Maritime positioning method based on fusion of numerical meteorological model and Beidou short message

Abstract

The invention belongs to the technical field of navigation positioning, and discloses an offshore positioning method based on fusion of a numerical meteorological model and a Beidou short message, so as to realize offshore second-level continuous high-precision positioning by using single Beidou short message equipment. According to the offshore positioning method based on fusion of the numerical meteorological model and the Beidou short message, a CNES real-time satellite orbit and clock error data are adopted, NWP model meteorological data are utilized to invert zenith troposphere delay, and a time baseline method considering NWP improvement is utilized to weaken time accumulation errors and improve time baseline positioning performance; and then, based on the improved time baseline offshore high-precision positioning method, the PPP and Beidou short message communication technologies are combined, so that the BDS / GNSS offshore high-precision positioning navigation target can be realized by utilizing a single Beidou short message device, and the high-precision positioning cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of navigation and positioning, and in particular relates to a maritime positioning method based on the fusion of a numerical meteorological model and Beidou short messages. Background Art

[0002] GNSS (Global Navigation Satellite System) navigation and positioning technology is widely used in land environments, but the difficulty of setting up base stations and communication transmission at sea restricts the application of GNSS in maritime positioning and navigation. At present, most domestic and foreign countries rely on base stations or maritime communication satellites built at sea to solve maritime communication problems, and then use RTK (real-time dynamic carrier phase difference) or PPP (precision point positioning) technology to achieve positioning in complex maritime environments, with a horizontal positioning accuracy of 10cm. However, the cost of building maritime base stations and maritime communication satellites is very expensive, which ordinary users cannot afford.

[0003] At present, the BeiDou short message service function of the BeiDou navigation satellite system (BDS) has become a preferred choice for maritime communication and data transmission. However, there are currently the following problems with BeiDou short messages in maritime data transmission: (1) Limited single communication capacity: The maximum length of a single communication content of a general civilian BeiDou short message terminal is 628 bits, about 78.5 bytes. (2) Limited communication frequency: After sending a communication command using BeiDou short messages, it takes 1 minute to continue sending the next communication content.

[0004] In order to overcome the shortcomings of limited communication capacity of Beidou short messages, relevant scholars have adopted effective measures such as simplifying data, compressing communication data and optimizing coding. Among these three measures, simplifying transmission data by using the nature and characteristics of navigation data is the most effective method. In order to overcome the shortcomings of limited frequency of Beidou short messages, there are currently two main solutions. One is to increase the number of short message devices, but as the number of devices increases, the communication cost also increases significantly. The second is time relative positioning technology (also known as time baseline method), which can achieve cm-level positioning within a short time interval, but as the time interval increases, time-varying error terms (satellite orbit, clock error, atmospheric delay, etc.) will have cumulative errors, resulting in the time baseline cannot provide high-precision positioning for a long time, which affects the time baseline at sea High-precision positioning and navigation performance. Summary of the invention

[0005] The purpose of the present invention is to propose a maritime positioning method based on the fusion of numerical meteorological model and Beidou short message, so as to realize continuous high-precision positioning at sea in seconds by using a single Beidou short message device.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: A method for marine positioning based on numerical meteorological model and Beidou short message fusion includes the following steps: Step 1. Use precise point positioning to obtain the dual-frequency ionospheric-free combined carrier observation value equation; Step 2. Perform inter-epoch differences on the two adjacent equations in the dual-frequency ionospheric-free combined carrier observation value equation to obtain the differential calculation equation; Step 3. Solve the error of the differential calculation equation; Step 4. Perform least squares solution on the difference calculation equation; Step 5. Subtract the pseudorange correction number at the set time from the average value of all pseudorange correction numbers in the epoch to form a compression coding scheme; where the pseudorange correction number is the sum of the zenith tropospheric delay correction number, the satellite orbit correction number and the clock correction number; Step 6. After transmitting the satellite orbit correction number and clock correction number represented in the state space to the mobile station through a compression coding scheme, the high-precision orbit and clock correction data used in positioning are restored; Step 7. Add the coordinates of the broadcast ephemeris to the satellite orbit correction number provided by the state space representation to determine whether the obtained coordinates are out of limit. If the obtained coordinates are not out of limit, then the correction number is not out of limit. Step 8. Transmit the compressed encoded data of the zenith tropospheric delay correction and orbit clock correction.

