CN114545447B - GNSS occultation ionization layer data correction method - Google Patents
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Abstract
The invention relates to the technical field of radio occultation detection and satellite application, and provides a method for correcting GNSS occultation ionization layer data, which comprises the following steps: acquiring occultation side observation data of a target observation satellite in a target ionization layer region within a preset time period, calculating to obtain a first time-space data of each occultation time target observation satellite LEO and a corresponding first GNSS occultation, calculating to obtain a second time-space data of the target observation satellite LEO according to the first time-space data, acquiring non-occultation side observation data of each occultation time target observation satellite LEO, preprocessing the occultation side observation data and the non-occultation side observation data, substituting the preprocessed occultation side observation data and the non-occultation side observation data into a resolving formula to calculate a total electron content TEC and a non-occultation side ionization layer total electron content TEC0 on a GNSS signal propagation path, and calculating a difference value of the TEC and the TEC0 to obtain a corrected oblique total electron content TEC'. The invention can effectively solve the problem of insufficient precision of the ionosphere data acquired in the related technology.
Description
Technical Field
The invention relates to the technical field of radio occultation detection and satellite application, in particular to a method for correcting GNSS occultation ionization layer data.
Background
Total Electron Content TEC (Total Electron Content) and its variation are important parameters for ionosphere morphology study, as well as for ionosphere correction in fine positioning, navigation and electrical wave science. The method is an important parameter for describing the form and structure of the ionized layer and is beneficial to researching the influence of the ionized layer on the propagation of electromagnetic waves. Currently, most TEC measurements are monitored by satellite navigation systems. Currently, the ionosphere forecast comprises a Klobuchar model, a Bent model, an IRI model, an ICED model, an FAIM model and the like, and a GPS (global positioning system) and a Beidou navigation satellite are main measuring tools. In practical applications, ionosphere prediction is the prediction of the electron content of grid points at a certain height above the ground at a future time. At present, the electron content with 5 ° longitude and 2.5 ° latitude is usually given every two hours internationally, so that 5183 (73 × 71) grid points are globally provided every two hours, and the hardware errors of TEC and GNSS measurement of the grid are obtained by using least square fitting.
However, in the process of implementing the technical solution of the invention in the embodiments of the present application, the inventor of the present application finds that the above technology has at least the following technical problems:
in ionospheric occultation observation, the total ionospheric electron content (TEC) above the LEO orbit of the low orbit observation satellite has a non-negligible effect on the occultation inversion, and the space between the ionospheric roof and the satellite guideway system is not a pure vacuum environment, in which there is rarefied air, plasma and dust. The GNSS obtains ionized layer data such as total electron content TEC, and sends the ionized layer data to an observation satellite positioned at the occultation side of the GNSS, the observation satellite is positioned at a near-earth orbit LEO near the top of an ionized layer, the data received by the observation satellite comprises oblique total electron content TEC' which is linearly penetrated through the ionized layer from the GNSS to the observation satellite and oblique total electron content TECO between the top of the ionized layer and a navigation satellite, and the observed value is larger than the oblique total electron content actually penetrating through the ionized layer of a target area. Therefore, the total electron content measured by the GNSS of the navigation satellite has a larger error with the total electron content of the actual ionosphere.
Therefore, for the reasons stated above, the present invention provides a method for correcting ionosphere data of GNSS occultation so as to obtain more accurate ionosphere TEC data.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a method for correcting ionosphere data of a GNSS occultation, which can solve the technical problem of insufficient accuracy of ionosphere data obtained in the prior art, and achieve the technical effects of improving accuracy of ionosphere observation data after correction, obtaining data efficiency, and improving user experience.
