Equatorial plasma bubble detection method and system based on GNSS

Abstract

The invention discloses a GNSS-based equatorial plasma bubble detection method and system, and relates to the technical field of equatorial plasma bubble detection. The method comprises the following steps: acquiring a GNSS observation file transmitted by a satellite and received by a receiver, and extracting pseudo-range data in the GNSS observation file; extracting TEC data in the GNSS observation file according to the extracted pseudo-range data; extracting an equator plasma bubble sequence based on the extracted TEC data; performing equator plasma bubble detection according to the equator plasma bubble sequence, and determining an equator plasma bubble event; wherein the TEC data is the total electron content calculated by using the GNSS observation file. According to the method provided by the invention, the problem of ambiguity calculation existing in cycle slip detection and TEC information extraction when the disturbance of TEC data extraction is relatively large by using the carrier phase data can be effectively solved, and meanwhile, the workload of equator plasma bubble detection is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of equatorial plasma bubble detection, and in particular to a GNSS-based equatorial plasma bubble detection method and system. Background Art

[0002] The ionosphere is an ionized region of the Earth's atmosphere, located mainly above 60 kilometers above the Earth's surface. It is a plasma composed of free electrons, positive and negative ions, neutral molecules and atoms. TEC (Total Electron Content) is an important parameter to describe the characteristics of the ionosphere. It refers to the total number of free electrons that a radio wave passes through when passing through the ionosphere at a unit frequency. 1 TEC unit is equal to 10 16 electrons / square meter.

[0003] Equatorial Plasma Bubble (EPB), the formation of equatorial plasma bubbles is believed to be caused by Rayleigh-Taylor (RT) instabilities in the F layer. After sunset, the electric field in the equatorial region is enhanced, which can cause the F layer to rise to a higher altitude, thereby increasing the growth rate of RT instabilities. This phenomenon mainly occurs in the F layer in the equatorial region, usually after sunset, during the night to midnight. EPB can have serious effects on navigation and communication systems because they interfere with radio signals propagating through the ionosphere, causing signal attenuation or scintillation.

[0004] Cycle slip is a special phenomenon in the carrier phase observation of the global navigation satellite system. It refers to the counter jumping by an integer number of cycles when the receiver reacquires the signal due to temporary interruption or loss of satellite signal. This phenomenon has a significant impact on positioning accuracy, so the detection and repair of cycle slip is an important part of GNSS data processing.

[0005] Therefore, in order to ensure the continuity and reliability of carrier phase observations and improve positioning accuracy and the reliability of positioning results, cycle slip detection is particularly necessary.

[0006] Commonly used cycle slip detection methods are: 1. Melbourne-Wubbena combination (MW combination): Use the combined observations of dual-frequency carrier phase and code pseudorange to detect / repair cycle slips. The MW combination eliminates the influence of the ionosphere, troposphere, clock error and geometric distance. When there is no cycle slip, the MW test quantity should fluctuate around a constant. When a cycle slip occurs, the test quantity will change suddenly.

[0007] 2. Dual-frequency ionospheric residual method (no geometric distance, GF combination method): The ionospheric residual of the dual-frequency carrier phase observation is used to detect / repair cycle slips. GF ​​combination eliminates the influence of geometric distance and is suitable for static and dynamic observation data, and is obviously affected by the observation sampling interval and satellite altitude angle.

[0008] Before processing the carrier phase data, the above two methods are generally used in combination to monitor and eliminate cycle slips, which is a large workload and will result in a certain amount of data loss.

[0009] In summary, in the process of processing TEC, the existing equatorial plasma bubble detection technology usually uses carrier phase data to process TEC, and it is necessary to first perform cycle slip detection, which will inevitably cause some data to be deleted. Especially when the TEC disturbance is relatively large, it is easy for some data that are not cycle slips to be identified as cycle slips due to the cycle slip detection process, thereby losing some usable data. In addition, there is an ambiguity resolution problem in extracting TEC information using carrier observation values, resulting in a large workload for equatorial plasma bubble detection. Summary of the invention

[0010] In order to overcome the problems of cycle slip detection and ambiguity resolution in the prior art of extracting TEC information using carrier observation values, which leads to data loss and large workload in equatorial plasma bubble detection, the present invention proposes an equatorial plasma bubble detection method and system based on GNSS, which can effectively solve the problems of cycle slip detection and ambiguity resolution in extracting TEC information when TEC disturbance is large, and effectively reduce the workload of equatorial plasma bubble detection.