[0007] In addition, based on the above-mentioned marine positioning method based on the fusion of numerical meteorological models and Beidou short messages, the present invention also proposes a computer-readable storage medium on which a program is stored; when the program is executed by a processor, it is used to implement the steps of the above-mentioned marine positioning method based on the fusion of numerical meteorological models and Beidou short messages.

[0008] The present invention has the following advantages: The present invention adopts CNES real-time satellite orbit and clock difference data, uses NWP model meteorological data to invert zenith tropospheric delay, and uses the improved time baseline method taking into account NWP to weaken the time accumulation error and improve the time baseline positioning performance; then based on the improved time baseline, the high-precision maritime positioning method is combined with PPP and Beidou short message communication technology to achieve BDS / GNSS maritime high-precision positioning and navigation targets using a single Beidou short message device, thereby saving the cost of high-precision positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of the marine positioning method based on the fusion of numerical meteorological model and Beidou short message of the present invention; Figure 2It is a time series diagram of the ENU direction positioning error of the vill observation station within 24 hours from 00:00:00 to 06:00:00; Figure 3 It is a time series diagram of the ENU direction positioning error of the vill observation station within 24 hours from 06:00:00 to 12:00:00; Figure 4 It is a time series diagram of the ENU direction positioning error of the vill observation station within 24 hours from 12:00:00 to 18:00:00; Figure 5 It is a time series diagram of the ENU direction positioning error of the vill observation station within 24 hours from 18:00:00 to 24:00:00; Figure 6 It is a time series diagram of the ENU direction positioning error of the vill observation station in the present invention within 24 hours during a 1-hour observation period (00:00:00-01:00:00); Figure 7 It is a time series diagram of the ENU direction positioning error of the vill observation station within 24 hours in a 1-hour observation period (06:00:00-07:00:00); Figure 8 It is a time series diagram of the ENU direction positioning error of the vill observation station in the present invention within 1 hour of observation period (12:00:00-13:00:00) within 24 hours; Fig. 9 It is a time series diagram of the ENU direction positioning error of the vill observation station in the present invention during a 1-hour observation period (18:00:00-19:00:00) within 24 hours; Fig.10 It is a time series diagram of ENU direction positioning error of vill measuring station of the present invention; Fig.11 This is a time series diagram of the ENU direction positioning error one hour before the vill station of the present invention. DETAILED DESCRIPTION

[0010] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1 In this embodiment, a method for marine positioning based on the fusion of numerical meteorological model and Beidou short message is proposed, including the following steps: Step 1. Use precise point positioning to obtain the dual-frequency ionospheric-free combined carrier observation value equation; Using broadcast ephemeris data and mobile station observation data, we pass through n epochs from a known point with a step length of 1 second, and perform standard point positioning (SPP) solution for each epoch. Then, we linearize the dual-frequency ionosphere-free combined carrier observation value to obtain the dual-frequency ionosphere-free combined carrier observation value equation: ; Formula (1) in, Epoch ( =1,2,3...,n) of the mobile station; is the ambiguity term of the carrier phase. When the satellite is continuously tracked and no cycle slip occurs, the ambiguity is constant; Epoch ( =1,2,3...,n) of the zenith tropospheric delay; and are the corresponding coefficient terms, is the tropospheric mapping function, =1,2,3...,n; is the carrier phase ionospheric-free combined observation value, =1,2,3...,n; and are satellite orbit and satellite clock error terms, respectively. =1,2,3...,n.

