CN115201870A - Multi-frequency multi-mode GNSS non-differential non-combination time transfer method with prior constraint - Google Patents
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Abstract
The invention discloses a multifrequency multimode GNSS non-differential non-combination time transfer method with prior constraint, which utilizes phase observation data of a reference station network and calculates satellite clock-to-frequency deviation based on multifrequency data; constructing a full-rank GNSS non-differential non-combination time transfer function model considering IFCB influence through parameter recombination based on multi-frequency multi-system observation information; constructing a random model based on spectral density; based on the constructed full-rank GNSS non-differential non-combination time transfer function model and the random model considering the IFCB influence, performing parameter estimation by adopting Kalman filtering to obtain receiver clock error information of the corresponding station; and comparing the receiver clock difference information of the two sites in time, so as to obtain the clock information of the other site through the clock information of one site and the time comparison information. The invention can improve the reliability and precision of time transmission.
Description
Technical Field
The invention relates to the field of high-precision positioning, in particular to a multifrequency multimode GNSS non-differential non-combination time transfer method with prior constraint.
Background
With the continuous development of navigation systems, the observation frequency of each large global navigation system is expanded from double frequency to triple frequency or even multi-frequency, which brings new ideas and opportunities for multi-frequency and multi-mode GNSS data fusion; multi-frequency multi-mode GNSS data can provide more visible satellites, richer frequencies and signals, and more robust geometric observation structures, which will further improve the service performance and reliability of GNSS, but are currently under exploration and research.
Disclosure of Invention
The invention mainly aims to provide a multifrequency multimode GNSS non-differential non-combination time transfer method with prior constraint, and improve the reliability and precision of time transfer.
In order to achieve the purpose, the technical scheme provided by the invention is as follows: the multifrequency multimode GNSS non-differential non-combination time transfer method with prior constraint comprises the following steps:
s1, calculating an IFCB (interference rejection ratio) based on multi-frequency data by using phase observation data of a reference station network;
s2, constructing a full-rank GNSS non-differential non-combination time transfer function model considering IFCB influence through parameter recombination based on multi-frequency multi-system observation information;
s3, constructing a random model based on spectral density:
3.1, obtaining the stability of station clocks of different stations according to the IGS station clock information;
3.2, fitting based on the corresponding relation between the stability and the noise coefficient to obtain a corresponding noise coefficient;
3.3, obtaining the stability of the sampling interval corresponding to time transfer according to the noise coefficient, and then obtaining corresponding process noise based on the corresponding relation between the spectral densities of the process noise;
3.4, adopting a plurality of measuring stations to prepare high-precision atomic clocks, and determining process noise according to a spectral density mean value obtained by Zhong Qundui according to station clock difference information;
s4, based on a constructed full-rank GNSS non-differential non-combination time transfer function model and a random model which take the influence of IFCB (Interfrequency Clock bias, satellite Zhong Pinjian deviation) into consideration, performing parameter estimation by adopting Kalman filtering to obtain receiver Clock error information of a corresponding station;
and S5, repeating the step S4 to obtain the receiver clock difference information of the other site, and comparing the receiver clock differences of the two sites in time so as to obtain the clock information of the other site through the clock information and the time comparison information of one site.
According to the method, the S1 specifically comprises the following steps:
1.1, obtaining IFCB information of a corresponding station through double-frequency pairwise combination difference and epoch difference of a single station;
1.2, calculating the change quantity among the epochs of the IFCBs of each satellite single epoch based on the elevation angle weighting mode according to the IFCB information of a plurality of stations in an observation network consisting of a certain number of observation stations; selecting an initial epoch, and obtaining the IFCB information of a single station single epoch through accumulation;
and 1.3, acquiring the IFCB correction value corresponding to the f frequency point based on the IFCB relation between the double-frequency IF combination and the non-combination.
