CN114355758B - High-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service - Google Patents
High-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service Download PDFInfo
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Abstract
The application relates to a high-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service. The method comprises the following steps: the local time is adjusted by acquiring bimodal GNSS observation values, broadcast ephemeris, precise ephemeris correction data and satellite-based augmentation correction data and calculating clock errors by adopting a corresponding method after the estimation variance is judged, so that the local time and the system time are traced. By adopting the method, the source tracing time is faster, and the precision is higher, so that the method is suitable for a precision time frequency system with higher requirements.
Description
Technical Field
The application relates to the technical field of time tracing, in particular to a high-precision time tracing method based on Beidou satellite-based enhancement and precise ephemeris service.
Background
The time frequency system is an important strategic resource for promoting national economy and national defense construction development, national standard time is required to provide support in key fields of national defense and military, traffic power, financial securities and the like, and the unified and stable time frequency system is constructed to meet the strategic requirements of national development. Because the difficulty of the inspection and calibration work of the time-frequency equipment is increased, and the equipment is easy to damage in the transportation process, the research of the high-precision remote time frequency tracing technology becomes an important subject in the military metering research field.
The time tracing technology based on the Global Navigation Satellite System (GNSS) has the advantages of high precision, all weather, full coverage and the like, and is a main means for remote time tracing at the present stage. At present, the remote source tracing of the national time frequency measurement standard device in China mainly depends on a Beidou No. two satellite navigation system which consists of 5 earth source tracing orbit satellites, 5 inclined earth source tracing orbit satellites and 4 middle orbit earth satellites. Limited by the number of satellites, the Beidou second system basically meets navigation positioning and time service in China and surrounding areas, and the time service precision of basic service is about 50 nanoseconds. With the continuous acceleration of the construction pace of satellite navigation systems, china builds a Beidou third satellite navigation system covering the world in 7 months in 2020. Compared with the Beidou second system, the Beidou third system is comprehensively upgraded in the aspects of satellite quantity, signal modulation, service types and the like, the time service precision of basic service can reach 10-20 nanoseconds, in addition, the sub-meter-level high-precision positioning service such as satellite-based enhancement and precise ephemeris is further provided on the basis of the basic navigation service, and the potential of new frequency, new-system Beidou navigation signals and Beidou new service in the aspects of time service and remote time traceability is urgently needed to be developed and researched.
In recent years, precision Point Positioning (PPP) technology based on Precision ephemeris service has become a research hotspot in the field of time-frequency measurement, and the technology uses pseudorange and high-Precision carrier phase observation values to perform time transmission and tracing under the assistance of Precision ephemeris. Unlike the broadcast ephemeris which is broadcast once every two hours, the precise ephemeris is broadcast at an interval of 5 to 60 seconds, and the precision of the ephemeris is obviously improved compared with the broadcast ephemeris, so that the uncertainty of PPP time transmission can reach a subnanosecond level, and the method is widely used by the Bureau International des points et Mesures (BIPM) and a plurality of time frequency laboratories to coordinate the calculation and maintenance of the universal time and the national standard time. However, due to the influence of carrier phase ambiguity and other factors, the PPP time tracing method needs 30 minutes of convergence time, is slow in convergence time, and seriously restricts the popularization of high-precision time tracing and time synchronization application based on the Beidou No. three system, so that the research of the mixed time tracing method based on the Beidou precise ephemeris service and the satellite-based enhanced service has important research significance for upgrading and updating the time metering device and improving the time tracing performance.
Disclosure of Invention
In view of the above, it is necessary to provide a time tracing method with high accuracy and high convergence rate.
A high-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service comprises the following steps:
acquiring a pseudo-range observation value and a carrier phase observation value at the current moment, wherein the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current-moment local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
performing clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain an estimated variance;
judging according to the estimated variance and a preset value, if the estimated variance is larger than the preset value, performing coarse control clock error calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain a standard clock error between the local time and the system time at the current moment;
if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error between the local time and the system time at the current moment;
adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local timestamp for acquiring the pseudo-range observed value and the carrier phase observed value at the next moment;
and until the local time of the next moment is converged to the system time, completing tracing the local time with the system standard time.
