CN108919634B - Beidou three-frequency non-differential non-combined observation value time transmission system and method - Google Patents
Beidou three-frequency non-differential non-combined observation value time transmission system and method Download PDFInfo
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Abstract
The invention discloses a Beidou three-frequency non-differential non-combined observation value time transmission system and a method, wherein the method comprises the following steps: acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation, antenna phase centers and other parameters of the China Beidou satellite navigation system of the two transmission time stations; carrying out data inspection, gross error elimination and cycle slip detection; performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, antenna phase deviation and the like; establishing an ionospheric layer virtual observation model with additional ionospheric layer prior information constraint, space domain constraint and time domain constraint; and constructing a three-frequency non-differential non-combination precise single-point positioning model, performing single-point positioning time service calculation on the corrected data to obtain comprehensive clock errors of the receivers of the two transmission time stations, comparing the comprehensive clock errors to obtain a time transmission error, and comparing the time transmission error with the standard time of one transmission time station to obtain the precise time of the other transmission time station. The invention can reduce observation noise and improve time transmission precision and reliability.
Description
Technical Field
The invention relates to the technical field of Beidou satellite transmission time, in particular to a Beidou three-frequency non-differential non-combined observation value time transmission system and method.
Background
Time transfer is an important component of keeping time synchronized between time laboratories and establishing and maintaining standard time scales. The time transfer precision is an important index for measuring the time synchronization performance, and influences the synchronization precision among time references. The time transfer method comprises common-view time transfer and full-view time transfer, and is widely applied to various time laboratories, but the time transfer methods are based on pseudo-range observation values, and also need to be based on satellite common-view conditions, the action range is limited, the traditional full-view method usually adopts ionosphere-free combination, observation noise is amplified, and the overall positioning time service precision and reliability are low.
Disclosure of Invention
The invention aims to provide a Beidou tri-band non-differential non-combined observation value time transmission system and a Beidou tri-band non-differential non-combined observation value time transmission method, which can reduce observation noise and improve time transmission precision and reliability.
In order to achieve the purpose, the invention provides the following scheme:
a Beidou three-frequency non-differential non-combined observation value time transfer method comprises the following steps:
acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation, an antenna phase center and other parameters of the China Beidou satellite navigation system of the two transmission time stations;
performing data inspection, gross error elimination and cycle slip detection on the phase observed value and the pseudo-range observed value to obtain preprocessed data;
performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, antenna phase deviation and the like on the preprocessed data;
establishing an ionospheric layer virtual observation model with additional ionospheric layer prior information constraint, space domain constraint and time domain constraint;
constructing a three-frequency non-differential non-combination precise single-point positioning model, and performing single-point positioning time service calculation on the corrected data to obtain the respective receiver comprehensive clock error of two transmission time stations;
comparing the comprehensive clock differences of the receivers of the two transmission time stations to obtain a time transmission difference;
and comparing the time transfer difference with the standard time of one transfer time station to obtain the precise time of the other transfer time station.
Optionally, the performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, and antenna phase deviation on the preprocessed data specifically includes:
the method comprises the following steps of correcting track errors based on a precision track product, and correcting precision clock errors based on a precision clock error product;
taking the additional ionospheric prior information, time domain and space domain related constraints and ionospheric delay errors as unknown parameters to carry out real-time estimation;
and correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the deviation change of the antenna phase center and the phase winding by adopting corresponding models.
Optionally, the constructing a virtual observation model of ionosphere prior information constraint, spatial domain constraint, and time domain constraint specifically includes:
the following model was used: VTEC ═ VTECGIM+GIM；
Constructing ionospheric prior information constraints;
wherein VTECGIMThe total electron content extracted by the grid ionosphere model is represented,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
the following model was used:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the end of the surface model, usually taking the value 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijRepresenting the coefficients of the model.
The following model was used:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
Optionally, the constructing a three-frequency non-differential non-combination precise single-point positioning model, and performing single-point positioning time service calculation on the corrected data to obtain respective receiver integrated clock errors of two transmission time stations specifically includes:
the three-frequency non-differential non-combination precise single-point positioning model is constructed as follows:
wherein, P and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is P1And P2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is an ambiguity term, comprises hardware delay deviation of a satellite and a receiver end, is observation noise, and IFB is receiver inter-frequency deviation; the DCB is pseudo range code inter-frequency deviation, the code deviation of the satellite end is provided by an international GNSS service center, and the code deviation is possessed among different frequencies
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is a satellite zenith angle, VTEC is the total electron content in the zenith direction, and the unit is TECU, and f (Z) is a mapping function for converting the VTEC in the zenith direction into an oblique path direction;
the random model was established as follows:
combining the established three-frequency non-differential non-combination precise single-point positioning model to perform single-point positioning time service resolving to obtain a receiving comprehensive clock error of the two stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, in radians.
