Improved method for generating ionospheric grid products, terminals, and readable storage media

Abstract

This application provides an improved method for generating ionospheric grid products, comprising: acquiring phase deviation products of reference stations within a preset area in real time; extracting the oblique path ionospheric delay and corresponding first precision information of each satellite from the reference stations based on the phase deviation products; performing polynomial iterative fitting on the oblique path ionospheric delay based on the first precision information; and if the fitting result meets preset conditions, calculating the ionospheric residual value of the grid points and the corresponding second precision information to output the oblique path ionospheric grid product. The method of this application can generate high-precision, highly continuous, and highly reliable oblique path ionospheric grid products.

Description

Technical Field

[0001] This invention relates to the field of satellite electronic systems technology, and in particular to an improved method for generating ionospheric grid products, a terminal, and a readable storage medium. Background Technology

[0002] When electromagnetic waves pass through the ionosphere, their propagation speed and path change. This deviation is called ionospheric delay, and its magnitude depends primarily on the electron density and signal frequency in the ionosphere. For GPS measurements, this deviation can reach tens of meters at the zenith and exceed 50 meters at an altitude angle of 5 degrees, making it the most significant source of error in GPS data processing. To eliminate or mitigate the effects of ionospheric delay, ionospheric delay correction models such as the Krobuscher model and ionospheric grid model are commonly used. Additionally, dual-frequency correction methods can be employed, either by linearly combining observations to eliminate ionospheric delay errors or by estimating ionospheric delay as a parameter. As a current hot research direction in the international satellite navigation field, PPP-RTK technology integrates the advantages of two positioning technologies: Precise Point Positioning (PPP) and Network Real-time Kinematic (NRTK). Its main idea is to use a ground-based regional reference station network to extract atmospheric enhancement corrections such as tropospheric delay and ionospheric delay and model them after achieving station-by-station PPP ambiguity fixation. Users can then obtain the corresponding regional atmospheric corrections based on the station location, and achieve rapid ambiguity fixation with the help of atmospheric corrections, obtaining centimeter-level positioning results in an instant or within seconds.

[0003] Existing methods for generating grid products are highly adaptable in regions with dense reference stations, small areas, and mid-to-high latitudes, providing high-precision ionospheric delay products for regional users. However, in areas with wide coverage and sparse reference stations, or in low-latitude regions with abnormally active ionospherics, they cannot accurately characterize the residual portion of the ionospheric delay at each grid point, and also lack corresponding accuracy information to assist users in PPP-RTK positioning. Furthermore, the lack of satellite detection and elimination of gross errors before grid modeling leads to a decrease in the accuracy and reliability of the grid products. Summary of the Invention

[0004] In view of this, the present invention provides an improved method for generating ionospheric grid products, a terminal, and a readable storage medium, which can generate slanted path ionospheric grid products with high precision, high continuity, and high reliability.

[0005] This application provides an improved method for generating ionospheric grid products, including:

[0006] Real-time acquisition of phase deviation products from reference stations within a preset area;

[0007] Based on the phase deviation product, the slant path ionospheric delay and corresponding first accuracy information of each satellite are extracted at the reference station;

[0008] Based on the first accuracy information, a polynomial iterative fitting is performed on the slant path ionospheric delay;

[0009] If the fitting results meet the preset conditions, the ionospheric residual values ​​of the grid points and the corresponding second precision information are calculated to output the slant path ionospheric grid product.

[0010] Optionally, the step of extracting the slant path ionospheric delay and corresponding first accuracy information of each satellite at the reference station based on the phase deviation product includes:

[0011] The PPP partial ambiguity is fixed at the reference station based on the phase deviation product;

[0012] Based on the fixed results, satellites and / or stations that do not meet the preset screening criteria are removed due to gross errors.

[0013] If the fixed result meets the preset filtering conditions, then the slant path ionospheric delay of each satellite in the reference station is extracted;

[0014] The first precision information of the slant path ionospheric delay is determined based on the fixed result.

[0015] Optionally, the preset filtering conditions include at least one of the following:

[0016] Unable to be fixed properly;

[0017] The accuracy of the positioning information obtained after normal fixation does not meet the preset threshold.

[0018] The accuracy of the positioning information obtained after normal fixation meets the preset threshold, and the satellite does not meet the preset conditions.

[0019] Optionally, after extracting the slant path ionospheric delay of each satellite in the reference station, the method further includes:

[0020] The gross error values ​​introduced by the reference station satellite in positioning calculation and ionospheric extraction are determined based on the change in ionospheric delay between satellite epochs.

