CN114563807A - Real-time three-frequency cycle slip detection method based on ionosphere refraction - Google Patents
Real-time three-frequency cycle slip detection method based on ionosphere refraction Download PDFInfo
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- CN114563807A CN114563807A CN202210465695.5A CN202210465695A CN114563807A CN 114563807 A CN114563807 A CN 114563807A CN 202210465695 A CN202210465695 A CN 202210465695A CN 114563807 A CN114563807 A CN 114563807A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
- G01S19/44—Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention discloses a real-time three-frequency cycle slip detection method based on ionosphere refraction, which comprises the following steps: s1, calculating a combined observed value of code and carrier phase in the GNSS system; s2, calculating the difference between continuous epochs when the ionosphere change is not considered based on the combined observed value; s3, calculating the difference between the continuous epochs by considering the ionospheric change between the continuous epochs; and S4, detecting the three-frequency cycle slip according to the difference between the continuous epochs. The method is not limited by sampling rate or ionosphere conditions, and can easily and effectively realize cycle slip detection of three-frequency data.
Description
Technical Field
The invention belongs to the technical field of satellite navigation system data processing, and particularly relates to a real-time three-frequency cycle slip detection method based on ionospheric refraction.
Background
At present, regarding the double-frequency cycle slip detection research, common methods include methods such as a high-difference method, an ionosphere residual method, polynomial fitting, phase combination, pseudo-range and the like; among them, the ionospheric residual method uses a combination of total ionospheric electron yield (TECR) and Melbourne-bubbena wide lane (MWWL) linear combinations to uniquely determine cycle slip at L1 and L2 frequencies.
With the development of GNSS, most GNSS receivers can receive tri-band signals, the appearance of new frequencies brings more degrees of freedom to the data combination of global navigation satellite systems, and experts and scholars at home and abroad develop research on tri-band cycle slip detection methods in recent years, and define linear combination of global navigation satellite system observation for the purpose of real-time cycle slip detection and correction, and research results show that: real-time cycle slip detection in a three-frequency navigation system can detect and repair all cycle slip combinations in three frequency carriers. Compared with double-frequency detection, a combination formed by three-frequency observation has the characteristics of long wavelength, small noise and small influence, so that the method is a simple and effective method, and the three-frequency cycle slip detection and restoration are beneficial to improving the cycle slip detection performance and realizing high-precision positioning of a single receiver.
Early researches on common methods (a height difference method, an ionospheric residual error method, polynomial fitting, phase combination, a pseudo-range method and other methods) for cycle slip detection are all double-frequency detection, and influence of ionospheric change on cycle slip detection is not related, so accurate real-time cycle slip detection cannot be carried out.
After three-frequency observation is started, a method for identifying three linear independent ionosphere-free combination models for cycle slip detection is provided, more information in different time periods needs to be reserved, so that the program becomes complex, the positioning precision can be reduced, cycle slip detection is performed by utilizing three-frequency linear combination, accurate cycle slip detection cannot be performed under the influence of an ionosphere scintillation condition or a low sampling rate, the positioning precision is reduced, and position misjudgment is caused.
Disclosure of Invention
Aiming at the defects in the prior art, the real-time three-frequency cycle slip detection method based on ionosphere refraction solves the problem of position misjudgment caused by low positioning accuracy of the existing three-frequency cycle slip detection method.
In order to achieve the purpose of the invention, the invention adopts the technical scheme that: a real-time three-frequency cycle slip detection method based on ionospheric refraction comprises the following steps:
s1, calculating a combined observed value of code and carrier phase in the GNSS system;
s2, calculating the difference between continuous epochs when the ionosphere change is not considered based on the combined observed value;
s3, calculating the difference between the continuous epochs by considering the ionospheric change between the continuous epochs;
and S4, detecting the three-frequency cycle slip according to the difference between the continuous epochs.