A Beidou tri-band non-differential non-combination observation value time transfer system comprises:
the observation value acquisition module is used for acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation, antenna phase centers and other parameters of the China Beidou satellite navigation system of the two transmission time stations;
the preprocessing module is used for carrying out data inspection, gross error rejection and cycle slip detection on the phase observation value and the pseudo-range observation value to obtain preprocessed data;
the correction module is used for carrying out error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere and antenna phase deviation on the preprocessed data;
the virtual observation model building module is used for building an ionospheric virtual observation model with additional ionospheric prior information constraint, space domain constraint and time domain constraint;
the resolving module is used for constructing a three-frequency non-differential non-combination precise single-point positioning model and performing single-point positioning time service resolving on the corrected data to obtain the respective receiver comprehensive clock errors of the two transmission time stations;
the time transfer difference calculation module is used for comparing the comprehensive clock differences of the receivers of the two transfer time stations to obtain a time transfer difference;
and the transmission time module is used for comparing the time transmission difference with the standard time of one of the transmission time stations to obtain the precise time of the other transmission time station.
Optionally, the correction module specifically includes:
the track parameter correcting unit corrects track errors based on the precise track product;
the satellite ephemeris error correction unit corrects the clock error based on the precise clock error product;
the ionospheric delay error correction unit is used for taking the additional ionospheric prior information, the time domain and space domain related constraints and the ionospheric delay error as unknown parameters to carry out real-time estimation;
and the satellite navigation related parameter correcting unit is used for correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the antenna phase center deviation change and the phase winding by adopting a corresponding model.
Optionally, the virtual observation model building module includes:
based on the grid ionosphere model, carrying out prior information constraint to obtain a prior information constraint equation; according to the space characteristics of the ionized layer, single-station modeling is carried out, model coefficients are solved, and a space domain constraint equation is formed; according to the time change characteristic of the ionized layer, constraining adjacent epochs to form a time domain constraint equation, which specifically comprises the following steps:
an ionospheric prior information constraint model construction unit, configured to employ the following model: VTEC ═ VTECGIM+GIM；
Constructing ionospheric prior information constraints;
wherein VTECGIMThe total electron content extracted by the grid ionosphere model is represented,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
an ionospheric spatial domain constraint model construction unit, configured to employ the following model:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the end of the surface model, usually taking the value 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijRepresenting the coefficients of the model.
An ionospheric time domain constraint model construction unit, configured to employ the following model:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
Optionally, the resolving module includes:
through model correction and parameter linearization, an observation equation is constructed, a random model is determined, and parameter estimation is performed to obtain the comprehensive clock error of the receivers of the two stations, which specifically comprises the following steps:
the three-frequency non-differential non-combination precise single-point positioning model building unit is used for building a three-frequency non-differential non-combination precise single-point positioning model as follows:
wherein, P and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is P1And P2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is an ambiguity term, comprises hardware delay deviation of a satellite and a receiver end, is observation noise, and IFB is receiver inter-frequency deviation; the DCB is pseudo range code inter-frequency deviation, the code deviation of the satellite end is provided by an international GNSS service center, and the code deviation is possessed among different frequencies
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is a satellite zenith angle, VTEC is the total electron content in the zenith direction, and the unit is TECU, and f (Z) is a mapping function for converting the VTEC in the zenith direction into an oblique path direction;
a stochastic model establishing unit, configured to establish a stochastic model as follows:
combining the established three-frequency non-differential non-combination precise single-point positioning model to perform single-point positioning time service resolving to obtain a comprehensive clock error of a receiver of two stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, in radians.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a Beidou tri-band non-differential non-combined observation value time transmission system and a method, which are based on a GPS precision Point location (PPP) technology to carry out a time transmission method combined with a Beidou tri-band non-differential non-combined observation value, construct a non-differential non-combined PPP model of a tri-band signal by adding ionosphere prior information constraint, space domain constraint and time domain constraint virtual observation equations, and realize the precision time transmission service of two stations by sharing Beidou system time, thereby effectively reducing observation noise, improving time transmission precision and obtaining ionosphere and hardware delay products.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for a person skilled in the art to obtain his drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a beidou three-frequency non-differential non-combined observation value time transfer method according to embodiment 1 of the present invention;
fig. 2 is a schematic structural diagram of a beidou three-frequency non-differential non-combined observation value time transmission system in embodiment 2 of the present invention;
fig. 3 is a schematic flow chart of a beidou three-frequency non-differential non-combined observation value time transfer method according to embodiment 3 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All embodiments that can be obtained by a person skilled in the art based on the embodiments of the present invention without any inventive step are within the scope of the present invention.