In one embodiment, before calculating the fine clock offset using the fine control clock offset, the method further includes: and at the last moment, after the standard clock offset is calculated by adopting the coarse control clock offset, the precise clock offset is calculated by adopting the precise control clock offset only when the estimated variance is less than a preset value for continuous preset times.
In one embodiment, the bimodal global satellite navigation system comprises: beidou satellite navigation system and GPS.
In one embodiment, the performing clock error calculation according to the pseudorange observation value, the carrier phase observation value, the broadcast ephemeris data, and the ephemeris correction data to obtain the estimated variance includes:
and calculating based on the pseudo-range observation value, the carrier phase observation value and various ephemeris data to obtain Kalman filtering estimation parameters and corresponding estimation variances.
In one embodiment, the coarse control clock difference calculation includes:
and performing standard single-point positioning calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain the standard clock error.
In one embodiment, the fine control clock difference calculation includes:
and calculating by using a precise single-point positioning according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error.
In one embodiment, when the precision clock error is obtained by using precision single-point positioning calculation, a precision clock error calculation mathematical model is used, and the precision clock error is obtained by solving the precision clock error calculation mathematical model, where the precision clock error calculation mathematical model is as follows:
in formula (1) and formula (2):
superscripts G, C and respectively represent GPS and BDS systems;
superscript s denotes satellite;
the subscript r denotes the receiver;
phi denotes the geometrical distance (m) between the receiver antenna and the satellite antenna phase center;
dt r and dt s Representing the clock difference(s) of the receiver and the satellite clock;
c represents the speed of light in vacuum (m/s);
d r,IF and
the hardware delay (m) of the receiver without ionosphere combination and the satellite pseudo range is represented;
D r,IF and
indicates the hardware delay (cycle) of the carrier phase at the non-receiver and satellite end of the ionosphere-free combination;
T w representing the station tropospheric delay moisture component (m);
λ IF represents a carrier wavelength (m);
N IF represents the carrier phase integer ambiguity (cycle);
τ IF and upsilon IF Unmodeled error and noise (m) representing pseudorange observations and carrier-phase observations.
In one embodiment, the adjusting the local time of the current time output by the atomic clock according to the standard clock offset or the precision clock offset to obtain the local time of the next time includes:
fitting the standard clock error or the precise clock error to correspondingly obtain an adjusting frequency and an adjusting phase;
and adjusting the local time of the current moment according to the adjusting frequency and the adjusting phase.
The application also provides a high accuracy time device of tracing to source based on big dipper astral reinforcing and precision ephemeris service, includes:
the observation value acquisition module is used for acquiring a pseudo-range observation value and a carrier phase observation value at the current moment, and the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current-moment local time output by the atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
the ephemeris data acquisition module is used for acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
the estimated variance obtaining module is used for carrying out clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data and obtaining an estimated variance;
a clock error calculation obtaining module, configured to perform a judgment according to the estimated variance and a preset value, and if the estimated variance is greater than the preset value, perform coarse control clock error calculation according to the pseudorange observation value, the broadcast ephemeris data, and the constellation enhancement correction data to obtain a standard clock error between local time and system time at the current time; if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain a precise clock error between the local time and the system time at the current moment;
the local time adjusting module is used for adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local timestamp for acquiring the pseudo-range observed value and the carrier phase observed value at the next moment;
and until the local time of the next moment is converged to the system time, completing tracing the local time with the system standard time.