[0011] The purpose of the present invention is achieved by the following technical solutions: A method for detecting equatorial plasma bubbles based on GNSS, the method comprising the following steps: Receive GNSS observation files transmitted by satellites, and extract pseudorange data from the data in the GNSS observation files; Extract TEC data in the GNSS observation file based on the extracted pseudorange data; Extract the equatorial plasma bubble sequence based on the extracted TEC data; performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

[0012] In the above technical scheme, by extracting pseudorange data from the GNSS observation file, the problem of cycle slip detection when the TEC disturbance is large can be effectively solved. The TEC data in the GNSS observation file is extracted according to the extracted pseudorange data, which can effectively solve the problems of cycle slip detection and ambiguity resolution in the process of extracting TEC information. Then, the equatorial plasma bubble sequence is extracted based on the extracted TEC data, and the equatorial plasma bubble detection is performed to determine the equatorial plasma bubble event. When the cycle slips are frequent or the disturbance is large, the observation of the equatorial plasma bubble can be completed, and the workload of the equatorial plasma bubble detection is effectively reduced.

[0013] Furthermore, the process of extracting pseudorange data from the data in the GNSS observation file includes: Extract the dual-frequency pseudorange observation value from the GNSS observation file. The expression is: ; According to the extracted dual-frequency pseudorange observations, the ionospheric analysis is performed to obtain the difference between the code measurement pseudorange observations, which is expressed as: ; in, Indicates the distance between the satellite and the measuring station; All represent bi-frequency observations; represents the pseudorange observation; represents the speed of light; represent the clock difference between satellite i and receiver j respectively; is the tropospheric delay; Represents receiver errors and satellite hardware errors at different frequencies; Represents the ionospheric delay at different frequencies; represents the signal frequency, and The superscript 2 represents square, and the subscripts 1 and 2 represent frequency 1 and frequency 2.

[0014] In the above technical solution, by using the dual-frequency pseudorange observation values ​​in the GNSS observation file and extracting the difference between the dual-frequency pseudorange observation values ​​to perform ionospheric analysis, some errors in the data processing process can be effectively eliminated.

[0015] Furthermore, the process of extracting TEC data in the GNSS observation file according to the extracted pseudorange data includes: Based on the code measurement pseudorange observation value, the ionospheric TEC data is extracted, and the expression is: ; in, is the signal frequency; , They are The code measurement pseudorange observation value on the frequency; B is the inter-frequency hardware delay deviation; Indicates the use and The ionospheric TEC is obtained by frequency.

[0016] Furthermore, the extracted ionospheric TEC data is processed absolutely to extract the absolute TEC data, which is expressed as: ; in, and The superscript 2 represents square, and the subscripts 1 and 2 represent frequency 1 and frequency 2.

[0017] In the above technical solution, TEC data in the GNSS observation file is extracted based on the extracted pseudorange data. Not only because the pseudorange data is relatively easy to obtain and has no cycle slips, but also it can effectively solve the problems of cycle slip detection and ambiguity resolution in the process of extracting TEC information.

[0018] Furthermore, the absolute TEC data is preprocessed to remove gross errors, and the broadcast ephemeris file is obtained; The broadcast ephemeris file is merged with the pre-processed absolute TEC data to obtain a new TEC data file; The SG filter is used to smooth and reduce noise on the new TEC data file, and the smoothed and reduced noise TEC data file is fitted, and the TEC data file obtained after fitting is used as the background TEC data file; The SG filter represents Savitzky-Golay filter.