The invention aims to provide a Beidou tri-band non-differential non-combined observation value time transmission system and a Beidou tri-band non-differential non-combined observation value time transmission method, which can reduce observation noise and improve time transmission precision and reliability.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic flow diagram of the beidou three-frequency non-differential non-combined observation value time transfer method of the invention.
As shown in fig. 1, a beidou three-frequency non-differential non-combined observation value time transfer method includes:
step 101: acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation, antenna phase centers and other parameters of the China Beidou satellite navigation system of the two transmission time stations;
step 102: performing data inspection, gross error elimination and cycle slip detection on the phase observed value and the pseudo-range observed value to obtain preprocessed data;
step 103: performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, antenna phase deviation and the like on the preprocessed data;
step 104: establishing an ionospheric layer virtual observation model with additional ionospheric layer prior information constraint, space domain constraint and time domain constraint;
step 105: constructing a three-frequency non-differential non-combination precise single-point positioning model, and performing single-point positioning time service calculation on the corrected data to obtain the respective receiver comprehensive clock error of two transmission time stations;
step 106: comparing the comprehensive clock differences of the receivers of the two transmission time stations to obtain a time transmission difference;
step 107: and comparing the time transfer difference with the standard time of one transfer time station to obtain the precise time of the other transfer time station.
The step 103: and performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, antenna phase deviation and the like on the preprocessed data, specifically comprising the following steps:
the track error is corrected through a precision track product, and the clock error is corrected through a precision clock error product;
taking the additional ionospheric prior information, time domain and space domain related constraints and ionospheric delay errors as unknown parameters to carry out real-time estimation;
and correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the deviation change of the antenna phase center and the phase winding by adopting corresponding models.
The step 104 is that: the method for constructing the ionospheric virtual observation model with additional ionospheric priori information constraints, space domain constraints and time domain constraints comprises the following steps:
based on the grid ionosphere model, carrying out prior information constraint to obtain a prior information constraint equation; according to the space characteristics of the ionized layer, single-station modeling is carried out, model coefficients are solved, and a space domain constraint equation is formed; according to the time change characteristic of the ionized layer, constraining adjacent epochs to form a time domain constraint equation, which specifically comprises the following steps:
the following model was used: VTEC ═ VTECGIM+GIM；
Constructing ionospheric prior information constraints;
wherein VTECGIMTotal electrons representing grid ionosphere model extractionThe content of the components is as follows,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
the following model was used:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the end of the surface model, usually taking the value 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijRepresenting the coefficients of the model.
The following model was used:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
The step 105 is as follows: constructing a three-frequency non-differential non-combination precise single-point positioning model, and performing single-point positioning time service calculation on the corrected data to obtain respective receiver comprehensive clock errors of two transmission time stations, wherein the method comprises the following steps:
through model correction and parameter linearization, an observation equation is constructed, a random model is determined, and parameter estimation is performed to obtain a comprehensive clock error of two stations, which specifically comprises the following steps:
the three-frequency non-differential non-combination precise single-point positioning model is constructed as follows:
wherein, P and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is P1And P2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is an ambiguity term, comprises hardware delay deviation of a satellite and a receiver end, is observation noise, and IFB is receiver inter-frequency deviation;the DCB is pseudo range code inter-frequency deviation, the code deviation of the satellite end is provided by an international GNSS service center, and the code deviation is possessed among different frequencies
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is a satellite zenith angle, VTEC is the total electron content in the zenith direction, and the unit is TECU, and f (Z) is a mapping function for converting the VTEC in the zenith direction into an oblique path direction;
the random model was established as follows:
combining the established three-frequency non-differential non-combination precise single-point positioning model to perform single-point positioning time service resolving to obtain a receiving comprehensive clock error of the two stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, in radians.
Fig. 2 is a schematic structural diagram of the beidou three-frequency non-differential non-combined observation value time transfer system of the invention.
