CN116318509B - PPP time-frequency transmission method based on ambiguity fixed residual posterior authority - Google Patents
PPP time-frequency transmission method based on ambiguity fixed residual posterior authority Download PDFInfo
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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
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
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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
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
- G01S19/04—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing carrier phase data
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- G—PHYSICS
- G04—HOROLOGY
- G04R—RADIO-CONTROLLED TIME-PIECES
- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
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- G—PHYSICS
- G04—HOROLOGY
- G04R—RADIO-CONTROLLED TIME-PIECES
- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
- G04R20/04—Tuning or receiving; Circuits therefor
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
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Abstract
The application relates to a PPP time-frequency transmission method based on fuzzy fixed residual posterior authentication. The method comprises the following steps: by the method for constructing the self-adaptive factor according to the ambiguity fixing residual error, the ambiguity constraint of the ambiguity fixing solution is reasonably set, once the ambiguity is fixed in error, the influence of the erroneous ambiguity fixing on clock error calculation and time frequency transmission can be avoided to the greatest extent, and the problem of insufficient ambiguity fixing reliability caused by imperfect error model is solved.
Description
Technical Field
The application relates to the technical field of satellite time transfer, in particular to a PPP time-frequency transfer method based on fuzzy fixed residual posterior fixed weight.
Background
GNSS time-frequency transfer plays an important role in the generation and maintenance of international atomic time and coordinated universal time scales. Early GNSS time-frequency transfer used only pseudorange observations, since the measurement noise of GNSS carrier phases was much smaller than pseudoranges, researchers began to employ precise point-of-time positioning (PPP) based time-frequency transfer methods in order to improve GNSS time-frequency transfer accuracy. Experimental results prove that compared with GNSS pseudo-range time-frequency transmission, PPP time-frequency transmission can remarkably improve the medium-short term stability of time-frequency transmission and effectively reduce the uncertainty of time transmission.
In the PPP mathematical model, carrier phase ambiguity is typically resolved to a floating solution that includes a non-integer portion, as the ambiguity parameters in non-differential form absorb the hardware delay error from the satellite receiver side. In order to fully utilize integer characteristics of ambiguity and improve PPP calculation accuracy, researchers propose various methods for fixing carrier phase integer ambiguity. The international GNSS service organisation analysis centers, represented by the french astronaut center, the german borzhutan center, began to provide PPP ambiguity fixing products for aiding in ambiguity fixing. In the field of geodetic measurement, PPP ambiguity-fixing methods are used to improve the accuracy of positioning. In the field of time-frequency metering, researchers have used integer phase Zhong Fa to fix carrier phase ambiguity, resulting in a more stable long-term frequency stability performance than PPP floating solutions. Although the prior studies demonstrate the advantages of time-frequency delivery based on a fixed solution of PPP ambiguity, there is still a problem with using this approach for time-frequency delivery.
Disclosure of Invention
Accordingly, in order to solve the above-described problems, it is necessary to provide a PPP time-frequency transmission method based on fuzzy fixed residual posterior decision weights, which can avoid the influence of error ambiguity fixing on time-frequency transmission.
A PPP time-frequency delivery method based on fuzzy fixed residual posterior authorization, the method comprising:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution;
establishing a MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity according to the MW combined form observation equation, and obtaining a narrow elane ambiguity fixation residual error at the current moment;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and an IGG function at the current moment, and calculating the anterior constraint condition according to the adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
In one embodiment, the adaptation factor is expressed as:
in the above formula, κ represents the adaptive factor, V represents the narrow-lane ambiguity fix residual at the current time, c 0 And c 1 A detection threshold representing the detection amount of narrow-lane ambiguity residual error.
In one embodiment, the posterior constraint obtained by calculating the posterior constraint according to the adaptive factor uses the following formula:
in the above-mentioned description of the invention,representing the posterior constraint, κ represents the adaptive factor, σ represents the posterior constraint.
In one embodiment, the method further comprises:
acquiring satellite orbit integer clock difference data;
before parameter filtering estimation is carried out on the PPP observation equation, the satellite orbit integer clock difference data is utilized to correct the PPP observation equation, and a corrected PPP observation equation is obtained;
and performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the corrected PPP observation equation according to the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station.