[0011] Step 2. Perform inter-epoch differences on the two adjacent equations in the dual-frequency ionospheric-free combined carrier observation value equation to obtain the differential calculation equation; Ignore the two adjacent sub-formulas in formula (1) and The difference between the two adjacent sub-formulas is obtained by performing the difference calculation equation between epochs: ; Formula (2) in, , , , = - , = - , =1,2,3...,n.

[0012] Step 3. Solve the error of the differential calculation equation; The satellite orbit error in equation (2) Satellite clock error The high-precision real-time orbit and clock products provided by the Global Navigation Satellite System (GNSS) and CNES (Centre National d'Etudes Spatiales) are used for constraints; the fifth generation atmospheric reanalysis dataset (ECMWF Reanalysis v5, ERA5) of the global climate provided by the European Centre for Mesoscale Weather Forecasts is used to calculate the hierarchical integration method. , so that , and It is no longer ignored, reducing the accumulation of errors.

[0013] Step 4. Perform least squares solution on the difference calculation equation; set up , after step 3, It is known that; the least squares solution of equation (2) is: ; Formula (3) in, express The weight corresponding to the epoch; assuming that the position coordinates of the first epoch are known, the coordinates of the nth epoch are: ; Formula (4).

[0014] As shown in formula (4), continuous positioning at the second level can be achieved by solving the problem epoch by epoch. At the same time, the numerical meteorological model is added to reduce the accumulation of errors.

[0015] Using the dual-frequency observation data of the vill station in Spain from 00:00:00 to 24:00:00 (GPST) on June 1, 2020, GPS L1L2, GLONASS L1L2, Gallileo E1E5a and BDS B1B3 dual-frequency data can be observed, including BDS-3 satellite dual-frequency data, with a sampling rate of 1s, and the receiver type is SEPT POLARX5. The data download address is: https: / / cddis.nasa.gov / archive / . In the experiment, the 24-hour data is evenly divided into 4 groups, each group is 6 hours, to verify the long-term positioning effect of the improved time baseline in different time periods. In addition, in order to analyze the short-term positioning effect of the improved time baseline, the positioning results of the first 1-hour observation period of each time period are selected for analysis. Table 1 shows the specific meaning of the observation period selected in the experiment. The download address of the broadcast ephemeris used in the experiment of this station is: ftp: / / cddis.gsfc.nasa.gov / pub / gps / data / campaign / mgex / daily / . The real-time precise ephemeris and clock products of the CNES Analysis Center are used, and the download address is: http: / / www.ppp-wizard.net / products / REAL_TIME. The reference coordinates for evaluating the accuracy of the positioning results are the SNX weekly solution coordinates provided by IGS, and the initial coordinates of the first epoch of the time baseline are the weekly solution coordinates, and the download address is: https: / / cddis.nasa.gov / archive / gps / products / .

[0016] The comparative processing strategies used in this experiment are shown in Table 2, where method 1 is the original time baseline model, and method 2 and method 3 are improved time baseline algorithms.

[0017] Table 1 Observation period grouping Specific period meaning

[0018] Table 2 Time baseline data processing strategy

[0019] Note: Saas model means Saastamoinen model.

[0020] First, the analysis of the 24-hour experimental results is shown. Figures 2 to 5Figure 3 is the time series of the ENU direction positioning error of the vill station in four observation periods within 24 hours. The blue, green and red parts in the figure represent the positioning errors in the E, N and U directions respectively. Table 3 shows the STD and RMS statistical results of the positioning errors in the four observation periods within 24 hours. Figures 2 to 5 As can be seen from Table 3, the positioning error time series of the three time baseline methods in different observation periods will show obvious cumulative errors as the observation time increases, among which the cumulative baseline error of method 1 is the most obvious. At the same time, the cumulative error characteristics of the three time baseline positioning errors in the four periods are also different. The cumulative error of method 1 has no obvious regularity, while the error time series of methods 2 and 3 show the characteristics of approximately linear changes, which is related to the relatively slow and uniform changes of the precise orbits used. The positioning accuracy of method 3 for the entire 24 hours is significantly better than that of the other two time baseline positioning methods. The average STD of the three directions of ENU within 24 hours is 0.085, 0.062 and 0.119 m, and the average RMS is 0.157, 095 and 0.176 m, respectively. Compared with method 2, the average STD of ENU direction positioning error within 24 hours of method 3 increased by 46.4, 34.1 and 44.4%, and the average RMS increased by 47.8, 37.7 and 41.8% respectively; compared with method 1, the average STD of ENU direction positioning error within 24 hours of method 3 increased by 86.5, 85.2 and 85.9%, and the average RMS increased by 82.1, 82.3 and 84.3% respectively. It can be seen that after using the real-time precise orbit clock error and the tropospheric delay data calculated by the NWP model, the positioning accuracy of the improved time baseline method is significantly improved compared with the original time baseline positioning accuracy.