[0019] Furthermore, the process of using SG filtering to smooth, reduce noise and perform fitting processing on the new TEC data file includes: Define a window size of ; In the window, use Order polynomial fit to data points; Calculate the window center point The smoothing value of , the expression is: ; in, Indicates the half-width of the window, Represents the total number of points in the window, , Represents the coefficients of the polynomial.

[0020] In the above technical scheme, the extracted absolute TEC data is processed to eliminate gross errors, which can effectively improve the data quality and the judgment of gross errors in the TEC estimation accuracy, so as to improve the stability of the pseudorange observation value; the SG filter is used to smooth the TEC data file for noise reduction and fitting, which can maintain the shape and characteristics of the signal, and provide higher stability and reliability for the subsequent extraction of the equatorial plasma bubble sequence.

[0021] Furthermore, the process of extracting the equatorial plasma bubble sequence based on the extracted TEC data includes: By smoothing the denoised TEC data file and the background TEC data file, the TEC sequence of the detrended item in the TEC data file is calculated. The expression is: ; The start and end time of the equatorial plasma bubble sequence is determined according to the detrended TEC sequence, and the start and end times are linearly fitted to obtain a partially fitted TEC sequence; The TEC sequence in the smoothed and denoised TEC data file is subtracted from the TEC sequence in the partially fitted TEC data file to obtain the equatorial plasma bubble sequence; in, represents the satellite altitude angle, represents the original TEC sequence after smoothing and noise reduction, FittedTEC represents the TEC data after fitting, and TEC sequence represents the time series of TEC data in the TEC data file.

[0022] Furthermore, the process of determining the equatorial plasma bubble event includes: A linear regression model is set up to learn the data variation law of the equatorial plasma bubble sequence, and an equatorial plasma bubble detection model that grasps the data variation law of the equatorial plasma bubble sequence is obtained; The equatorial plasma bubble detection model is used to judge the equatorial plasma bubble event according to the equatorial plasma bubble sequence. The judgment expression is: ; in, Event represents the equatorial plasma bubble event, MaxdTEC represents the maximum TEC depletion in the extracted equatorial plasma bubble sequence, and Duration represents the duration in the equatorial plasma bubble sequence.

[0023] Furthermore, the process of determining the start time and the end time of the equatorial plasma bubble sequence according to the TEC sequence of the detrended term and performing linear fitting on the start time and the end time includes: Define a straight line , for any two points on the line and , calculate the slope of the straight line y, the expression is: ; According to the slope m, calculate the intercept of the straight line y, the expression is: ; Based on the slope m and the intercept b, the linear fitting equation is obtained, which is expressed as follows: ; Here, y represents a straight line in the TEC data, and x represents the time data.

[0024] In the above technical scheme, the detrended TEC sequence (dTEC) can be obtained by subtracting the original TEC before fitting and the TEC after fitting, which is helpful to obtain the start time and end time of the EPBs sequence. Moreover, using the dTEC sequence (modifieddTEC) to extract the equatorial plasma bubble sequence can better obtain a good TEC depletion curve, and can more intuitively determine the equatorial plasma bubble event from the data.

[0025] A GNSS-based equatorial plasma bubble detection system, the system comprising: A receiving module, used for receiving GNSS observation files transmitted by satellites; A processing module, used for extracting pseudo-range data from the data in the GNSS observation file, and extracting TEC data from the GNSS observation file according to the extracted pseudo-range data; The processing module is also used to extract the equatorial plasma bubble sequence based on the extracted TEC data; A detection module, used for performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