As shown in fig. 2, a beidou three-frequency non-differential non-combined observation value time transmission system includes:
the observation value acquisition module 201 is used for acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation, antenna phase centers and other parameters of the China Beidou satellite navigation system of the two transmission time stations;
the preprocessing module 202 is configured to perform data inspection, gross error rejection and cycle slip detection on the phase observation value and the pseudo-range observation value to obtain preprocessed data;
a correction module 203, configured to perform error model correction on the preprocessed data, such as ephemeris, tide, relativity, earth rotation, atmosphere, and antenna phase deviation;
a virtual observation model construction module 204, configured to construct an ionospheric virtual observation model with additional ionospheric prior information constraints, spatial domain constraints, and time domain constraints;
the resolving module 205 is used for constructing a three-frequency non-differential non-combination precise single-point positioning model and performing single-point positioning time service resolving on the corrected data to obtain respective receiver comprehensive clock errors of two transmission time stations;
a time transfer difference calculation module 206, configured to compare the respective receiver integrated clock differences of the two transfer time stations to obtain a time transfer difference;
and the transmission time module 207 is used for comparing the time transmission difference with the standard time of one transmission time station to obtain the precise time of the other transmission time station.
The correction module 203 specifically includes:
the track parameter correction unit is used for correcting track errors based on the precision track product;
the satellite ephemeris error correction unit is used for correcting the clock error based on the precise clock error product;
the ionospheric delay error correction unit is used for taking the additional ionospheric prior information, the time domain and space domain related constraints and the ionospheric delay error as unknown parameters to carry out real-time estimation;
and the satellite navigation related parameter correcting unit is used for correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the antenna phase center deviation change and the phase winding by adopting a corresponding model.
The virtual observation model building module 204 includes:
based on the grid ionosphere model, carrying out prior information constraint to obtain a prior information constraint equation; according to the space characteristics of the ionized layer, single-station modeling is carried out, model coefficients are solved, and a space domain constraint equation is formed; according to the time change characteristic of the ionized layer, constraining adjacent epochs to form a time domain constraint equation, which specifically comprises the following steps:
ionospheric prior informationA constraint model construction unit for adopting the following models: VTEC ═ VTECGIM+GIM；
Constructing ionospheric prior information constraints;
wherein VTECGIMThe total electron content extracted by the grid ionosphere model is represented,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
an ionospheric spatial domain constraint model construction unit, configured to employ the following model:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the end of the surface model, usually taking the value 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijRepresenting the coefficients of the model.
An ionospheric time domain constraint model construction unit, configured to employ the following model:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
The resolving module 205 includes:
through model correction and parameter linearization, an observation equation is constructed, a random model is determined, and parameter estimation is performed to obtain a comprehensive clock error of two stations, which specifically comprises the following steps:
for the model establishment, firstly, a function model is established, ionosphere delay adopts a parameter estimation method with constraint conditions, troposphere delay errors are corrected by adopting an empirical model, and the residual part of the ionosphere delay errors is estimated by adopting a piecewise constant or random walk model.
The three-frequency non-differential non-combination precise single-point positioning model building unit is used for building a three-frequency non-differential non-combination precise single-point positioning model as follows:
wherein, P and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is P1And P2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is an ambiguity term, comprises hardware delay deviation of a satellite and a receiver end, is observation noise, and IFB is receiver inter-frequency deviation; the DCB is pseudo range code inter-frequency deviation, the code deviation of the satellite end is provided by an international GNSS service center, and the code deviation is possessed among different frequencies
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is a satellite zenith angle, VTEC is the total electron content in the zenith direction, and the unit is TECU, and f (Z) is a mapping function for converting the VTEC in the zenith direction into an oblique path direction;
a stochastic model establishing unit, configured to establish a stochastic model as follows:
combining the established three-frequency non-differential non-combination precise single-point positioning model to perform single-point positioning time service resolving to obtain a receiving comprehensive clock error of the two stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, and the unit is radian;
the hardware delay deviation DCB of the satellite terminal is corrected by adopting a product published by IGS, and the DCB of the receiver terminal is used for parameter estimation; the satellite ephemeris error is corrected by adopting a correction number broadcasted in real time, the receiver clock error is corrected by a time difference parameter and then estimated as Gaussian white noise, and the local time of the user relative to the NTSC reference time is obtained. Multipath effects, which are temporarily not corrected by a reliable model or method, can be treated as observation noise. The stochastic model can be comprehensively determined according to the pseudo range, the phase observation value and the model precision and by matching with the satellite altitude angle.