In one embodiment, the method further comprises:
acquiring satellite wide lane deviation data;
and before the ambiguity is fixed in a whole circle according to the MW combined form observation equation, correcting the ambiguity by using the satellite wide lane deviation data to obtain a corrected MW combined form observation equation.
In one embodiment, the ambiguity fixing for the widelane ambiguity, the narrow elane ambiguity, and the ionospheric-free ambiguity sequentially according to the MW combining form observation equation includes:
fixing the wide lane ambiguity in a whole week by adopting a direct rounding method according to the MW combined form observation equation and satellite wide lane deviation data;
adopting a least square drop correlation algorithm to fix the narrow lane ambiguity in a whole cycle;
and carrying out linear combination according to the widelane ambiguity and the narrow elane ambiguity, and then carrying out ambiguity fixing on the ionospheric-free ambiguity.
A PPP time-frequency delivery device based on fuzzy fixed residual posterior authorization, the device comprising:
the observation value receiving module is used for acquiring pseudo-range and carrier phase observation values respectively received by the double-frequency receivers of the two observation stations, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks the broadcasting signals of the navigation satellite;
the primary parameter filtering estimation module is used for constructing a PPP observation equation in a ionosphere-free combination form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating solution;
the ambiguity fixing module is used for constructing an MW combined form observation equation, sequentially fixing the ambiguities of the wide-lane ambiguities, the narrow-lane ambiguities and the ionosphere-free ambiguities in a whole circle according to the MW combined form observation equation, and obtaining a narrow-lane ambiguities fixing residual error at the current moment;
the posterior constraint condition determining module is used for constructing a virtual observation equation by using the fixed wide lane, the fixed narrow lane and the ionosphere-free ambiguity, and determining the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
the posterior constraint condition calculation module is used for constructing a self-adaptive factor according to the narrow-lane ambiguity fixed residual error and the IGG function at the current moment, and calculating the posterior constraint condition according to the self-adaptive factor to obtain a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity;
the secondary parameter filtering estimation module is used for carrying out secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and the real-time transfer module is used for calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transfer result.
A computer device comprising a memory storing a computer program and a processor which when executing the computer program performs the steps of:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution;
establishing a MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity according to the MW combined form observation equation, and obtaining a narrow elane ambiguity fixation residual error at the current moment;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and an IGG function at the current moment, and calculating the anterior constraint condition according to the adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
A computer readable storage medium having stored thereon a computer program which when executed by a processor performs the steps of:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution;
establishing a MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity according to the MW combined form observation equation, and obtaining a narrow elane ambiguity fixation residual error at the current moment;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and an IGG function at the current moment, and calculating the anterior constraint condition according to the adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
According to the PPP time-frequency transfer method based on fuzzy fixed residual posterior fixed weight, the pseudo range and the carrier phase observed value which are respectively received by the dual-frequency receivers of two observation stations are obtained, the PPP observation equation in the form of ionosphere-free combination is constructed according to the pseudo range and the carrier phase observed value, parameter filtering estimation is carried out on the PPP observation equation, the wide lane ambiguity, the narrow lane ambiguity and the ionosphere-free ambiguity are sequentially carried out for ambiguity fixing, the narrow lane ambiguity fixed residual at the current moment is obtained, the anterior constraint condition is determined according to the narrow lane ambiguity fixed residual, the adaptive factor is constructed according to the narrow lane ambiguity fixed residual and the IGG function, the posterior constraint condition is calculated according to the adaptive factor, finally the updating calculation of the ambiguity fixed solution is carried out according to the posterior constraint condition, the accurate clock difference of the corresponding observation station is obtained, and the difference between the dual-frequency receivers in the two observation stations is calculated, so that the real-time transfer result is obtained. By adopting the method, the influence of error ambiguity fixation on time frequency transmission can be avoided, so that the time frequency transmission precision is improved.
