A single-station ionospheric disturbance detection system and method

Abstract

The application provides a single-station real-time ionospheric disturbance detection method, which uses VTEC values estimated by observation values of Beidou GEO satellites, combines spatial information of the station and time information of the observation data, selects a multi-scale filtering window, and obtains high-time-resolution VTEC disturbance values in real time. Compared with GPS satellites, the GEO satellites of the Beidou system reduce the interpolation error caused by the spatial change of the piercing point. Compared with the ionospheric disturbance detection method of one filtering, the spatial and temporal characteristics of the ionospheric change are considered, and the rationality of the disturbance detection result is increased. Compared with the sliding quartile method, the required external data amount is reduced, and the calculation complexity is reduced. The method adopted by the application takes into account the calculation complexity and the rationality of the calculation result, and provides reliable support for ionospheric research.

Description

Technical Field

[0001] This invention relates to the field of real-time ionospheric disturbance detection, specifically to a detection system and method for ionospheric disturbances based on observation data from a global satellite navigation system. Background Technology

[0002] Common GNSS ionospheric disturbance detection methods rely on Global Positioning System (GPS) observations to obtain the Vertical Total Electron Content (VTEC) sequence, employing two methods: sliding filter to remove the trend term and sliding quartering. However, GPS satellite observations have the following drawbacks: the visibility time of a single satellite at its corresponding station is relatively short within a day, and the ionospheric penetration point formed by the satellite and ground station changes simultaneously in time and space, making it impossible to obtain the continuous variation of VTEC values ​​at a fixed point over time.

[0003] The sliding filter detrending method has the following drawbacks:

[0004] 1. The problem of selecting the filter window: The sliding filter method is used to analyze the obtained VTEC sequence of the ionosphere. The method has low complexity and does not require the introduction of external products. However, it does not take into account the complexity of the changes in the ionosphere itself, which leads to different degrees of reasonableness of the perturbation under different conditions. The perturbation value obtained often cannot reflect the changes in the electron content of the ionosphere.

[0005] 2. Poor performance during periods of ionospheric activity: The spatiotemporal changes of the ionosphere during periods of ionospheric activity are very complex, and the sliding filter method cannot accurately detect small-scale disturbances, resulting in a certain deviation between the obtained disturbance information and the actual situation.

[0006] The drawbacks of the sliding quarter-part method are as follows:

[0007] 1. The spatiotemporal resolution of external products is low:

[0008] The commonly used sliding quarter-interval method requires the use of Global Ionospheric Maps (GIM) products from organizations such as the European Orbit Determination Centre (CODE) and the International GNSS Service (IGS) for auxiliary calculations. Regardless of the product, the temporal and spatial resolution is low, which can lead to unsatisfactory calculation results in some regions and time periods.

[0009] 2. Requires a large number of known values:

[0010] Regardless of whether external products are introduced, the sliding quarter-interval method requires known VTEC calculation values ​​over a certain period as background when calculating VTEC background values, thus losing its real-time characteristic. When data analysis centers or partial calculation results are missing, it will affect the efficiency and accuracy of the final disturbance detection and increase the computational complexity. Summary of the Invention

[0011] The purpose of this invention is to provide a computer host that is easy to test and repair, so as to solve the problems mentioned in the background art.

[0012] To achieve the above objectives, the present invention provides an ionospheric disturbance detection system above a single monitoring station, characterized in that it includes an ionospheric VTEC value estimation module, a filter window selection module, and a VTEC disturbance value acquisition module.

[0013] The ionospheric VTEC value estimation module is used to estimate the total electron content value in real time based on the observation values ​​of GEO satellites, and to obtain the VTEC time series above the puncture point formed by the line connecting the station and the GEO satellite according to the single-layer projection model.

[0014] The filter window selection module is used to select the size of the filter window based on the spatial information of the station and the temporal information of the observation data.

[0015] The VTEC disturbance value acquisition module is used to acquire real-time VTEC disturbance values ​​based on the sliding median filtering and Savitzky-Golay filtering methods, combined with different filtering window sizes.

[0016] Specifically, the ionospheric VTEC value estimation module uses a non-differential, non-combined, precise single-point positioning method to estimate the STEC value; and uses a single-layer projection function model to calculate the VTEC value.

[0017] Specifically, the filter window selection module sets a default initial filter window size T1 for mesoscale ionospheric disturbances.

[0018] Specifically, T1 is set to 12.5 minutes.

[0019] Specifically, the final VTEC perturbation sequence has a time resolution of 30 seconds.

