Method for calculating total inclined electrons of ionized layer without pseudo-range error disturbance

Abstract

The invention provides a pseudo-range error disturbance-free ionized layer tilt electron total amount calculation method. The method comprises the following steps of reading a navigation file and an observation file; based on the phase observation value in the observation file, cycle slip detection is carried out, and an observation value corresponding to the moment when cycle slip occurs is eliminated; obtaining a phase-based relative STEC sequence based on the phase observation values which are not removed; based on the pseudo-range observation value which is not removed, smoothing is carried out, and absolute STEC is obtained by combining a navigation star and a receiver differential code deviation; calculating a relative STEC sequence of phase observation and a phase smoothing pseudo range to obtain an absolute STEC deviation; and S5, correcting the relative STEC sequence of the phase observation through the deviation in the step S5 to obtain an absolute STEC sequence of the phase observation. The beneficial effects of the invention are that the method improves the STEC inversion precision, can obtain an ionized layer tilt electron total amount sequence with better continuity than a phase smoothing pseudo-range algorithm, and can greatly improve the application rate in the ionized layer research fields of high-precision ionized layer correction / modeling, ionized layer disturbance and abnormal change and the like.

Description

Technical Field

[0001] The invention belongs to the field of ionospheric tilt total electron quantity calculation, and in particular relates to a method for ionospheric tilt total electron quantity calculation without pseudorange error disturbance. Background Art

[0002] Ionospheric delay error is an important error source that affects the GNSS positioning mode and service range. The acquisition of high-precision ionospheric slant total electron content (STEC) is a key factor in ionospheric grid modeling and ionospheric space environment monitoring. With the increase of ground-based GNSS observations, ground-based STEC has gradually become an important source of ionospheric data. The STEC accuracy obtained by the original phase-smoothed pseudorange algorithm may not meet the requirements of high-frequency and high-precision ionospheric modeling. Therefore, the invention of a new high-precision ionospheric STEC extraction method suitable for ground-based observations is of great significance to the accurate modeling of the ionosphere and the improvement of satellite navigation, positioning, and timing accuracy. Summary of the invention

[0003] In view of this, the present invention aims to propose a method for calculating the total ionospheric tilt electron count without pseudorange error disturbance, so as to solve the current problem that the current ground-based STEC inversion is mostly based on a phase smoothing pseudorange algorithm, which is difficult to eliminate the influence of GNSS pseudorange observation errors.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows: A method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance comprises the following steps: S1. Read navigation files and observation files; S2. Based on the phase observation values ​​in the observation file, cycle slip detection is performed and the observation values ​​corresponding to the time when the cycle slip occurs are eliminated; S3, obtaining a phase-based relative STEC sequence based on the phase observations that are not eliminated; S4, based on the pseudo-range observations that have not been eliminated, use hatch filtering for smoothing, and combine the navigation satellite and receiver differential code deviations to obtain absolute STEC; S5, calculating the deviation of the absolute STEC obtained by the phase-based relative STEC sequence in step S3 and the phase-smoothed pseudorange in step S4; S6. Correct the relative STEC sequence based on the phase by the deviation in step S5 to obtain the absolute STEC sequence of the phase observation.

[0005] Furthermore, in step S1, the navigation file and the observation file are read, including: Read the navigation file, obtain the corresponding parameters of broadcast orbits 1-7, calculate the coordinates of the navigation satellite and the altitude angle between the satellite and the receiver; Read the observation file, obtain the observation type data from the observation file, and extract the observation values ​​of C2I, C6I, L2I, and L6I of the first epoch of the C20 satellite.

[0006] Furthermore, in step S2, phase cycle slip detection is performed and the observation value corresponding to the time when the cycle slip occurs is eliminated, including: Geometry-Free is used to detect cycle slips. The cycle slip detection formulas are shown in formulas (1) to (3): (1); (2); (3); Among them, in formula (1) to formula (3), is the sequence subscript, , is the wavelength of bands 1 and 2, in meters, , are the phase observations of bands 1 and 2, respectively, in cycles; When , it is considered that a cycle slip has occurred.