[0021] Table 3 Statistics of 24-hour ENU direction positioning errors in four observation periods at the vill station

[0022] The following is an analysis of the 1-hour experimental results. To further understand the improvement effect of the improved time baseline algorithm in the short term, Figures 6 to 9 The time series of the ENU positioning error in the first hour of the four observation periods of the vill station are shown. The blue, green and red parts in the figure represent the positioning errors in the E, N and U directions respectively. Table 4 shows the STD and RMS statistical results of the ENU positioning error in the first hour of the four observation periods. Figures 6 to 9As can be seen from Table 4, method 1 shows a particularly obvious cumulative error in different observation periods, and the time variation sequence has no obvious regularity, while the accuracy of method 2 and method 3 is almost unaffected within 20 minutes. Method 3 has the best positioning accuracy and stability in the four observation periods. The average STD of the ENU direction positioning error in the four observation periods is 0.012, 0.006 and 0.017 m, and the average RMS is 0.024, 0.011 and 0.034 m, respectively. Compared with method 2, the average STD of the ENU direction positioning error in the four observation periods of method 3 is improved by 43.8, 43.4 and 34.8%, and the average RMS is improved by 46.1, 46.2 and 36.4%, respectively; compared with method 1, the average STD is improved by 85.1, 91.9 and 87.0%, and the average RMS is improved by 74.5, 93.1 and 80.1%, respectively. The improved time baseline method has significantly improved positioning accuracy compared with the original method.

[0023] Table 4 Statistics of ENU direction positioning errors in 1 hour during 4 observation periods at the vill station

[0024] It can be seen from this that the improved time baseline, that is, the time baseline with the addition of zenith tropospheric delay correction and orbital clock correction, has significantly improved positioning accuracy compared to the original time accumulation baseline, and its positioning accuracy is at the centimeter level within 1 hour.

[0025] Step 5. Subtract the pseudorange correction number at the set time from the average value of all pseudorange correction numbers in the epoch to form a compression coding scheme; wherein the pseudorange correction number is the sum of the zenith tropospheric delay correction number, the satellite orbit correction number and the clock correction number; The base station module sends the corrections of the pseudorange and carrier phase observations of the dual-frequency ionosphere-free combination every minute. The corrections are calculated as follows: ; Formula (5) in, and are pseudorange and carrier phase corrections respectively; is the calculated geometric distance from the satellite to the receiver; and are satellite orbit error and satellite clock error respectively; is the receiver clock error; is the fuzziness parameter; is the corresponding wavelength; is the tropospheric delay in the zenith direction; is the mapping function; and is the multipath effect and observation noise; and They are the dual-frequency ionosphere-free combined pseudorange and carrier phase observation values, respectively; In order to simplify the data, the pseudorange correction number is subtracted from the average value of the epoch for all common-view satellites in the same epoch to simplify the data. The specific processing method is shown in formula (6): ; Formula (6) After receiving the simplified correction number coded data sent by the Beidou short message, the correction number sent by the base station is obtained by decoding, and the observation equation is formed by the pseudorange and carrier phase correction number received by the mobile station receiver every minute: ; Formula (7) in, is the mobile station location; is the design matrix coefficient; and It is a dual-frequency ionospheric-free combined pseudorange and carrier phase observation value; is the mobile station receiver clock error; is the tropospheric delay in the zenith direction of the mobile station; is the tropospheric mapping function; is the ambiguity term of the ionospheric-free carrier phase; is the wavelength; and are the satellite orbit and clock error terms respectively.