According to the method, the 1.1 specifically comprises the following steps:
satellite clock error obtained based on L1/L2 IF combination
Wherein dt S To be free from hardware delay, the satellite clock offset, b vi For the time-varying part of the satellite phase delay at the i (i =1,2) th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay of the ith frequency point is c is the vacuum light speed, and the satellite clock error alpha is obtained based on the L1/L3 IF combination 1i ＝(f 1 2 )/(f 1 2 -f i 2 )，β 1i ＝-(f i 2 )/(f 1 2 -f i 2 )，b vi For the time-varying part of the satellite phase delay at the i (i =1,3) th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay of the ith frequency point is represented by IFCB
In the formula b diff Diff (L) for the corresponding initial phase ambiguity difference 1 ,L 2 ,L 3 )＝L if,12 -L if,13 I.e. the difference of two combinations of two dual-frequency observations, d diff Hardware delay differences between time-invariant receiver phase and satellite phase, b diff And d diff By difference between epochs
The elimination of the water is realized by the following steps,
is the amount of change between IFCB epochs, diff (L) for station r 1 ,L 2 ,L 3 )＝L if,12 -L if,13 ，L if,12 And L if,13 The combined observed value of the two deionization layers of the double-frequency is taken as k is epoch identification, namely the IFCB information of the corresponding station can be obtained through the double-frequency two-to-two combined difference of the single station and the difference between epochs
According to the method, in the 1.2, the change amount between epochs of each satellite single epoch IFCB
r is the number of the measuring stations, n is the maximum number of the measuring stations,
for corresponding weight value related to altitude
Corresponding is the altitude value.
According to the method, the full-rank GNSS non-differential non-combination time transfer function model considering the IFCB influence is as follows:
in the formula
And
respectively are observed values of pseudo range and phase after the station satellite distance and the satellite clock error are corrected,
the linear three-dimensional position vector is obtained, T is a system identifier type, S is a satellite number, and r is a corresponding receiver number; f is the frequency number, f =1,2,3, c is the vacuum light velocity,
to absorb the receiver clock offset of the pseudorange bias,
is the coefficient of the ionospheric slant delay,
is the ionospheric delay of the 1 st frequency bin,
in order to delay the tropospheric tilt,
as a projection function, ISB T In order to be a deviation between the systems,
in order to absorb the phase ambiguity of pseudo range deviation and phase deviation, the phase ambiguity of pseudo range deviation and phase deviation is absorbed, and therefore the phase ambiguity has a floating solution characteristic and corresponds to the IFB information of multi-frequency and multi-mode
And IFCB information
Is composed of
Wherein,
λ f for the wavelength corresponding to the frequency f,
for the pseudorange bias at the receiver end,
corresponds to L 1 /L 2 And L 1 /L f IFCB information between.
According to the method, in the GNSS non-differential non-combination time transfer function model of the full rank considering the influence of the IFCB, if the corresponding system is a non-reference system, the corresponding ISB parameter ISB is added T (ii) a Adding IFB parameter at 3 rd frequency point of pseudo range
According to the method, the 3.1 specifically comprises the following steps: extracting a Zhong Zhongcha sequence of an external hydrogen atom station in an IGS net solution clock error product, and analyzing the stability of different smoothing time by using Hadamard variance;
the 3.2 specifically comprises the following steps: according to the corresponding relation expression between the noise coefficient and the Hadamard variance
Fitting to obtain a corresponding noise coefficient; wherein
Stability results obtained for the Hadamard variance corresponding to the hydrogen clock, q 0 For phase-modulating white noise coefficients, q 1 Is a frequency modulation white noise coefficient, q 2 For frequency-modulated random walk noise figure, q 3 Is the frequency modulation random running noise coefficient, tau is the corresponding smooth time;
in said 3.3, the corresponding relation between the process noise spectral densities is
Wherein
For a determined process noise, c is the vacuum speed of light;
according to the method, in the process of solving based on Kalman filtering parameters, the S4 combines the receiver clock error estimated value of the previous epoch to obtain the one-step predicted value of the current receiver clock error and the variance thereof through one-step prediction
For a one-step predictor of the state vector at time k,
is the state vector at the moment of k-1; phi (phi) of k,k-1 In order to be a state transition matrix,
in order to predict the error variance matrix in one step,
is the variance of the state vector at the time k-1; the prior constraint of the receiver clock error added with the process noise is that the variance after adding the one-step prediction variance corresponding to the corresponding receiver clock error to the process noise information is
And then introducing the filter into a filtering process to carry out parameter solution.