Drawings
Fig. 1 is a flow chart of a PPP time-frequency transfer method based on fuzzy fixed residual posterior authentication in one embodiment;
FIG. 2 is a schematic diagram of an adaptive factor change curve in one embodiment;
FIG. 3 is a schematic diagram showing a comparison analysis of the time-frequency transfer results of PPP ambiguity-resolved in experimental verification;
FIG. 4 is a schematic diagram of a comparison analysis of the difference sequence between the results of time-frequency transmission by the method and the results transmitted by the International measuring office in experimental verification;
FIG. 5 is a graph showing a comparative analysis of corrected ALLAN bias between the results of time-frequency transmissions by the present method and the results of transmissions by the International measuring office in experimental verification;
FIG. 6 is a block flow diagram of a PPP time-frequency delivery method based on fuzzy fixed residual posterior authorization in another embodiment;
FIG. 7 is a block diagram of a PPP time-frequency delivery device based on fuzzy fixed residual posterior authorization in one embodiment;
fig. 8 is an internal structural diagram of a computer device in one embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
Aiming at the problem that in the existing seed difference calculating method based on ambiguity fixing, because the ambiguity is strongly related to a clock difference parameter, under the condition of ambiguity fixing errors, the error ambiguity fixing result can seriously affect the PPP clock difference calculating result, and a random model used in the existing PPP fixed seed difference calculating is obtained according to a priori experience value, the influence of different fixed product quality on the PPP fixed seed difference calculating result cannot be reflected, a time frequency transfer method based on PPP ambiguity fixed residual posterior determination weight is provided, as shown in figure 1, and the method comprises the following steps:
step S100, pseudo-range and carrier phase observation values respectively received by double-frequency receivers of two observation stations are obtained, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
step S110, constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and the carrier phase observation value, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating solution;
step S120, constructing a MW combined form observation equation, sequentially fixing the ambiguities of the wide lane ambiguity, the narrow lane ambiguity and the ionosphere-free ambiguity for the whole week according to the MW combined form observation equation, and obtaining a narrow lane ambiguity fixing residual error at the current moment;
step S130, constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a pre-experimental constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
step S140, constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and the IGG function at the current moment, and calculating a posterior constraint condition according to the adaptive factor to obtain a posterior constraint condition of a virtual observation equation on the ambiguity whole-week constraint;
step S150, carrying out secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
step S160, calculating the difference between the clock differences of the dual-frequency receivers in the two observation stations to obtain a real-time transmission result.
In this embodiment, by proposing a PPP time-frequency transmission method based on fuzzy fixed residual posterior decision, not only the influence of error ambiguity fixation on frequency transmission can be avoided, but also the stability of PPP time-frequency transmission results at different smooth times can be effectively improved.
First, in step S100, the pseudo-range and carrier phase observations broadcast by the navigation satellites are received by the dual-frequency receivers of the two observers, respectively, and the received signals are transmitted in the frequency (f 1 =1575.42 MHz) and L2 (f 2 =1227.6 MHz) pseudorange P i s And carrier phaseThe observations can be expressed as:
in formula (1), ρ s Representing the geometrical distance between the satellite and the receiver, c representing the speed of light, dt r And dt (dt) s Respectively representing the clock difference of the dual-frequency receiver and the clock difference of the satellite, T s Andrepresenting tropospheric delay error and ionospheric delay error, b r,i And B r,i Pseudo-range and carrier phase hardware delay, respectively, at the receiver side>And->Pseudo-range and carrier phase hardware delay, respectively, of the satellite side>Representing carrier phase integer ambiguity, lambda i Representing carrier wavelength, < >>And->The measurement noise of the pseudo-range and carrier phase are represented, respectively.
In step S110, an observation combination in the form of a dual-frequency pseudo-range and carrier-phase ionosphere-free combination, i.e., a PPP observation equation, is constructed from the received observation data, which can be expressed as:
wherein:
in formula (2), α IF And beta IF Representing ionosphere-free combined coefficients, b r,IF ，B r,IF And->Pseudo-range and carrier phase deviation, lambda, of receiver and satellite IF Indicating ionosphere free combined form wavelength, +.>Representing ionosphere-free combined carrier phase ambiguity, < >>Representing widelane ambiguity,)>And->The pseudorange and the observed noise of the carrier are represented, respectively.