A computer device comprising a memory storing a computer program and a processor implementing the following steps when the computer program is executed:
acquiring a pseudo-range observation value and a carrier phase observation value at the current moment, wherein the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current-moment local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
performing clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain an estimated variance;
judging according to the estimated variance and a preset value, if the estimated variance is larger than the preset value, performing coarse control clock error calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain a standard clock error between the local time and the system time at the current moment;
if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error between the local time and the system time at the current moment;
adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local time stamp of the pseudo-range observed value and the carrier phase observed value obtained at the next moment;
and completing tracing to the system standard time by the local time until the local time of the next moment is converged to the system time.
A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, carries out the steps of:
acquiring a pseudo-range observation value and a carrier phase observation value at the current moment, wherein the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current-moment local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
performing clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain an estimated variance;
judging according to the estimated variance and a preset value, if the estimated variance is larger than the preset value, performing coarse control clock error calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain a standard clock error between the local time and the system time at the current moment;
if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain a precise clock error between the local time and the system time at the current moment;
adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local timestamp for acquiring the pseudo-range observed value and the carrier phase observed value at the next moment;
and completing tracing to the system standard time by the local time until the local time of the next moment is converged to the system time.
According to the high-precision time tracing method based on the Beidou satellite-based augmentation and the precise ephemeris service, the local time is adjusted by acquiring the bimodal GNSS observation value and calculating the clock difference by adopting a corresponding method after the estimation variance is judged, so that the local time and the system time are traced. The time tracing method has the advantages of faster tracing time and higher precision, and is suitable for a precision time frequency system with higher requirements.
Drawings
FIG. 1 is a schematic flow chart diagram of a time tracing method in one embodiment;
FIG. 2 is a diagram illustrating results of a conventional GNSS time tracing experiment in one embodiment;
FIG. 3 is a schematic diagram of the time-tracing experimental results based on Beidou satellite-based augmentation and ephemeris services in one embodiment;
FIG. 4 is a block diagram of an embodiment of a time tracing apparatus;
FIG. 5 is a block diagram of a time tracing apparatus according to another embodiment;
FIG. 6 is a diagram illustrating an internal structure of a computer device according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more clearly understood, the present application 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 present application and are not intended to limit the present application.
As mentioned above, in the existing time tracing technology, GNSS time tracing is the most effective in the current time tracing technology. However, the method has a real-time application scenario that the convergence speed is slow, and the method cannot be quickly applied to nanosecond time tracing and the like. The reason why the nanosecond time tracing precision cannot be achieved is that: firstly, the broadcast ephemeris error used by the traditional GNSS time tracing is large, wherein the satellite orbit precision is meter level, and the satellite clock error precision is nanosecond level; secondly, the traditional GNSS time tracing uses pseudo-range observation values to transmit time information, and the pseudo-range measurement precision is about +/-3 m and is easily influenced by multipath errors; thirdly, the traditional GNSS tracing source delays errors such as ionosphere and troposphere to correct the accuracy is low.
In view of the above problems, as shown in fig. 1, the present application provides a high-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service, which specifically includes the following steps:
step S100, obtaining a pseudo-range observation value and a carrier phase observation value at the current moment, wherein the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current moment local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
step S110, acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
step S120, performing clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data, and obtaining an estimated variance;
step S130, judging according to the estimated variance and a preset value, if the estimated variance is larger than the preset value, performing coarse control clock error calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain a standard clock error between the local time and the system time at the current moment;
if the estimated variance is smaller than the preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precision ephemeris correction data to obtain a precision clock error between the local time of the current moment and the system time S140, and adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precision clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local timestamp for acquiring the pseudo-range observed value and the carrier phase observed value at the next moment;
and until the local time of the next moment is converged to the system time, completing tracing the local time with the system standard time.
In this embodiment, the local time is continuously adjusted by the method to trace the source of the local time and the system time, and when the adjustment parameter is calculated, the clock offset between the local time and the system time is calculated by using a bimodal GNSS observation value, precision ephemeris correction which is more accurate than broadcast ephemeris data and satellite-based enhanced correction data, so that the calculated clock offset is more accurate, and the estimation variance is judged aiming at the slower clock offset calculation process, and the tracing time is accelerated by performing rough control clock offset calculation and then adopting a precise control clock offset calculation mode.