[0020] A method for real-time detection of the total electron content of the ionosphere, comprising the following steps:

[0021] Step 1: Determine the spatial location of the station to be analyzed and the time information of the observation data, and obtain auxiliary files such as broadcast ephemeris files required for the non-differential non-combined precise single-point positioning method;

[0022] Step 2: Perform non-differential and non-combined precise single-point positioning calculations to obtain the STEC value, and further calculate the VTEC value based on the single-layer projection model;

[0023] The non-difference and non-combination method introduces precise external constraints and employs least-squares joint adjustment to simultaneously estimate the ambiguity parameters of each satellite, improving the accuracy and reliability of ambiguity determination. Compared to phase-smoothing pseudorange ionosphere, it can significantly reduce the impact of multipath effects and observation noise. Its observation model is as follows:

[0024]

[0025] Where I1 and I2 are the ionospheric parameters to be estimated, and in the formula, and These are the pseudorange observations at frequencies L1 and L2 under the corresponding path. τ represents the distance between the satellite and the receiver, c represents the speed of light, and τ represents the speed of light. i To correspond to the clock bias of the satellite, τ j Then ε is the clock bias of the corresponding receiver, and ε1 is the observation noise of the pseudorange observation; and Let N1 and N2 be the carrier phase observations at frequencies L1 and L2, respectively, and let N1 and N2 be the integer ambiguities of the carrier phase observations at frequencies L1 and L2, respectively. Let ε2 be the... and The observation noise. The specific expressions for the remaining symbols are as follows:

[0026]

[0027] Where f1 and f2 are the corresponding frequencies, B s and B r These represent the differential code deviations obtained at different frequencies for the satellite and receiver, respectively.

[0028] The ionospheric observations can be solved using the above two equations. However, these observations include DCB parameters, and the receiver clock error and ambiguity parameters also contain corresponding DCB parameters. DCB parameters often exhibit stable time-varying characteristics, thus not affecting the estimation of ionospheric and ambiguity parameters. The main difference between the non-difference, non-combination method and the phase-smooth pseudorange method lies in the different DCB parameters at the satellite end. Finally, after specific parameter calculations, the ionospheric delay model can be obtained as follows:

[0029]

[0030] In the formula, This refers to the ionospheric delay calculated by the non-differential, non-combined PPP solution, where I1 is the actual ionospheric delay (in meters) from the receiver to the satellite line of sight at frequency f1; DCBr and This refers to the DCB of the BeiDou system signal receiver and the DCB at the satellite end. The ionospheric projection function model is as follows:

[0031]

[0032] Where STEC represents the total electron content along the oblique path, and VTEC represents the total electron content in the vertical direction. This invention selects the simplest single-layer model as follows:

[0033]

[0034] Where cosZ is the zenith distance of the station.

[0035] Specifically, in step 3, based on the local time of the station, the day is divided into noon (12:00-16:00) and other time periods; and based on the latitude of the station, it is divided into low-latitude regions (latitude less than 30 degrees) and mid-to-high latitude regions (latitude greater than or equal to 30 degrees), with preset filter window sizes of T2 (noon in low-latitude regions), T3 (other time periods in low-latitude regions), T4 (noon in mid-to-high latitude regions) and T5 (other time periods in mid-to-high latitude regions);

[0036] Specifically, in step 4, a filtering model is selected, and the VTEC background value is calculated based on the filtering window size. The VTEC disturbance value is then further calculated using the ionospheric disturbance calculation equation; where T2, T3, T4, and T5 are preset durations. The ionospheric disturbance calculation equation is as follows:

[0037] dVTEC filter =VTEC T1 -VTEC Tn

[0038] Among them, VTEC T1 This is the sequence obtained by first filtering and calculating the VTEC values ​​according to the first filtering window T1. Tn For VTEC T1 The sequence obtained by filtering based on the second filtering window Tn, dVTEC filter The resulting VTEC perturbation sequence is given, where the subscript "filter" represents the selected filtering method. The filtering models mentioned are as follows, and the median filtering model is as follows:

[0039]

[0040] in, This represents the trend term obtained after filtering calculation. In the median filtering model, N... wThis refers to the selected window size, and Med represents finding the median value in the corresponding sequence; the SG filtering model is as follows:

[0041]

[0042] in, This represents the trend term obtained after filtering calculation. In the SG filtering model, a is the trend term obtained after filtering calculation. i n represents the filter coefficients. a n b These represent the number of epochs before and after the current epoch, respectively, which is the size of the sliding window.