The technical scheme adopted by the method comprises the following steps:
acquiring occultation side observation data of a target ionization layer region of a target observation satellite in a preset time period, and performing data decoding and occultation event separation on the occultation side observation data to obtain occultation side observation data of an independent GNSS occultation event;
performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite to obtain first time-space data of the target observation satellite and a corresponding first GNSS occultation at each occultation moment;
calculating second space-time data of the target observation satellite according to the first space-time data, wherein the second space-time data is space-time data of the target observation satellite at a non-occultation side intersection point, the non-occultation side intersection point is an intersection point of a connecting line between the target observation satellite and the first GNSS satellite and the running orbit of the target observation satellite, and the intersection point is positioned at a non-occultation side;
acquiring non-occultation side observation data of the target observation satellite at each occultation time within the preset time period, wherein the non-occultation side observation data are data of the target observation satellite observing a second GNSS satellite at the intersection point, and the space position of the second GNSS satellite is located at the space position of first time-space data of the first GNSS satellite;
preprocessing the occultation side observation data and the non-occultation side observation data to obtain processed occultation side observation data and non-occultation side observation data, wherein the preprocessing mode comprises the following steps: cycle slip detection and restoration processing, multipath elimination processing and gross error elimination processing;
and calculating the total electron content TEC on the GNSS signal propagation path according to the processed occultation side observation data and the following calculation formula:
wherein L is 1 And L 2 Respectively representing two-frequency carrier phase observed values at the occultation side, N representing the whole-cycle ambiguity of a combined carrier phase at the occultation side, lambda representing the wavelength of the combined carrier phase, and epsilon representing noise at the occultation side;
and calculating the total electron content TEC0 of the ionized layer on the non-occultation side according to the observation data on the non-occultation side and the following calculation formula:
wherein,
and
representing a non-masker-side dual-frequency carrier phase observation, N 0 Representing the integer ambiguity of the non-masker side combined carrier phase 0 Representing non-masker-side noise;
the corrected total electron content TEC' is calculated by the following formula: TEC' = TEC-TEC0.
Further, the predetermined period of time is at least three months.
Furthermore, the target ionization layer area is located in the ionized layer F2 area, and the height of the ionized layer F2 area from the sea level is 200km-600km.
Further, the observation data includes: the GNSS occultation event comprises B1 frequency point carrier phase data, B3 frequency point carrier phase data, a B1 signal-to-noise ratio and a B3 signal-to-noise ratio, wherein the frequency of the B1 frequency point carrier phase data adopts 1561.098MHz, the frequency of the B3 frequency point carrier phase data adopts 1268.520MHz, and the world time of the GNSS occultation event and the longitude and latitude of the position of the GNSS occultation event.
Further, the cycle slip detection and repair processing on the observation data comprises: and detecting the cycle slip of the GNSS ionospheric occultation observation data by using a high order difference method, and detecting and repairing the carrier phase cycle slip greater than 0.5 cycle.
Further, the multipath cancellation processing of the observation data includes: calculating space-time data of each occultation time according to the observation data in a preset time period, wherein the space-time data comprises world time of occultation of an occultation event and longitude and latitude of the position of the occultation event;
extracting ionosphere path space-time data when a signal transmission path refraction point in the GNSS occultation event space-time data is in an ionosphere F2 layer;
and calculating by adopting a linear interpolation algorithm to obtain the ionosphere path space-time data in the global range, and eliminating the space-time data except the ionosphere path space-time data, wherein the longitude and the latitude are respectively subjected to interpolation calculation at intervals of 2 degrees.
Further, the step of performing gross error elimination on the observation data of the independent GNSS occultation event to obtain processed observation data includes: and judging whether the second derivative of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data is greater than 0.3, if so, determining that the GNSS occultation observation data has gross errors, and performing interpolation to replace the gross errors by using an average interpolation method of adjacent epochs to obtain the processed observation data.
Furthermore, 20Hz is adopted for sampling when the occultation side observation data are obtained, and 1Hz is adopted for sampling when the non-occultation side observation data are obtained.
Further, performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite to obtain the first time-space data of the target observation satellite and the corresponding first GNSS occultation at each occultation time includes: carrying out Lagrange interpolation aiming at the LEO positioning data to obtain LEO satellite space-time data of each occultation moment;
and performing Lagrange interpolation on a GNSS navigation ephemeris file published by an IGS website to obtain the GNSS satellite space-time data at each occultation moment.