In steps S100 and S110, the pseudorange observation value and the carrier phase observation value generate a local timestamp according to the current-time local time output by the atomic clock, and the broadcast ephemeris data and the precise ephemeris data both include the system time, so that when the observation value and the ephemeris data are subsequently used for calculation, the clock difference between the local time and the system time can be obtained, and the clock difference is also reflected in the estimation variance obtained by calculation according to the precise ephemeris data, the pseudorange observation value, and the carrier phase observation value.
In order to increase the reliability of the time tracing method, a bimodal global satellite navigation system is utilized to acquire observation data.
In one embodiment, the bimodal global satellite navigation system, i.e. bimodal GNSS, comprises: beidou satellite navigation system and GPS.
In step S110, the broadcast ephemeris data and the ephemeris enhancement correction data are used for performing a coarse control clock error calculation, and the ephemeris correction data are used for performing a fine control clock error calculation.
In order to increase the time tracing speed, in this embodiment, the clock offset estimation variance estimated by the precise single-point positioning parameter is used as a reference index, and a process of adjusting the local time is divided into a coarse adjustment stage and a fine adjustment stage.
In step S120, a clock error is calculated according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris, and the ephemeris correction data, so as to obtain an estimated variance. And calculating the pseudo-range observation value, the carrier phase observation value and various ephemeris data to obtain Kalman filtering estimation parameters and corresponding estimation variances.
In step S130, by determining the estimated variance and a preset value, if the estimated variance is greater than the preset value, a standard clock error is obtained by using a coarse control clock error calculation; and if the estimation variance is smaller than the preset value, the estimation of the precise single-point positioning parameters is considered to be convergent at the moment, and the fine adjustment stage can be switched to perform fine adjustment on the local time.
It should be noted that, since the method is a process of continuously adjusting the local time, that is, performing a clock difference calculation on data received at each time (for example, once per second) (where the data includes observation data received by using the dual-mode global satellite navigation system and ephemeris data acquired from the dual-mode global satellite navigation system or the network), and continuously adjusting the local time, in this process, the local time is continuously close to the system time, so that the local time is infinitely close to the system time.
Before calculating the precision clock error by adopting the precision control clock error, the method further comprises the following steps: and at the last moment, after the standard clock offset is calculated by adopting the coarse control clock offset, the precise clock offset is calculated by adopting the precise control clock offset only when the estimated variance is less than a preset value for continuous preset times.
Specifically, when the variance is estimated at the local time and the system time at the first moment, if the estimated variance is smaller than a preset value, the accurate clock offset can be obtained by directly adopting the accurate control clock offset calculation, and the local time is accurately adjusted. And if the estimation variance calculated at the first moment is greater than the preset value, calculating by adopting a coarse control clock error to obtain a standard clock error, performing coarse adjustment on the local time, after the local time is continuously subjected to coarse adjustment, enabling the estimation variance to be smaller and smaller until the estimation variance is smaller than the preset value, and at the moment, performing coarse adjustment on the local time until the local time is continuously preset for times, and if the estimation variance is smaller than the preset value, performing fine adjustment on the local time.
In one embodiment, the coarse control clock difference calculation comprises: and performing standard single-point positioning calculation according to the pseudo-range observation value, the broadcast ephemeris and the satellite-based enhanced correction data to obtain the standard clock error. Because the standard positioning calculation does not need to estimate the ambiguity parameter, the clock error result has high convergence speed but lower overall precision.
Specifically, the pseudo-range observed value of the dual-frequency ionosphere-free combination is used in the standard clock error calculation. And before clock error calculation, observation data is preprocessed, and abnormal clock error data is eliminated.
In one embodiment, the predetermined value is 1ns.
In one embodiment, the predetermined number of times is 10.
In one embodiment, the fine control clock difference calculation comprises: and calculating by using a precise single-point positioning method according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris and the precise ephemeris correction data to obtain the precise clock error.