[0026] Compared with the prior art, the present invention has the following beneficial effects: The present invention proposes a GNSS-based equatorial plasma bubble detection method and system. By extracting pseudorange data from a GNSS observation file, the problem of cycle slip detection when TEC disturbance is large can be effectively solved. TEC data in the GNSS observation file is extracted according to the extracted pseudorange data, which can effectively solve the problems of cycle slip detection and ambiguity resolution in the process of extracting TEC information. Then, an equatorial plasma bubble sequence is extracted based on the extracted TEC data, and equatorial plasma bubble detection is performed to determine equatorial plasma bubble events. When cycle slips are frequent or disturbances are large, the observation of equatorial plasma bubbles can be completed, and the workload of equatorial plasma bubble detection is effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of the steps of a GNSS-based equatorial plasma bubble detection method provided in an embodiment of the present application; Figure 2 Schematic diagram of the GNSS-based equatorial plasma bubble detection principle provided in the embodiment of the present application; Figure 3 A comparison chart of satellite data experiments in 2014 provided in the embodiments of the present application; Figure 4 A comparison chart of satellite data experiments in 2023 provided in an embodiment of the present application; Figure 5 A structural block diagram of a GNSS-based equatorial plasma bubble detection system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Preferred embodiments of the present invention are provided in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0030] Embodiment 1: This embodiment provides a method for detecting equatorial plasma bubbles based on GNSS. Figure 1 , the method comprises the following steps: Step S1: receiving a GNSS observation file transmitted by a satellite, and extracting pseudorange data through the data in the GNSS observation file; Step S2: extracting TEC data in the GNSS observation file according to the extracted pseudorange data; Step S3: extracting the equatorial plasma bubble sequence based on the extracted TEC data; Step S4: performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

[0031] As a preferred embodiment, in step S1, see Figure 2,The process of extracting pseudorange data from the data in the GNSS observation file includes: Extract the dual-frequency pseudorange observation value from the GNSS observation file. The expression is: (1) in, Indicates the distance between the satellite and the station; All represent bi-frequency observations; represents the pseudorange observation; represents the speed of light; represent the clock difference between satellite i and receiver j respectively; is the tropospheric delay; Represents receiver errors and satellite hardware errors at different frequencies; Represents the ionospheric delay at different frequencies.

[0032] Among them, when only considering the first-order ionospheric delay error, the expression is: (2) Where TEC stands for total electron content, and the unit is 10 16 Number of electrons ; f is the signal frequency, the unit is The unit is m. Combining equations (1) and (2), the equation can be written as follows: (3) in, ; k=1,2.

[0033] According to the extracted dual-frequency pseudorange observations, the ionospheric analysis is performed to obtain the difference between the code measurement pseudorange observations, which is expressed as: (4) in, are the hardware delays of receiver j and satellite i respectively.

[0034] It can be understood that by using the dual-frequency pseudorange observations in the GNSS observation file and extracting the difference between the dual-frequency pseudorange observations for ionospheric analysis, some errors in the data processing process can be effectively eliminated.

[0035] In step S2, the process of extracting TEC data in the GNSS observation file according to the extracted pseudorange data includes: Based on the code measurement pseudorange observation value, the ionospheric TEC data is extracted, and the expression is: (5) in, is the signal frequency; , They are The code measurement pseudorange observation value on the frequency; B is the inter-frequency hardware delay deviation; Indicates the use and The ionospheric TEC obtained by frequency, and The superscript 2 represents square, and the subscripts 1 and 2 represent frequency 1 and frequency 2.

[0036] Further, see Figure 2 , perform absolute processing on the extracted ionospheric TEC data and extract the absolute TEC data. The expression is: (6) It can be understood that extracting TEC data in the GNSS observation file based on the extracted pseudorange data is not only because the pseudorange data is relatively easy to obtain and has no cycle slips, but also can effectively solve the problems of cycle slip detection and ambiguity resolution in the process of extracting TEC information.

[0037] As a preferred embodiment, see Figure 2 , pre-process the absolute TEC data and obtain the broadcast ephemeris file; The broadcast ephemeris file is merged with the pre-processed absolute TEC data to obtain a new TEC data file; The SG filter is used to smooth and reduce noise on the new TEC data file, and the smoothed and reduced noise TEC data file is fitted, and the TEC data file obtained after fitting is used as the background TEC data file; Specifically, the coordinates and satellite altitude angle MF are calculated by broadcast ephemeris file, and the process of preprocessing the absolute TEC data includes removing the absolute TEC data with a satellite altitude cutoff angle lower than 15°, retaining the absolute TEC data with an altitude cutoff angle greater than or equal to 15°, and then further screening these data to remove the data with a continuous time of less than 20 minutes, and completing the gross error removal processing of the extracted absolute TEC data; The SG filter represents Savitzky-Golay filter.