Further, the observation data of the independent GNSS masker event is preprocessed, and the preprocessing method further includes: and eliminating abnormal data of the GNSS occultation observation data and the space-time data thereof, and unifying all parameters of the space-time data of different GNSS occultation systems and different occultation tasks into the same physical quantity and the same unit.
The technical scheme provided by the embodiment of the invention at least brings the following beneficial technical effects:
compared with the related technology, the ionosphere observation data obtained by the method is higher in accuracy, simpler and more efficient in mode, the detected target ionosphere region is not limited, the ionosphere can cover the whole world, a novel ionosphere data correction method is provided, and user experience is improved.
Drawings
FIG. 1 is a flowchart of a method for correcting GNSS masker ionization layer data according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating a GNSS masker ionosphere data acquisition method according to an embodiment of the present invention;
reference numerals:
a target observation satellite-1, a GNSS satellite-2 and a non-occultation side intersection point-3.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The terms first, second and the like in the description and in the claims and the drawings of the present invention are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged as appropriate in order to facilitate the embodiments of the invention described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps S or elements is not necessarily limited to those steps S or elements expressly listed, but may include other steps S and elements not expressly listed or inherent to such process, method, article, or apparatus.
For better understanding of the solution of the present invention, the solution in the embodiment of the present invention is described clearly and completely below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, not the whole embodiment. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Examples
An embodiment of the present invention provides a method for correcting GNSS occultation ionosphere data, where fig. 1 is a flowchart of a method for correcting GNSS occultation ionosphere data according to an embodiment of the present invention, and fig. 2 is a schematic diagram of a method for acquiring GNSS occultation ionosphere data according to an embodiment of the present invention, as shown in fig. 1 and fig. 2, including:
and S10, acquiring occultation side observation data of the target ionization layer region of the target observation satellite 1 in a preset time period, and performing data decoding and occultation event separation on the occultation side observation data to obtain occultation side observation data of the independent GNSS occultation event.
Specifically, the occultation side observation data of the target observation satellite 1 for the target ionization region in the predetermined time period includes: and decoding GNSS observation information from a 0-level occultation data file downloaded from the low earth orbit satellite LEO to obtain GNSS occultation ionosphere observation data.
Preferably, the predetermined period of time is at least three months.
Preferably, the average is calculated from ionospheric observer data over at least three months.
In occultation observation, the positioning receiver samples data at a sampling rate of 1Hz to realize positioning and speed measurement of the LEO satellite. The codeless receiver for occultation observation increases the signal sampling rate from 0.1Hz to 50Hz only when occultation event occurs. The most original radio occultation data is called a 0-level occultation data file, and telemetered original phase data and ephemeris data are downloaded from MicroLab-1; removing a header file for communication from the original phase data, and converting the header file into a formatted time sequence file containing GPS amplitude and phase information, namely generating a level 1 occultation data file; after the influence of the relative motion of the satellite and the clock error of the satellite is removed from the level 1 data, additional phase delay data completely caused by the earth atmosphere, namely a level 2 occultation data file, is obtained. Each level 2 occultation profile file corresponds to an occultation event, including LEO and GPS satellite position and velocity information during occultation, and additional phase delay and amplitude data for the dual-frequency electrical wave signal. The time sequence with the additional phase delay is filtered and subjected to differential processing to obtain Doppler frequency shift of electric waves, further deducing the change of the radio wave ray bending angle along with the height, separating ray bending caused by ionized layers and neutral atmosphere respectively by using a double-frequency bending angle data linear combination method, inverting the atmospheric refractive index from the bending angle caused by the neutral atmosphere by using an Abel integral inversion formula under the assumption that the atmospheric local earth is symmetrical, further deducing atmospheric parameters such as atmospheric temperature, pressure, low troposphere water vapor and the like of dry air, and generating an atmospheric occultation three-level data file. Profile information of the electron density of the ionized layer can be obtained from the bending angle caused by the ionized layer, and a third-level occultation data file of the ionized layer is generated.