Specifically, when the precise clock error is obtained by utilizing precise single-point positioning calculation, a precise clock error calculation mathematical model is adopted, and the precise clock error is obtained after solving the precise clock error calculation mathematical model, wherein the precise clock error calculation mathematical model is as follows:
in formula (1) and formula (2):
superscripts G, C and respectively represent GPS and BDS systems;
superscript s denotes satellite;
subscript r denotes the receiver;
phi denotes the geometrical distance (m) between the receiver antenna and the satellite antenna phase center;
dt r and dt s Representing the clock difference(s) of the receiver and the satellite clocks;
c represents the speed of light in vacuum (m/s);
d r,IF and
hardware delay (m) of a receiver and a satellite-side pseudo range without ionosphere combination is shown;
D r,IF and
the hardware delay (cycle) of the non-receiver and the satellite-side carrier phase without the ionized layer combination is shown;
T w representing the station tropospheric delay moisture component (m);
λ IF represents a carrier wavelength (m);
N IF represents the carrier phase integer ambiguity (week);
τ IF and upsilon IF Unmodeled error and noise (m) representing pseudorange observations and carrier-phase observations.
In one embodiment, the working frequency bands of the GPS and BDS systems are respectively GPS: l1, L2, BDS: b1 and B2.
For a dual-mode GNSS receiver, hardware delays generated by the same receiver processing signals from different navigation systems are different, and the hardware delay deviation between these systems is also called Inter-System Biases (ISBs), and equations (1) and (2) distinguish the hardware delays of different navigation systems respectively. In a precision clock error calculation model of a dual-mode carrier phase observation value, clock error of a GPS system is used as a reference value, and clock errors of other systems are expressed in a form of the sum of the GPS clock error and ISB, namely:
in summary, the estimated parameter vector for dual-mode GNSS carrier phase clock difference calculation is:
estimating the parameters includes: 1 receiver clock error parameter, 1 ISB parameter between GPS and BDS, 1 zenith troposphere delay wet component, and ambiguity parameter with quantity equal to total satellite number of observation system.
In the embodiment, the station position is constrained using a priori coordinate constraint method, and the satellite observation cut-off height angle is set to 10.
In the present embodiment, in terms of stochastic model setup, an observation noise level is decided using a stochastic model based on satellite altitude; the initial standard deviation of the clock error is set to 60m; setting the initial standard deviation of the ISB parameters as 10m; initial standard deviation of tropospheric delay moisture content was set to 0.6m; setting the initial standard deviation of the ambiguity parameter as 60m; setting the initial standard deviation of the GPS carrier phase and the pseudo-range observed value as 3mm and 0.3m; initial standard deviations of BDS and Galileo phase and pseudorange observations are set to 6mm and 0.6m, where the initial standard deviations of the carrier and pseudorange are set to 10mm and 1m for BDS GEO satellites due to poor orbital clock error quality.
In step S140, adjusting the local time of the current time output by the atomic clock according to the standard clock error or the precision clock error, and obtaining the local time of the next time includes:
fitting the standard clock error or the precise clock error to correspondingly obtain an adjusting frequency and an adjusting phase;
and adjusting the local time of the current moment according to the adjusting frequency and the adjusting phase.
In one embodiment, the local time (time frequency signal) output by the atomic clock is frequency and phase adjusted by using a direct digital frequency synthesis technology.
While the local time is continuously adjusted, a 1PPS (one second pulse) signal is output as uniform time for each device. Here the 1PPS is generated from the local time.
Next, according to the experimental data of the high-precision time tracing method and the traditional GNSS time tracing method provided by the present application:
fig. 2 shows a measurement result of a 1PPS signal in a conventional GNSS time tracing experiment within 1 hour of startup operation, starting from a 1PPS signal output by 1 device, a phase change of a 1PPS signal output by another 1 device is measured. The maximum value of the phase deviation in the figure is 3.3ns, the minimum value is-8.2 ns, and the root mean square error of the phase deviation is about 2.9ns. Because the standard single-point positioning algorithm is independent of the carrier phase observed value, the algorithm does not need to be converged, but the overall fluctuation amplitude of data is very large.
