2b correction signal broadcast by the four-antenna GNSS receiver; The monitoring service platform is accessed through a browser, is responsible for receiving real-time sea surface height data transmitted by the buoy, and provides display and analysis of real-time monitoring data.

10. The deep sea surface height measurement system based on Beidou PPP-B2b according to claim 9 is characterized in that: The hardware of the system includes: a buoy (8); The buoy (8) comprises an integrated equipment platform (9) located above and an equipment bin (5) located below; The equipment platform (9) is equipped with a four-antenna GNSS receiver (1), a short message antenna (2), a barometer (3), and a solar panel (4); The equipment cabin (5) is provided with a data processing module inside; the pressure gauge (7) is arranged at the outer lower end of the equipment cabin (5); A crash barrier (6) is installed on the periphery of the equipment cabin (5).

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