Step S20, performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite 1 to obtain the target observation satellite 1 and the first time-space data of the corresponding first GNSS occultation at each occultation time.
In a preferred embodiment, the occultation-side data during load observation is 20Hz, and interpolation and time synchronization are required to be performed on 1Hz LEO orbit data and 20Hz occultation orbit data are calculated, for example, by using an average interpolation method, interpolation calculation is performed in a target ionization layer region by adopting longitude and latitude at intervals of 2 degrees.
Step S30, second space-time data of the target observation satellite 1 is obtained through calculation according to the first space-time data, the second space-time data is space-time data of the target observation satellite 1 located at a non-occultation side intersection point 3, the non-occultation side intersection point 3 is an intersection point 3 of a connecting line between the target observation satellite 1 and the first GNSS satellite and an operation orbit of the target observation satellite 1, and the intersection point 3 is located on a non-occultation side.
Specifically, the position of an intersection point 3 between a connecting line between the target observation satellite 1 and the first GNSS satellite and the orbit of the target observation satellite 1 is calculated and obtained through first space-time data of the target observation satellite 1 and the corresponding GNSS satellite 2, and second space-time data of the target observation satellite 1 is further calculated and obtained.
Step S40, acquiring non-occultation-side observation data of the target observation satellite 1 at each occultation time within the predetermined time period, where the non-occultation-side observation data is data of the target observation satellite 1 observing a second GNSS satellite at the intersection point 3, and a spatial position of the second GNSS satellite is located at a spatial position of first space-time data of the first GNSS satellite.
Specifically, through the second spatio-temporal data of the target observation satellite 1 and the first spatio-temporal data corresponding to the first GNSS satellite in the embodiment of the present invention, the spatio-temporal data of one GNSS satellite 2 located closest to the first spatio-temporal data spatial position of the first GNSS satellite at the time point of the second spatio-temporal data is calculated, that is, the second spatio-temporal data of the second GNSS satellite.
It should be noted that the second GNSS satellite is a GNSS satellite 2 located closest to the first space-time data space position of the first GNSS satellite at the second time-space data time point. When the position of the target observation satellite 1 is located at the non-occultation intersection point 3, the position of the corresponding first GNSS satellite is no longer located at the spatial position of the first space-time data, so that a GNSS satellite located at the first space-time data spatial position of the first GNSS satellite at the time point of the second space-time data is required to be obtained as a second GNSS satellite, and the observation data of the second GNSS satellite is obtained. Further, non-occultation side observation data for a predetermined period of time, for example, three months, is obtained, and an average value is found by calculation.
Step S50, preprocessing the occultation side observation data and the non-occultation side observation data to obtain processed occultation side observation data and non-occultation side observation data, wherein the preprocessing mode comprises the following steps: cycle slip detection and restoration processing, multipath elimination processing and gross error elimination processing.
Specifically, the cycle slip detection and repair processing method includes performing cycle slip detection on a carrier phase in the GNSS occultation event data by using a high-order difference method, and performing cycle slip repair on carrier phase data in which cycle slip occurs to obtain continuously observed carrier phase data. Preferably, a high difference method is adopted to detect the cycle slip of the GNSS ionospheric occultation observation data, and the cycle slip of the carrier phase greater than 0.5 cycle is detected and repaired.
In GNSS measurement, a satellite signal (reflected wave) reflected by an object in the vicinity of a station to be measured is received by a receiver antenna, and interference occurs with a signal (direct wave) directly from a satellite, so that an observed value deviates from a true value, thereby causing a multipath error. In the embodiment of the invention, the spatiotemporal data of each occultation time is calculated according to the ionosphere observation data in a preset time period, and the spatiotemporal data comprises the world time of occultation of the occultation event and the latitude and longitude of the occultation event position; extracting ionosphere path time-space data when a signal transmission path refraction point in the GNSS occultation event time-space data is in an ionosphere F2 layer; and calculating by adopting a linear interpolation algorithm to obtain the ionosphere path space-time data in the global range, and eliminating the space-time data except the ionosphere path space-time data, wherein the longitude and the latitude are respectively subjected to interpolation calculation at intervals of 2 degrees.
