A method and system for constructing an ionospheric grid model based on a low-Earth orbit satellite constellation

Abstract

The present invention discloses a method and system for constructing an ionospheric grid model based on a low-earth orbit satellite constellation, which obtains GNSS observation data and low-earth orbit satellite observation data; respectively processes the GNSS observation data and the low-earth orbit satellite observation data by using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid; performs a fitting process on the grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid to obtain a fitting model; processes the low-earth orbit satellite observation data by using spherical harmonic functions to obtain a second low-earth orbit satellite ionospheric grid; and encrypts the second low-earth orbit satellite ionospheric grid into the first GNSS ionospheric grid through the fitting model to obtain an ionospheric grid model. The beneficial effect of the present invention is to construct an ionospheric grid model with smaller processing accuracy and higher update speed, which can meet the application requirements of the accuracy and update speed in the PPP-PTK positioning technology.

Description

Technical Field

[0001] The present invention relates to the technical field of ionospheric grid construction. Specifically, it relates to a method and system for constructing an ionospheric grid model based on a low-earth orbit satellite constellation. Background Art

[0002] The ionosphere has a certain impact on human spaceflight, navigation, communication, etc. In the field of satellite navigation and positioning, the ionosphere is one of the most troublesome error sources affecting the performance of GNSS navigation services. To meet the increasing demands of human production activities for the rapidity, high precision, and low cost of navigation and positioning, it continuously promotes the iterative update of navigation and positioning technologies. Currently, the PPP-RTK positioning technology is one of the forefront hot research directions in the field of navigation and positioning. The PPP-RTK technology broadcasts information such as GNSS precise orbits / clocks, ionospheric corrections, tropospheric corrections, phase hardware delays (UPD), and ranging code hardware delays (DCB) to assist users in quickly achieving fixed ambiguity solutions and obtaining high-precision positioning results. The refinement degree and update rate of ionospheric correction information are crucial conditions for the effective application of PPP-RTK positioning technology. Currently, the main global ionospheric grid products are made by solving the observation data of ground GNSS tracking stations to produce ionospheric products with a size of 5° in longitude and 2.5° in latitude. The fastest update speed is within 24 hours, and the update speed of ionospheric grid products with higher precision is in weeks. Moreover, the fastest global ionospheric grid products all have a delay characteristic of about one day. However, in the existing technology for the accuracy of ionospheric grid division, in the grid accuracy directly divided by the observation data of GNSS tracking stations, the application requirements for accuracy and update speed in PPP-PTK positioning technology cannot be achieved.

[0003] In view of this, this application is specifically proposed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the ionospheric grid constructed by the existing technology using GNSS observation data cannot meet the application requirements for accuracy and update speed in PPP-PTK positioning technology. The purpose is to provide a method and system for constructing an ionospheric grid model based on a low-earth orbit satellite constellation, which realizes a finer accuracy division of the ionospheric grid and can meet the application requirements for accuracy and update speed in PPP-PTK positioning technology.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation, the method steps include:

[0007] Obtain GNSS observation data and low-earth orbit satellite observation data;

[0008] The spherical harmonic function is used to process the GNSS observation data and the low-earth orbit satellite observation data respectively, and a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid are obtained;

[0009] The grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid are fitted to obtain a fitting model;

[0010] The spherical harmonic function is used to process the low-earth orbit satellite observation data to obtain a second low-earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-earth orbit satellite ionospheric grid is less than that of the first low-earth orbit satellite ionospheric grid;

[0011] Through the fitting model, the second low-earth orbit satellite ionospheric grid is encrypted into the first GNSS ionospheric grid to obtain an ionospheric grid model.

[0012] In the traditional method for constructing an ionospheric grid, usually only single GNSS observation data is used to produce ionospheric grid models with different accuracies. However, when using this method to construct an ionospheric grid model, the minimum production accuracy is at 5° longitude and 2.5° latitude, and it is impossible to construct an ionospheric grid model with a smaller accuracy, thus unable to meet the application requirements for accuracy and update speed in the PPP-PTK positioning technology; the present invention provides a method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation. By combining the collected low-earth orbit satellite observation data and GNSS observation data, an ionospheric grid model with a smaller processing accuracy and a higher update speed is constructed, which can meet the application requirements for accuracy and update speed in the PPP-PTK positioning technology.

