Method for Inverting Ship Position and Meteorological Data Based on Ocean Tidal Load

Abstract

The present invention discloses a method for ship positioning and meteorological data inversion based on ocean tidal loading, including: calculating the initial position information of the ship based on the single-point positioning mode, and simultaneously obtaining the GNSS real-time data stream and the correction information stream of the satellite ephemeris and clock; constructing a grid centered on the initial position, performing convolution integration on the grid points according to the global tidal model and the Green's function to obtain the tidal loading at 9 grid points including the initial position, and then in the 4 grid regions formed by the 9 grid points, taking the average value of each vertex as the tidal loading correction of the region, using the ship's navigation direction information to judge the driving area of the ship in the next epoch, and taking the tidal loading influence of this region as an error term; calculating the tidal loading correction of the corresponding grid region according to the error term, and then performing real-time kinematic PPP solution using the real-time data stream and the correction information stream to obtain high-precision ship position information and meteorological data.

Description

Technical Field

[0001] The present invention belongs to the fields of ship navigation and positioning, meteorological parameter detection, etc., and relates to a ship positioning and meteorological data inversion method based on ocean tide loading. Background Art

[0002] With the rapid development of the Global Navigation Satellite System (GNSS), due to its advantages of all-weather, high precision, small receiver volume, complete functions, simple operation, etc., it has been widely applied to ship navigation and positioning. Whether it is ocean navigation, ship turning, or dead reckoning, time synchronization, clock setting, and even anchoring, GNSS is used. In the past, it was not easy to measure an accurate ship position in the vast ocean during extremely high winds and waves and extremely bad weather. However, with the development of the new generation of GNSS, it has made it possible to obtain the position information of a ship by using GNSS technology for navigation and positioning, whether in the vast sea or in a harsh climate environment. In current ship navigation, the maximum speed of a ship can reach a navigation speed of 70 - 80 knots per hour (about 36 m / s). Obtaining the real-time position of the ship at such a speed can effectively ensure the navigation safety of the ship.

[0003] The emergence of the real-time kinematic PPP technology can well solve the problem of real-time position calculation of ships. This technical means is a new GNSS positioning technology developed in recent years. It can use a single receiver to perform static or dynamic independent operations globally, without the need to set up a reference station, and is not limited by the operation distance. It has broad application prospects in regional or global scientific investigations, airborne dynamic measurements, marine surveys, etc. Currently, it has also become a new research hotspot in the field of GNSS navigation and positioning, and a series of research results have been obtained. With the support of various real-time GNSS orbit correction products and real-time data streams, the real-time data processing of precise point positioning can achieve very high positioning results. Currently, the real-time precise point positioning technology (RealTime Precise Point Positioning, RT-PPP) has become one of the research frontiers and hotspots in the current satellite navigation and positioning field, and will also be one of the main technical means for future real-time high-precision dynamic positioning.

[0004] When a ship is sailing in the vast ocean, the changes in the marine weather are particularly important for the ship's navigation. Using GNSS technology to invert the tropospheric zenith delay and atmospheric observation information such as PWV has become a widely used technology. In marine positioning and real-time marine meteorological data inversion, ocean tides are also a very important influencing factor. Due to the tidal forces of the sun and the moon, the sea surface rises and falls periodically, resulting in periodic deformation of the seabed load. In GNSS position solution, the influence of the ocean tide model can reach the centimeter or even decimeter level. Therefore, in high-precision data processing, the influence of ocean tide load cannot be ignored.

[0005] Currently, the commonly used ocean tide models globally mainly include DUT10, EOT11a, FES2004, GOT4.7, HAMTIDE11a, TPX07.2, Nao.99b, etc. Since their maximum spatial resolution can reach 0.125° * 0.125°, and the coverage range is relatively wide, during the high-speed navigation of ships, it is impossible to accurately obtain the influence degree of the current position's real-time tide load, and it is also difficult to correct the influence size of the tide load in the form of a model in data processing. These also provide an opportunity for the research and application of obtaining smaller-resolution ocean tide loads in real-time dynamic PPP positioning and meteorological inversion for high-precision real-time dynamics. Summary of the Invention

[0006] The present invention discloses a ship positioning and meteorological data inversion method based on ocean tide load, which can correct the positioning error caused by tide load in the form of a model during ship navigation to obtain the high-precision position and meteorological information of high-speed navigation ships.

[0007] The present invention is realized through the following technical solutions.

[0008] A ship positioning and meteorological data inversion method based on ocean tide load includes:

[0009] Calculating the initial position information of the ship based on the single-point positioning mode, and simultaneously obtaining the GNSS real-time data stream and the correction information stream of the satellite ephemeris and clock;

[0010] Constructing a grid centered on the initial position, performing convolution integration on the grid points according to the global tide model and the Green's function to obtain the tide loads on 9 grid points including the initial position, and then, within the 4 grid regions formed by the 9 grid points, taking the average value of each vertex as the tide load correction of the region. Using the ship's navigation direction information, judging the ship's traveling region in the next epoch, and taking the influence of the tide load in this region as an error term;

[0011] Calculate the tidal load correction for the corresponding grid area according to the error term, and then use the real-time data stream and the corrected information stream to perform real-time dynamic PPP solution to obtain high-precision ship position information and meteorological data.