A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein: when the processor executes the computer program, the steps of the multifrequency multi-mode GNSS nondifferential and non-combined time transfer method with attached prior constraints are realized.
A computer-readable storage medium having stored thereon a computer program, characterized in that: the computer program is executed by a processor to realize the steps of the above multi-frequency multi-mode GNSS non-differential non-combination time transfer method with attached prior constraint.
The invention has the following beneficial effects: on the basis of a non-combined PPP model, a multi-GNSS system is processed in a combined mode, the multi-GNSS system is expanded to a time transfer model which is compatible with double frequency, triple frequency and multiple frequency, the time-varying characteristic of phase deviation of different frequency points is considered, satellite clock inter-frequency deviation correction is added to the function model, the multi-frequency time transfer function model is effectively refined, and therefore the reliability of time transfer is improved; meanwhile, the characteristics of strong correlation between the stability and the epoch of the high-performance atomic clock are fully considered, the process noise is added to the receiver clock error parameter in the time transfer model, the random model is optimized, and the time transfer precision can be effectively guaranteed.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a flow chart of a method of an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
As shown in fig. 1, the present invention provides a multifrequency multi-mode GNSS non-differential non-combination time transfer method with a priori constraints, which includes the following steps:
s1, calculating the IFCB by using the phase observation data of the reference station network based on the multi-frequency data.
Research shows that due to inconsistency among observation signals of the GNSS, significant IFCB exists among satellite clock errors obtained by different observation combinations, and the difference has a time-varying characteristic; in double-difference relative positioning, the influence of the deviation can be effectively solved, however, the influence of the IFCB needs to be fully considered in a non-difference three-frequency or even multi-frequency GNSS phase observation equation.
The following explains the solving process of the IFCB in the single system:
1.1, obtaining the IFCB information of the corresponding station through the double-frequency pairwise combination difference and the difference between epochs of the single station.
Taking a tri-band IFCB solution as an example, corresponding IFCB information can be obtained according to a difference between satellite clock differences of two sets of ionospheric-free (IF) ionospheric combinations of L1/L2 and L1/L3. Satellite clock error obtained based on L1/L2 IF combination
Wherein dt S To be free from hardware delay, the satellite clock offset, b vi (i =1,2) is the time-varying part of the satellite phase delay at the i-th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay of the ith frequency point, c is the vacuum light velocity, and the satellite clock error obtained by the L1/L3 IF combination is expressed as
Wherein alpha is 1i ＝(f 1 2 )/(f 1 2 -f i 2 )，β 1i ＝-(f i 2 )/(f 1 2 -f i 2 )，b vi (i =1,3) is the time-varying part of the satellite phase delay at the i-th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay of the ith frequency point is represented by IFCB
In the formula
Diff (L) for the corresponding initial phase ambiguity difference 1 ,L 2 ,L 3 )＝L if,12 -L if,13 Namely the difference value of the two-frequency observed values combined two by two,
hard for time-invariant receiver phase and satellite phaseThe difference in the element delay is such that,
and
by difference between epochs
Elimination, diff (L) 1 ,L 2 ,L 3 )＝L if,12 -L if,13 ，L if,12 And L if,13 And k is epoch identification. And then, accumulating according to the initial epoch to obtain the IFCB information of the corresponding site single epoch, wherein the IFCB information of the corresponding initial epoch can be forcibly set to be 0, the deviation can be absorbed by the phase ambiguity parameter of the floating point, and the time transfer of the PPP is not influenced.