[0013] Preferably, the step of using the spherical harmonic function to process the GNSS observation data and the low-earth orbit satellite observation data respectively to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid specifically is:

[0014] The ionospheric pierce point TEC value is inverted according to the GNSS observation data, and the GNSS observation data is processed by a 15×15 order spherical harmonic function to obtain the first GNSS ionospheric grid;

[0015] The ionospheric pierce point TEC value is inverted according to the low-earth orbit satellite observation data, and the low-earth orbit satellite observation data is processed by a 15×15 order spherical harmonic function to obtain the first low-earth orbit satellite ionospheric grid.

[0016] Preferably, the specific method for obtaining the fitting model includes:

[0017] Perform a difference operation on the TEC values of each grid point of the first GNSS ionospheric grid and the TEC values of each grid point of the first low-earth orbit satellite ionospheric grid, and count the residual results;

[0018] According to the parameters of each grid point of the first GNSS ionospheric grid and the parameters of each grid point of the first low-earth orbit satellite ionospheric grid, use the residual result as a fitting result item, and perform fitting using a high-order polynomial to obtain a fitting model.

[0019] Preferably, in the fitting model, the fitting equation is specifically:

[0020] RMS = a1L + a2B + a3LB + a4L 2 + a5B 2 + a6L 2 B 2 +…

[0021] RMS is the residual result, L is the grid point accuracy, B is the grid point latitude, and a is the parameter.

[0022] Preferably, the GNSS observation data is the L-band carrier data of GNSS and the ranging code data of GNSS.

[0023] Preferably, the low-earth orbit satellite observation data is the L-band carrier data of the low-earth orbit satellite and the ranging code data of the low-earth orbit satellite.

[0024] Preferably, the grid accuracy of both the first GNSS ionospheric grid and the first low-earth orbit satellite ionospheric grid is 5° longitude and 2.5° latitude.

[0025] Preferably, the accuracy of the grid points of the second low-earth orbit satellite ionospheric grid is 2.5° longitude and 2.5° latitude.

[0026] Preferably, the specific sub-steps for obtaining the ionospheric grid model include:

[0027] Through the fitting model, divide the accuracy of the first GNSS ionospheric grid into 2.5° longitude and 2.5° latitude according to the grid accuracy of the second low-earth orbit satellite ionospheric grid;

[0028] Integrate the grid points obtained after division to obtain the ionospheric grid model.

[0029] The present invention also provides an ionospheric grid model construction system based on a low-earth orbit satellite constellation. The system includes a data acquisition module, a first data processing module, a fitting module, a second data processing module, and an encryption module;

[0030] The data acquisition module is used to acquire GNSS observation data and low-earth orbit satellite observation data;

[0031] The first data processing module is configured to process the GNSS observation data and the low-earth orbit satellite observation data respectively using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid;

[0032] The fitting module is configured to perform fitting processing on the grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid to obtain a fitting model;

[0033] The second data processing module is configured to process the low-earth orbit satellite observation data using spherical harmonic functions to obtain a second low-earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-earth orbit satellite ionospheric grid is less than that of the first low-earth orbit satellite ionospheric grid;

[0034] The encryption module is configured to encrypt the second low-earth orbit satellite ionospheric grid into the first GNSS ionospheric grid through the fitting model to obtain an ionospheric grid model.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] A method and system for constructing an ionospheric grid model based on a low-earth orbit satellite constellation provided by an embodiment of the present invention, by combining the collected low-earth orbit satellite observation data and GNSS observation data, constructs an ionospheric grid model with smaller processing accuracy and higher update speed, and can meet the application requirements of accuracy and update speed in PPP-PTK positioning technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a schematic flow chart of the method

[0039] Figure 2 It is a schematic diagram of the system DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions thereof of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0041] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring aspects of the present invention.