Preferably, whether the second derivative of the L1/L2 dual-frequency carrier phase data of the GNSS masker observation data is larger than 0.3 is judged, if yes, the GNSS masker observation data is determined to have a gross error, and an average interpolation method of adjacent epochs is used for interpolation to replace the gross error, so that the processed observation data is obtained.
Specifically, the quality of the GNSS occultation observation data is detected according to the smoothness of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data. When the second derivative of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data is larger than 0.3, determining that the GNSS occultation observation data has gross errors, and performing interpolation to replace the gross errors by using an average interpolation method of adjacent epochs to obtain the processed GNSS occultation observation data.
Step S60, calculating the total electron content TEC on the GNSS signal propagation path according to the processed occultation side observation data and the following calculation formula:
wherein L is 1 And L 2 Respectively representing the observed values of the two-frequency carrier phase at the occultation side, N representing the ambiguity of the whole cycle of the combined carrier phase at the occultation side, and lambda representing the combinationThe wavelength of the carrier phase, epsilon, represents the masker-side noise.
Preferably, the following observation equation is firstly established according to ionospheric occultation observation data and space-time data:
wherein phi 1 And phi 2 The two frequency points of the GNSS are respectively expressed by carrier waves multiplied by respective wavelengths in a unit of meter. f. of 1 And f 2 Respectively, representing frequencies corresponding to GNSS dual frequencies. TEC denotes total electron content size in TECU. N is a radical of 1 And N 2 Respectively representing the carrier phase integer ambiguity at two frequency points. Epsilon represents the carrier phase noise after double frequency combination, and the unit is meter.
And then calculating the total TEC on the signal propagation path by using a formula as follows:
wherein L is 1 And L 2 Respectively representing the observation values of the two-frequency carrier phase at the occultation side, N representing the ambiguity of the whole cycle of the combined carrier phase at the occultation side, lambda representing the wavelength of the combined carrier phase, and epsilon representing the noise at the occultation side.
S70, calculating the total electron content TEC0 of the ionized layer on the non-occultation side according to the observation data on the non-occultation side and a calculation formula as follows:
wherein,
and
representing a non-masker-side dual-frequency carrier phase observation, N 0 Representing the integer ambiguity of the non-masker side combined carrier phase 0 Representing non-masker side noise.
Step S80, calculating the corrected inclined total electron content TEC' by the following formula: TEC' = TEC-TEC0.
Therefore, in the embodiment of the invention, ionospheric observation data of a occultation side and a non-occultation side are acquired and calculated in different modes, data are preprocessed, and deviation generated by subtracting the non-occultation side observation data from the occultation side observation data is used for obtaining corrected ionospheric observation data, so that compared with the prior art, the ionospheric observation data has at least the following technical effects: the acquired ionosphere observation data has higher precision, the mode is simpler and more efficient, the detected target ionosphere region is not limited, the global coverage can be realized, a new ionosphere data correction method is provided, and the user experience is improved.
In a preferred embodiment, the predetermined period of time is at least three months.
In the embodiment of the invention, because the target observation satellite 1 observes the GNSS satellite 2 and receives the ionosphere data sent by the GNSS satellite 2, and because the measurement of the total electron content in the ionosphere is influenced by various factors, such as measurement errors, solar activity and the like, the measurement is unstable, the data in a longer time needs to be acquired and the average value needs to be calculated, so that the accuracy of acquiring the data can be improved.
In a preferred embodiment, the target ionosphere region is located in the ionosphere F2 region, and the height of the ionosphere F2 region from the sea level is 200km-600km.
It should be noted that, in the ionosphere F2 layer with a height of about 200-600km, the ionosphere region has the highest electron density and exists all the time, and is the region with the most serious radio wave refraction and scattering, so that the ionosphere F2 layer is taken as the target ionosphere region, the properties of the ionosphere can be reflected most accurately and comprehensively, and the accuracy of acquiring ionosphere data is further improved.