[0021] Remove the gross errors.

[0022] Optionally, the step of performing polynomial iterative fitting on the slant path ionospheric delay based on the first accuracy information includes:

[0023] Different weighting ratios are set for the stations based on the first accuracy information;

[0024] Polynomial fitting is performed on the slant path ionospheric delay of each satellite based on the weight ratio.

[0025] Optionally, the preset conditions include:

[0026] The post-test residual is less than or equal to 4 times the standard error;

[0027] The method further includes:

[0028] If the post-test residual is greater than 4 times the mean error, the corresponding station is removed and the fitting continues until the fitting result meets the preset conditions.

[0029] Optionally, the calculation of the ionospheric residual values ​​of the grid points and the corresponding second precision information includes:

[0030] Based on the principle of proximity, the residual part of the fitted oblique path ionospheric delay is assigned to the corresponding grid points, and the second precision information of the grid points is obtained according to the error propagation law.

[0031] Polynomial fitting is performed on the residual portion to obtain the ionospheric residual value at the grid point.

[0032] Optionally, the method further includes:

[0033] The ionospheric residual value and the second accuracy information are sent to the user.

[0034] This application also provides a terminal, including: a memory and a processor, wherein the memory stores a program for generating ionospheric grid products, and when the processor executes the program for generating ionospheric grid products, it implements the steps of the improved method for generating ionospheric grid products as described above.

[0035] This application also provides a computer storage medium storing computer program instructions; when the computer program instructions are executed by a processor, they implement the method for generating the improved ionospheric grid product as described above.

[0036] In summary, the improved ionospheric grid product generation method, terminal, and readable storage medium provided by this invention include: real-time acquisition of phase deviation products of reference stations within a preset area; extraction of the oblique path ionospheric delay and corresponding first precision information of each satellite from the reference stations based on the phase deviation products; polynomial iterative fitting of the oblique path ionospheric delay based on the first precision information; and calculation of the ionospheric residual value of the grid points and corresponding second precision information, if the fitting result meets preset conditions, to output the oblique path ionospheric grid product. The method of this application can generate high-precision, highly continuous, and highly reliable oblique path ionospheric grid products.

[0037] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0038] Figure 1 This is a schematic flowchart illustrating a method for generating an ionospheric grid product according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram illustrating the specific process of generating an ionospheric grid product according to an embodiment of the present invention. Detailed Implementation

[0040] To further illustrate the technical means and effects adopted by the present invention in order to achieve the intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0041] Figure 1 This is a schematic flowchart illustrating an improved method for generating ionospheric grid products according to an embodiment of the present invention. Figure 2 This is a schematic flowchart illustrating a method for generating an ionospheric grid product according to an embodiment of the present invention. Please refer to... Figure 1 and Figure 2 This invention provides an improved method for generating ionospheric grid products, comprising:

[0042] Step 201: Obtain the phase deviation product of the reference station within the preset area in real time.

[0043] To achieve PPP-RTK, the key lies in providing users with high-precision, high-continuity, and high-reliability regional tropospheric and ionospheric corrections. Ionospheric delay is affected by dispersion effects and equipment hardware delays, requiring individual processing for each satellite. Furthermore, the oblique path ionospheric delay of the same satellite within a certain region exhibits strong spatiotemporal correlation; therefore, a gridded approach can be used to model the oblique path ionospheric delay. To improve the accuracy and reliability of oblique path ionospheric grid products, operators can divide large areas into smaller areas and increase the density of stations in sparsely populated areas and low-latitude regions. However, this approach leads to a geometric increase in operating costs, including substantial station construction and subsequent maintenance costs. Additionally, this method suffers from drawbacks such as the lack of detection and removal of outlier satellites and the inability to simultaneously provide users with grid point ionospheric delay values ​​and corresponding accuracy information. Therefore, this method is not feasible for commercial operation.

[0044] To address the aforementioned issues, this embodiment first obtains phase deviation products from reference stations within a preset area in real time, including real-time orbit, clock error, and UPD (Uncalibrated Phase Delay) products, etc. UPD products, also known as fractional phase deviations, absorb various deviations during PPP calculations, causing phase ambiguities to lose their integer characteristics and only be estimated as floating-point numbers, thus limiting further improvements in PPP performance. To solve this problem, the UPD products can be accurately estimated first, and then the integer characteristics of the ambiguities can be restored using the UPD products.

