A high-precision ocean timing method and system based on Beidou satellite

Abstract

The invention discloses a method and system for high-precision ocean timing based on Beidou satellites, which belongs to the field of satellite timing technology, including: establishing a position parameter random model based on the motion state of the ocean; establishing a signal-to-noise ratio random model based on the Beidou-3 PPP-B2b accuracy and the signal-to-noise ratio of the satellite on the ocean; adding the position parameter random model and the signal-to-noise ratio random model into the PPP equation to generate receiver clock error parameters; and transferring the receiver clock error parameters into a clock calibrator module for clock training. The method and system for high-precision ocean timing based on Beidou satellites, by receiving the orbit and clock error correction numbers broadcasted by the Beidou-3 satellite precise point positioning service (PPP-B2b), overcomes the problems of no Internet, no base station, complex environment and low timing accuracy in the existing ocean, and realizes high-precision single-station timing in a deep sea environment, and the timing accuracy can even reach the sub-nanosecond level, thereby providing high-precision time information services for the establishment of an ocean space-time benchmark.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite timing, and in particular relates to a high-precision ocean timing method and system based on Beidou satellites. Background Art

[0002] Timing service is one of the main functions of GNSS, which can provide high-precision time information in real time. However, in deep sea environments, due to the complex environment, the lack of reference base stations, and the lack of network, its timing accuracy and reliability still have certain problems.

[0003] On land, the receiver can be considered to be stationary, the network communication conditions are relatively good, and there are a large number of CORS stations that can provide corresponding services. However, in the deep sea environment, the receiver is always in motion with the fluctuation of the sea surface environment, and the elevation direction of the position parameter and the receiver clock error parameter have a strong correlation, which makes it difficult to completely separate the receiver clock error parameter from the position elevation parameter, resulting in low timing accuracy. Currently, ocean timing is mostly based on the pseudorange single point positioning model (SPP), which is only based on pseudorange observations. Its accuracy is low and it is difficult to meet high-precision time requirements. Therefore, in deep sea timing, a reliable deep sea timing method to improve timing accuracy is very important.

[0004] Currently, satellite timing methods mainly include: (1) single-station satellite timing, which is mostly based on pseudo-range single-point positioning method with an accuracy of about 10 to 20 nanoseconds; (2) common view timing and full view timing, which are based on pseudo-range observations and require a network to transmit data, with an accuracy of about 2 to 5 nanoseconds; (3) PPP high-precision timing method based on analysis center products, with an accuracy of about 1 ns.

[0005] Currently, ocean timing is mostly based on the first method. Although the third method can achieve nanosecond to sub-nanosecond accuracy, it is difficult to apply to deep sea timing because the third method relies on the network to transmit correction data and is difficult to apply to the dynamic ocean environment.

[0006] Although the current satellite timing has achieved certain results, the current satellite timing method (SPP) is still not enough to meet the high-precision requirements in the deep sea environment, and the timing accuracy is about (10-20ns). If a satellite is rented for communication, it will be expensive, which is not conducive to large-scale application. The PPP timing method based on the analysis center product can achieve high-precision timing with a timing accuracy of about 1 nanosecond, but it is difficult to transmit the corresponding correction number through the Internet in an ocean environment without a network, and this PPP timing method will fail. In addition, the current satellite timing is applied to static stations on land, while the stations on the ocean are always in motion. There is no good solution for this dynamic high-precision satellite timing. Therefore, it is necessary to develop a new high-precision ocean timing method and system based on Beidou satellites to solve the existing problems. Summary of the invention

[0007] The purpose of the present invention is to provide a high-precision ocean timing method and system based on Beidou satellites to solve the problem of low ocean timing accuracy.

[0008] To achieve the above object, the present invention provides the following technical solution: a high-precision ocean timing method based on Beidou satellite, comprising the following steps:

[0009] Build a receiver clock model and determine the process noise of the random walk model;

[0010] Establish a random model of position parameters that takes into account the ocean motion state to reduce the correlation between the receiver clock error and the coordinate elevation direction;

[0011] Establish a signal-to-noise ratio stochastic model considering the accuracy of BeiDou-3 PPP-B2b and the signal-to-noise ratio of satellites over the ocean;

[0012] Generate receiver clock error parameters;

[0013] Clock training uses the PPP timing method based on the PPP-B2b correction number of Beidou-3 to estimate the receiver clock error in real time, achieve high-precision synchronization with the local synchronization clock of the Beidou clock, and complete high-precision ocean timing.