[0026] Step 6. After transmitting the satellite orbit correction and clock correction of the state space representation (SSR) to the mobile station through a compression coding scheme, the high-precision orbit and clock correction data used in positioning are restored; In order to reduce the impact of satellite orbit and clock error on positioning results, the base station module receives the state space correction number issued by CNES according to the visible satellite PRN number, and transmits the correction number to the mobile station through the Beidou short message terminal; after receiving the state space orbit and clock error correction number, the mobile station needs to restore it to the high-precision orbit and clock error data used in positioning; The state space representation correction number is: ; Formula (8) in, is the data age; , and They are Corrections of the satellite position along the radial, tangential and normal directions at the reference time; , and They are The rate of change of the corrections of the satellite position along the radial, tangential and normal directions at the reference time; , and are the fitting parameters of the second-order polynomial representing the reference time of the precise clock error data broadcast in the state space.

[0027] Step 7. Add the coordinates of the broadcast ephemeris to the satellite orbit correction number provided by the state space representation to determine whether the obtained coordinates are out of limit. If the obtained coordinates are not out of limit, then the correction number is not out of limit. Step 7.1. Calculation Orbital correction at any time : ; Formula (9) Step 7.2. Calculate the unit vectors of the three directions of RAC in the satellite fixed system : ; Formula (10) in, and are the position and velocity vector of the satellite in the earth fixed system calculated by the broadcast ephemeris at the time; Step 7.3. Convert the orbit correction number from the orbit coordinate system to the Earth-fixed coordinate system to obtain the precise orbit coordinates of the corrected satellite: ; Formula (11) in, , and is the precise coordinates of the satellite after correction; , and are the satellite coordinates calculated using broadcast ephemeris; Step 7.4. Determine the calculated recovery , and Whether it is within the tolerance range, the tolerance range is set according to the needs. If it is, the correction number is within the limit and it is retained to proceed to the next step; if the correction number exceeds the limit, the correction number that exceeds the limit is abandoned.

[0028] Step 8. Transmit the compressed coded data of the zenith tropospheric delay correction and orbital clock correction; Using the compression coding scheme of step 5, the zenith tropospheric correction of the numerical meteorological model calculated in step 3 and the orbital clock correction calculated in step 6 are transmitted; wherein the zenith tropospheric correction of the numerical meteorological model and the orbital clock correction together constitute the formula (6) , and then compress the data through formula (6), and then send the compressed coded data to the mobile station module through the Beidou short message device; the data is compressed through formula (6), which adapts to the characteristics of small bandwidth of Beidou short message communication, and the single transmission data increases.

[0029] Add the precise compressed coded data (i.e., zenith tropospheric delay correction and orbital clock correction) transmitted by a single Beidou short message device in steps 5-7 to the error solution of the differential calculation equation in step 3, and then add the solved error to the time baseline in step 4 to reduce error accumulation; Record the captured satellite PRN. If the common view satellite changes, it is necessary to send satellite information to the base station in time so that the base station can replace the correction number corresponding to the satellite to be sent, as well as some other abnormal situations (such as data transmission interruption, correction data abnormality, etc.) to ensure the accuracy and stability of the positioning results.

[0030] The experimental results of adding steps 5-7 are analyzed below.

[0031] When calculating various correction numbers, it is necessary to consider the numerical characteristics of the correction numbers for encoding, and then send the various correction numbers to the mobile station module through the Beidou short message terminal, that is, add them to the improved time baseline.