[0045] Step 202: Extract the slant path ionospheric delay and corresponding first accuracy information of each satellite from the reference station based on the phase deviation product.

[0046] In this embodiment, partial ambiguity fixing of the PPP (Phase-Based Positioning) is performed at the reference station based on the acquired phase deviation product. Outlier satellites that do not meet preset screening criteria are then removed based on the fixing results. The preset screening criteria can be: if the fixing result indicates that the satellite cannot be fixed normally, or the accuracy value of the positioning information obtained after normal fixing does not meet a preset threshold, then the corresponding station is removed. For example, stations that cannot be fixed, or stations whose fixed positioning accuracy is greater than 10cm in the horizontal direction and / or greater than 15cm in the vertical direction, are removed without further steps. Alternatively, the preset criteria can be: the accuracy value of the positioning information obtained after normal fixing meets a preset threshold, but the satellite does not meet the preset criteria. For example, for reference stations that can be fixed normally and pass the positioning accuracy test, each satellite is checked, and satellites with an elevation angle below 12° and a continuous observation time below 5 minutes are removed. By detecting and removing outlier satellites before modeling the ionospheric delay grid, the influence of outlier satellites on the oblique path ionospheric grid product is suppressed.

[0047] If the fixed results meet the preset filtering conditions, the oblique path ionospheric delay of each satellite in the reference station is extracted, and the first precision information of the oblique path ionospheric delay is determined based on the fixed results. After extracting the oblique path ionospheric delay of each satellite in the reference station, the process also includes:

[0048] The gross error values ​​introduced by the reference station satellite in positioning calculation and ionospheric extraction are determined based on the change in ionospheric delay between satellite epochs.

[0049] Remove gross errors.

[0050] Specifically, the method determines whether a particular satellite at a given station has introduced gross errors in positioning and ionospheric delay extraction by calculating the change in ionospheric delay between satellite epochs. Gross errors are then eliminated. The threshold for determining whether gross errors have been introduced depends on the sampling interval of the grid product. It is important to note that when a reference station is fixing partial ambiguity in PPP, the replacement of the reference satellite will cause an overall jump in the extracted ionospheric delay compared to the previous epoch. Therefore, the determination and elimination of gross errors should be performed after removing the mean deviation.

[0051] It should be noted that the expression (1.1) for extracting the slant path ionospheric delay of each satellite at each reference station is as follows:

[0052]

[0053] In the formula, s represents the satellite; r represents the station (i.e., the receiver); WL and NL represent wide-lane and narrow-lane combinations, respectively; λ and γ are the wavelength and ionospheric mapping factor, respectively. These are the real-valued ambiguities at frequencies 1 and 2, including the effects of receiver and satellite hardware delays. This represents the corresponding form of real (or integer) ambiguity that does not include the effects of receiver and satellite hardware delays; b r b s These represent the hardware delays at the receiver and satellite, respectively; I represents the slant path ionospheric delay at frequency 1.

[0054] After fixing the PPP ambiguity of the reference station, high-precision non-integer-cycle wide-lane ambiguity and non-integer-cycle narrow-lane ambiguity can be obtained. Based on equation (1.1), high-precision extraction of the oblique path ionospheric delay can be achieved. Subsequently, a grid product reflecting the spatiotemporal characteristics of the ionospheric delay can be generated using polynomial fitting and residual information fitting. Selecting the regional center point, polynomial (1.2) is established based on the latitude and longitude relationship between the station and the regional center point:

[0055] I = C 00 +C 01 (lat-lat0)+C 10 (lon-lon0)+C 11 (lat-lat0)(lon-lon0)

[0056] In the above formula, lon and lat are the latitude and longitude of the modeling station, lon0 and lat0 are the latitude and longitude of the regional center point, and C is the latitude and longitude of the regional center point. 00 C 01 C 10 C 11These are the model coefficients. The residual portion of the ionosphere along the oblique path in the polynomial model is modeled using a grid. For a given satellite, the ionospheric residual at each grid point can be obtained using inverse distance weighted interpolation, based on the location of each grid point and the locations of all observable reference stations.