[0038] Specifically, the process of using SG filtering to smooth, reduce noise and fit the new TEC data file includes: Define a window size of ; In the window, use Order polynomial fit to data points; Calculate the window center point The smoothing value of , the expression is: (7) in, Indicates the half-width of the window, Represents the total number of points in the window, , Represents the coefficients of the polynomial.

[0039] Specifically, set a data sequence , for each data point For smoothing, select a data point window, where Is half the window width.

[0040] For each window, select a Polynomial To fit the data points within the window, the polynomial is in the following form:

[0041] in, are the coefficients of the polynomial, which are determined by the least squares method so that the polynomial best fits the data points within the window.

[0042] For each data point in the window ,have:

[0043] in, The range is from arrive , is the error term. The goal is to minimize the sum of squared errors:

[0044] By solving this least squares problem, we can get the coefficients According to the coefficients of the polynomial, the center point of the window can be calculated The estimated value of is:

[0045] This process is repeated on the entire data sequence to obtain a smoothed data sequence .

[0046] It can be understood that removing gross errors from the extracted absolute TEC data can effectively improve the data quality and the TEC estimation accuracy for gross errors, so as to improve the stability of pseudorange observations; using SG filtering to smooth, reduce noise and fit the TEC data file can maintain the shape and characteristics of the signal, providing higher stability and reliability for the subsequent extraction of the equatorial plasma bubble sequence.

[0047] In step S3, the process of extracting the equatorial plasma bubble sequence based on the extracted TEC data includes: By smoothing the denoised TEC data file and the background TEC data file, the TEC sequence of the detrended item in the TEC data file is calculated. The expression is: (8) The start and end time of the equatorial plasma bubble sequence is determined according to the detrended TEC sequence, and the start and end times are linearly fitted to obtain a partially fitted TEC sequence; The TEC sequence in the smoothed and denoised TEC data file is subtracted from the TEC sequence in the partially fitted TEC data file to obtain the equatorial plasma bubble sequence; Wherein, MF represents the satellite altitude angle, and the MF is calculated from the broadcast ephemeris file. represents the original TEC sequence after smoothing and noise reduction, FittedTEC represents the TEC data after fitting, and TEC sequence represents the time series of TEC data in the TEC data file.

[0048] Furthermore, the process of determining the equatorial plasma bubble event includes: A linear regression model is set up to learn the data variation law of the equatorial plasma bubble sequence, and an equatorial plasma bubble detection model that grasps the data variation law of the equatorial plasma bubble sequence is obtained; The equatorial plasma bubble detection model is used to judge the equatorial plasma bubble event according to the equatorial plasma bubble sequence. The judgment expression is: (9) in, (Equatorial plasma bubble event) represents the equatorial plasma bubble event, MaxdTEC represents the maximum TEC depletion in the extracted equatorial plasma bubble sequence, and Duration represents the duration in the equatorial plasma bubble sequence.

[0049] TEC depletion mainly occurs in spring and autumn, and is usually concentrated at night. If the maximum TEC depletion (i.e., depth) is greater than 5TECU and lasts longer than 10 minutes, the TEC depletion can be identified as an EPBs event.

[0050] Furthermore, the process of determining the start time and the end time of the equatorial plasma bubble sequence according to the TEC sequence of the detrended term and performing linear fitting on the start time and the end time includes: Define a straight line , for any two points on the line and , calculate the slope of the straight line y, the expression is: ; Based on the slope m, use one of the points to solve Axis intercept , the expression is: ; Will Substituting the value of into the above formula, we get: ; After merging, we can get the intercept of the calculated line y, the expression is: ; Based on the slope m and the intercept b, the linear fitting equation is obtained, which is expressed as follows: ; Here, y represents a straight line in the TEC data, and x represents the time data.