Fig. 3 shows a measurement result of a 1PPS signal within 1 hour after starting up the device by the high-precision time tracing method based on the beidou-star-based augmentation and the precise ephemeris service provided by the patent, and 1PPS signal output by 1 device is taken as a starting point, and phase change of the 1PPS signal output by another 1 device is obtained through measurement. Where the maximum value of the phase deviation is 1.2ns, the minimum value is-2.0 ns, and the root mean square error is about 0.5ns. In the convergence stage of the precise single-point positioning algorithm, in order to shorten the convergence time used by the time tracing device, the clock error calculation precision of the standard single-point positioning algorithm based on the pseudo-range is improved by adopting the satellite-based enhanced data, so that the device before the algorithm convergence can operate and have higher time tracing precision.
The above experimental results are combined to draw the following conclusions:
the time tracing method provided by the patent takes both time tracing precision and convergence time into consideration, and solves the problems of slow convergence and poor precision of the traditional GNSS time tracing method. In the coarse control stage, calculating clock error by using a standard single-point positioning algorithm based on satellite-based enhanced service to perform clock control; in the fine control stage, the clock difference is calculated by using a precise single-point positioning algorithm based on precise ephemeris service to perform clock control, so that the time tracing precision of the coarse control stage is effectively ensured, the time convergence problem of the precise single-point positioning algorithm is avoided, and the method has a good practical engineering application prospect.
By adopting the method in each node of the distributed system, the local time can be traced to a uniform time reference, and the problem of sub-nanosecond time tracing in the distributed system is solved. The research result not only can meet the dual requirements of the national defense and military field on the time traceability precision and flexibility, but also can provide reference for the time traceability problems in the scientific researches such as cross-regional precision time service, rapid backup of time scale, very Long Baseline Interferometry (VLBI) and the like.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not limited to being performed in the exact order illustrated and, unless explicitly stated herein, may be performed in other orders. Moreover, at least a portion of the steps in fig. 1 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performance of the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.
In one embodiment, as shown in fig. 4, there is provided a high-precision time tracing apparatus based on beidou-star-based augmentation and precise ephemeris service, including: an observation value obtaining module 200, an ephemeris data obtaining module 210, an estimated variance obtaining module 220, a clock error calculating obtaining module 230, and a local time adjusting module 240, wherein:
an observation value obtaining module 200, configured to obtain a pseudo-range observation value and a carrier phase observation value at a current time, where the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to a current-time local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
an ephemeris data acquisition module 210, configured to acquire broadcast ephemeris data, ephemeris correction data, and ephemeris enhancement correction data; wherein both ephemeris correction data comprise system time;
an estimated variance obtaining module 220, configured to perform clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data, and the precise ephemeris correction data, and obtain an estimated variance;
a clock error calculation obtaining module 230, configured to perform a judgment according to the estimated variance and a preset value, and if the estimated variance is greater than the preset value, perform coarse control clock error calculation according to the pseudorange observation value, the broadcast ephemeris data, and the constellation enhancement correction data to obtain a standard clock error between the local time and the system time at the current time; if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error between the local time and the system time at the current moment;
a local time adjusting module 240, configured to adjust a local time of the current time output by the atomic clock according to the standard clock difference or the precision clock difference, so as to obtain a local time of a next time; the local time of the next moment is used for generating a local time stamp of the pseudo-range observed value and the carrier phase observed value obtained at the next moment;
and until the local time of the next moment is converged to the system time, completing tracing the local time with the system standard time.