[0057] Optionally, after removing satellites that may have gross errors from certain stations, it is necessary to first determine the accuracy information of the oblique path ionospheric delay extracted from each station before performing grid modeling of the region. As shown in Equation (1.1), the key to extracting oblique path ionospheric delay using phase observations is accurately solving the ambiguity parameters. Therefore, the first accuracy information of the oblique path ionospheric delay is set based on the fractional part of the wide / narrow lane ambiguity after fixing the PPP partial ambiguity, in order to generate a grid product with higher accuracy that more accurately characterizes the spatiotemporal distribution characteristics of the regional ionospheric delay. The specific rules for the first accuracy information are as follows:

[0058]

[0059] In the formula, 1) and 2) are for stations with narrow lane fixed, 1) is applicable to satellites participating in narrow lane fixed, 2) is applicable to satellites participating in wide lane fixed but not narrow lane fixed; 3) is for stations with wide lane fixed and is applicable to satellites not participating in wide lane fixed.

[0060] Step 203: Perform polynomial iterative fitting on the slant path ionospheric delay based on the first accuracy information.

[0061] In this embodiment, different weighting ratios are set for the stations based on the first accuracy information;

[0062] Polynomial fitting was performed on the slant path ionospheric delay of each satellite based on the weight ratio.

[0063] Specifically, the polynomial coefficients of the ionospheric delay are fitted satellite-by-satellite using regional reference stations. Instead of treating all stations participating in the polynomial coefficient fitting with equal weight, different weights are established based on the first-order accuracy information of the slant path ionospheric delay. Stations with post-verification residuals exceeding four times the standard error are then removed. The polynomial coefficient fitting is iteratively performed until preset conditions are met. These preset conditions include: post-verification residuals less than or equal to four times the standard error. If the post-verification residuals are greater than four times the standard error, the corresponding station is removed, and the fitting process continues until the fitting result meets the preset conditions.

[0064] Step 204: If the fitting result meets the preset conditions, calculate the ionospheric residual value of the grid points and the corresponding second precision information to output the slant path ionospheric grid product.

[0065] Optionally, the ionospheric residual values ​​of the grid points and the corresponding second-precision information are calculated, including:

[0066] Based on the principle of proximity, the residual part of the fitted oblique path ionospheric delay is assigned to the corresponding grid points, and the second precision information of the grid points is obtained according to the error propagation law.

[0067] Polynomial fitting was performed on the residual part to obtain the ionospheric residual values ​​at the grid points;

[0068] Send ionospheric residual values ​​and second-precision information to the user.

[0069] In this embodiment, the residual portion of the ionospheric delay along the oblique path at the reference station after polynomial coefficient fitting is assigned to grid points using the nearest-neighbor principle, and the second-precision information of the corresponding grid points is obtained through the error propagation law. It should be noted that in statistics, because variables contain errors, the function is also affected by these errors; this is called error propagation. The law describing this relationship is called the error propagation law. The error propagation law describes the relationship between the error in the observed value and the error in the observed function. Error propagation laws include the error propagation law for linear functions and the error propagation law for nonlinear functions.

[0070] Within a certain distance range (e.g., 200km), local area network stations for modeling are searched sequentially from closest to furthest from the grid point. Once at least three (and at most five) stations that meet the criteria are found, the ionospheric delay residue corresponding to a satellite at that grid point can be obtained by fitting the following polynomial model.

[0071] ΔI=B 00 +B 01 (lat-lat0)+B 10 (Lon-lon0) (1.4)

[0072] In the above formula, B 00 B 01 and B 10 Here are the coefficients of the polynomial model, lon0 and lat0 are the latitude and longitude of the grid points to be modeled, and B is the modeling result after modeling. 00 This represents the ionospheric residual value at that grid point. The following example illustrates the method for obtaining the second-precision information of the grid points. Let's assume that a satellite has three stations participating in fitting the ionospheric residual at a certain grid point. The following equation can be established:

[0073] V = HX - l (1.5)

[0074] The coefficient matrix H and the weight matrix P can be represented as (1.6):

[0075]

[0076] Solving this equation using least squares, the polynomial model X can be expressed as:

[0077] X=(H T PH)- 1 (H T Pl) (1.7)

[0078] Let Nbb = (H T PH) -1 The accuracy information of the satellite at that grid point can then be represented as Nbb(1,1). The ionospheric residual value of the grid point is then broadcast along with the corresponding second accuracy information, providing users with accuracy information on the ionospheric residual for each satellite and each grid point. Users can flexibly utilize grid products more accurately based on this accuracy information to assist in positioning.