In a preferred embodiment, the observation data comprises: the GNSS occultation event comprises B1 frequency point carrier phase data, B3 frequency point carrier phase data, a B1 signal-to-noise ratio and a B3 signal-to-noise ratio, wherein the frequency of the B1 frequency point carrier phase data adopts 1561.098MHz, the frequency of the B3 frequency point carrier phase data adopts 1268.520MHz, and the world time of the GNSS occultation event and the longitude and latitude of the position of the GNSS occultation event.
In the embodiment of the invention, the dual-frequency carrier is adoptedThe data transmission is carried out, the information contained in the ionized layer data can be accurately transmitted, and meanwhile, the total electronic content TEC can be conveniently calculated through the dual-frequency carrier data information:
preferably, the cycle slip is jointly detected and repaired by using a dual-frequency carrier phase observation value combination method, so that the error is reduced, and the precision of obtaining the ionization layer data is improved.
In a preferred embodiment, the cycle slip detection and repair processing on the observation data comprises: and detecting the cycle slip of the GNSS ionosphere occultation observation data by adopting a high-order difference method, and detecting and repairing the carrier phase cycle slip which is more than 0.5 cycle.
Specifically, the principle of the elevation difference method is similar to that of a polynomial fitting method, but complex matrix calculation is not needed, and meanwhile, jump caused by cycle slip can be amplified. Although the observation noise is amplified, when the sampling interval is small, the amplified noise does not affect the cycle slip detection. The high-order difference method can eliminate the influence of the error with unchangeable epoch and the influence of the error which can be fitted by using a low-order curve and changes along with the epoch, and the ionosphere data accuracy is improved, meanwhile, the operation is simpler, and the efficiency is higher.
In a preferred embodiment, the multipath cancellation processing of the observation data includes: calculating space-time data of each occultation time according to the observation data in a preset time period, wherein the space-time data comprises world time of occultation of an occultation event and longitude and latitude of the position of the occultation event;
extracting ionosphere path space-time data when a signal transmission path refraction point in the GNSS occultation event space-time data is in an ionosphere F2 layer;
and calculating by adopting a linear interpolation algorithm to obtain the ionosphere path space-time data in the global range, and eliminating the space-time data except the ionosphere path space-time data, wherein the longitude and the latitude are respectively subjected to interpolation calculation at intervals of 2 degrees.
In GNSS measurement, a satellite signal (reflected wave) reflected by an object in the vicinity of a station to be measured is received by a receiver antenna, and interferes with a signal (direct wave) directly from a satellite, so that an observed value deviates from a true value to generate a multipath error. In the embodiment of the invention, the spatiotemporal data of each occultation time is calculated according to the ionosphere observation data in the preset time period, and the spatiotemporal data comprises the world time of occultation of the occultation event and the longitude and latitude of the occultation event position; extracting ionosphere path time-space data when a signal transmission path refraction point in the GNSS occultation event time-space data is in an ionosphere F2 layer; and calculating by adopting a linear interpolation algorithm to obtain the ionosphere path space-time data in the global scope, and eliminating the space-time data except the ionosphere path space-time data, wherein the latitude and longitude are respectively subjected to interpolation calculation at intervals of 2 degrees. Therefore, space-time data in the global range is obtained, multipath errors are eliminated to the maximum extent, and the precision of ionosphere data acquisition is further improved.
In a preferred embodiment, the performing coarse subtraction on the observation data of the independent GNSS masker event to obtain the processed observation data includes: and judging whether the second derivative of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data is larger than 0.3, if so, determining that the GNSS occultation observation data has gross errors, and performing interpolation to replace the gross errors by using an average interpolation method of adjacent epochs to obtain the processed observation data.
Specifically, the quality of the GNSS occultation observation data is detected according to the smoothness of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data. When the second derivative of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data is larger than 0.3, determining that the GNSS occultation observation data has gross errors, and performing interpolation to replace the gross errors by using an average interpolation method of adjacent epochs to obtain the processed GNSS occultation observation data, so that the precision of ionospheric data acquisition can be improved, and errors can be reduced.