Further, in the step S1, the encoded combined observation valueP abc Comprises the following steps:
a combined observation of the carrier phases
Comprises the following steps:
in the formula (I), the compound is shown in the specification,ρwhich is the geometric distance between the satellite and the station,β abc for the amplification factor of the encoded ionospheric delay,
，I 1is a delay of the ionosphereL 1，T abc To encode the corresponding tropospheric delay of the observation,m abc in order to code the multipath effects observed for the code,cin order to be the speed of light in a vacuum,
to encode the time error between the corresponding satellite and the receiver,d abc in order to encode the hardware delay corresponding to the observation,
for noise observed in the code, subscriptsabcRepresents a linear coded combined observation anda+b+c=1，f i in order to be the frequency of the signal,i=1,2,3；
λ lmn is the wavelength of the phase of the carrier wave,φ lmn for the purpose of carrier phase observation,β lmn the amplification factor of the ionospheric delay for the carrier phase,
，T lmn the corresponding tropospheric delay is observed for the carrier phase,m lmn the corresponding multipath effects are observed for the carrier phase,
the time error between the corresponding satellite and the receiver is observed for the carrier phase,d lmn the corresponding hardware delay is observed for the carrier phase,N lmn for the integrated ambiguity corresponding to the carrier phase observation,e lmn noise observed for carrier phase, not subscriptl,m,nIs a sub-symbol, subscriptlmnRepresenting a linear phase combination observation.
Further, the calculation formula of the difference between the consecutive epochs in the step S2 is as follows:
in the formula (I), the compound is shown in the specification,
an operator of the difference between consecutive epochs.
Further, in step S3, when the difference between the consecutive epochs is calculated and considered when the ionosphere changes, the changes of the set multipath effect, the observation noise and the hardware delay are relatively stable between the consecutive epochs, and the clock error is eliminated by the non-geometric combination;
meanwhile, the difference between the set continuous epochs is obtained by non-geometric observation, and the change of an ionized layer between the continuous epochs is obtained by observing the carrier phase
Comprises the following steps:
in the formula (I), the compound is shown in the specification,λ i is a signaliThe carrier-phase wavelength of (a) is,φ i is a signaliIs observed in the carrier phase of the carrier wave,λ j is a signaljThe carrier-phase wavelength of (a) is,φ j is a signaljIs observed in the carrier phase of the carrier wave,k j1is a signaljThe symbol of (a) is,k i1is a signaliThe symbol of (2).
Further, in step S3, the difference between the consecutive epochs obtained by considering the ionospheric change between the consecutive epochs is:
in the formula (I), the compound is shown in the specification,
。
further, in step S4, the method for detecting the three-frequency cycle slip specifically includes:
when the difference between consecutive epochs
Satisfy the requirement of
Detecting a three-frequency cycle slip;
wherein the content of the first and second substances,
the observed coefficients are combined for the linear phase,
is a difference of
The variance of (c) is calculated by the formula:
in the formula (I), the compound is shown in the specification,i、jandkare all signals.
Further, when determining the coefficients of the linear phase combination observation, the following rule is set:
(1) the effect of the ionosphere is eliminated;
(2) tropospheric and multipath noise is not amplified;
(3) variation of ionosphere according to signal frequencyf i It is determined that,i=1,3, andl,m,nsatisfy the requirement ofl∙n<0 and-l|≅|n|。
The invention has the beneficial effects that:
(1) the sequence of the data of different sampling intervals or the data collected near the magnetic storm center does not approximately meet normal distribution, and the ionosphere change can be eliminated through the dual-frequency phase observation value by utilizing the advantage of combining the observation value with the three-frequency data, so that the improved value can be reasonably used for cycle slip detection;
(2) for small cycle slips, even cycle slips within 0.05 cycle can be improved by using an appropriate frequency combination;
(3) in the detection process, the condition of misjudgment or omission does not occur to all the manually added cycle slips;
(4) the method also has higher performance in real-time data detection.
Drawings
FIG. 1 is a flow chart of a real-time three-frequency cycle slip detection method based on ionospheric refraction.
Fig. 2 is a sequence of 1s and 30s observed interval ionospheric delay variations.
Fig. 3 is a histogram of the ionospheric variation frequency distribution in which (a) is a 1s observation interval and (b) is a 30s observation interval.
Fig. 4 shows the noise variance at different observation sampling rates.
Detailed Description
The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.
Example 1:
the embodiment of the invention provides a real-time three-frequency cycle slip detection method based on ionospheric refraction, which comprises the following steps as shown in figure 1:
s1, calculating a combined observed value of code and carrier phase in the GNSS system;
s2, calculating the difference between continuous epochs when the ionosphere change is not considered based on the combined observed value;
s3, calculating the difference between the continuous epochs by considering the ionospheric change between the continuous epochs;
and S4, detecting the three-frequency cycle slip according to the difference between the continuous epochs.