[0032] After receiving the satellite observation sent, the user receiving end records the satellite PRN number. Since the receiver captures the GNSS signal of the same satellite in a short time, the observation value information of the satellite corresponding to the PRN is directly sent when sending GNSS observation data in the next minute, which can further save bandwidth. If the satellite at the previous moment cannot be captured or a new satellite appears, the Beidou short message terminal on the mobile end will send PRN information to remind the Beidou short message terminal at the base station to change the satellite information, so as to realize the timely update of satellite observation information. Table 5 shows the GNSS data sent every minute and the corresponding coding scheme.

[0033] Table 5 GNSS transmission data type and coding scheme

[0034] At present, the single communication capacity of a single Beidou short message terminal is 14,000 bits. Based on the calculation of 8 bits per byte, a single Beidou short message can send correction data for up to about 70 satellites, which can fully meet the number of high-precision positioning satellites at sea (the altitude cutoff angle is 15°), effectively reducing communication costs compared to communication satellites or other commercial services.

[0035] The experimental results are presented and analyzed below.

[0036] The experiment selected the vill and roag stations located in Spain, with a baseline length of about 483.5 km, a sampling rate of 1s, and an observation period of 00:00:00-06:00:00 (GPST) on June 1, 2020. In the experiment, the vill station was used as a mobile station and the roag station was used as a reference station. The positioning results of the mobile station vill station used the coordinate solution results published by igs as the reference true value to calculate the positioning error. The two stations can observe the dual-frequency pseudorange and carrier phase observations of GPS / GLONASS / Galileo / BDS including BDS-3, and the receiver type is SEPT POLARX5. In order to study the improvement effect of the improved time baseline method, three groups of comparative experiments were used, namely method1, method2 and method3. The data processing strategies are shown in Table 6, where method2 and method3 are improved methods of method1.

[0037] Table 6 Positioning solution strategy

[0038] Note: Saas model means Saastamoinen model.

[0039] Fig.10 and 11The red part (rtk) represents the RTK positioning error result of the mobile station, and the blue part (time-relative) represents the time-base positioning error result. Fig.10 and 11 It can be clearly seen that the time baseline positioning results of method 1 have obvious cumulative errors, among which the maximum cumulative error in the U direction is about 0.2 meters. The cumulative errors of method 2 and method 3 are significantly reduced, and the time baseline positioning error is more stable, which further illustrates the impact of satellite orbit and clock error accuracy on the time baseline method. Compared with the N and E directions, method 3 significantly accelerates the convergence speed in the U direction of method 2 in the first 30 minutes. This is because the high-precision NWP model tropospheric delay is used to correct the tropospheric error, which accelerates the convergence speed in the U direction.

[0040] Table 7 shows the STD and RMS statistical results of the ENU positioning error after the static medium-long baseline vill mobile station converged for half an hour. The STD of the ENU error in the three directions of method 3 is 0.008, 0.010 and 0.014m, respectively, which is 60.0, 56.5 and 70.2% higher than that of method 1, and 20.0, 9.1 and 26.3% higher than that of method 2; the RMS is 0.018, 0.015 and 0.030m, which is 50.0, 48.3 and 47.4% higher than that of method 1, and 10, 6.3 and 6.3% higher than that of method 2. All three methods can achieve centimeter-level positioning accuracy. Method 3 has higher accuracy and is more recommended for use in practice.

[0041] Table 7 Statistics of ENU positioning error results at vill station

[0042] Example 2 This embodiment describes a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, the program is used for the steps of a marine positioning method based on the fusion of a numerical meteorological model and Beidou short messages.

[0043] The computer-readable storage medium may be an internal storage unit of any device or apparatus with data processing capabilities, such as a hard disk or memory, or an external storage device of any device with data processing capabilities, such as a plug-in hard disk, a smart media card (SMC), an SD card, a flash card, etc., equipped on the device.

[0044] So far, the present embodiment has been described in detail in conjunction with the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the present invention. The maritime positioning method and computer-readable storage medium based on the fusion of numerical meteorological model and Beidou short message of the present invention adopt CNES real-time satellite orbit and clock difference data, use NWP model meteorological data to invert zenith tropospheric delay, and use the improved time baseline method taking into account NWP to weaken the time accumulation error and improve the time baseline positioning performance; then based on the improved time baseline, the high-precision maritime positioning method, combined with PPP and Beidou short message communication technology, can achieve BDS / GNSS maritime high-precision positioning navigation targets using a single Beidou short message device, saving the cost of high-precision positioning.