[0043] Specifically, the filter window size T2 is 60 minutes, the filter window size T3 is 180 minutes, the filter window size T4 is 80 minutes, and the filter window size T5 is 240 minutes.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] 1. By fully considering the complexity of ionospheric changes, a two-stage filtering method was adopted, combined with different filter window sizes, to achieve ionospheric disturbance detection that better matches the spatial and temporal information characteristics of the station; at the same time, the observation values ​​of the Beidou GEO satellite were selected to eliminate the influence of changes in the spatial position of the puncture point;

[0046] 2. The multi-filter window selection adopted in this invention fully considers the temporal and spatial characteristics of ionospheric changes, and each filter window is more in line with the geographical location of the station and the temporal information of the observation data. Compared with the traditional filter window selection, the obtained VTEC background value is more reasonable and convincing, thereby improving the accuracy of the obtained VTEC disturbance value. Compared with the sliding quarter interval method, it reduces the complexity of the VTEC background value calculation process, and does not require external products or data support from other time periods, making the detection process more real-time.

[0047] 3. The disturbance values ​​obtained by this invention have a high time resolution and fully consider the spatial characteristics of the station, which can provide methodological support for geomagnetic storm prediction and analysis. It can be used for precise single-point positioning during periods of ionospheric activity, improving its positioning accuracy and reliability during the corresponding period. Attached Figure Description

[0048] Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] like Figure 1 As shown in the embodiment, the method provided is a method for detecting the perturbation of the total electron content in the vertical direction of the ionosphere. The technical solution adopted by the present invention includes an ionospheric VTEC value estimation module, a filter window selection module, and a VTEC perturbation value acquisition module. In specific implementation, a step-by-step processing method can be adopted to store and analyze the intermediate results of each part.

[0051] The VTEC value estimation module is used to process observation data to obtain the ionospheric delay of the corresponding station, acquire external files such as broadcast ephemeris files, precise orbit files, clock error files and antenna correction files required for calculation, and perform calculation in conjunction with the observation data files. Based on the calculated ionospheric delay, the STEC value is obtained, and then the VTEC time series is obtained.

[0052] The filter window selection module has a default window size of T1 for the first filter, which is 12.5 minutes selected based on the MSTID feature. The size of the second filter window combines the spatial information (latitude value) of the station and the temporal information of the observation data (whether it is local noon), and fully considers the complex characteristics of ionospheric changes. T2, T3, T4 and T5 are selected as filter window sizes for noon in low latitude regions, other time periods in low latitude regions, noon in mid-to-high latitude regions and other time periods in mid-to-high latitude regions, respectively. Since ionospheric activity is more intense at noon, the values ​​of the T1 and T3 windows are smaller, selected as 60 minutes and 80 minutes, respectively; T2 and T4 are selected as 180 minutes and 240 minutes, respectively.

[0053] The VTEC perturbation value acquisition module is used to calculate the VTEC perturbation sequence. According to the selected filtering window, the original VTEC sequence is filtered twice, and the difference between the trend value of the first filter and the trend value of the second filter is calculated as the final VTEC perturbation value.

[0054] The specific implementation principle of the non-differential non-combination PPP method has been described in a large number of documents, and will not be elaborated upon in this invention.

[0055] In practice, the spatial information of the stations to be processed and the temporal information of the observation data can be summarized first, and the corresponding auxiliary files can be obtained. Then, the raw VTEC sequence can be acquired and stored. The summarized information determines the size of the first filtering window (fixed value, 12.5 minutes) and the size of the second filtering window (related to the latitude of the station and the time period of the observation data). In the example, the station distribution includes low-latitude and mid-to-high-latitude regions, and the processing time includes noon and other time periods.

[0056] A method for real-time detection of the total electron content of the ionosphere, comprising the following steps:

[0057] Step 1: Identify the stations to be analyzed, obtain broadcast ephemeris files and other products, and perform non-differential, non-combined precise single-point positioning analysis in conjunction with BeiDou GEO satellite observation data. Select a single-layer projection model, and finally obtain the VTEC raw sequence and store it in the VTEC database. In the specific implementation process, the ionospheric delay is first obtained according to the non-differential, non-combined PPP method, and its observation model is as follows:

[0058]

[0059] Where I1 and I2 are the ionospheric parameters to be estimated, and in the formula, and These are the pseudorange observations at frequencies L1 and L2 under the corresponding path. τ represents the distance between the satellite and the receiver, c represents the speed of light, and τ represents the speed of light. i To correspond to the clock bias of the satellite, τ j Then ε is the clock bias of the corresponding receiver, and ε1 is the observation noise of the pseudorange observation; and Let N1 and N2 be the carrier phase observations at frequencies L1 and L2, respectively, and let N1 and N2 be the integer ambiguities of the carrier phase observations at frequencies L1 and L2, respectively. Let ε2 be the... and The observation noise. The specific expressions for the remaining symbols are as follows:

[0060]

[0061] Where f1 and f2 are the corresponding frequencies, B s and B r These represent the differential code deviations obtained at different frequencies for the satellite and receiver, respectively.