[0007] Further, in step S3, a phase-based relative STEC sequence is obtained, including: The measurement accuracy is 10 13 Order of magnitude, the calculation formula is shown in (4): (4); In formula (4), , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observations of bands 1 and 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz, For the receiver and The relative STEC between satellites is in TECU, where is the subscript relative to the STEC sequence.

[0008] Furthermore, in step S4, based on the pseudo-range observation values ​​that have not been eliminated, hatch filtering is used for smoothing, and the absolute STEC is obtained by combining the differential code deviation between the navigation star and the receiver, including: Use hatch to smooth the pseudorange observations in the observation file. The calculation is shown in (5): P S ( k ) = 1 M P ( k ) + M − 1 M [ P S ( k − 1 ) + ( f i ( k ) l i − f i ( k − 1 ) l i )] (5); In formula (5), For band The wavelength, in meters, , for the band Phase observation, in weeks, Indicates that the subscript is The original pseudorange observation value of Indicates that the subscript is The smoothed pseudorange observation value is is the weight value, usually 45; Based on the smoothed pseudorange, the ambiguity between observations of different observation types is calculated. The calculation formula is shown in (6): (6); In formula (6), is the fuzziness, is the number of pseudo-range observations to be smoothed, usually 45. is the subscript of the pseudorange and phase to be smoothed. , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , They are the frequencies of band 1 and 2 respectively, in Hz; Before performing absolute STEC calculation, the pseudorange needs to be quality checked. If the difference between pseudoranges of multiple adjacent epochs is greater than 0.017 m, the absolute STEC calculation will not be performed; After passing the quality inspection, the absolute STEC is calculated by combining the differential code deviation between the navigation star and the receiver provided by CAS. The calculation formula is shown in (7): (7); In formula (7), is the subscript of pseudorange and phase, , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz, is the speed of light, , , are the DCB values ​​of the satellite and receiver respectively, For the receiver and The relative STEC between satellites is in TECU, where is the subscript of the absolute STEC sequence.

[0009] Furthermore, in step S5, the deviation of the absolute STEC obtained by calculating the phase-based relative STEC sequence and the phase-smoothed pseudorange includes: Only the relative change of TEC can be obtained. The obtained TEC is closer to the true value. The measurement accuracy is 10 13 Order of magnitude, The measurement accuracy is 10 16 order of magnitude, so it is calculated arc by arc and epoch by epoch and The difference is calculated by weighted average method, taking the altitude angle in step S1 as the weight. , the formula is shown in (8): (8); Among them, in formula (8), For the receiver and The relative STEC between satellites, is the subscript relative to the STEC sequence, For the receiver and The absolute STEC between satellites, is the subscript of the absolute STEC sequence, For the The square of the sine of the altitude angle of the observation, is the weighted difference between absolute STEC and relative STEC.

[0010] Further, in step S6, the relative STEC sequence based on the phase is corrected by the deviation in step S5 to obtain the absolute STEC sequence of the phase observation, including: After obtaining the correction term, add it to the relative TEC epoch by epoch, as shown in formula (9): (9); In formula (9), The corrected receiver and STEC between satellites, Subscript the sequence.

[0011] Compared with the prior art, the method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance described in the present invention has the following advantages: The present invention discloses a method for calculating the total ionospheric tilt electron quantity without pseudorange error disturbance. The method improves the STEC inversion accuracy and can obtain an ionospheric tilt electron quantity sequence with better continuity than a phase smoothing pseudorange algorithm. The method can greatly increase the application rate in ionospheric research fields such as high-precision ionospheric correction / modeling, ionospheric disturbance and abnormal change. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 The present invention is a flowchart of the method described in the embodiment of the present invention. DETAILED DESCRIPTION