In a preferred embodiment, the occultation side observation data is acquired by sampling at 20Hz, and the non-occultation side observation data is acquired by sampling at 1 Hz.
Specifically, 20Hz is adopted for sampling the obtained occultation side observation data, 1Hz is adopted for sampling the obtained non-occultation side observation data, interpolation and time synchronization are needed to be carried out on the target observation satellite 1 orbit data, and the occultation orbit data with the frequency of 20Hz is calculated. Therefore, the observation data of the occultation side and the non-occultation side can be accurately acquired, the acquisition of the data is facilitated, and the convenience and the high efficiency of acquiring the ionospheric data are improved.
In a preferred embodiment, performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite 1 to obtain the first time-space data of the target observation satellite 1 and the corresponding first GNSS occultation at each occultation time includes: performing Lagrange interpolation on LEO positioning data to obtain LEO satellite space-time data of each occultation moment;
and performing Lagrange interpolation on a GNSS navigation ephemeris file published by an IGS website to obtain the GNSS satellite 2 space-time data at each occultation moment.
Specifically, the lagrangian interpolation method can provide a polynomial function which just passes through a plurality of known points on a two-dimensional plane, namely the lagrangian interpolation method is adopted to conveniently calculate the polynomial function of the space-time data of the GNSS satellite 2 at each occultation moment so as to conveniently calculate the space-time data of the LEO satellite and the GNSS satellite 2 at each occultation moment, and the calculation is more convenient and efficient.
In a preferred embodiment, the method further includes preprocessing the observation data of the independent GNSS masker event, where the preprocessing includes: and eliminating abnormal data of the GNSS occultation observation data and the space-time data thereof, and unifying all parameters of the space-time data of different GNSS occultation systems and different occultation tasks into the same physical quantity and the same unit.
Specifically, abnormal data of the GNSS occultation observation data and the space-time data thereof are removed, accidental errors are reduced, and the precision of ionosphere data is further improved. The method has the advantages that all parameters of the space-time data of different GNSS occultation systems and different occultation tasks are unified into the same physical quantity and the same unit, data acquisition can be simultaneously carried out on the GNSS satellites 2 of different systems, for example, the navigation satellites of a GPS system and a Beidou system are simultaneously subjected to acquisition of ionosphere data and space-time data, all parameters of the space-time data of different GNSS occultation systems and different occultation tasks are unified into the same physical quantity and the same unit, so that ionosphere data of a plurality of navigation systems can be simultaneously acquired and utilized, so that navigation system resources are utilized to the maximum extent, the compatibility is stronger, the data acquisition is more convenient and efficient, and the user experience is improved.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A method for correcting GNSS occultation ionization layer data is characterized by comprising the following steps:
acquiring occultation side observation data of a target ionization layer region of a target observation satellite in a preset time period, and performing data decoding and occultation event separation on the occultation side observation data to obtain occultation side observation data of an independent GNSS occultation event;
performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite to obtain first time-space data of the target observation satellite and a corresponding first GNSS satellite at each occultation moment;
calculating second space-time data of the target observation satellite according to the first space-time data, wherein the second space-time data is space-time data of the target observation satellite at a non-occultation side intersection point, the non-occultation side intersection point is an intersection point of a connecting line between the target observation satellite and the first GNSS satellite and the running orbit of the target observation satellite, and the intersection point is positioned at a non-occultation side;
acquiring non-occultation side observation data of the target observation satellite at each occultation time within the preset time period, wherein the non-occultation side observation data are data of the target observation satellite observing a second GNSS satellite at the intersection point, and the space position of the second GNSS satellite is located at the space position of first time-space data of the first GNSS satellite;
preprocessing the occultation side observation data and the non-occultation side observation data to obtain processed occultation side observation data and non-occultation side observation data, wherein the preprocessing mode comprises the following steps: cycle slip detection and restoration processing, multipath elimination processing and gross error elimination processing;
and calculating the total electron content TEC on the GNSS signal propagation path according to the processed occultation side observation data and the following calculation formula:
wherein L is 1 And L 2 Respectively representing the two-frequency carrier phase observed values at the occultation side, f 1 Represents L 1 Signal frequency of (f) 2 Represents L 2 N represents the whole-cycle ambiguity of the combined carrier phase at the occultation side, λ represents the wavelength of the combined carrier phase, and ∈ represents the noise at the occultation side;
and calculating the total electron content TEC0 of the ionized layer on the non-occultation side according to the observation data on the non-occultation side and the following calculation formula:
wherein,
and
representing a non-masker-side dual-frequency carrier phase observation, N 0 Representing the integer ambiguity of the non-masker side combined carrier phase 0 Representing non-masker-side noise;
the corrected total electron content TEC' is calculated by the following formula: TEC' = TEC-TEC0.