As can be seen from equation (2), the ionospheric-free combined observations contain pseudorange and carrier-phase bias associated with the receiver and satellite. And errors such as ambiguity parameters, receiver pseudo-range deviation, receiver carrier phase deviation and the like are mixed together and cannot be separated.
In order to avoid the influence of the deviation on the fixation of the ambiguity, the observation equation is subjected to the re-parameterization treatment, and the rewriteable method is adopted as follows:
wherein,
cdt r,P ＝cdt r +b r,IF
in the formula (3) of the present invention,and (3) representing an ambiguity floating solution, wherein the ambiguity floating solution comprises a receiver position, a clock error and a carrier ambiguity floating solution.
In this embodiment, the ambiguity resolution is calculated using a kalman filtering method.
In step S120, a MW combined form observation equation is constructed, and the ambiguities of the widelane ambiguity, the narrow elane ambiguity, and the ionospheric-free ambiguity are sequentially fixed according to the equation.
Further, after the ambiguity floating solution is obtained, an observation equation of the wide lane carrier and the narrow lane pseudo range is constructed, and the reconstructed observation equation of the wide lane carrier and the narrow lane pseudo range is subtracted to obtain an observation equation of MW combination:
specifically, an observation equation of the wide lane carrier and the narrow lane pseudo-range is constructed, and the observation equation is expressed as follows:
wherein,
in the formula (4) of the present invention,representing a wide lane carrier,/->Representing narrow roadway pseudoranges, alpha WL And beta WL Combination coefficient, alpha, representing MW combined observations NL And beta NL And the combination coefficient of the observation values of the narrow lane is represented.
Subtracting the wide lane carrier and the narrow lane pseudo-range observation equation to obtain an MW combined observation equation:
wherein,
next, to eliminate the effect of receiver hardware delay errors on the widelane ambiguity fix, the widelane ambiguity fix is performed using the MW combining form observation equation:
in the formula (6) of the present invention,representing widelane ambiguity lambda WL Indicating widelane ambiguity wavelength, +.>Representing a widelane ambiguity residual. In view of the longer wavelength of the widelane ambiguities, the fixation of the widelane ambiguities can be performed by direct rounding.
Further, according to the ambiguity parameter without ionosphere form and the wide lane ambiguity parameter, calculating can obtain the initial ambiguity solution in narrow lane form
In the formula (7), lambda IF Represents ambiguity wavelength in ionosphere-free form, lambda NL The wavelength of the narrow-lane ambiguity is represented, and σ represents the observed noise of the narrow-lane ambiguity equation.
And then adopting a least square drop correlation algorithm to fix the narrow lane ambiguity, so as to obtain the final solution of the narrow lane ambiguity:
in the formula (8) of the present invention,representing an unfixed narrow-lane ambiguity initial solution vector,>representing a fixed narrow-lane ambiguity integer solution vector,/->Representing an unfixed ambiguity covariance matrix, n representing the ambiguity vector dimension.
In step S130, a virtual observation equation is constructed using the fixed wide lane, narrow lane, and ionospheric-free ambiguity, the equation being equation (9). And determining the anterior constraint condition of the virtual observation equation according to the historical data of the narrow-lane ambiguity fixed residual error:
in the formula (9), a represents a coefficient matrix, X represents an estimated parameter vector, σ represents an observed noise level of narrow-lane ambiguity, that is, a calculated a priori constraint condition, the larger the variance, the larger the observed noise, the more relaxed the constraint, and the lower the confidence of the ambiguity estimation.
In the prior art, σ obtained by solving is a fixed value, and in practice, σ should be floating, which also results in the receiver clock difference T in the following n Ambiguity parametersAnd larger errors exist when the tropospheric parameters ZTD are re-solved.
In this embodiment, the adaptive factor is updated according to the construction.