[0042] Throughout the specification, references to "one embodiment", "an embodiment", "an example", or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "one embodiment", "an embodiment", "an example", or "an example" throughout the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Additionally, those of ordinary skill in the art will understand that the diagrams provided herein are for illustrative purposes only and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] In the description of the present invention, the orientation or positional relationships indicated by the terms "front", "rear", "left", "right", "upper", "lower", "vertical", "horizontal", "high", "low", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as limiting the scope of protection of the present invention.

[0044] Embodiment 1

[0045] This embodiment discloses a method for constructing an ionospheric grid model based on a low-Earth orbit satellite constellation. This embodiment mainly obtains the observation data of low-Earth orbit satellites and GNSS observation data simultaneously. Since the observation data of low-Earth orbit satellites can more directly construct an ionospheric grid product with a smaller accuracy, this embodiment encrypts the ionospheric grid with finer and smaller accuracy divided by low-Earth orbit satellites into the ionospheric grid model established by GNSS observation data, and can obtain a more accurate ionospheric grid model. As Figure 1 shown, the method steps include:

[0046] S1: Obtain GNSS observation data and low-Earth orbit satellite observation data;

[0047] In step S1, mainly two types of observation data are obtained. The observation data mainly refers to the navigation satellites corresponding to various types of data, the ranging signals transmitted by low-earth orbit satellites. Therefore, the GNSS observation data is the L-band carrier data of GNSS and the ranging code data of GNSS; the low-earth orbit satellite observation data is the L-band carrier data of the low-earth orbit satellite and the ranging code data of the low-earth orbit satellite. A GNSS receiver and a low-earth orbit satellite receiver are used to achieve long-term tracking of GNSS satellites and low-earth orbit satellites, and receive carrier and ranging code observation data.

[0048] S2: The GNSS observation data and the low-earth orbit satellite observation data are respectively processed using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid;

[0049] The specific process of respectively processing the GNSS observation data and the low-earth orbit satellite observation data using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid is as follows:

[0050] Invert the TEC value of the ionospheric piercing point based on the GNSS observation data, and process the GNSS observation data using a 15×15 order spherical harmonic function to obtain the first GNSS ionospheric grid;

[0051] Invert the TEC value of the ionospheric piercing point based on the low-earth orbit satellite observation data, and process the low-earth orbit satellite observation data using a 15×15 order spherical harmonic function to obtain the first low-earth orbit satellite ionospheric grid.

[0052] The grid accuracy of both the first GNSS ionospheric grid and the first low-earth orbit satellite ionospheric grid is 5° in longitude and 2.5° in latitude.

[0053] In step S2, mainly an ionospheric grid model with corresponding accuracy is made through the spherical harmonic function model. In step S2, the accuracy of the constructed first GNSS ionospheric grid and the first low-earth orbit satellite ionospheric grid is 5° in longitude and 2.5° in latitude. That is, the constructed accuracy is based on the minimum accuracy constructed from the GNSS observation data alone to establish an ionospheric grid model with a smaller accuracy.

[0054] S3: Perform fitting processing on the grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid to obtain a fitting model;

[0055] The specific method for obtaining the fitting model includes:

[0056] Perform a difference operation on the electron content TEC values of each grid point of the first GNSS ionospheric grid and the electron content TEC values of each grid point of the first low-earth orbit satellite ionospheric grid, and statistically analyze the residual results;

[0057] According to the parameters of each grid point of the first GNSS ionospheric grid and the parameters of each grid point of the first low-earth orbit satellite ionospheric grid, taking the residual result as a fitting result item, a high-order polynomial is used for fitting to obtain a fitting model.

[0058] In the fitting model, the fitting equation is specifically:

[0059] RMS = a1L + a2B + a3LB + a4L 2 + a5B 2 + a6L 2 B 2 +…

[0060] RMS is the residual result, L is the grid point accuracy, B is the grid point latitude, and a is the parameter.

[0061] By fitting the ionospheric grid parameters of two different types to construct a fitting model, the finally constructed ionospheric grid model can be updated in real time, and at the same time, the accuracy of the constructed ionospheric grid model can be improved.