In the embodiment of the present invention, the observation results of code and carrier phase in the GNSS system are represented as follows:
based on the theory of combining three-frequency data, the combined observed value of the encoding in step S1 in this embodiment is obtained by assuming that the sub-symbols l, m, n are assumed to belong to the integer domain, and a, b, c are real numbersP abc Comprises the following steps:
in this embodiment, the combined observed value of the carrier phases is:
in the formula (I), the compound is shown in the specification,ρwhich is the geometric distance between the satellite and the station,β abc for the amplification factor of the encoded ionospheric delay,
，I 1is a delay of the ionosphereL 1，T abc To encode the corresponding tropospheric delay of the observation,m abc in order to code the multipath effects observed for the code,cin order to be the speed of light in a vacuum,
to encode the time error between the corresponding satellite and the receiver,d abc in order to encode the corresponding hardware delay observed,
for noise observed in the code, subscriptsabcRepresents a linear coded combined observation anda+b+c=1，f i in order to be the frequency of the signal,i=1,2,3；
λ lmn is the wavelength of the phase of the carrier wave,φ lmn for the purpose of carrier phase observation,β lmn the amplification factor of the ionospheric delay for the carrier phase,
，T lmn the corresponding tropospheric delay is observed for the carrier phase,m lmn the corresponding multipath effects are observed for the carrier phase,
the time error between the corresponding satellite and the receiver is observed for the carrier phase,d lmn the corresponding hardware delay is observed for the carrier phase,N lmn for the integrated ambiguity corresponding to the carrier phase observation,e lmn noise observed for carrier phase, not subscriptl,m,nIs a sub-symbol, subscriptlmnRepresenting a linear phase combination observation.
From the expressions (3) and (4), the integrated ambiguity in the epoch is obtainedN lmn ：
Wherein, the first and the second end of the pipe are connected with each other,
and
based on the combined ambiguities k and k-1 in the epochs, the difference between epochs can be expressed as:
because of a small number of complex modeling errors, e.g.m,eAndεcan be minimized by the difference between consecutive durations, tropospheric and clock errors are eliminated by forming carrier-minus-code combinations, and thus, ignoringcδd rs 、c(δd lmn -δd abc )、δTAndδ N lmn thereby obtainingThe calculation formula of the difference between the consecutive epochs in step S2 of the present embodiment is:
in the formula (I), the compound is shown in the specification,
an operator of the difference between consecutive epochs.
In the real-time cycle slip detection, the amplification factor of the ionospheric delay is small, so that the formula in the calculation is
Always neglected, but the influence of other factors, such as magnetic storm, may cause misjudgment of cycle slip in data preprocessing, so the change of ionosphere should be considered in the CSD in the present implementation.
In step S3 of the embodiment of the present invention, when the ionospheric variation is considered, the ionospheric with dispersive characteristics receives the influence of several factors, especially solar radiation, so the ionospheric activity in the same region often varies with the degree of solar radiation caused by the earth rotation, and usually this influence is often ignored or attenuated by the ionospheric free-combination, however, due to the sampling rate or ionospheric activity, the ionospheric activity in formula (7) is affected by several factors, especially solar radiation
Drastic changes may occur that may result in cycle slip detection failures.
Due to the parameter in formula (2)NIn step S3 of the present embodiment, when the difference between consecutive epochs is considered in the calculation, the changes of the set multipath effect, the observed noise and the hardware delay are relatively stable between consecutive epochs, and the clock error is eliminated by non-geometric combination;
meanwhile, the difference between the set continuous epochs is obtained by non-geometric observation, and the change of an ionized layer between the continuous epochs is obtained by observing the carrier phase
Comprises the following steps:
in the formula (I), the compound is shown in the specification,λ i is a signaliThe carrier-phase wavelength of (a) is,φ i is a signaliIs observed in the carrier phase of the carrier wave,λ j is a signaljThe carrier-phase wavelength of (a) is,φ j is a signaljIs observed in the carrier phase of the carrier wave,k j1is a signaljThe symbol of (a) is,k i1is a signaliThe symbol of (2).
From equation (8) in this embodiment, the ionospheric changes can be observed from carrier phase between successive epochs.