In step S140, when the adaptive factor is constructed according to the narrow-lane ambiguity fixed residual and the IGG function, a large amount of historical data of the narrow-lane ambiguity fixed residual is analyzed, statistical features are extracted, and an IGG function segmentation threshold is determined, and then the adaptive factor may be also expressed as the narrow-lane residual detection amount:
in the formula (10), κ represents an adaptive factor, V represents a narrow lane ambiguity fixed residual, i.e., a narrow lane residual detection quantity, c 0 And c 1 And the detection threshold of the narrow-lane ambiguity residual error monitoring is represented. Wherein solving for V uses the following formula:
the posterior constraint condition is calculated according to the self-adaptive factor, and the following formula is adopted:
in the formula (12) of the present invention,representing the posterior constraint, κ represents the adaptive factor, σ represents the posterior constraint.
The change curve of the adaptive factor along with the residual is shown in fig. 2, and can be seen from the graph, after the adaptive factor, when the residual in a narrow lane is too large, the noise level of the ambiguity is considered to be large at the moment, so that the variance expansion is performed through the adaptive factor, when the residual in the narrow lane is small, the ambiguity is considered to be normal, and the adaptive factor is 1 at the moment.
Then, in step S150, the PPP observation equation is subjected to secondary filtering estimation with the addition of the ambiguity whole-cycle constraint according to the virtual observation equation and the posterior constraint condition, and the estimation parameters are updated and solved, which comprises the following steps:
in formula (13), X 1 An updated solution vector representing the estimated parameters,representing the updated calculated constraint equation variance matrix, < ->Representing a constraint equation variance matrix prior to updating the calculation, wherein estimating the parameters includes: accurate clock difference T of receiver n Ambiguity parameter->Tropospheric parameters ZTD.
And finally, performing secondary difference on the two station measurement clock difference results obtained through calculation to obtain a PPP time frequency transmission final result:
T Δ ＝T m -T n ＝(T m -T ref )-(T n -T ref )＝dt m,L -dt n,L (14)
in formula (14), T m And T n Respectively represent the local time of two different stations, T ref Representing the system time of the GESS.
In this embodiment, satellite orbit integer clock difference data is also obtained, and is corrected by the satellite orbit integer clock difference data before parameter filtering estimation is performed on the PPP observation equation, so as to obtain a corrected PPP observation equation. And performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the corrected PPP observation equation according to the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station.
In this embodiment, satellite wide-lane deviation data is also obtained, and is corrected before the ambiguity is fixed in a whole week according to the MW combination form observation equation, so as to obtain a corrected MW combination form observation equation.
In this embodiment, the satellite orbit integer clock difference data and the satellite wide lane deviation data are obtained from an internet channel.
Experiments were also performed herein to verify the methods presented herein, as shown in fig. 3, showing the observation station data for USN7 and USN8 transferred results at approximately julian day 59216. As can be seen from the figure, when the traditional PPP ambiguity fixing method is adopted for time transfer, the fluctuation of the time frequency transfer result of PPP fixed solution is larger. This is because in the case of anomalous observations, the presence of measurement noise causes ambiguity fixing errors, affecting the time-frequency transfer result of the PPP fixing solution. In this case, the use of the adaptive factor expansion variance can achieve a good effect, and the influence of the erroneous fixation on the calculation result of the clock error is reduced by the adaptive factor expansion variance. As can be seen from fig. 3, the fixed residual posterior weighting method proposed herein can improve the reliability of carrier phase integer ambiguity fixation, and the time-frequency transmission result has smaller fluctuation and is more stable.
As shown in fig. 4, the time transfer results of the PPP ambiguity floating solution, the PPP ambiguity fixed solution (IPPP) adopted by the international metering office, and the PPP ambiguity fixed solution of the method herein are compared with the time transfer results of the fiber link with higher accuracy as reference values. As shown, the time-transfer result of the two PPP ambiguity-fixed solutions fluctuates less than the PPP floating solution result. The standard deviations of the calculated time-transfer results for the PPP ambiguity-floating solution, the IPPP ambiguity-fixed solution, and the PPP ambiguity-fixed solution of the methods herein compared to the fiber results were approximately 140ps, 85ps, and 83ps, respectively. The standard deviation of the method is slightly lower than the PPP ambiguity fixed solution (IPPP) method adopted by the International metering office.