[0062] S4: Process the low-earth orbit satellite observation data using spherical harmonic functions to obtain a second low-earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-earth orbit satellite ionospheric grid is less than that of the first low-earth orbit satellite ionospheric grid; Invert the TEC value of the ionospheric piercing point using the low-earth orbit satellite observation data, and use a 15×15 order spherical harmonic function model to produce the second low-earth orbit satellite ionospheric grid. The piercing point means that the carrier ranging signal emitted by the satellite is regarded as a continuous ray, the ionosphere is compressed into a spherical surface, and the intersection point when the ray passes through the spherical surface is the piercing point.

[0063] In this embodiment, the accuracy of the grid points of the constructed second low-earth orbit satellite ionospheric grid is 2.5° in longitude and 2.5° in latitude. However, as long as the accuracy of the constructed second low-earth orbit satellite ionospheric grid is less than 5° in longitude and 2.5° in latitude, it is not specifically limited.

[0064] S5: Through the fitting model, encrypt the second low-earth orbit satellite ionospheric grid into the first GNSS ionospheric grid to obtain an ionospheric grid model.

[0065] The specific sub-steps for obtaining the ionospheric grid model include:

[0066] Through the fitting model, divide the accuracy of the first GNSS ionospheric grid into 2.5° in longitude and 2.5° in latitude according to the grid accuracy divided by the second low-earth orbit satellite ionospheric grid;

[0067] Integrate the grid points obtained after division to obtain an ionospheric grid model.

[0068] Using a polynomial fitting model, the ionospheric grid of the second low-earth orbit satellite (longitude 2.5°, latitude 2.5°) is reduced to the first GNSS ionospheric grid (longitude 5°, latitude 2.5°), realizing the encryption of the first GNSS ionospheric grid. The final encryption result means that the first GNSS ionospheric grid (longitude 5°, latitude 2.5°) is divided into grids of (longitude 2.5°, latitude 2.5°) by using the ionospheric grid of the second low-earth orbit satellite (longitude 2.5°, latitude 2.5°). According to the GNSS global ionospheric grid division rules, the grid encryption points and the far points are integrated to form a new GNSS global ionospheric grid product (longitude 2.5°, latitude 2.5°), thus realizing the refinement and rapid update of the GNSS global ionospheric grid product again.

[0069] A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation disclosed in this embodiment uses the global ionospheric observation data of low-earth orbit satellites to establish a refined and high-update-rate global ionospheric grid product. The fitting model can reduce the low-earth orbit satellite ionospheric product to the original GNSS ionospheric grid product, realizing the refinement and rapid update rate of the original GNSS ionospheric product; it can meet the application requirements of the PPP-RTK positioning technology, quickly assist in fixing the ambiguity in positioning, and improve the positioning accuracy and convergence time; this method makes up for the defect of the single means of making the global ionospheric grid product in the case of limited number of ground stations.

[0070] Embodiment 2

[0071] This embodiment discloses an ionospheric grid model construction system based on a low-earth orbit satellite constellation. This embodiment is to implement the construction method in Embodiment 1, as Figure 2 shown, the system includes a data acquisition module, a first data processing module, a fitting module, a second data processing module, and an encryption module;

[0072] The data acquisition module is used to acquire GNSS observation data and low-earth orbit satellite observation data;

[0073] The first data processing module is used to process the GNSS observation data and the low-earth orbit satellite observation data respectively by using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid;

[0074] The fitting module is used to perform fitting processing on the grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid to obtain a fitting model;

[0075] The second data processing module is configured to process the low-earth orbit satellite observation data by using spherical harmonic functions to obtain a second low-earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-earth orbit satellite ionospheric grid is less than that of the first low-earth orbit satellite ionospheric grid;

[0076] The encryption module is configured to encrypt the second low-earth orbit satellite ionospheric grid into the first GNSS ionospheric grid through a fitting model to obtain an ionospheric grid model.