[0062] After removing the DCB information from the result and performing specific parameter calculations, the ionospheric delay model can be obtained as follows:

[0063]

[0064] In the formula, This refers to the ionospheric delay calculated by the non-differential, non-combined PPP solution, where I1 is the actual ionospheric delay (in meters) from the receiver to the satellite line of sight at frequency f1; DCB r and This refers to the DCB of the BeiDou system signal receiver and the DCB of the satellite.

[0065] Step 2: Based on the station information and the epoch information of the observation data, the original VTEC sequence is matched with different filter window sizes. The window size of the second filter is preset in advance. Combined with the spatiotemporal variation characteristics of the ionosphere, it is divided into four cases: T2, T3, T4, and T5. The information of VTEC sequence in the VTEC database is amplified.

[0066] Step 3: Based on the original VTEC series and the corresponding filter window size, perform two filtering operations and calculate the corresponding VTEC perturbation values. Two methods are provided: moving median filtering and SG filtering. The different results are stored separately. Specifically, the median filtering model is as follows:

[0067]

[0068] in, This represents the trend term obtained after filtering calculation. In the median filtering model, N... w This refers to the selected window size, and Med represents finding the median value in the corresponding sequence; SG filtering is a filtering method based on local polynomial least squares fitting in the time domain, and the specific model is as follows:

[0069]

[0070] in, This represents the trend term obtained after filtering calculation. In the SG filtering model, a is the trend term obtained after filtering calculation. i n represents the filter coefficients. a n b These represent the number of epochs before and after the current epoch, i.e., the sliding window size. Background value extraction is performed using two filtering methods with different window sizes:

[0071]

[0072] The window size is selected as T during the first filtering. f1 =12.5min, this time is based on the typical duration of MSTID, t Med and t SG This is the sequence obtained after the first filtering process.

[0073]

[0074] The size of the second filtering window is determined based on the latitude of the station and the time period information of the observation epoch. Med and I SG This is the sequence obtained after the second filtering process. The difference between the two filtering results yields the perturbed sequence:

[0075]

[0076] dVTEC Med and dVTEC SG These are the VTEC perturbation sequences obtained by the two methods.

[0077] Background value extraction based on two filtering processes: Compared with the single filtering process, the two filtering processes weaken the influence of the complex changes in the ionosphere itself by using filtering windows of different sizes. At the same time, compared with the sliding quarter interval method, the computational complexity is significantly reduced. The VTEC perturbation value is obtained by directly subtracting the background values ​​obtained by the two filtering processes.

[0078] Selection of filter window size based on spatiotemporal information of observation data: The ionosphere has obvious spatiotemporal variation characteristics, so the same filter window may have significantly different detection effects in different regions and time periods; This invention takes into account the characteristics of the ionosphere being significantly affected by latitude changes and time changes within a day, and provides different filter windows under different spatiotemporal characteristics, increasing the rationality of VTEC disturbance value detection.

[0079] In practice, computer software can be used to automate the above methods and processes.

[0080] This invention acquires VTEC sequences in real time by obtaining auxiliary files such as broadcast ephemeris and combining them with observation data from BeiDou GEO satellites at the observation station; and selects multiple filter window sizes based on the spatiotemporal characteristics of the observation data to finally obtain VTEC perturbation sequences that conform to the spatiotemporal variation characteristics of the ionosphere.

[0081] In the description of this invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "other end," "upper," "side," "top," "inner," "front," "center," "both ends," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0082] Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," "third," or "fourth" may explicitly or implicitly include at least one of those features.