1.2, calculating the change quantity among the epochs of the IFCBs of each satellite single epoch based on the elevation angle weighting mode according to the IFCB information of a plurality of stations in an observation network consisting of a certain number of observation stations; and selecting an initial epoch, and obtaining the IFCB information of the single station single epoch by accumulation.
The IFCB of the kth epoch rstep station can be expressed as
Variation of corresponding single station single epoch IFCB
k is the corresponding epoch number.
Obtain the variation between the epochs of the single station IFCB from 1.1 as
Then, the inter-epoch difference IFCB values of a plurality of stations in an observation network consisting of a certain number of observation stations uniformly distributed in the world are calculated based on a mode of altitude angle weighting to obtain the inter-epoch variation of each satellite unit IFCB
r is the number of the test stations, n is the maximum number of the test stations,
for corresponding weight value related to altitude
Corresponding is the altitude value. The selected initial epoch may then be accumulated
Acquiring single epoch IFCB information of a station r, wherein k is a corresponding epoch number and k 0 The initial epoch number.
1.3, obtaining the IFCB correction value corresponding to the f frequency point based on the IFCB relation between the combination and the non-combination of the dual-frequency IF (Ionosphere Free).
Obtaining corresponding deionization layer combined IFCB information delta based on the 1 st frequency point, the 2 nd frequency point, the 1 st frequency point and the f th frequency point by taking three frequencies as reference if，1f The IFCB information of each frequency point can be according to the corresponding relation delta uc,f ＝-δ if,1f /β 1f And (4) obtaining.
And S2, constructing a full-rank GNSS non-differential non-combination time transfer function model considering the influence of the IFCB through parameter recombination based on multi-frequency multi-system observation information.
The non-difference non-combination PPP time transfer model directly constructs an observation equation from the original observed values on each frequency, the observed values are independent of each other, correlation cannot be generated due to combination of the observed values, the realization is more convenient, the accurate establishment of a random model is facilitated, and meanwhile, the observation equation is established based on the original observed values of each frequency point, so that the noise of the observed values cannot be amplified. Therefore, the non-differential non-combined PPP can effectively make up for the defects of the traditional deionization layer combined model, can better adapt to the development of the current multi-frequency multi-mode satellite navigation system, and greatly promotes the application of the PPP technology in the aspect of time transmission.
The model of Precision Point Positioning (PPP) time transfer with non-differential combination is:
wherein,
and
respectively an observed value of the pseudo-range and the phase,
for the centroid geometry, T denotes the system type, S denotes the satellite number, r the corresponding receiver number, f the frequency number (f =1,2,3.), c the vacuum light velocity,
and dt T,S Respectively the receiver clock offset and the satellite clock offset,
as a function of tropospheric projection, Z r In order to delay the tropospheric tilt,
is the coefficient of the ionospheric slant delay,
for the carrier phase wavelength corresponding to the frequency f,
is the diagonal ionospheric delay of the first frequency bin,
and
for frequency-dependent receptionHardware delay of the machine pseudorange and hardware delay of the satellite pseudorange, which are carrier phase ambiguities, absorb the phase hardware delays at the receiver end and at the satellite end,
is the sum of pseudorange observation noise and other unmodeled errors,
is the sum of the carrier phase observation noise and other unmodeled errors.