In embodiments of the invention, as the ionospheric activity level or sampling rate varies, the ionospheric variation between durations will approach a normal distribution, and thus the statistical discipline of CSD is
These conditions are not valid, so the ionospheric variation should be considered in equation (7), and the difference between the consecutive epochs obtained in step S3 of the present embodiment, taking into account the ionospheric variation between the consecutive epochs, is:
in the formula (I), the compound is shown in the specification,
。
in step S4 of the embodiment of the present invention, the method for detecting three-frequency cycle slip specifically includes:
when the difference between consecutive epochs
Satisfy the requirement of
Detecting a three-frequency cycle slip;
in the embodiment of the present invention, it is,
is a difference of
The variance of (a) is calculated by the formula:
in the embodiment of the present invention, in the formula (10)i、jAndkare all signals, based on equation (10), assumingσ P1 =σ P2 =σ P3 =0.3m，σ L1 =σ L2 =σ L3=0.01 period, respective carrier wavelength λ1≈19.03cm，λ2Approximately equal to 24.42cm and lambda325.48cm, when abc = [1,0 ] is selected]It can be known from the formula (10),
depends onσ P 。
In the embodiment of the present invention, it is,
the coefficients for the linear phase combination observation can be taken to be 3,4 (with corresponding confidence levels of 99.7% and 99.9%, respectively). As can be seen from the above-mentioned detection formula,
not only depends on the noise of the coding observation, but also on the decisionBased on the observation of whether the optimal phase combination coefficient is the optimal phase combination coefficient of the three-cycle slip, in step S4, the following rule is set when determining the coefficient observed by the linear phase combination:
(1) the effect of the ionosphere is eliminated;
(2) tropospheric and multipath noise is not amplified;
(3) variation of ionosphere according to signal frequencyf i It is determined that,i=1,3, andl,m,nsatisfy the requirement ofl∙n<0 and-l|≅|n|。
Example 2:
in the embodiment of the invention, an example based on the three-frequency cycle slip detection method is provided:
in an embodiment of the present invention, the processing combination of phase observations l, m, and n is set to [ -6,1,7]And the combination of the encoded observations a, b, c is set to [1,0 ]]Assuming realistic noise of GPS observations asσ P1 =σ P2 =σ P3 =0.3m，σ φ For evaluation of the performance of the method of the present embodiment, three-frequency GPS data from the IGS JFNG station was processed with a data interval of 1 second and a truncation elevation of 10 °.
In this embodiment, in order to analyze the characteristics of ionospheric changes obtained at different sampling rates, data under quiet ionospheric activity conditions are collected from a JFNG satellite tracking station of International GPS Service (IGS), and the result obtained through calculation is as shown in fig. 2, and it is apparent from fig. 2 that ionospheric change sequences are distributed on both sides of zero at an observation interval of 1s, and there is a significant difference in 30 s. The corresponding histogram is shown in fig. 3, with 1s being represented by a normal distribution with a mean value of 0 (fig. 3 (a)), and with 30s values indicating a high effect of ionospheric effects (fig. 3 (b)).
In the present embodiment, in order to further verify the relation between the noise variance and the observation interval, ionospheric variations at different observation intervals at 1s, 5 s, 10 s, 15 s, 20 s, 25 s and 30s are calculated respectively, and the corresponding noise variance is shown in fig. 4. This figure shows that the noise variance increases with increasing sampling rate, and therefore the effect of ionospheric variations must be taken into account when performing cycle slip detection.
In the embodiment, in order to evaluate the performance of the method under the triple-frequency data with different sampling intervals, the data of the satellite tracking station are sampled, and the sampling intervals are respectively 1s, 5 s, 10 s, 15 s, 20 s, 25 s and 30 s. And adding artificial jump in all satellite observation and deriving ionospheric variation. Since the epochs and amplitudes of the jumps are known a priori, as the sampling rate increases, the performance of the method deteriorates when the expected values of ionospheric changes are ignored, which can be the case when two epochs are missed and five epochs are misjudged. However, all artificially added jumps can be correctly detected by the improved method, and the detection values are approximately normally distributed on both sides of the X-axis.
Claims (7)
1. A real-time three-frequency cycle slip detection method based on ionospheric refraction is characterized by comprising the following steps:
s1, calculating a combined observed value of code and carrier phase in the GNSS system;
s2, calculating the difference between continuous epochs when the ionosphere change is not considered based on the combined observed value;
s3, calculating the difference between the continuous epochs by considering the ionospheric change between the continuous epochs;
and S4, detecting the three-frequency cycle slip according to the difference between the continuous epochs.