[0014] Preferably, the step of establishing a receiver clock model and determining the process noise of the random walk model comprises the following steps:

[0015] The receiver is placed on land for continuous static observation for a period of time to obtain the data of the receiver clock. The data of the receiver clock during this period of time is analyzed to determine whether there is a clock jump phenomenon. If a clock jump phenomenon exists, a receiver clock jump detection algorithm is established, and the threshold of clock jump detection is determined according to the size of the receiver clock jump. Subsequently, the Allan variance is used to analyze the characteristics of the receiver clock and a receiver clock model is established according to the Allan variance value of the corresponding sampling interval. Specifically, the receiver clock error of the receiver is calculated using the GPS precise single-point positioning method, and then the Allan variance is used to calculate the Allan variance value of the receiver clock error. Then, the Allan variance value of the corresponding sampling interval is calculated according to the calculation formula of the Allan variance; a random walk model is used to estimate the receiver clock error parameters, and the process noise of the random walk model is determined by the Allan variance.

[0016] Preferably, the threshold does not exceed 2 ns.

[0017] Preferably, the method of establishing a random model of position parameters to reduce the correlation between the receiver clock error and the coordinate elevation direction comprises the following steps:

[0018] Place the receiver on an ocean buoy, collect at least one week of observation data, calculate the coordinates of the receiver, and then obtain the coordinate sequence of the ocean motion carrier, analyze the motion state and characteristics of the ocean motion carrier, deeply mine the coordinate sequence of the carrier on the ocean, obtain the corresponding noise and characteristics, and use the size of the noise as random noise, as the random noise of the receiver position parameters in the subsequent Kalman filter parameter estimator, so as to reduce the correlation between the receiver clock error and the coordinate elevation direction.

[0019] Preferably, the established signal-to-noise ratio random model considering the BeiDou-3 PPP-B2b accuracy and the satellite signal-to-noise ratio over the ocean is solved:

[0020] Collect PPP-B2b corrections for a period of time, decode and merge them with broadcast ephemeris to generate precise ephemeris; compare the generated precise ephemeris with the existing final precise ephemeris, analyze the accuracy of the orbit and clock generated by the real-time corrections provided by PPP-B2b, and add this accuracy and signal-to-noise ratio to the random model of PPP to achieve the final solution. Analyzing the accuracy of the orbit and clock generated by the real-time corrections provided by PPP-B2b includes: comparing the real-time merged satellite orbit and clock products with the subsequent products to obtain the accuracy of the real-time merged products;

[0021] Preferably, the generating of the receiver clock error parameters comprises the following steps:

[0022] The receiver installed on the ocean moving carrier receives the broadcast ephemeris, observation values, and PPP-B2b corrections; decodes the PPP-B2b corrections and generates precise ephemeris in real time with the broadcast ephemeris. The precise ephemeris includes precise orbit and precise clock error. The precise orbit generation formula is:

[0023]

[0024] Where X is the precision track; (e r ,e a ,e c ) Transformation matrix in the three directions of meridian, normal and tangential; X brd Satellite coordinates calculated from broadcast ephemeris; △C is the PPP-B2b correction number broadcast by BeiDou-3; and r is the satellite velocity and position vector; δC r ,δC a ,δC c It is the correction number in radial, normal and tangential directions;

[0025] The precise clock error calculation formula can be expressed as:

[0026]

[0027] t brd The satellite clock error calculated by broadcast ephemeris; t is the generated precise ephemeris; △t is the PPP-B2b clock error correction number broadcast by BeiDou-3; the PPP function model is constructed by combining the observations and various error models. The model adopts an ionosphere-free combination model, and the established receiver clock model, the position parameter random model considering the ocean motion state, and the signal-to-noise ratio random model considering the BeiDou-3 PPP-B2b accuracy and the satellite signal-to-noise ratio over the ocean are added to the PPP equation to solve the receiver clock error.

[0028] Preferably, the clock training includes the following steps: using a constant temperature crystal oscillator as the clock source of the timing device, using the PPP timing method based on the PPP-B2b correction number broadcast by Beidou-3 to estimate the receiver clock error in real time, and transmitting the receiver clock error to the clock calibrator module of FPGA+ARM to adjust the constant temperature crystal oscillator in real time to achieve high-precision synchronization with the local synchronization clock of the Beidou clock, wherein the clock calibrator includes a local voltage-controlled crystal oscillator and a D / A conversion module, and outputs 1PPS and 10MHz clock information.