[0077] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments 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 principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for constructing an ionospheric grid model based on a low Earth orbit satellite constellation, characterized in that The method steps include: Obtain GNSS observation data and low-earth orbit satellite observation data; Use spherical harmonic functions to process the GNSS observation data and the low-earth orbit satellite observation data respectively to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid; Perform fitting processing on the grid points of the first GNSS ionospheric grid and the grid points of the first low-earth orbit satellite ionospheric grid to obtain a fitting model; Use spherical harmonic functions to process the low-earth orbit satellite observation data to obtain a second low-earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-earth orbit satellite ionospheric grid is less than that of the first low-earth orbit satellite ionospheric grid; Through the fitting model, encrypt the second low-earth orbit satellite ionospheric grid into the first GNSS ionospheric grid to obtain an ionospheric grid model.

2. The method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 1, wherein The specific process of using spherical harmonic functions to process the GNSS observation data and the low-earth orbit satellite observation data respectively to obtain a first GNSS ionospheric grid and a first low-earth orbit satellite ionospheric grid is as follows: Invert the TEC value of the ionospheric piercing point according to the GNSS observation data, and use a 15×15 order spherical harmonic function to process the GNSS observation data to obtain the first GNSS ionospheric grid; Invert the TEC value of the ionospheric piercing point according to the low-earth orbit satellite observation data, and use a 15×15 order spherical harmonic function to process the low-earth orbit satellite observation data to obtain a first low-earth orbit satellite ionospheric grid.

3. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 2, wherein The specific method for obtaining the fitting model includes: Perform a difference operation on the electron content TEC values of each grid point of the first GNSS ionospheric grid and the electron content TEC values of each grid point of the first low-earth orbit satellite ionospheric grid, and statistically analyze the residual results; According to the parameters of each grid point of the first GNSS ionospheric grid and the parameters of each grid point of the first low-earth orbit satellite ionospheric grid, use the residual results as the fitting result items and perform fitting using a high-order polynomial to obtain a fitting model.

4. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 3, characterized in that In the fitting model, the fitting equation is specifically: RMS = a1L + a2B + a3LB + a4L 2 + a5B 2 + a6L 2 B 2 +… RMS is the residual result, L is the grid point accuracy, B is the grid point latitude, and a is a parameter.

5. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 1, characterized in that The GNSS observation data is the L-band carrier data of GNSS and the ranging code data of GNSS.

6. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 1, characterized in that The low-earth orbit satellite observation data is the L-band carrier data of the low-earth orbit satellite and the ranging code data of the low-earth orbit satellite.

7. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 1, characterized in that, The grid accuracy of the first GNSS ionospheric grid and the first low-earth orbit satellite ionospheric grid is both 5° in longitude and 2.5° in latitude.

8. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 7, characterized in that The accuracy of the grid points of the second low-earth orbit satellite ionospheric grid is 2.5° in longitude and 2.5° in latitude.

9. A method for constructing an ionospheric grid model based on a low-earth orbit satellite constellation according to claim 8, characterized in that, The specific sub-steps for obtaining the ionospheric grid model include: Through the fitting model, use the grid accuracy divided by the second low-earth orbit satellite ionospheric grid to divide the accuracy of the first GNSS ionospheric grid into 2.5° in longitude and 2.5° in latitude; Integrate the grid points obtained after division to obtain an ionospheric grid model.

10. An ionospheric grid model construction system based on a low Earth orbit satellite constellation, characterized in that, The system includes a data acquisition module, a first data processing module, a fitting module, a second data processing module, and an encryption module; The data acquisition module is used to acquire GNSS observation data and low-Earth orbit satellite observation data; The first data processing module is used to process the GNSS observation data and the low-Earth orbit satellite observation data respectively by using spherical harmonic functions to obtain a first GNSS ionospheric grid and a first low-Earth orbit satellite ionospheric grid; The fitting module is used to perform fitting processing on the grid points of the first GNSS ionospheric grid and the grid points of the first low-Earth orbit satellite ionospheric grid to obtain a fitting model; The second data processing module is used to process the low-Earth orbit satellite observation data by using spherical harmonic functions to obtain a second low-Earth orbit satellite ionospheric grid, and the grid point accuracy of the second low-Earth orbit satellite ionospheric grid is less than the grid point accuracy of the first low-Earth orbit satellite ionospheric grid; The encryption module is used to encrypt the second low-Earth orbit satellite ionospheric grid into the first GNSS ionospheric grid through the fitting model to obtain an ionospheric grid model.

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