In the non-differential non-combined observation equation, the satellite clock error is considered
Absorbing the time-invariant part d of pseudo-range hardware delay in L1/L2 1 And d 2 De-ionospheric compositional effects, and time-varying portion of phase hardware delay
And
the combined effect of deionization can be expressed as
dt s In order to absorb satellite clock error without hardware delay, the receiver clock error absorbs hardware delay b of pseudo range at receiver end r,1 And b r,2 The combination of the deionization layers can be expressed as
Considering the time-varying characteristic of the 3 rd frequency point phase hardware delay, corresponding IFCB information delta needs to be added to the phase observed value uc,3 The correction is performed, and the corresponding observation equation can be expressed as:
the observation equation has the rank deficiency problem caused by the correlation of various parameters, so that parameter recombination is required; meanwhile, because the absorbed pseudo range deviation of the 3 rd frequency point is different from the 1 st and 2 nd frequency points, the pseudo range observed value is correspondingly added with inter frequency deviation (IFB) correction, the corresponding ionized layer delay absorbs the pseudo range deviation information of the receiver end and the satellite end on the 1 st and 2 nd frequency points, and the phase ambiguity absorbs the time-invariant information of phase hardware delay, so that the corresponding phase ambiguity information is still kept unchanged in a continuous arc section without cycle slip, and an observation equation after parameter recombination can be expressed as:
wherein the combined ionosphere
Inter-frequency offset IFB r Phase ambiguity of individual frequency points
IFCB correction information
Pseudorange bias correction xi f And phase deviation correction information η f The corresponding parameter expression form is:
for a pseudo-range observed value, the time-varying characteristic of the corresponding inter-frequency deviation is relatively small to pseudo-range observation noise, so that the time-varying characteristic can be ignored, the DCB information in the corresponding phase observed value needs to be corrected, and an observation equation after clock error correction of an external DCB product and an MGEX satellite can be expressed as follows:
in view of
And existence between the non-combined IFCB and the L1/L3 combined IFCB
The corresponding relation of (3), namely the IFCB information of L3 can be obtained based on the IFCB information of L1/L3, and then the carrier phase observed value on L3 is corrected; based on the method, the relation between the ionospheric elimination combination and the non-combination IFCBs of other frequency points can be constructed, namely
Wherein delta if,1f Can be based on L1/L2 according to L1/L2 and L1/L f Is determined based on the flow in S1.
The corresponding three-frequency multi-mode GNSS time transfer function model can be represented as:
according to the characteristics of the non-combination model, three frequencies can be expanded to multiple frequencies, and the expression of the multiple frequency model is as follows:
in the formula
And
respectively are observed values of a pseudo range and a phase after the satellite range and the satellite clock error are corrected,
is a linearized three-dimensional position vector, T is a system identifier type, S is a satellite number, and r is a pairThe corresponding receiver number; f is the frequency number, f =1,2,3, c is the vacuum speed of light,
to absorb the receiver clock error of the pseudorange bias,
is the coefficient of the ionospheric slant delay,
is the ionospheric delay of the 1 st frequency bin,
in order to delay the tropospheric tilt,
as a projection function, ISB T In order to be a deviation between the systems,
in order to absorb pseudo range bias and phase ambiguity of phase bias, the phase ambiguity absorbs hardware delay of a receiver end and a satellite end, and therefore the IFB has a floating solution characteristic and corresponds to multi-frequency multi-mode
And IFCB information
Is composed of
Wherein
λ f For the wavelength corresponding to the frequency f,
for the pseudorange bias at the receiver end,
corresponds to L 1 /L 2 And L 1 /L f IFCB information between.
IFB corresponding to multi-frequency and multi-mode is
In the multi-frequency multi-system combined function model, when the corresponding system is a non-reference system, the corresponding ISB parameter ISB needs to be added T (ii) a The f (f =3,4.) frequency point of pseudo range adds IFB parameter
S3, constructing a random model based on spectral density:
in conventional PPP and clock error calculation, the receiver clock error is generally used as white noise to carry out parameter estimation by epoch, and constraint information that the variation of the receiver clock error parameter between adjacent epochs is possibly stable is not fully explored; the method fully considers the steady change characteristics among the hydrogen atomic clock epochs, determines the relation between the noise coefficient and the stability according to the stability of the atomic clock, obtains the process noise of a time transfer corresponding sampling interval, introduces a random model of parameter estimation, and updates the variance of the receiver clock error parameters.