[0029] The present invention also discloses a Beidou satellite-based marine high-precision timing system, comprising:

[0030] A receiver clock model building module is used to build a receiver clock model and determine the process noise of the random walk model;

[0031] The module for establishing the random model of position parameters is used to establish the random model of position parameters taking into account the ocean motion state, and reduce the correlation between the receiver clock error and the coordinate elevation direction;

[0032] The signal-to-noise ratio random model building module is used to build a signal-to-noise ratio random model that takes into account the accuracy of BeiDou-3 PPP-B2b and the signal-to-noise ratio of satellites over the ocean;

[0033] A clock error parameter generation module, used to generate receiver clock error parameters;

[0034] The clock training module is used to estimate the receiver clock error in real time using the PPP timing method based on the PPP-B2b correction number of Beidou-3, achieve high-precision synchronization with the local synchronization clock of the Beidou clock, and complete high-precision marine timing.

[0035] The technical effects and advantages of the present invention are as follows: the Beidou satellite-based high-precision ocean timing method and system, by receiving the orbit and clock correction numbers broadcast by the Beidou-3 satellite precise point positioning service (PPP-B2b), overcomes the existing problems of no Internet, no base station, complex environment and low timing accuracy in the ocean, and realizes high-precision single-station timing in a deep sea environment. The timing accuracy can even reach the sub-nanosecond level, thereby providing high-precision time information services for the establishment of an ocean space-time benchmark. The present invention is not only applicable to ocean timing, but also to land, so it has the advantages of a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flowchart of the method according to an embodiment of the present invention;

[0037] Figure 2 A flow chart of modeling a receiver clock in the method according to an embodiment of the present invention;

[0038] Figure 3 This is a flowchart of the implementation of the timing device based on BeiDou-3 in the method described in an embodiment of the present invention;

[0039] Figure 4 The figure is a functional block diagram of the system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Embodiment 1

[0042] like Figure 1As shown, the present invention discloses a high-precision ocean timing method based on Beidou satellite, comprising the following steps:

[0043] Build a receiver clock model and determine the process noise of the random walk model;

[0044] Establish a random model of position parameters that takes into account the ocean motion state to reduce the correlation between the receiver clock error and the coordinate elevation direction;

[0045] A signal-to-noise ratio stochastic model considering the BeiDou Precise Point Positioning Service (PPP-B2b) accuracy and the satellite signal-to-noise ratio over the ocean is established;

[0046] Generate receiver clock error parameters;

[0047] Clock training uses the PPP timing method based on Beidou's PPP-B2b correction number to estimate the receiver clock error in real time, achieve high-precision synchronization with the local synchronization clock of the Beidou clock, and complete high-precision ocean timing.

[0048] The following is a detailed description of the above steps based on the specific content:

[0049] Step 1: Establish a receiver clock model;

[0050] The receiver is placed on land for continuous static observation for one week to obtain the data of the receiver clock. The data of the receiver clock for one week is analyzed to determine whether there is a clock jump phenomenon. If there is a clock jump phenomenon, a receiver clock jump detection algorithm is established. The threshold of clock jump detection is determined according to the size of the receiver clock jump. Then, the Allan variance is used to analyze the characteristics of the receiver clock and the receiver clock model is established according to the Allan variance value of the corresponding sampling interval. The random walk model is used to estimate the receiver clock error parameters. The process noise of the random walk model is determined by the Allan variance. The implementation process is as follows: Figure 2 shown.

[0051] Step 2: Establish a random model of position parameters taking into account the ocean motion state;

[0052] Place the receiver on an ocean buoy, collect observation data for at least one week, calculate the coordinates of the receiver afterwards, and then obtain the coordinate sequence of the ocean moving carrier, analyze the motion state and characteristics of the ocean moving carrier, deeply explore the coordinate sequence of the carrier on the ocean, obtain the corresponding noise, characteristics, etc., and use the size of the noise as random noise, as the random noise of the receiver position parameter in the subsequent Kalman filter parameter estimator, to reduce the correlation between the receiver clock error and the coordinate elevation direction. The Precise Point Positioning method (PPP) calculates the coordinate sequence of the receiver; the coordinate sequence of the receiver is the same as the coordinate sequence of the ocean moving carrier, and the receiver is tied to the ocean moving carrier; the Allan variance is used to analyze the coordinate sequence of the carrier to obtain the motion noise of the ocean moving carrier.