For specific limitations of the high-precision time tracing apparatus based on the beidou satellite-based enhancement and the ephemeris service, reference may be made to the above limitations of the high-precision time tracing method based on the beidou satellite-based enhancement and the ephemeris service, which are not described herein again. The modules in the time tracing apparatus using the dual-mode GNSS observation may be implemented in whole or in part by software, hardware, and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
In another embodiment, as shown in fig. 5, a high-precision time tracing apparatus based on Beidou satellite-based augmentation and precise ephemeris service is provided, which includes a GNSS receiving module, a data processing and transmitting module, a precise frequency modulation phase shift module, and an atomic clock module;
the atomic clock module is used for outputting local time;
the GNSS receiving module is used for receiving a bimodal pseudo-range observation value and a carrier phase observation value at the current moment, and the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the local time at the current moment output by the atomic clock;
the data processing and transmitting module is used for acquiring broadcast ephemeris, ephemeris correction and satellite-based augmentation correction data from a dual-mode global satellite navigation system or a network; wherein both ephemeris correction data comprise system time; calculating according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris and the precise ephemeris correction data to obtain an estimated variance; judging according to the estimated variance and a preset value, and if the estimated variance is larger than the preset value, calculating a standard clock error between the local time and the system time at the current moment by adopting a coarse control clock error; if the estimated variance is smaller than a preset value, calculating the precise clock error between the local time of the current moment and the system time by adopting a precise control clock error;
the precise frequency modulation phase shift module is used for adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a pseudo-range observation value and a local timestamp of the carrier phase observation value which are obtained at the next moment; and tracing the source of the local time and the system time until the local time of the next moment converges to the system time.
Specifically, the GNSS receiving module outputs the received bimodal carrier phase and pseudo-range original observed value to the data processing and transmitting module in a serial port communication manner, the data processing module performs clock error calculation by using observed data and real-time ephemeris data obtained by a wireless network card, and calculates the clock error to generate adjustment data after preprocessing, and inputs the adjustment data into the precision frequency modulation phase shifting module, and the precision frequency modulation phase shifting module performs frequency modulation operation, synchronous frequency division and phase shifting operation on an original signal (i.e., local time, such as 10 MHz) in sequence according to the adjustment data to obtain a post-1 PPS signal, wherein the post-driven 10MHz signal is used as an external frequency source of the multimode GNSS receiving module.
In one embodiment, the atomic clock module adopts an external rubidium atomic clock and an external clock based on a direct digital frequency synthesis technology, the frequency accuracy and stability of the clock are higher than those of a common crystal oscillator, and the frequency modulation and phase shifting precision is higher.
For specific limitations of the high-precision time tracing apparatus based on the beidou satellite-based enhancement and the ephemeris service, reference may be made to the above limitations of the high-precision time tracing method based on the beidou satellite-based enhancement and the ephemeris service, which are not described herein again.
In one embodiment, a computer device is provided, which may be a terminal. 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 comprises a nonvolatile 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 operating system and the computer program to run on the non-volatile storage medium. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to realize a high-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service. 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, a key, a track ball or a touch pad arranged on the shell of the computer equipment, an external keyboard, a touch pad or a mouse and the like.
Those skilled in the art will appreciate that the architecture shown in fig. 6 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.
In an embodiment, a computer device is provided, comprising a memory in which a computer program is stored and a processor, which when executing the computer program performs the steps of the method in the above embodiments.