[0012] Advantages of the present invention:

[0013] The present invention utilizes the currently widely used global ocean tide model FES2004. Based on the approximate position of the ship obtained by GNSS, a grid is constructed with the ship's position as the center and a distance of 100 m in each of the four directions of east, west, south, and north of the ship. Using the coordinates of 9 grid points including the ship's position point, the SPOTL software is used to calculate the magnitude of the tidal load effect at the current moment. The 9 grid points can form four closed areas. The average tidal load effect magnitude of 4 grid points is obtained separately in each area as the tidal load effect of this area. Using the sailing direction of the ship, it is judged which area the ship will sail to in the next epoch, and the tidal load correction value of this area is added as an error term to the positioning solution of RT-PPP. Using the real-time GNSS data stream and the correction information of real-time clock error and satellite ephemeris, high-precision ship position information and meteorological data above the ship are effectively obtained, which has great technical advantages and application prospects for ensuring ship navigation. Description of the drawings

[0014] Figure 1 It is a flow chart of the ship positioning and meteorological data inversion method based on ocean tidal load of the present invention;

[0015] Figure 2 It is a flow chart of real-time dynamic tidal load grid construction and correction of the present invention. Detailed implementation manners

[0016] The present invention will be described in detail below with reference to the drawings.

[0017] As Figure 1 shown, a ship positioning and meteorological data inversion method based on ocean tidal load in this embodiment specifically includes:

[0018] Step 1: Calculate the initial position information of the ship based on the single-point positioning mode, and at the same time obtain the real-time GNSS data stream and the correction information stream of the satellite ephemeris and clock;

[0019] In specific implementation, the initial position information of the ship generally needs to combine multi-system GNSS observation data and broadcast ephemeris information, and generally includes:

[0020] (1) Real-time data stream: Since the ship is moving at high speed and its position is changing every moment, it is necessary to be able to receive the GNSS data stream in real time and ensure that the data stream has a high time resolution. Therefore, the time resolution in this embodiment is set to 1 s.

[0021] (2) Real-time satellite and clock error correction information flow. In this embodiment, the commonly used CLK93 is selected as the real-time correction information for satellite clock error and ephemeris, and is added to the broadcast ephemeris to make the ephemeris and clock error information have higher accuracy.

[0022] After obtaining the above information, it is classified and sorted, and a corresponding database is established for storage; in addition, various model files should also be downloaded synchronously, including the correction files of PCO and PCV, which are stored in the database to prepare for real-time dynamic PPP correction.

[0023] Step 2: Construct a grid centered on the initial position, perform convolution integration on the grid points according to the global tidal model and Green's function to obtain the tidal load on 9 grid points including the initial position, and then in the 4 grid regions formed by the 9 grid points, take the average value of each vertex as the tidal load correction of this region. Use the ship's navigation direction information to judge the ship's driving area in the next epoch, and take the tidal load impact of this region as an error term.

[0024] Specifically, when implementing, since the maximum navigation speed of the ship is about 36 m / s, and in the current real-time data processing, the time interval of the data stream is 1 s, that is, within 1 s, the ship can travel about 36 m at most. Usually, within a range of 100 m, the change of tidal load is small. Therefore, in this embodiment, a grid is constructed with a distance of 100 m around the ship's coordinates as the center.

[0025] In this embodiment, the global tidal model selects the FES2004 global tidal model provided by the SPOLT software. The specific calculation method is as follows:

[0026]

[0027] In the formula, ρ represents the seawater density, is the spherical coordinate of the measuring station, is the spherical coordinate of the load point. The above coordinates correspond to the spherical coordinates of the center point of each grid of the global ocean tide model. θ represents and the spherical angle between them, which is obtained according to , A is the azimuth angle between the measuring station and the load point, is the instantaneous tide height corresponding to the load point , ds' is the load surface element, and G(θ,A) is the displacement load Green's function related to the azimuth angle A;

[0028] Using 11 tidal wave coefficients provided by FES2004, perform the corresponding tidal wave coefficient superposition calculation. The formula is as follows:

[0029]

[0030] In the formula, N is the total number of tidal constituents. Generally, 11 tidal waves (M2, S2, N2, K2, K1, O1, P1, Q1, M f , M m , S sa ) are considered for the correction of the measured displacement by the ocean tide model. Among them, there are 4 semi-diurnal tidal waves (subscript 2), 4 diurnal tidal waves (subscript 1), and three long-period tidal waves (M f , M m , S sa ); and δ P径向 , δ P东西 , δ P南北 are the amplitudes and phases corresponding to the vertical, east-west, and north-south directions of each tidal wave P at the measuring station respectively; ω P is the angular velocity of each tidal wave, χ P is the initial astronomical argument phase corresponding to each tidal wave. The initial astronomical arguments of each tidal wave change with the positions of the sun and the moon; t is the time corresponding to the calculation of the initial astronomical argument phase, are the displacement influence values in the vertical (U), east-west (E), and north-south (N) directions of the measuring station caused by the ocean tide load. For each tidal constituent, χ p can be calculated according to astronomical parameters.