[0079] The improved method for generating ionospheric grid products according to embodiments of the present invention includes: acquiring phase deviation products of reference stations within a preset area in real time; extracting the oblique path ionospheric delay and corresponding first precision information of each satellite from the reference stations based on the phase deviation products; performing polynomial iterative fitting on the oblique path ionospheric delay based on the first precision information; and if the fitting result meets preset conditions, calculating the ionospheric residual value of the grid points and the corresponding second precision information to output the oblique path ionospheric grid product. The method of this application can generate high-precision, highly continuous, and highly reliable oblique path ionospheric grid products.

[0080] For details on the specific process of executing the above method steps in this embodiment, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

[0081] This application also provides a terminal, including: a memory and a processor, wherein the memory stores a program for generating ionospheric grid products, and when the processor executes the program for generating ionospheric grid products, it implements the steps of the improved method for generating ionospheric grid products as described above.

[0082] This invention also provides a readable storage medium storing computer program instructions; when executed by a processor, the computer program instructions implement the improved method for generating ionospheric grid products as described above.

[0083] For details on the specific process of executing the above method steps in this embodiment, please refer to the relevant descriptions in the above embodiments, which will not be repeated here.

[0084] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0085] In this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, which includes not only the elements listed but also other elements not expressly listed.

[0086] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An improved method for generating ionospheric grid products, characterized in that, include: Real-time acquisition of phase deviation products from reference stations within a preset area; Based on the phase deviation product, the slant path ionospheric delay and corresponding first accuracy information of each satellite are extracted at the reference station; Based on the first accuracy information, a polynomial iterative fitting is performed on the slant path ionospheric delay; If the fitting results meet the preset conditions, the ionospheric residual values ​​of the grid points and the corresponding second precision information are calculated to output the slant path ionospheric grid product. The calculation of the ionospheric residual values ​​of the grid points and the corresponding second precision information includes: Based on the principle of proximity, the residual part of the fitted oblique path ionospheric delay is assigned to the corresponding grid points, and the second precision information of the grid points is obtained according to the error propagation law. Polynomial fitting is performed on the residual portion to obtain the ionospheric residual value at the grid point.

2. The method for generating the ionospheric grid product according to claim 1, characterized in that, The step of extracting the slant path ionospheric delay and corresponding first accuracy information of each satellite at the reference station based on the phase deviation product includes: The PPP partial ambiguity is fixed at the reference station based on the phase deviation product; Based on the fixed results, satellites and / or stations that do not meet the preset screening criteria are removed due to gross errors. If the fixed result meets the preset filtering conditions, then the slant path ionospheric delay of each satellite in the reference station is extracted; The first precision information of the slant path ionospheric delay is determined based on the fixed result.

3. The method for generating an ionospheric grid product according to claim 2, characterized in that, The preset filtering conditions include at least one of the following: Unable to be fixed properly; The accuracy of the positioning information obtained after normal fixation does not meet the preset threshold. The accuracy of the positioning information obtained after normal fixation meets the preset threshold, and the satellite does not meet the preset conditions.

4. The method for generating an ionospheric grid product according to claim 2, characterized in that, After extracting the slant path ionospheric delay of each satellite in the reference station, the method further includes: The gross error values ​​introduced by the reference station satellite in positioning calculation and ionospheric extraction are determined based on the change in ionospheric delay between satellite epochs. Remove the gross errors.

5. The method for generating an ionospheric grid product according to claim 1, characterized in that, The step of performing polynomial iterative fitting on the slant path ionospheric delay based on the first accuracy information includes: Different weighting ratios are set for the stations based on the first accuracy information; Polynomial fitting is performed on the slant path ionospheric delay of each satellite based on the weight ratio.

6. The method for generating an ionospheric grid product according to claim 1, characterized in that, The preset conditions include: The post-test residual is less than or equal to 4 times the standard error; The method further includes: If the post-test residual is greater than 4 times the mean error, the corresponding station is removed and the fitting continues until the fitting result meets the preset conditions.

7. The method for generating the improved ionospheric grid product according to claim 1, characterized in that, The method further includes: The ionospheric residual value and the second accuracy information are sent to the user.

8. A terminal, characterized in that, The terminal includes a memory and a processor, wherein the memory stores a program for generating ionospheric grid products, and when the processor executes the program for generating ionospheric grid products, it implements the steps of the improved method for generating ionospheric grid products as described in any one of claims 1 to 7.

9. A readable storage medium, characterized in that, The readable storage medium stores computer program instructions; when executed by a processor, the readable storage medium implements the improved method for generating an ionospheric grid product as described in any one of claims 1-7.

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