[0083] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. An ionospheric disturbance detection system above a single monitoring station, characterized in that: It includes an ionospheric VTEC value estimation module, a filter window selection module, and a VTEC perturbation value acquisition module. The ionospheric VTEC value estimation module is used to estimate the total electron content value in real time based on the observation values ​​of GEO satellites, and to obtain the VTEC time series above the puncture point formed by the line connecting the station and the GEO satellite according to the single-layer projection model. The filter window selection module is used to select the size of the filter window based on the spatial information of the station and the temporal information of the observation data. The filter window selection module is specifically used to: divide the day into a noon period (12:00-16:00) and other periods according to the local time of the station; and divide the area into low-latitude regions (latitude less than 30 degrees) and mid-to-high-latitude regions (latitude greater than or equal to 30 degrees) according to the latitude value of the station, and preset filter window sizes of T2, T3, T4 and T5 respectively; wherein, T2 corresponds to the noon period in low-latitude regions, T3 corresponds to other periods in low-latitude regions, T4 corresponds to the noon period in mid-to-high-latitude regions, and T5 corresponds to other periods in mid-to-high-latitude regions. The VTEC disturbance value acquisition module is used to acquire real-time VTEC disturbance values ​​based on the sliding median filtering and Savitzky-Golay filtering methods, combined with different filtering window sizes. The VTEC perturbation value acquisition module is specifically used to: perform a first filtering on the VTEC value using a first filtering window T1 to obtain a first sequence, then perform a second filtering on the first sequence using a second filtering window Tn to obtain a second sequence, and subtract the first sequence from the second sequence to obtain the corresponding VTEC perturbation sequence.

2. The ionospheric disturbance detection system above a single station according to claim 1, characterized in that: The ionospheric VTEC value estimation module uses a non-differential, non-combined, precise single-point positioning method to estimate the STEC value; and uses a single-layer projection function model to calculate the VTEC value.

3. The ionospheric disturbance detection system above a single station according to claim 1, characterized in that: The filter window selection module sets a default initial filter window size T1 for mesoscale ionospheric disturbances, with T1 being 12.5 minutes.

4. An ionospheric disturbance detection system above a single station according to any one of claims 1-3, characterized in that: The final VTEC perturbation sequence has a time resolution of 30 seconds.

5. The ionospheric disturbance detection system above a single station according to claim 1, characterized in that: The filter window size T2 is 60 minutes, the filter window size T3 is 180 minutes, the filter window size T4 is 80 minutes, and the filter window size T5 is 240 minutes.

6. A method for detecting ionospheric disturbances above a single monitoring station, characterized in that, Includes the following steps: Step 1: Determine the spatial location of the station to be analyzed and the time information of the observation data, and obtain auxiliary files such as broadcast ephemeris files required for the non-differential non-combined precise single-point positioning method; Step 2: Perform non-differential and non-combined precise single-point positioning calculations to obtain the STEC value, and further calculate the VTEC value based on the single-layer projection model; Step 3: Divide the day into noon and other time periods according to the local time of the station; and divide the area into low latitude and mid-to-high latitude regions according to the latitude value of the station, and preset the filter window size to T2, T3, T4 and T5 respectively. Step 4: Select the filtering model, calculate the VTEC background value according to the filtering window size, and further calculate the VTEC disturbance value according to the ionospheric disturbance calculation equation. Step 4 specifically includes: using a first filtering window T1 to perform a first filtering on the VTEC value to obtain a first sequence, then using a second filtering window Tn to perform a second filtering on the first sequence to obtain a second sequence, and subtracting the first sequence from the second sequence to obtain the corresponding VTEC perturbation sequence.

7. The method for detecting ionospheric disturbances above a single monitoring station according to claim 6, characterized in that: The equations for calculating ionospheric disturbances are as follows: in, This is the sequence obtained from the first filtering calculation of the VTEC value based on the first filtering window T1. for The sequence obtained by filtering based on the second filtering window Tn. The obtained VTEC perturbation sequence is given by the subscript filter, which represents the selected filtering method.

8. The method for detecting ionospheric disturbances above a single monitoring station according to claim 6, characterized in that: The filtering models mentioned include the median filtering model and the Savitzky-Golay filtering model, wherein: The median filtering model is as follows: in, This represents the trend term obtained after filtering calculations. In the median filtering model, This refers to the selected window size, and Med represents finding the median value in the corresponding sequence; The Savitzky-Golay filter model is as follows: in, This represents the trend term obtained after filtering calculation. In the SG filtering model, the formula is: These are the filter coefficients. , These represent the number of epochs before and after the current epoch, respectively, which is the size of the sliding window.

9. The method for detecting ionospheric disturbances above a single monitoring station according to claim 6, characterized in that: In step 3, the filter window size T2 is 60 minutes, the filter window size T3 is 180 minutes, the filter window size T4 is 80 minutes, and the filter window size T5 is 240 minutes.

10. The method for detecting ionospheric disturbances above a single monitoring station according to claim 6, characterized in that: The value of the first filtering window T1 mentioned in step 3 is 12.5 minutes.

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