As shown in fig. 5, corrected alian deviation (MDEV) results are shown for PPP ambiguity-resolving, ambiguity-fixing solutions adopted by the international metering office, and time-transfer results of the methods herein. Clearly, the frequency stability of the time-transfer result of the ambiguity-fixed solution is better than BIPM PPP. When the smoothing time reaches 35 days, the PPP ambiguity floating solution, the original PPP ambiguity fixing solution, and the frequency stabilization values of the methods herein are about 3.3E-16, 2.1E-16, and 1.7E-16, respectively. Compared with the existing prior PPP ambiguity fixed solution method, the method improves the frequency stability by about 20%, and proves that the method can effectively improve the frequency stability of PPP fixed solution time transmission.
In one embodiment, a frame flow chart of the present method is also provided, as shown in FIG. 6.
In the PPP time frequency transmission method based on the fuzzy fixed residual posterior fixed weight, the fuzzy constraint of the fuzzy fixed solution is reasonably set by a method of constructing the self-adaptive factor according to the fuzzy fixed residual, once the fuzzy is fixed in error, the influence of the erroneous fuzzy fixation on the calculation of the clock error can be avoided to the greatest extent, and the problem of insufficient fuzzy fixation reliability caused by imperfect error model is solved. According to the method, the influence of measurement noise in the PPP ambiguity fixed equation on the clock difference estimation is considered, the observation noise of the PPP ambiguity fixed observation equation is dynamically adjusted through the self-adaptive factor, and the fixed noise contained in the clock difference parameter is weakened, so that the stability of time-frequency transmission in different smooth time is effectively improved.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, nor do the order in which the sub-steps or stages are performed necessarily performed in sequence, but may be performed alternately or alternately with at least a portion of other steps or sub-steps of other steps.
In one embodiment, as shown in fig. 7, there is provided a PPP time-frequency transfer device based on fuzzy fixed residual posterior authorization, including: the system comprises an observation receiving module 200, a primary parameter filtering estimating module 210, an ambiguity fixing module 220, a pre-test constraint condition determining module 230, a post-test constraint condition calculating module 240, a secondary parameter filtering estimating module 250 and a real-time transfer module 260, wherein:
the observation value receiving module 200 is configured to obtain pseudo-range and carrier phase observation values received by dual-frequency receivers of two observation stations respectively, where the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks the broadcast signals of the navigation satellite;
a primary parameter filtering estimation module 210, configured to construct a PPP observation equation in a ionosphere-free combination form according to the pseudo-range and carrier phase observations, and perform parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error, and a carrier ambiguity floating solution;
the ambiguity fixing module 220 is configured to construct an MW combination form observation equation, sequentially fix the ambiguities of the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity over the whole period according to the MW combination form observation equation, and obtain a narrow elane ambiguity fixing residual error at the current moment;
the pre-test constraint condition determining module 230 is configured to construct a virtual observation equation using the fixed ionosphere-free ambiguity, and determine a pre-test constraint condition of the virtual observation equation according to historical data of a narrow-lane ambiguity fixed residual;
the posterior constraint calculation module 240 is configured to construct an adaptive factor according to the narrow-lane ambiguity fixed residual error at the current moment and the IGG function, and calculate the posterior constraint according to the adaptive factor to obtain a posterior constraint of the virtual observation equation;
the secondary parameter filtering estimation module 250 is configured to perform secondary filtering estimation of the global constraint of the additional ambiguity on the PPP observation equation according to the posterior constraint condition, so as to obtain an accurate clock difference of the corresponding observation station;
the real-time transfer module 260 is configured to calculate a difference between clock differences of the dual-frequency receivers in the two observation stations, and obtain a real-time transfer result.
For specific limitations on the PPP time-frequency transfer device based on the fuzzy fixed residual posterior authorization, reference may be made to the above limitation on the PPP time-frequency transfer method based on the fuzzy fixed residual posterior authorization, which is not described herein. The modules in the time-frequency transmission device based on the PPP fuzzy fixed residual posterior authentication can be realized in whole or in part by software, hardware and a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
In one embodiment, a computer device is provided, which may be a terminal, and the internal structure thereof may be as shown in fig. 8. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program when executed by a processor implements a time-frequency delivery method based on PPP fuzzy fixed residual posterior authentication. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be keys, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.