[0053] Step 3: Establish a signal-to-noise ratio random model that takes into account the BeiDou-3 PPP-B2b (Precise Point Positioning Service) accuracy and the satellite signal-to-noise ratio over the ocean;

[0054] Collect one week's PPP-B2b corrections, decode them and merge them with the broadcast ephemeris to generate precise ephemeris. Compare the generated precise ephemeris with the final precise ephemeris provided by Wuhan University, analyze the accuracy of the orbit and clock errors generated by the real-time corrections provided by PPP-B2b, and add this accuracy and signal-to-noise ratio to the random model of PPP to achieve the final solution.

[0055] Step 4: Generate receiver clock error parameters;

[0056] The GNSS receiver installed on the moving carrier on the ocean receives the broadcast ephemeris, observation values, and PPP-B2b corrections; decodes PPP-B2b and generates precise ephemeris in real time with the broadcast ephemeris. The precise ephemeris includes precise orbit and precise clock error. The precise orbit generation formula is:

[0057]

[0058] Where X is the precision track; (e r ,e a ,e c ) Transformation matrix in the three directions of meridian, normal and tangential; X brd Satellite coordinates calculated from broadcast ephemeris; △C is the PPP-B2b correction number broadcast by BeiDou-3; and r are the satellite velocity and position vectors.

[0059] The precise clock error calculation formula can be expressed as:

[0060]

[0061] t brdSatellite clock error calculated by broadcast ephemeris; t is the generated precise ephemeris; △t is the PPP-B2b clock error correction number broadcast by BeiDou-3. Combining the observation values ​​and various error models, various error models include: atmospheric error, phase winding, antenna phase center change, etc., to construct a PPP function model. The present invention proposes a PPP function model based on the PPP-B2b correction number broadcast by BeiDou-3. The model adopts an ionosphere-free combination model. The difference between this model and the traditional real-time PPP time transfer is that it does not need to transmit the correction number through the network, but directly decodes the correction information on the B2b signal, which is more reliable; then, the receiver clock model established in the above steps 1-3 and the random model considering the sea surface motion characteristics and signal-to-noise ratio are added to the PPP equation to solve the receiver clock error. PPP stands for Precise Point Positioning, which means precise point positioning method in Chinese;

[0062] Step 5: Clock taming;

[0063] In order to meet the requirement of low cost, a constant temperature crystal oscillator is used as the clock source of the timing device. The PPP timing method based on the PPP-B2b correction number broadcast by Beidou-3 proposed in the present invention is used to estimate the receiver clock difference in real time, and the receiver clock difference is transmitted to the clock calibrator module of the FPGA+ARM of the timing device to adjust the constant temperature crystal oscillator in real time to achieve high-precision synchronization with the local synchronous clock of the Beidou clock, wherein the clock calibrator module includes a local voltage-controlled crystal oscillator and a D / A conversion module, and outputs 1PPS and 10MHz. Figure 3 Implement a flow chart for the timing device.

[0064] Embodiment 2

[0065] like Figure 4 As shown, the present invention also discloses a high-precision marine timing system based on Beidou satellite, comprising:

[0066] A receiver clock model building module is used to build a receiver clock model and determine the process noise of the random walk model;

[0067] The module for establishing the random model of position parameters is used to establish the random model of position parameters taking into account the ocean motion state, and reduce the correlation between the receiver clock error and the coordinate elevation direction;

[0068] The signal-to-noise ratio random model building module is used to build a random model that takes into account the accuracy of BeiDou-3 PPP-B2b and the signal-to-noise ratio of satellites over the ocean;

[0069] A clock error parameter generation module, used to generate receiver clock error parameters;

[0070] The clock training module is used to estimate the receiver clock error in real time using the PPP timing method based on the PPP-B2b correction number of Beidou-3, achieve high-precision synchronization with the local synchronization clock of the Beidou clock, and complete high-precision marine timing.