Fig. 3 is a schematic flow chart of a beidou three-frequency non-differential non-combined observation value time transfer method according to embodiment 3 of the present invention. As shown in fig. 3, the observation data collected on the survey station, the precise orbit, the clock error, the ionosphere products, and the auxiliary products (earth rotation parameters, DCB correction, antenna files, etc.) required for data processing are collected;
based on the grid ionosphere model, carrying out prior information constraint to obtain a prior information constraint equation; according to the space characteristics of the ionized layer, single-station modeling is carried out, model coefficients are solved, and a space domain constraint equation is formed; and according to the time change characteristic of the ionized layer, constraining adjacent epochs to form a time domain constraint equation.
And (3) establishing an observation equation through model correction and parameter linearization, determining a random model, and performing parameter estimation to obtain the comprehensive clock error of the receiver of each station.
And comparing the comprehensive clock errors among the stations to obtain the time transmission error, and realizing the time transmission function of the user station by depending on the standard time of the reference station.
And a high-precision phase observation value is adopted, so that the precision of time transfer is improved.
According to the Beidou tri-band non-differential non-combined observation value time transmission system and method, the high-precision phase observation value is used for carrying out time transmission calculation, the limitation that a conventional common-view method is used, only a low-precision pseudo-range observation value is used in a full-view method is made up, and the time transmission precision is greatly improved; the overall time transmission precision and reliability can be improved by adopting the three-frequency observation value, and the time transmission precision and reliability can be improved by adopting the three-frequency observation value as well as abundant frequency combinations; by adopting the non-differential non-combination model, the observation noise is greatly reduced, and the time transfer precision is improved; meanwhile, abundant ionosphere and hardware delay products are obtained.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to assist understanding of the methods and core concepts of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (6)
1. A Beidou three-frequency non-differential non-combined observation value time transfer method is characterized by comprising the following steps:
obtaining phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation and antenna phase center parameters of the China Beidou satellite navigation system of the two transmission time stations;
performing data inspection, gross error elimination and cycle slip detection on the phase observed value and the pseudo-range observed value to obtain preprocessed data;
performing error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere, antenna phase deviation and the like on the preprocessed data;
establishing an ionospheric layer virtual observation model with additional ionospheric layer prior information constraint, space domain constraint and time domain constraint;
constructing a three-frequency non-differential non-combination precise single-point positioning model, performing single-point positioning time service calculation on the corrected data, and obtaining respective receiver comprehensive clock errors of two transmission time stations, wherein the method specifically comprises the following steps:
the three-frequency non-differential non-combination precise single-point positioning model is constructed as follows:
wherein, p and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is p1And p2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is ambiguity term, including hardware delay deviation of satellite and receiver end, as observation noise, DCB is pseudo range code frequency deviation, code deviation of satellite end is provided by international GNSS service center, and different frequencies have
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is satellite zenith angle, VTEC is skyThe total electron content in the vertex direction is in a unit of TECU, and f (Z) is a mapping function for converting VTEC in the zenith direction into an oblique path direction;
the random model was established as follows:
performing precise single-point positioning time service calculation on the correction data by combining the established three-frequency non-differential non-combination precise single-point positioning model to obtain respective receiver comprehensive clock differences of two transmission time stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, and the unit is radian;
comparing the comprehensive clock differences of the receivers of the two transmission time stations to obtain a time transmission difference;
and comparing the time transfer difference with the standard time of one transfer time station to obtain the precise time of the other transfer time station.
2. The method for transmitting the Beidou tri-band non-differential non-combined observation value time according to claim 1, wherein the error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere and antenna phase deviation is performed on the preprocessed data, and specifically comprises:
track errors are corrected through a precise track, and clock error errors are corrected through a precise clock error;
taking the additional ionospheric prior information, time domain and space domain related constraints and ionospheric delay errors as unknown parameters to carry out real-time estimation;
and correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the deviation change of the antenna phase center and the phase winding by adopting corresponding models.