2. The method of claim 1, wherein the step S1 is performed by encoding the combined observationP abc Comprises the following steps:
combined observed value of carrier phase
Comprises the following steps:
in the formula (I), the compound is shown in the specification,ρwhich is the geometric distance between the satellite and the station,β abc for the amplification factor of the encoded ionospheric delay,
，I 1is a delay of the ionosphereL 1，T abc To encode the corresponding tropospheric delay of the observation,m abc in order to code the multipath effects observed for the code,cin order to be the speed of light in a vacuum,
to encode the time error between the corresponding satellite and the receiver,d abc in order to encode the hardware delay corresponding to the observation,
for noise observed in the code, subscriptsabcRepresents a linear coded combined observation anda+b+c=1，f i in order to be the frequency of the signal,i=1,2,3；
λ lmn is the wavelength of the phase of the carrier wave,φ lmn for the purpose of carrier phase observation,β lmn the amplification factor of the ionospheric delay for the carrier phase,
，T lmn the corresponding tropospheric delay is observed for the carrier phase,m lmn the corresponding multipath effects are observed for the carrier phase,
the time error between the corresponding satellite and the receiver is observed for the carrier phase,d lmn the corresponding hardware delay is observed for the carrier phase,N lmn for the integrated ambiguity corresponding to the carrier phase observation,e lmn noise observed for carrier phase, not subscriptl,m,nIs a sub-symbol, subscriptlmnRepresenting a linear phase combination observation.
3. The method for real-time three-frequency cycle slip detection based on ionospheric refraction of claim 2, wherein the difference between consecutive epochs in step S2 is calculated by the formula:
in the formula (I), the compound is shown in the specification,
an operator of differences between consecutive epochs.
4. The method according to claim 3, wherein in step S3, when the difference between the successive epochs is considered in the calculation, the changes of the set multipath effect, the observation noise and the hardware delay are relatively stable between the successive epochs, and the clock error is eliminated by the geometrical combination-free method;
meanwhile, the difference between the set continuous epochs is obtained by non-geometric observation, and the change of an ionized layer between the continuous epochs is obtained by observing the carrier phase
Comprises the following steps:
in the formula (I), the compound is shown in the specification,λ i is a signaliThe carrier-phase wavelength of (a) is,φ i is a signaliIs observed in the carrier phase of the carrier wave,λ j is a signaljThe carrier-phase wavelength of (a) is,φ j is a signaljIs observed in the carrier phase of the carrier wave,k j1is a signaljThe symbol of (a) is,k i1is a signaliThe symbol of (2).
5. The method according to claim 4, wherein the difference between the consecutive epochs obtained by considering the ionospheric variation between the consecutive epochs in step S3 is:
in the formula (I), the compound is shown in the specification,
。
6. the real-time three-frequency cycle slip detection method based on ionospheric refraction of claim 5, wherein in step S4, the method for detecting three-frequency cycle slips specifically comprises:
when the difference between consecutive epochs
Satisfy the requirement of
Detecting a three-frequency cycle slip;
wherein the content of the first and second substances,
the observed coefficients are combined for the linear phase,
is a difference of
The variance of (c) is calculated by the formula:
in the formula (I), the compound is shown in the specification,i、jandkare all signals.
7. The method of claim 6, wherein the following rules are set for determining the linear phase combination observation coefficients:
(1) the effect of the ionosphere is eliminated;
(2) tropospheric and multipath noise is not amplified;
(3) ionosphere variation according to signal frequencyf i It is determined that,i=1,3, andl,m,nsatisfy the requirement ofl∙n<0 and-l|≅|n|。
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| CN102650692A (en) * | 2011-02-25 | 2012-08-29 | 中国人民解放军61081部队 | Method for detecting and repairing cycle slip by utilizing BeiDou three-frequency observed quantity |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102650692A (en) * | 2011-02-25 | 2012-08-29 | 中国人民解放军61081部队 | Method for detecting and repairing cycle slip by utilizing BeiDou three-frequency observed quantity |
| US20210255336A1 (en) * | 2020-02-14 | 2021-08-19 | Swift Navigation, Inc. | System and method for reconverging gnss position estimates |
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