In an embodiment, a computer-readable storage medium is provided, on which a computer program is stored, which computer program, when being executed by a processor, carries out the steps of the method in the above-mentioned embodiments.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in the embodiments provided herein may include non-volatile and/or volatile memory, among others. Non-volatile 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), rambus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
All possible combinations of the technical features in the above embodiments may not be described for the sake of brevity, but should be considered as being within the scope of the present disclosure as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (8)
1. The high-precision time tracing method based on Beidou satellite-based augmentation and precise ephemeris service is characterized by comprising the following steps:
obtaining a pseudo-range observation value and a carrier phase observation value at the current moment, wherein the pseudo-range observation value and the carrier phase observation value generate a local timestamp according to the current moment local time output by an atomic clock; wherein the pseudo-range observation value and the carrier phase observation value are obtained by a bimodal global satellite navigation system;
acquiring broadcast ephemeris data, precise ephemeris correction data and satellite-based augmentation correction data; wherein both ephemeris correction data comprise system time;
performing clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain an estimated variance;
judging according to the estimated variance and a preset value, if the estimated variance is larger than the preset value, performing coarse control clock error calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain a standard clock error between the local time and the system time at the current moment;
if the estimation variance is smaller than a preset value, performing fine control clock error calculation according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error between the local time and the system time at the current moment;
adjusting the local time of the current moment output by the atomic clock according to the standard clock error or the precise clock error to obtain the local time of the next moment; the local time of the next moment is used for generating a local time stamp of the pseudo-range observed value and the carrier phase observed value obtained at the next moment;
and completing tracing to the system standard time by the local time until the local time of the next moment is converged to the system time.
2. The method for high-precision time tracing according to claim 1, wherein before calculating the precision clock offset using the fine control clock offset, further comprising: and at the last moment, after the standard clock offset is calculated by adopting the coarse control clock offset, the precise clock offset is calculated by adopting the precise control clock offset only when the estimated variance is less than the preset value for continuous preset times.
3. The method of claim 2, wherein the bimodal global satellite navigation system comprises: beidou satellite navigation system and GPS.
4. The high-precision time tracing method according to claim 3, wherein said performing clock error calculation according to the pseudorange observation, the carrier phase observation, the broadcast ephemeris data, and the ephemeris correction data to obtain the estimated variance comprises:
and calculating based on the pseudo-range observation value, the carrier phase observation value and various ephemeris data to obtain Kalman filtering estimation parameters and corresponding estimation variances.
5. The high accuracy time tracing method of claim 4, wherein the coarse control clock error calculation comprises:
and performing standard single-point positioning calculation according to the pseudo-range observation value, the broadcast ephemeris data and the satellite-based enhanced correction data to obtain the standard clock error.
6. The high-precision time tracing method according to claim 4, wherein the fine control clock error calculation includes:
and calculating by using precise single-point positioning according to the pseudo-range observation value, the carrier phase observation value, the broadcast ephemeris data and the precise ephemeris correction data to obtain the precise clock error.
7. The high-precision time tracing method according to claim 6, wherein when the precision clock error is obtained by using precision single-point positioning calculation, a precision clock error calculation mathematical model is adopted, and the precision clock error is obtained after solving the precision clock error calculation mathematical model, and the precision clock error calculation mathematical model is:
in formula (1) and formula (2):
superscripts G, C and respectively represent GPS and BDS systems;
superscript s denotes satellite;
the subscript r denotes the receiver;
phi represents the geometric distance between the receiver antenna and the satellite antenna phase center, and the unit is m;
dt r represents the clock difference of the receiver clock, with the unit of s;
c represents the speed of light in vacuum, and the unit is m/s;
d r,IF and
the hardware delay of the receiver without the ionosphere combination and the satellite pseudo range is shown, and the unit of the hardware delay is m;
D r,IF and
the hardware delay of the carrier phase of the non-receiver and the satellite end without the ionosphere combination is shown, and the unit of the hardware delay is week;
T w represents the wet component of the tropospheric delay of the rover in m;
λ IF represents the carrier wavelength in m;
N IF represents the carrier phase integer ambiguity, which is expressed in units of cycles;
τ IF and upsilon IF Unmodeled error and noise, in units of m, representing pseudorange observations and carrier-phase observations.
8. The time tracing method according to claim 1, wherein the adjusting the local time of the current time output by the atomic clock according to the standard clock offset or the precision clock offset to obtain the local time of the next time comprises:
fitting the standard clock error or the precise clock error to correspondingly obtain an adjusting frequency and an adjusting phase;
and adjusting the local time of the current moment according to the adjusting frequency and the adjusting phase.
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