Firstly, extracting a Zhong Zhongcha sequence of an external hydrogen atom station in an IGS network solution clock error product, and determining the stability of different smoothing time by adopting a Hadamard variance which can effectively solve the frequency drift influence in consideration of the frequency drift characteristic of a hydrogen clock; and then based on the noise (phase modulated white noise q) 0 White frequency modulation noise q 1 Frequency modulated random walk noise q 2 And frequency modulated random running noise q 3 ) And fitting a corresponding relational expression between the coefficient and the Hadamard variance to obtain a corresponding noise coefficient, and determining process noise corresponding to the sampling rate according to the sampling interval and the noise coefficient by using a formula.
3.1, acquiring the stability of the station clocks of different stations according to the IGS station clock information; and extracting a Zhong Zhongcha sequence of an external hydrogen atom station in an IGS net solution clock error product, and analyzing the stability of different smoothing times by using Hadamard variance.
3.2, fitting to obtain a corresponding noise coefficient based on the corresponding relation between the stability and the noise coefficient; the 3.2 specifically comprises the following steps: according to the corresponding relation expression between the noise coefficient and the Hadamard variance
Fitting to obtain a corresponding noise coefficient; wherein
Stability results obtained for the Hadamard variance corresponding to the hydrogen clock, q 0 For phase-modulating white noise coefficients, q 1 Is a frequency modulation white noise coefficient, q 2 For frequency-modulated random walk noise figure, q 3 For the frequency modulated random running noise figure, τ is the smoothing time.
3.3, obtaining the stability of the sampling interval corresponding to time transfer according to the noise coefficient, and then obtaining corresponding process noise based on the corresponding relation between the spectral densities of the process noise; wherein the corresponding relationship between the process noise spectral densities is
Wherein
For a certain process noise, c is the vacuum light speed.
3.4, adopting a plurality of measuring stations to be equipped with high-precision atomic clocks, and determining process noise according to the spectral density mean value obtained by Zhong Qundui according to the clock difference information of the stations.
And S4, based on the constructed full-rank GNSS non-differential non-combination time transfer function model and the random model considering the IFCB influence, performing parameter estimation by adopting Kalman filtering to obtain receiver clock error information of the corresponding station. In the process of solving based on Kalman filtering parameters, a receiver clock error estimation value of the previous epoch is combined, and a current receiver clock error one-step prediction value and a variance thereof are obtained through one-step prediction
For a one-step predictor of the state vector at time k,
is the state vector at the moment of k-1; phi k,k-1 In order to be a state transition matrix,
in order to predict the error variance matrix in one step,
is the variance of the state vector at the time of k-1; the prior constraint of the receiver clock error of the additive process noise is that the variance after the one-step prediction variance corresponding to the corresponding receiver clock error is added with the process noise information can be expressed as
And then introducing the filter into a filtering process to carry out parameter solution.
And S5, repeating the step S4 to obtain the receiver clock difference information of the other site, and comparing the receiver clock differences of the two sites in time so as to obtain the clock information of the other site through the clock information and the time comparison information of one site.
The method makes full use of the GNSS observation information of the multi-frequency and multi-system, considers the time-varying characteristic of phase deviation among frequency points and the characteristics of stable variation and high correlation among epochs corresponding to the high-performance atomic clock, and constructs a strict and steady non-differential non-combination time transfer algorithm.
According to the method, multi-Frequency multi-mode GNSS observation data is adopted for modeling, the influence of the time-varying characteristic of the phase deviation corresponding to each Frequency point on the satellite clock error is considered, and the corresponding Inter-Frequency clock error Bias (IFCB) correction is added at the third Frequency point; meanwhile, a high-performance atomic clock is adopted in time transfer, the high performance of the atomic clock guarantees the stable change of satellite clock difference epochs, and corresponding prior information constraint is added to the receiver clock difference in a time transfer model. According to the method, multi-frequency multi-mode observation data are fully utilized to construct a full-rank flexible non-differential non-combination carrier phase time transfer model compatible with a multi-frequency multi-mode GNSS, so that the reliability of time transfer is improved; the accuracy of time transfer is improved by correcting and optimizing the stochastic model to account for deviations between satellite clock frequencies.