[0051] It can be understood that by subtracting the original TEC before fitting from the TEC after fitting, the detrended TEC sequence (dTEC) can be obtained, which is helpful to obtain the start time and end time of the EPBs sequence. Moreover, using the dTEC sequence (modifieddTEC) to extract the equatorial plasma bubble sequence can better obtain a good TEC depletion curve, and can more intuitively determine the equatorial plasma bubble event from the data.

[0052] In this embodiment, by extracting pseudorange data from the GNSS observation file, the problem of cycle slip detection when the TEC disturbance is large can be effectively solved. The TEC data in the GNSS observation file is extracted according to the extracted pseudorange data, which can effectively solve the problems of cycle slip detection and ambiguity resolution in the process of extracting TEC information. Then, the equatorial plasma bubble sequence is extracted based on the extracted TEC data, and equatorial plasma bubble detection is performed to determine the equatorial plasma bubble event. When the cycle slips are frequent or the disturbance is large, the observation of the equatorial plasma bubble can be completed, and the workload of equatorial plasma bubble detection is effectively reduced.

[0053] Embodiment 2: This embodiment provides corresponding experimental data for the first embodiment, which are as follows: Take the location of the Hong Kong HKSL station (22.372°N, 113.928°E) as an example: The two times chosen are 2014 and 2023, both of which are years of high solar activity and more prone to equatorial plasma bubble (EPB) events.

[0054] ①On 14 February 2014 (annual day 45), the HKSL station detected the equatorial plasma bubble phenomenon via the G01 satellite at 15:45UT-16:15UT.

[0055] A: Input the observation file and ephemeris file into the equatorial plasma bubble detection model. The model will use the pseudorange data extracted from the GNSS observation file (o file, sampling rate 30s) of the HKSL station obtained at the IGS station. According to formula (6), the total electron content (TEC) data can be obtained by dual-frequency pseudorange measurement; B: No pre-processing such as cycle slip detection is required. Only the satellite elevation angle and the continuous time data need to be judged. Data with too low satellite elevation angle (<15°) and continuous time less than 20 minutes need to be screened out. C: The obtained TEC data is denoised using Savitzky-Golay filtering (SG filtering), with the order set to 3 and the sliding window set to 330s (11 data) to make the obtained TEC data smoother, in preparation for subsequent work; D: Fit the denoised TEC data, use SG filtering, set the order to 3, and the sliding window to 1 hour (121 data), and you can get the background TEC. Then subtract the fitted data (background TEC) from the original data to get the detrended TEC data (dTEC), which is generally used to judge the changes in TEC data.

[0056] E: Based on the dTEC data, we can get the start and end time of the data change, that is, the start and end time of the EPB time. Therefore, we can perform a linear fit on the data during this period to obtain partially fitted TEC data.

[0057] After subtracting the TEC data from the partially fitted TEC data, the improved dTEC data can be obtained. Compared with the dTEC calculated initially, this data can better reflect the size of EPB depletion and other information, which is conducive to the analysis of EPB events.

[0058] See also Figure 3 , Figure 3 a TEC data obtained using carrier phase data (ObservedTEC), fitted TEC data (FittedTEC), and partially fitted TEC data (PartialFittedTEC); Figure 3 b dTEC data (dTEC) obtained using carrier phase data, modified dTEC data (ModifeddTEC); Figure 3 c TEC data obtained using pseudorange data (ObservedTEC), fitted TEC data (FittedTEC), and partially fitted TEC data (PartialFittedTEC); Figure 3d dTEC data (dTEC) obtained using pseudorange data, and improved dTEC data (ModifeddTEC).

[0059] Depend on Figure 3 It can be seen that the EPB consumption obtained by extracting the carrier phase data is 12TECU, and the EPB occurrence time is 30min; while the EPB consumption obtained by extracting the pseudorange data is 10TECU, and the EPB occurrence time is 30min; both types of data can be used to determine that an EPB event occurred in this time period, and the obtained EPB consumptions are basically the same. Therefore, the EPB data extracted by the method proposed in the present invention is feasible and reliable.