[0013] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0014] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0015] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0016] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0017] like Figure 1As shown, a method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance is provided. The method can read the navigation file data of the ground-based GNSS, and calculate the altitude angle and azimuth angle of each navigation satellite based on the approximate coordinates of the ground station. The observation file data is read, the observation values ​​of the corresponding observation type are extracted, the cycle slip is eliminated, and the relative STEC is obtained for each continuous arc segment of each satellite, epoch by epoch. At the same time, the pseudorange is smoothed by phase, and the absolute STEC in the continuous arc segment is calculated by using the smoothed pseudorange and DCB parameters. The difference between the absolute STEC and the relative STEC is calculated for each arc segment and epoch by epoch. Based on the altitude angle, the difference between the absolute STEC and the relative STEC of each epoch in the arc segment is weighted averaged to obtain the STEC correction item of each arc segment. The relative STEC of each epoch is added with the corrected STEC to obtain the final STEC. The specific process is as follows: a) Read navigation and observation files Read the navigation file, obtain the corresponding parameters of broadcast orbits 1-7, and calculate the coordinates of the navigation satellite and the altitude angle between the satellite and the receiver based on the above parameters. Read the observation file, obtain the specified observation type data from the observation file, and extract the observation values ​​of C2I, C6I, L2I, and L6I of the first epoch of the C20 satellite.

[0018] b) Perform phase cycle slip detection and repair Cycle slips will affect the accuracy of TEC inversion. Therefore, it is necessary to remove the data with cycle slips. This paper adopts Geometry-Free (GF) to detect cycle slips. The cycle slip detection formulas are shown in (1) to (3): (1); (2); (3); Among them, in formula (1) to formula (3), is the sequence subscript, , is the wavelength of bands 1 and 2, in meters, , are the phase observations of bands 1 and 2, respectively, in cycles; When , it can be considered that a cycle slip has occurred.

[0019] c) Obtaining relative STEC sequence of phase-smoothed pseudoranges The measurement accuracy is 10 13 The order of magnitude can accurately reflect the changes in STEC. The calculation formula is shown in (4): (4); In formula (4), , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observations of bands 1 and 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz, For the receiver and The relative STEC between satellites is in TECU, where is the subscript relative to the STEC sequence.

[0020] d) Based on the pseudo-range observations that have not been eliminated, the absolute STEC is obtained by using hatch filtering for smoothing and combining the differential code bias (DCB) between the navigation star and the receiver provided by the Chinese Academy of Sciences (CAS). Since the pseudorange quality is affected by noise and multipath, the time series is relatively discrete, so hatch is used to smooth it. The calculation is shown in (5): P S ( k ) = 1 M P ( k ) + M − 1 M [ P S ( k − 1 ) + ( f i ( k ) l i − f i ( k − 1 ) l i )] (5); In formula (5), For band The wavelength, in meters, , for the band Phase observation, in weeks, Indicates that the subscript is The original pseudorange observation value of Indicates that the subscript is The smoothed pseudorange observation value is is the weight value, usually 45.

[0021] Based on the smoothed pseudorange, the ambiguity between observations of different observation types is calculated. The calculation formula is shown in (6): (6); In formula (6), is the fuzziness, is the number of pseudo-range observations to be smoothed, usually 45. is the subscript of the pseudorange and phase to be smoothed. , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , They are the frequencies of band 1 and 2 respectively, in Hz.

[0022] Before performing absolute STEC calculation, the pseudorange quality must be tested. If the difference in pseudoranges between adjacent epochs is greater than 0.017 m for multiple times, absolute STEC calculation will not be performed.

[0023] After passing the quality inspection, the absolute STEC is calculated in combination with the DCB parameters provided by CAS. The calculation formula is shown in (7): (7); In formula (7), is the subscript of pseudorange and phase, , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz, is the speed of light, , , are the DCB values ​​of the satellite and receiver respectively, For the receiver and The relative STEC between satellites is in TECU, where is the subscript of the absolute STEC sequence.

[0024] e) Calculate the deviation between the relative STEC sequence of phase observations and the absolute STEC obtained by phase smoothing pseudorange Only the relative change of TEC can be obtained. The obtained TEC is closer to the true value. The measurement accuracy is 10 13 Order of magnitude, The measurement accuracy is 10 16 Order of magnitude. Therefore, it can be calculated arc by arc and epoch by epoch. and The difference is calculated by weighted average method with the altitude angle as the weight. , the formula is shown in (8): (8); Among them, in formula (8), For the receiver and The relative STEC between satellites, is the subscript relative to the STEC sequence, For the receiver and The absolute STEC between satellites, is the subscript of the absolute STEC sequence, For the The square of the sine of the altitude angle of the observation, is the weighted difference between absolute STEC and relative STEC.