[0045] Of course, the above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It should be noted that all equivalent substitutions and obvious deformation forms made by any technician familiar with the field under the guidance of this specification fall within the essential scope of this specification and should be protected by the present invention.

Claims

1. A marine positioning method based on the fusion of numerical meteorological model and Beidou short message, characterized in that: The steps include: Step 1. Use precise point positioning to obtain the dual-frequency ionospheric-free combined carrier observation value equation; Step 2. Perform inter-epoch differences on the two adjacent equations in the dual-frequency ionospheric-free combined carrier observation value equation to obtain the differential calculation equation; Step 3. Solve the error of the differential calculation equation; Step 4. Perform least squares solution on the difference calculation equation; Step 5. Subtract the pseudorange correction number at the set time from the average value of all pseudorange correction numbers in the epoch to form a compression coding scheme; where the pseudorange correction number is the sum of the zenith tropospheric delay correction number, the satellite orbit correction number and the clock correction number; Step 6. After transmitting the satellite orbit correction number and clock correction number represented in the state space to the mobile station through a compression coding scheme, the high-precision orbit and clock correction data used in positioning are restored; Step 7. Add the coordinates of the broadcast ephemeris to the satellite orbit correction number provided by the state space representation to determine whether the obtained coordinates are out of limit. If the obtained coordinates are not out of limit, then the correction number is not out of limit. Step 8. Transmit the compressed encoded data of the zenith tropospheric delay correction and orbit clock correction.

2. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 1 is characterized in that: The step 1 is specifically as follows: Using broadcast ephemeris data and mobile station observation data, we pass through n epochs from a known point with a step length of 1 second, perform standard single-point positioning on each epoch, and linearize the dual-frequency ionosphere-free combined carrier observation value to obtain the dual-frequency ionosphere-free combined carrier observation value equation: ; Formula (1) in, epoch The coordinates of the mobile station, =1,2,3...,n; is the ambiguity term of the carrier phase. When the satellite is continuously tracked and no cycle slip occurs, the ambiguity is constant. epoch The zenith tropospheric delay of =1,2,3...,n; and are the corresponding coefficient terms, is the tropospheric mapping function, =1,2,3...,n; is the carrier phase ionospheric-free combined observation value, =1,2,3...,n; and are satellite orbit and satellite clock error terms, respectively. =1,2,3...,n.

3. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 2 is characterized in that: The step 2 is specifically as follows: Ignore the two adjacent sub-formulas in formula (1) and The difference between the two adjacent sub-formulas is obtained by performing the difference calculation equation between epochs: ; Formula (2) in, ， ， ， ， ， =1,2,3...,n。 4. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 3 is characterized in that: The step 3 is specifically as follows: The satellite orbit error in equation (2) Satellite clock error High-precision real-time orbit and clock products are used for constraints; the fifth-generation atmospheric reanalysis data set of global climate provided by the European Centre for Mesoscale Weather Forecasts is used to calculate the .

5. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 4 is characterized in that: The step 4 is specifically as follows: set up , after step 3, It is known that; the least squares solution of equation (2) is: ; Formula (3) in, express The weight corresponding to the epoch; assuming that the position coordinates of the first epoch are known, the coordinates of the nth epoch are: ; Formula (4).