[0060] ②On February 18, 2023 (annual day 49), the HKSL station detected the equatorial plasma bubble phenomenon through the G17 satellite at 11:57UT-13:15UT.

[0061] TEC data can be obtained by following the same steps as in ①. By comparing the TEC data obtained using carrier phase data and pseudorange data, it can be seen that due to cycle slip detection, the carrier phase data filters out the data during the EPB event.

[0062] See also Figure 4 , Figure 4 a TEC data obtained using carrier phase data; Figure 4 b TEC data obtained using pseudorange data; Figure 4 c TEC data obtained using pseudorange data (ObservedTEC), fitted TEC data (FittedTEC), and partially fitted TEC data (PartialFittedTEC); Figure 4 d dTEC data (dTEC) obtained using pseudorange data, and improved dTEC data (ModifieddTEC).

[0063] In this processing, the obtained TEC data is denoised using Savitzky-Golay filtering (SG filtering). Since the pseudo-range data noise obtained from this satellite is relatively large, the order is set to 3 and the sliding window is 15 minutes (31 data) to make the obtained TEC data smoother; The denoised TEC data is fitted, and the SG filter is used. The order is also set to 3, and the sliding window is 1 hour (121 data). The background TEC can be obtained. Then the original data is subtracted from the fitted data (background TEC) to obtain the detrended TEC data (dTEC), which is generally used to judge the changes in TEC data.

[0064] Depend on Figure 4 It can be seen from a that after a series of operations such as calculating the integer ambiguity and detecting the cycle slip, the data of the carrier phase data during the EPB event is deleted, resulting in the inability to extract the relevant information of the EPB; Figure 4 As can be seen in b, the pseudorange data during the EPB event is reliable, without excessive disturbances and jumps, and can be used. After processing according to the previous steps, the pseudorange data is used to obtain the EPB consumption of this event is approximately 33TECU, and the disturbance time is 78min; thus, it can be judged that the EPB event occurred during this period.

[0065] Embodiment three: This embodiment provides a GNSS-based equatorial plasma bubble detection system. Figure 5 , the system comprising: A receiving module, used for receiving GNSS observation files transmitted by satellites; A processing module, used for extracting pseudo-range data from the data in the GNSS observation file, and extracting TEC data from the GNSS observation file according to the extracted pseudo-range data; The processing module is also used to extract the equatorial plasma bubble sequence based on the extracted TEC data; A detection module, used for performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

[0066] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for detecting equatorial plasma bubbles based on GNSS, characterized in that: The method comprises the following steps: Receive GNSS observation files transmitted by satellites, and extract pseudorange data from the data in the GNSS observation files; Extract TEC data in the GNSS observation file based on the extracted pseudorange data; Extract the equatorial plasma bubble sequence based on the extracted TEC data; performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

2. The GNSS-based equatorial plasma bubble detection method according to claim 1, characterized in that: The process of extracting pseudorange data from the data in the GNSS observation file includes: Extract the dual-frequency pseudorange observation value from the GNSS observation file. The expression is: ； According to the extracted dual-frequency pseudorange observations, the ionospheric analysis is performed to obtain the difference between the code measurement pseudorange observations, which is expressed as: ； in, Indicates the distance between the satellite and the station; All represent bi-frequency observations; represents the pseudorange observation; represents the speed of light; represent the clock difference between satellite i and receiver j respectively; is the tropospheric delay; Represents receiver errors and satellite hardware errors at different frequencies; Represents the ionospheric delay at different frequencies; represents the signal frequency, and The superscript 2 represents square, and the subscripts 1 and 2 represent frequency 1 and frequency 2.

3. The GNSS-based equatorial plasma bubble detection method according to claim 2, characterized in that: The process of extracting TEC data in the GNSS observation file based on the extracted pseudorange data includes: Based on the code measurement pseudorange observation value, the ionospheric TEC data is extracted, and the expression is: ； in, is the signal frequency; , They are The code measurement pseudorange observation value on the frequency; B is the inter-frequency hardware delay deviation; Indicates the use and The ionospheric TEC is obtained by frequency.