3. The method for time transfer of the Beidou tri-band non-differential non-combined observation value as claimed in claim 1, wherein the constructing of the virtual observation model of ionosphere prior information constraint, spatial domain constraint and temporal domain constraint specifically comprises:
the following model was used:
VTEC＝VTECGIM+GIM；
constructing ionospheric prior information constraints;
wherein VTECGIMThe total electron content extracted by the grid ionosphere model is represented,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
the following model was used:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the order of the surface model, usually taken to be 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijCoefficients representing the model;
the following model was used:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
4. The utility model provides a big dipper three frequency non-difference non-combination observation value time transfer system which characterized in that includes:
the observation value acquisition module is used for acquiring phase observation values, pseudo-range observation values, satellite ephemeris, earth rotation and antenna phase center parameters of the China Beidou satellite navigation system of the two transmission time stations;
the preprocessing module is used for carrying out data inspection, gross error elimination and cycle slip detection on the phase observation value and the pseudo-range observation value number to obtain preprocessed data;
the correction module is used for carrying out error model correction such as ephemeris, tide, relativity, earth rotation, atmosphere and antenna phase deviation on the preprocessed data;
the virtual observation model building module is used for building an ionospheric virtual observation model with additional ionospheric prior information constraint, space domain constraint and time domain constraint;
the resolving module is used for constructing a three-frequency non-differential non-combination precise single-point positioning model and performing single-point positioning time service resolving on the corrected data to obtain the respective receiver comprehensive clock errors of the two transmission time stations;
the resolving module specifically comprises:
the three-frequency non-differential non-combination precise single-point positioning model building unit is used for building a three-frequency non-differential non-combination precise single-point positioning model as follows:
wherein, p and phi are respectively pseudo range and carrier phase observed value, and f is frequency; frequency coefficient
ρ is the geometric distance from the satellite to the survey station, c is the speed of light, dt12Is p1And p2Receiver clock offset, dt, for ionosphere-free combined observationssIs the satellite clock error, dtropIs tropospheric delay; m represents the comprehensive errors of solid tide, sea tide, earth rotation, relativistic effect, antenna phase center deviation, turning and multipath; n is ambiguity term, including hardware delay deviation of satellite and receiver end, as observation noise, DCB is pseudo range code frequency deviation, code deviation of satellite end is provided by international GNSS service center, and different frequencies have
Relation of (d)ionIs the ionospheric delay at a frequency of L1, dionVTEC, the corner mark s stands for satellite,
z is a satellite zenith angle, VTEC is the total electron content in the zenith direction, and the unit is TECU, and f (Z) is a mapping function for converting the VTEC in the zenith direction into an oblique path direction;
a stochastic model establishing unit, configured to establish a stochastic model as follows:
performing precise single-point positioning time service calculation on the correction data by combining the established three-frequency non-differential non-combination precise single-point positioning model to obtain respective receiver comprehensive clock differences of two transmission time stations;
wherein I is an identity matrix; sigma0A/sin (e) is the error in unit weight; a is constant, the phase value is 0.002-0.003m, and the pseudo range value is 0.2-2.0 m; e is the satellite altitude, and the unit is radian;
the time transfer difference calculation module is used for comparing the comprehensive clock differences of the receivers of the two transfer time stations to obtain a time transfer difference;
and the transmission time module is used for comparing the time transmission difference with the standard time of one of the transmission time stations to obtain the precise time of the other transmission time station.
5. The Beidou tri-band non-differential non-combined observation value time transfer system according to claim 4, wherein the correction module specifically comprises:
the track parameter correcting unit is used for correcting track errors;
the satellite ephemeris error correction unit is used for correcting the clock error;
the ionospheric delay error correction unit is used for taking the additional ionospheric prior information, the time domain and space domain related constraints and the ionospheric delay error as unknown parameters to carry out real-time estimation;
and the satellite navigation related parameter correcting unit is used for correcting the solid tide, the sea tide, the polar motion, the relativistic effect, the antenna phase center deviation change and the phase winding by adopting a corresponding model.
6. The Beidou tri-band non-differential non-combined observation value time transfer system according to claim 4, wherein the virtual observation model building module specifically comprises:
an ionospheric prior information constraint model construction unit, configured to employ the following model:
VTEC＝VTECGIM+GIM；
constructing ionospheric prior information constraints;
wherein VTECGIMThe total electron content extracted by the grid ionosphere model is represented,GIMrepresenting the prior model error, σpriorThe value is 0.3-0.6 m, B represents the latitude of the ionosphere puncture point, and t represents the local time in hours;
an ionospheric spatial domain constraint model construction unit, configured to employ the following model:
VTEC＝VTECspace+space；
establishing ionospheric space domain constraints;
where m and n are the order of the surface model, usually taken to be 2,
and λ is the latitude and longitude of the puncture point,
and λ0For the latitude and longitude of the station, EijCoefficients representing the model;
an ionospheric time domain constraint model construction unit, configured to employ the following model:
VTEC＝VTEClast+ΔVTEC+temp；
establishing ionospheric time domain constraints;
wherein, the delta VTEC is the epoch change of the ionosphere VTEC,
is the variance of Δ VTEC in m2The value range is 0.009-0.025m2。
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