[0031] Step 3: Calculate the tidal load correction for the corresponding grid area according to the error term, and then use the real-time data stream and the corrected information stream to perform real-time dynamic PPP solution to obtain high-precision ship position information and meteorological data;

[0032] In specific implementation, usually, during the dynamic PPP solution process, antenna phase winding is added, phase center correction is performed, an earth rotation correction model is introduced, and the ionospheric error is corrected by using the dual-frequency ionosphere-free combination. Furthermore, using the magnitude of the tidal influence obtained in real time, the tropospheric delay is estimated as an unknown parameter to obtain high-precision ship position information and meteorological data.

[0033] Therefore, in this embodiment, after obtaining the high-precision ship position information and meteorological data, the tropospheric data is further inversed and imaged in real time; specifically as follows:

[0034] Using the data processing method of real-time dynamic PPP, the mapping function model and the sass model are used to add the tropospheric zenith delay and the tropospheric horizontal gradient as parameters to be estimated into the real-time data solution, and the calculated tropospheric information and the real-time position information are combined. The solution result is input into the screen terminal to obtain a real-time plotted ship navigation trajectory map and a tropospheric change map. The specific process uses the following formula:

[0035]

[0036]

[0037] In the formula, s, r, and i represent satellite, receiver, and frequency number, represent phase and pseudorange observations in meters, ρ represents the geometric distance between the satellite and the receiver, c represents the speed of light in vacuum, dt r , dt s represent receiver clock error and satellite clock error, I represents ionospheric error, represents tropospheric error, λ represents wavelength factor, N represents integer ambiguity, represents receiver and satellite phase deviation, represents receiver and satellite pseudorange deviation, represents pseudorange and phase noise.

[0038]

[0039]

[0040] In the formula, Z T,r is the tropospheric zenith delay, Z H，r is the dry delay, m H (El) is the dry mapping function, is the wet mapping function. When estimating the troposphere, the dry delay is estimated using the Saas model, and the mapping function is solved using NMF, where Z T,r , G N,r , G E,r are estimated as unknown parameters.

[0041] In summary, the above are only the preferred examples of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for ship positioning and meteorological data inversion based on ocean tidal loading, characterized in that, Including: Calculating the initial position information of the ship based on the single-point positioning mode, and simultaneously obtaining the GNSS real-time data stream, as well as the satellite ephemeris and clock correction information stream; Constructing a grid centered on the initial position, performing convolution integration on the grid points according to the global tidal model and the Green's function to obtain the tidal load on 9 grid points including the initial position, and then in the 4 grid regions formed by the 9 grid points, taking the mean value of each vertex as the tidal load correction of this region. Using the ship's navigation direction information, judging the driving area of the ship in the next epoch, and taking the tidal load influence of this region as an error term; Calculating the tidal load correction of the corresponding grid region according to the error term, and then performing real-time kinematic PPP solution using the real-time data stream and correction information stream to obtain high-precision ship position information and meteorological data; After obtaining the high-precision ship position information and meteorological data, further inversing the tropospheric data and visualizing the data in real time, specifically using the following method: Using the data processing method of real-time kinematic PPP, using the mapping function model and the sass model, adding the tropospheric zenith delay and the tropospheric horizontal gradient as parameters to be estimated into the real-time data solution, and combining the calculated tropospheric information and real-time position information, and inputting the solution result into the screen terminal to obtain the real-time plotted ship navigation track map and tropospheric change map.

2. The ship positioning and meteorological data inversion method based on ocean tide load according to claim 1, characterized in that After obtaining the GNSS real-time data stream, as well as the satellite ephemeris and clock correction information stream, classifying and sorting them, and establishing a corresponding database for storage.

3. The ship positioning and meteorological data inversion method based on ocean tide load according to claim 2, characterized in that After establishing the corresponding database for storage, synchronously downloading various model files, including the correction files of PCO and PCV, and storing them in the database.

4. A method for ship positioning and meteorological data inversion based on ocean tidal loading according to claim 1 or 2 or 3, characterized in that, Selecting to construct a grid centered on the coordinates of the ship with a distance of 100m around it.

5. A ship positioning and meteorological data inversion method based on ocean tidal load according to claim 1 or 2 or 3, characterized in that The global tidal model is selected to adopt the FES2004 global tidal model provided by the SPOLT software.

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