6. The method for marine positioning based on the fusion of numerical meteorological model and Beidou short message according to claim 5, characterized in that: The step 5 is specifically as follows: The base station module sends the corrections of the pseudorange and carrier phase observations of the dual-frequency ionosphere-free combination every minute. The corrections are calculated as follows: ; Formula (5) in, and are pseudorange and carrier phase corrections respectively; is the calculated geometric distance from the satellite to the receiver; and are satellite orbit error and satellite clock error respectively; is the receiver clock error; is the fuzziness parameter; is the corresponding wavelength; is the tropospheric delay in the zenith direction; is the mapping function; and is the multipath effect and observation noise; and They are the dual-frequency ionosphere-free combined pseudorange and carrier phase observation values, respectively; In order to simplify the data, the pseudorange correction number is subtracted from the average value of the epoch for all common-view satellites in the same epoch to simplify the data. The specific processing method is shown in formula (6): ; Formula (6) After receiving the simplified correction number coded data sent by the Beidou short message, the correction number sent by the base station is obtained by decoding, and the observation equation is formed by the pseudorange and carrier phase correction number received by the mobile station receiver every minute: ; Formula (7) in, is the mobile station location; is the design matrix coefficient; and It is a dual-frequency ionospheric-free combined pseudorange and carrier phase observation value; is the mobile station receiver clock error; is the tropospheric delay in the zenith direction of the mobile station; is the tropospheric mapping function; is the ambiguity term of the ionospheric-free carrier phase; is the wavelength; and are the satellite orbit and clock error terms respectively.

7. The method for marine positioning based on the fusion of numerical meteorological model and Beidou short message according to claim 6 is characterized in that: The step 6 is specifically as follows: In order to reduce the influence of satellite orbit and clock error on positioning results, the base station module receives the state space correction number according to the visible satellite PRN number, and transmits the correction number to the mobile station through the Beidou short message terminal; after receiving the state space orbit and clock error correction number, the mobile station needs to restore it to the high-precision orbit and clock error data used in positioning; The state space representation correction number is: ; Formula (8) in, is the data age; , and They are Corrections of the satellite position along the radial, tangential and normal directions at the reference time; , and They are The rate of change of the corrections of the satellite position along the radial, tangential and normal directions at the reference time; , and are the fitting parameters of the second-order polynomial representing the reference time of the precise clock error data broadcast in the state space.

8. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 7 is characterized in that: The step 7 is specifically as follows: Step 7.

1. Calculation Orbital correction at any time : ； Formula (9) Step 7.

2. Calculate the unit vectors of the three directions of RAC in the satellite fixed system : ; Formula (10) in, and are the position and velocity vector of the satellite in the earth fixed system calculated by the broadcast ephemeris at the time; Step 7.

3. Convert the orbit correction number from the orbit coordinate system to the Earth-fixed coordinate system to obtain the precise orbit coordinates of the corrected satellite: ; Formula (11) in, , and is the precise coordinates of the satellite after correction; , and are the satellite coordinates calculated using broadcast ephemeris; Step 7.

4. Determine the calculated recovery , and Whether it is within the tolerance range, the tolerance range is set according to the needs. If it is, the correction number is within the limit and it is retained to proceed to the next step; if the correction number exceeds the limit, the correction number that exceeds the limit is abandoned.

9. The marine positioning method based on the fusion of numerical meteorological model and Beidou short message according to claim 8 is characterized in that: The step 8 is specifically as follows: Using the compression coding scheme of step 5, the zenith tropospheric correction of the numerical meteorological model calculated in step 3 and the orbital clock correction calculated in step 6 are transmitted; wherein the zenith tropospheric correction of the numerical meteorological model and the orbital clock correction together constitute the formula (6) , and then compress the data through formula (6), and then send the compressed coded data to the mobile station module through the Beidou short message device; The compressed coded data of the zenith tropospheric delay correction and orbital clock correction transmitted by a single Beidou short message device in steps 5-7 are added to the error solution of the differential calculation equation in step 3, and then the solved error is added to the time baseline in step 4 to reduce error accumulation; Record the captured satellite PRN. If the common view satellite changes, satellite information needs to be sent to the base station so that the base station can replace the correction number corresponding to the satellite to be sent to ensure the accuracy and stability of the positioning result.

10. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by the processor, the steps of the marine positioning method based on the fusion of numerical meteorological model and Beidou short message as described in any one of claims 1 to 9 are implemented.

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