The invention also provides a computer device, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor executes the computer program to realize the steps of the multi-frequency multi-mode GNSS non-differential non-combined time transfer method with the prior constraint.
The present invention also provides a computer readable storage medium, on which a computer program is stored, which, when being executed by a processor, implements the steps of the above-mentioned multi-frequency multi-mode GNSS non-differential non-combined time transfer method with a priori constraint.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (10)
1. The multifrequency multimode GNSS non-difference non-combination time transfer method with prior constraint is characterized by comprising the following steps of:
s1, calculating an IFCB (interference rejection ratio) based on multi-frequency data by using phase observation data of a reference station network;
s2, constructing a full-rank GNSS non-differential non-combination time transfer function model considering the influence of the IFCB through parameter recombination based on multi-frequency multi-system observation information;
s3, constructing a random model based on spectral density:
3.1, obtaining the stability of station clocks of different stations according to the IGS station clock information;
3.2, fitting to obtain a corresponding noise coefficient based on the corresponding relation between the stability and the noise coefficient;
3.3, obtaining the stability of the sampling interval corresponding to time transfer according to the noise coefficient, and then obtaining corresponding process noise based on the corresponding relation between the process noise spectral densities;
3.4, adopting a plurality of measuring stations to be provided with high-precision atomic clocks, and determining process noise according to a spectral density mean value obtained by Zhong Qundui according to station clock difference information;
s4, based on the constructed full-rank GNSS non-differential non-combination time transfer function model and the random model considering the IFCB influence, performing parameter estimation by adopting Kalman filtering to obtain receiver clock error information of the corresponding station;
and S5, repeating the step S4 to obtain the receiver clock difference information of the other site, and comparing the receiver clock differences of the two sites in time so as to obtain the clock information of the other site through the clock information and the time comparison information of one site.
2. The multi-frequency multi-mode GNSS non-differential non-combined time transfer method according to claim 1, wherein S1 specifically is:
1.1, obtaining IFCB information of a corresponding station through double-frequency pairwise combination difference and epoch difference of a single station;
1.2, calculating the change quantity among epochs of IFCBs of each satellite single epoch based on the altitude angle weighting mode of IFCB information of a plurality of stations in an observation network consisting of a certain number of observation stations; selecting an initial epoch, and obtaining IFCB information of each epoch of the single station through accumulation;
1.3, obtaining the IFCB correction value corresponding to the f frequency point based on the IFCB relation between the combination and the non-combination of the dual-frequency Ionosphere Free (IF).
3. The multi-frequency multi-mode GNSS non-differential non-combined time transfer method with a priori constraint according to claim 2, wherein 1.1 is specifically:
satellite clock error obtained based on L1/L2 IF combination
Wherein dt S For guards not affected by hardware delayDifference of star and clock b vi For the time-varying part of the satellite phase delay at the i (i =1,2) th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay of the ith frequency point, c is the vacuum light velocity, and the satellite clock error obtained by the L1/L3 IF combination is expressed as
Wherein alpha is 1i ＝(f 1 2 )/(f 1 2 -f i 2 )，β 1i ＝-(f i 2 )/(f 1 2 -f i 2 )，b vi For the time-varying part of the satellite phase delay at the i (i =1,3) th frequency point, d i The time-invariant part of the satellite pseudo-range hardware delay at the ith frequency point, therefore the IFCB expression
Is shown as
In the formula b diff Diff (L) for the corresponding initial phase ambiguity difference 1 ,L 2 ,L 3 )＝L if,12 -L if,13 Namely the difference value of the two-frequency observed values combined two by two,
hardware delay differences between time-invariant receiver phase and satellite phase, b diff And d diff By difference between epochs
The elimination of the water is realized by the following steps,
is the variation between IFCB epochs of site r, diff (L) 1 ,L 2 ,L 3 )＝L if,12 -L if,13 ，L if,12 And L if,13 For the combined observed value of two deionization layers in double frequency, k is epoch identification, i.e. by singleStation dual-frequency pairwise combination difference and epoch difference to obtain IFCB information of corresponding station
4. The method as claimed in claim 3, wherein the 1.2 is a variation between epochs of each satellite single epoch IFCB
r is the number of the measuring stations, n is the maximum number of the measuring stations,
for corresponding weight value related to altitude
Corresponding is the altitude value.