It will be appreciated by those skilled in the art that the structure shown in fig. 8 is merely a block diagram of some of the structures associated with the present application and is not limiting of the computer device to which the present application may be applied, and that a particular computer device may include more or fewer components than shown, or may combine certain components, or have a different arrangement of components.
In one embodiment, a computer device is provided comprising a memory and a processor, the memory having stored therein a computer program, the processor when executing the computer program performing the steps of:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution;
establishing a MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity according to the MW combined form observation equation, and obtaining a narrow elane ambiguity fixation residual error at the current moment;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and an IGG function at the current moment, and calculating the anterior constraint condition according to the adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
In one embodiment, a computer readable storage medium is provided having a computer program stored thereon, which when executed by a processor, performs the steps of:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, and carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution;
establishing a MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on the widelane ambiguity, the narrow elane ambiguity and the ionosphere-free ambiguity according to the MW combined form observation equation, and obtaining a narrow elane ambiguity fixation residual error at the current moment;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error and an IGG function at the current moment, and calculating the anterior constraint condition according to the adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-cycle constraint of the ambiguity;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the various embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), memory bus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.
Claims (1)
1. The PPP time-frequency transmission method based on fuzzy fixed residual posterior authentication is characterized by comprising the following steps:
acquiring pseudo-range and carrier phase observation values received by a dual-frequency receiver of two observation stations respectively, wherein the pseudo-range and carrier phase observation values are generated after the receiver locks and tracks a navigation satellite broadcasting signal;
constructing a PPP observation equation in a ionosphere-free combined form according to the pseudo-range and carrier phase observation values, carrying out parameter filtering estimation on the PPP observation equation to obtain a receiver position, a clock error and a carrier ambiguity floating point solution, wherein before carrying out parameter filtering estimation on the PPP observation equation, correcting the PPP observation equation by utilizing satellite orbit integer clock error data to obtain a corrected PPP observation equation, and carrying out secondary filtering estimation of additional ambiguity integer constraint on the corrected PPP observation equation according to a posterior constraint condition to obtain an accurate clock error of a corresponding observation station;
establishing a MW combined form observation equation, correcting the MW combined form observation equation by using satellite wide lane deviation data to obtain a corrected MW combined form observation equation, sequentially carrying out ambiguity whole-week fixation on wide lane ambiguity, narrow lane ambiguity and ionosphere-free ambiguity according to the corrected MW combined form observation equation, and obtaining a narrow lane ambiguity fixation residual error at the current moment, wherein the method comprises the following steps: according to the corrected MW combined form observation equation and satellite wide lane deviation data, adopting a direct rounding method to fix the wide lane ambiguity, adopting a least square drop correlation algorithm to fix the narrow lane ambiguity in a whole circle, and carrying out linear combination according to the wide lane ambiguity and the narrow lane ambiguity to fix the ionosphere-free ambiguity;
constructing a virtual observation equation by using the fixed wide lane, narrow lane and ionosphere-free ambiguity, and determining a posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity according to the historical data of the narrow lane ambiguity fixed residual error;
constructing an adaptive factor according to the narrow-lane ambiguity fixed residual error at the current moment and an IGG function, wherein the adaptive factor is expressed as:
in the above formula, κ represents the adaptive factor, V represents the narrow-lane ambiguity fix residual at the current time, c 0 And c 1 A detection threshold representing a narrow-lane ambiguity residual detection amount;
and then calculating the posterior constraint condition according to the self-adaptive factor to obtain the posterior constraint condition of the virtual observation equation on the whole-week constraint of the ambiguity, wherein the posterior constraint condition is calculated according to the self-adaptive factor by adopting the following formula:
in the above-mentioned description of the invention,representing the posterior constraint, κ representing the adaptive factor, σ representing the posterior constraint;
performing secondary filtering estimation of the whole-cycle constraint of the additional ambiguity on the PPP observation equation according to the virtual observation equation and the posterior constraint condition to obtain the accurate clock difference of the corresponding observation station;
and calculating the difference value between the clock differences of the double-frequency receivers in the two observation stations to obtain a real-time transmission result.
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