4. The GNSS-based equatorial plasma bubble detection method according to claim 3, characterized in that: The extracted ionospheric TEC data is processed absolutely to extract the absolute TEC data. The expression is: ； in, and The superscript 2 represents square, and the subscripts 1 and 2 represent frequency 1 and frequency 2.

5. The GNSS-based equatorial plasma bubble detection method according to claim 4, characterized in that: Perform preprocessing to remove gross errors on the absolute TEC data and obtain the broadcast ephemeris file; The broadcast ephemeris file is merged with the pre-processed absolute TEC data to obtain a new TEC data file; The SG filter is used to smooth and reduce noise on the new TEC data file, and the smoothed and reduced noise TEC data file is fitted, and the TEC data file obtained after fitting is used as the background TEC data file; The SG filter represents Savitzky-Golay filter.

6. The GNSS-based equatorial plasma bubble detection method according to claim 5, characterized in that: The process of smoothing, denoising and fitting the new TEC data file using SG filtering includes: Define a window size of ; In the window, use Order polynomial fit to data points; Calculate the window center point The smoothing value of , the expression is: ； in, Indicates the half-width of the window, Represents the total number of points in the window, , Represents the coefficients of the polynomial.

7. The GNSS-based equatorial plasma bubble detection method according to claim 5, characterized in that: The process of extracting the equatorial plasma bubble sequence based on the extracted TEC data includes: By smoothing the denoised TEC data file and the background TEC data file, the TEC sequence of the detrended item in the TEC data file is calculated. The expression is: ； The start and end time of the equatorial plasma bubble sequence is determined according to the detrended TEC sequence, and the start and end times are linearly fitted to obtain a partially fitted TEC sequence; The TEC sequence in the smoothed and denoised TEC data file is subtracted from the TEC sequence in the partially fitted TEC data file to obtain the equatorial plasma bubble sequence; in, represents the satellite altitude angle, represents the original TEC sequence after smoothing and noise reduction, FittedTEC represents the TEC data after fitting, and TEC sequence represents the time series of TEC data in the TEC data file.

8. The GNSS-based equatorial plasma bubble detection method according to claim 7, characterized in that: The process of identifying equatorial plasma bubble events involves: A linear regression model is set up to learn the data variation law of the equatorial plasma bubble sequence, and an equatorial plasma bubble detection model that grasps the data variation law of the equatorial plasma bubble sequence is obtained; The equatorial plasma bubble detection model is used to judge the equatorial plasma bubble event according to the equatorial plasma bubble sequence. The judgment expression is: ； in, Event represents the equatorial plasma bubble event, MaxdTEC represents the maximum TEC depletion in the extracted equatorial plasma bubble sequence, and Duration represents the duration in the equatorial plasma bubble sequence.

9. The GNSS-based equatorial plasma bubble detection method according to claim 7, characterized in that: The process of determining the start and end time of the equatorial plasma bubble sequence based on the detrended TEC sequence and linearly fitting the start and end time includes: Define a straight line , for any two points on the line and , calculate the slope of the straight line y, the expression is: ； According to the slope m, calculate the intercept of the straight line y, the expression is: ； Based on the slope m and the intercept b, the linear fitting equation is obtained, which is expressed as follows: ； Here, y represents a straight line in the TEC data, and x represents the time data.

10. A GNSS-based equatorial plasma bubble detection system, characterized in that: The system comprises: A receiving module, used for receiving GNSS observation files transmitted by satellites; A processing module, used for extracting pseudo-range data from the data in the GNSS observation file, and extracting TEC data from the GNSS observation file according to the extracted pseudo-range data; The processing module is also used to extract the equatorial plasma bubble sequence based on the extracted TEC data; A detection module, used for performing equatorial plasma bubble detection according to the equatorial plasma bubble sequence to determine the equatorial plasma bubble event; Among them, TEC data is the total electron content calculated using GNSS observation files.

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