5. The multi-frequency multi-mode GNSS non-differential non-combined time transfer method with a priori constraint according to claim 1, wherein the full rank GNSS non-differential non-combined time transfer function model considering the IFCB influence is as follows:
in the formula
And
respectively are observed values of pseudo range and phase after the station satellite distance and the satellite clock error are corrected,
the linear three-dimensional position vector is obtained, T is a system identifier type, S is a satellite number, and r is a corresponding receiver number; f is the frequency number, f =1,2,3, c is the vacuum speed of light,
to absorb the receiver clock offset of the pseudorange bias,
is the coefficient of the ionospheric slant delay,
is the ionospheric delay of the 1 st frequency bin,
in order to delay the tropospheric tilt,
as a projection function, ISB T In order to be a deviation between the systems,
in order to absorb pseudo range bias and phase ambiguity of phase bias, the phase ambiguity absorbs hardware delay of a receiver end and a satellite end, and therefore the IFB has a floating solution characteristic and corresponds to multi-frequency multi-mode
And IFCB information
Is composed of
Wherein
λ f Is the wavelength corresponding to the frequency f,
for the pseudorange bias at the receiver end,
corresponds to L 1 /L 2 And L 1 /L f IFCB information between.
6. The multi-frequency multi-mode GNSS non-differential non-combined time transfer method of claim 5, wherein in the full-rank GNSS non-differential non-combined time transfer function model considering IFCB influence, if the corresponding system is a non-reference system, the corresponding ISB parameter ISB is added T (ii) a Adding IFB parameter at 3 rd frequency point of pseudo range
7. The multi-frequency multi-mode GNSS non-differential non-combined time transfer method with a priori constraint according to claim 1, wherein 3.1 is specifically: extracting a Zhong Zhongcha sequence of an external hydrogen atom station in an IGS net solution clock error product, and analyzing the stability of different smoothing time by using Hadamard variance;
the 3.2 specifically comprises the following steps: according to the corresponding relation expression between the noise coefficient and the Hadamard variance
Fitting to obtain a corresponding noise coefficient; wherein
Stability results obtained for the Hadamard variance corresponding to the hydrogen clock, q 0 For modulating white noise coefficients, q 1 Is a frequency modulation white noise coefficient, q 2 For frequency-modulated random walk noise figure, q 3 Is the frequency modulation random running noise coefficient, tau is the corresponding smoothing time;
in said 3.3, the corresponding relation between the process noise spectral densities is
Wherein
For a certain process noise, c is the vacuum light speed.
8. The multifrequency multimode GNSS nondifferential and non-combined time transfer method according to claim 1, wherein S4 combines a receiver clock error estimation value of a previous epoch in a Kalman filtering parameter solution-based process, and obtains a current receiver clock error one-step prediction value and a variance thereof through one-step prediction
For a one-step predictor of the state vector at time k,
is the state vector at the moment of k-1; phi k,k-1 In order to be a state transition matrix,
in order to predict the error variance matrix in one step,
is the variance of the state vector at the time k-1; the prior constraint of the receiver clock error added with the process noise is that the variance after adding the one-step prediction variance corresponding to the corresponding receiver clock error to the process noise information is
And then introducing the filter into a filtering process to carry out parameter solution.
9. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein: the processor, when executing the computer program, performs the steps of the a priori constrained multifrequency multimode GNSS non-differential non-combined time transfer method of any of the preceding claims 1 to 8.
10. A computer-readable storage medium having stored thereon a computer program, characterized in that: the computer program when executed by a processor implements the steps of the a priori constrained multifrequency multimode GNSS non-differential non-combined time transfer method of any of the preceding claims 1 to 8.
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