2. The method of claim 1, wherein the predetermined period of time is at least three months.
3. The method of claim 1, wherein the target ionosphere region is located in an ionosphere F2 region, and the ionosphere F2 region is located at a height from sea level of 200km to 600km.
4. The method of claim 1, wherein the observation data comprises: the GNSS occultation event comprises B1 frequency point carrier phase data, B3 frequency point carrier phase data, a B1 signal-to-noise ratio and a B3 signal-to-noise ratio, wherein the frequency of the B1 frequency point carrier phase data adopts 1561.098MHz, the frequency of the B3 frequency point carrier phase data adopts 1268.520MHz, and the world time of the GNSS occultation event and the longitude and latitude of the position of the GNSS occultation event.
5. The method according to any one of claims 1 to 4, wherein the performing cycle slip detection and repair processing on the observation data comprises: and detecting the cycle slip of the GNSS ionospheric occultation observation data by using a high order difference method, and detecting and repairing the carrier phase cycle slip greater than 0.5 cycle.
6. The method of claim 5, wherein the performing multipath cancellation processing on the observation data comprises: calculating space-time data of each occultation moment according to the observation data in a preset time period, wherein the space-time data comprises world time of occultation of the occultation event and longitude and latitude of the occultation event position;
extracting ionosphere path space-time data when a signal transmission path refraction point in the GNSS occultation event space-time data is in an ionosphere F2 layer;
and calculating by adopting a linear interpolation algorithm to obtain the ionosphere path space-time data in the global range, and eliminating the space-time data except the ionosphere path space-time data, wherein the longitude and the latitude are respectively subjected to interpolation calculation at intervals of 2 degrees.
7. The method as claimed in claim 6, wherein the step of performing gross error elimination on the observation data of the independent GNSS occultation event includes: and judging whether the second derivative of the L1/L2 double-frequency carrier phase data of the GNSS occultation observation data is greater than 0.3, if so, determining that the GNSS occultation observation data has gross errors, and performing interpolation to replace the gross errors by using an average interpolation method of adjacent epochs to obtain the processed observation data.
8. The method of claim 7, wherein the occultation-side observation data is sampled at 20Hz, and the non-occultation-side observation data is sampled at 1 Hz.
9. The method as claimed in claim 7, wherein the step of performing data interpolation and time synchronization calculation according to the orbit data of the target observation satellite to obtain the first time-space data of the target observation satellite and the corresponding first GNSS satellite at each occultation time comprises: carrying out Lagrange interpolation aiming at the LEO positioning data to obtain LEO satellite space-time data of each occultation moment;
and performing Lagrange interpolation on a GNSS navigation ephemeris file published by an IGS website to obtain the GNSS satellite space-time data at each occultation moment.
10. The method of claim 7, wherein the method for modifying GNSS masker ionosphere data is further characterized by preprocessing observation data of the independent GNSS masker event, and the preprocessing further comprises: and eliminating abnormal data of the GNSS occultation observation data and the space-time data thereof, and unifying all parameters of the space-time data of different GNSS occultation systems and different occultation tasks into the same physical quantity and the same unit.
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