[0071] The present invention overcomes the problems of no Internet, no base station, complex environment and low timing accuracy in the existing ocean by receiving the orbit and clock correction numbers broadcast by the BeiDou-3 satellite precise single-point positioning service, and realizes high-precision single-station timing in deep sea environment. The timing accuracy can even reach sub-nanosecond level, thereby providing high-precision time information service for the establishment of ocean space-time benchmark.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-precision ocean timing method based on Beidou satellite, characterized in that: include: Build a receiver clock model and determine the process noise of the random walk model; Establish a random model of location parameters; Establish a signal-to-noise ratio random model based on Beidou satellite accuracy and signal-to-noise ratio; The receiver clock model, location parameter random model and signal-to-noise ratio random model are added to the PPP equation to generate the receiver clock error parameters; The receiver clock error parameters are passed into the clock calibrator module for clock taming; The establishing of the receiver clock model comprises: The receiver is continuously observed statically on land to obtain the receiver clock data, and the receiver clock data is analyzed to determine whether there is a clock jump phenomenon; If clock jumps exist, a receiver clock jump detection algorithm is established. The threshold of clock jump detection is determined according to the size of the receiver clock jump. The characteristics of the receiver clock are analyzed using the Allan variance and the receiver clock model is established according to the Allan variance value of the corresponding sampling interval. The location parameter random model includes: Place the receiver on the ocean moving carrier, collect observation data, calculate the coordinates of the receiver, obtain the coordinate sequence of the ocean moving carrier, analyze the motion state and characteristics of the ocean moving carrier, obtain the corresponding noise and characteristics, and use the size of the noise as the random noise of the receiver position parameter in the Kalman filter parameter estimator; The signal-to-noise ratio stochastic model includes: The PPP-B2b corrections of the set time are collected, decoded and merged with the broadcast ephemeris to generate precise ephemeris; the generated precise ephemeris is compared with the final precise ephemeris, the real-time accuracy provided by PPP-B2b is analyzed, and the accuracy and signal-to-noise ratio are added to the random model of the PPP equation for solution.

2. The method for high-precision ocean timing based on Beidou satellite according to claim 1, characterized in that: The threshold value does not exceed 2 ns.

3. The method for high-precision ocean timing based on Beidou satellite according to claim 1, characterized in that: The process noise of the random walk model is determined by estimating receiver clock error parameters using the random walk model and determining the process noise of the random walk model by Allan variance.

4. The method for high-precision ocean timing based on Beidou satellite according to claim 1, characterized in that: Generating receiver clock error parameters comprises the following steps: The receiver installed on the ocean moving carrier receives the broadcast ephemeris, observation values, and PPP-B2b corrections; decodes the PPP-B2b corrections and generates precise ephemeris in real time with the broadcast ephemeris. The precise ephemeris includes precise orbit and precise clock error. The precise orbit generation formula is: Where X is the precision track; (e r ,e a ,e c ) Transformation matrix in the three directions of meridian, normal and tangential; X brd Satellite coordinates calculated by broadcast ephemeris; △C is the orbit correction number in PPP-B2b broadcast by Beidou; and Represent the satellite velocity and position vector respectively; δC r ,δC a ,δC c It is the correction number in radial, normal and tangential directions; The precise clock error calculation formula can be expressed as: t brd represents the satellite clock error calculated from the broadcast ephemeris; t represents the generated precise satellite clock error; Represents the speed of light, △t represents the PPP-B2b clock correction number broadcast by Beidou; the PPP function model is constructed by combining the observation value and the error model, and the established receiver clock model, position parameter random model and signal-to-noise ratio random model are added to the PPP equation, and the receiver clock error is obtained by Kalman filtering.

5. The method for high-precision ocean timing based on Beidou satellite according to claim 1, characterized in that: Clock training includes the following steps: using a constant temperature crystal oscillator as the clock source of the timing device, transmitting the receiver clock error to the clock calibrator module of the timing device to adjust the constant temperature crystal oscillator in real time.

6. The method for high-precision ocean timing based on Beidou satellite according to claim 5, characterized in that: The clock calibrator module includes a local voltage-controlled crystal oscillator and a D / A conversion module, and outputs 1PPS and 10MHz clock information.

7. A system for implementing the Beidou satellite-based high-precision marine timing method according to any one of claims 1 to 6, characterized in that: The system comprises: A receiver clock model building module is used to build a receiver clock model and determine the process noise of the random walk model; A position parameter random model building module is used to build a position parameter random model; The signal-to-noise ratio random model building module is used to build a signal-to-noise ratio random model based on Beidou satellite accuracy and satellite signal-to-noise ratio; A clock error parameter generation module is used to add a receiver clock model, a position parameter random model and a signal-to-noise ratio random model into the PPP equation to generate a receiver clock error parameter; The clock training module is used to transfer the receiver clock error parameters to the clock calibrator module for clock training.

Images