[0025] f) Correcting the relative STEC sequence of the phase observation by the deviation in step e) to obtain the absolute STEC sequence of the phase observation After obtaining the correction term for each arc segment, the correction term is added to the relative TEC epoch by epoch, as shown in formula (9): (9); In formula (9), The corrected receiver and STEC between satellites, Subscript the sequence.

[0026] This method uses the ionospheric STEC obtained by the phase smoothing pseudorange algorithm as a benchmark and corrects the high-precision STEC sequence obtained by GNSS dual-frequency phase observations. It can sensitively capture small changes in the ionosphere and improve the robustness of STEC inversion.

[0027] Example 1 The observation file abmf0010.20o and the navigation file brdm0010.20p are input, and the STEC of the first arc of the C20 satellite is calculated using four observation types: C2I, C6I, L2I, and L6I.

[0028] a) Read navigation and observation files In the STEC calculation process, the length of an arc segment is usually taken as 45. The C2I, C6I, L2I, and L6I values ​​of the first arc segment of C20 are shown in Table 1.

[0029] Table 1 Values ​​of the first arc segment observation type ; The GNSS broadcast ephemeris values ​​corresponding to the first arc segment of C20 are shown in Table 2.

[0030] Table 2 GNSS broadcast ephemeris observation values ​​corresponding to the first arc segment ; The corresponding elevation angle of the first arc segment of C20 is shown in Table 3.

[0031] Table 3 Altitude angle corresponding to the first arc segment ; b) Perform phase cycle slip detection and repair Based on the L2I and L6I observations, the GF method is used to calculate , the first arc The values ​​are shown in Table 4.

[0032] Table 4 The first arc segment Numeric ; c) Obtaining relative STEC sequence of phase-smoothed pseudoranges Use formula (4) to calculate the first arc segment , the results are shown in Table 5.

[0033] Table 5 The first arc segment Numeric ; d) The relative STEC sequence obtained by DCB correction of navigation satellites and low-orbit satellites based on CAS is obtained by obtaining absolute STEC from phase-smoothed pseudoranges Based on formulas (5) to (7), calculate the absolute , the results are shown in Table 6.

[0034] Table 6 The first arc segment Numeric ; e) Calculate the deviation between the relative STEC sequence of phase observations and the absolute STEC obtained by phase smoothing pseudorange Use formula (8) to calculate the first epoch The values ​​are shown in Table 7.

[0035] Table 7 The first arc segment Numeric ; f) Correcting the relative STEC sequence of the phase observation by the deviation in step e) to obtain the absolute STEC sequence of the phase observation After obtaining the correction items for each arc segment, add the correction items to the relative TEC epoch by epoch. The final STEC value is calculated using formula (9): , the results are shown in Table 8.

[0036] Table 8 The first epoch final value ; This method improves the STEC inversion accuracy and can obtain an ionospheric tilt total electron count sequence with better continuity than the phase smoothing pseudorange algorithm, which can greatly increase the application rate in ionospheric research fields such as high-precision ionospheric correction / modeling, ionospheric disturbances and abnormal changes.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance, characterized in that: The following steps are involved: S1. Read navigation files and observation files; S2. Based on the phase observation values ​​in the observation file, cycle slip detection is performed and the observation values ​​corresponding to the time when the cycle slip occurs are eliminated; S3, obtaining a phase-based relative STEC sequence based on the phase observations that are not eliminated; S4, based on the pseudo-range observations that have not been eliminated, use hatch filtering for smoothing, and combine the navigation satellite and receiver differential code deviations to obtain absolute STEC; S5, calculating the deviation of the absolute STEC obtained by the phase-based relative STEC sequence in step S3 and the phase-smoothed pseudorange in step S4; S6. Correct the relative STEC sequence based on the phase by the deviation in step S5 to obtain the absolute STEC sequence of the phase observation.

2. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 1, characterized in that: In step S1, the navigation file and the observation file are read, including: Read the navigation file, obtain the corresponding parameters of broadcast orbits 1-7, calculate the coordinates of the navigation satellite and the altitude angle between the satellite and the receiver; Read the observation file, obtain the observation type data from the observation file, and extract the observation values ​​of C2I, C6I, L2I, and L6I of the first epoch of the C20 satellite.

3. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 2, characterized in that: In step S2, phase cycle slip detection is performed and the observation value corresponding to the time when the cycle slip occurs is eliminated, including: Geometry-Free is used to detect cycle slips. The cycle slip detection formulas are shown in formulas (1) to (3): (1)； (2)； (3)； Among them, in formula (1) to formula (3), is the sequence subscript, , is the wavelength of bands 1 and 2, in meters, , are the phase observations of bands 1 and 2, in cycles; When , it is considered that a cycle slip has occurred.

4. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 3, characterized in that: In step S3, a phase-based relative STEC sequence is obtained, including: The measurement accuracy is 10 13 Order of magnitude, the calculation formula is shown in (4): (4)； In formula (4), , are the wavelengths of bands 1 and 2 respectively, in meters. , They are the phase observations of bands 1 and 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz. For the receiver and The relative STEC between satellites is in TECU, where is the subscript relative to the STEC sequence.

5. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 4, characterized in that: In step S4, based on the pseudo-range observations that have not been eliminated, hatch filtering is used for smoothing, and the absolute STEC is obtained by combining the differential code deviation between the navigation star and the receiver, including: Use hatch to smooth the pseudorange observations in the observation file. The calculation is shown in (5): (5)； In formula (5), For band The wavelength, in meters, , for the band Phase observation, in weeks, Indicates that the subscript is The original pseudorange observation value of Indicates that the subscript is The smoothed pseudorange observation value is is the weight value, usually 45; Based on the smoothed pseudorange, the ambiguity between observations of different observation types is calculated. The calculation formula is shown in (6): (6)； In formula (6), is the fuzziness, is the number of pseudo-range observations to be smoothed, usually 45. is the subscript of the pseudorange and phase to be smoothed. , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , They are the frequencies of band 1 and 2 respectively, in Hz; Before performing absolute STEC calculation, the pseudorange needs to be quality checked. If the difference between pseudoranges of multiple adjacent epochs is greater than 0.017 m, the absolute STEC calculation will not be performed; After passing the quality inspection, the absolute STEC is calculated in combination with the differential code deviation provided by CAS. The calculation formula is shown in (7): (7)； In formula (7), is the subscript of pseudorange and phase, , are the wavelengths of bands 1 and 2 respectively, in meters. , are the phase observation values ​​of band 1 and band 2, in cycles. , are the frequencies of band 1 and 2 respectively, in Hz. is the speed of light, , , are the DCB values ​​of the satellite and receiver respectively, For the receiver and The relative STEC between satellites is in TECU, where is the subscript of the absolute STEC sequence.

6. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 5, characterized in that: In step S5, the deviation of the absolute STEC obtained by the phase-based relative STEC sequence and the phase-smoothed pseudorange is calculated, including: Only the relative change of TEC can be obtained. The obtained TEC is closer to the true value. The measurement accuracy is 10 13 Order of magnitude, The measurement accuracy is 10 16 order of magnitude, so it is calculated arc by arc and epoch by epoch and The difference is calculated by weighted average method, taking the altitude angle in step S1 as the weight. , the formula is shown in (8): (8)； In formula (8), For the receiver and The relative STEC between satellites, is the subscript relative to the STEC sequence, For the receiver and The absolute STEC between satellites, is the subscript of the absolute STEC sequence, For the The square of the sine of the altitude angle of the observation, is the weighted difference between absolute STEC and relative STEC.

7. The method for calculating the total amount of ionospheric tilt electrons without pseudorange error disturbance according to claim 6, characterized in that: In step S6, the relative STEC sequence based on the phase is corrected by the deviation in step S5 to obtain the absolute STEC sequence of the phase observation, including: After obtaining the correction term, add it to the relative TEC epoch by epoch, as shown in formula (9): (9)； In formula (9), The corrected receiver and STEC between satellites, Subscript the sequence.

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