CN101609143B - Satellite timing method based on wide area differential reinforcement - Google Patents

Abstract

The invention relates to a satellite timing method based on wide area differential reinforcement, which is technically characterized in that each difference station carries out pseudo-range observation of a code phase and a carrier phase, and a main difference station and a satellite navigation system have synchronous time and can both measure a position of a code phase observation value and a carrier phase observation value of a pseudo range. The invention has the main effects of enhancing the accuracy of satellite navigation, and utilizing the method to cause the satellite navigation to achieve 1 nsec to 3 nsec and secondly, simplifying the configuration of a ground monitor system, and lowering the construction cost of a difference network.

Description

A kind of satellite timing method that strengthens based on GPS wide area differential GPS

Technical field

The present invention relates to a kind of satellite timing method that strengthens based on GPS wide area differential GPS, is to utilize the differential technique of satellite navigation system and the technology of satellite timing method to reach the method that time service improves the satellite time service precision.

Background technology

The satellite time service is the time service of satellite navigation system, one of the three big functions of locating and test the speed, and at present, defends time service and mainly relies on the ground monitoring system measurement and in the navigation message of satellite, provide, and the satellite time service precision that is provided by navigation message is greatly about about 20nsec.For the needs user of high precision timing more, it is too rough that this precision seems.Therefore, be necessary to study the method that can further improve the satellite time service precision.

The real-time of satellite time service requires high; And traditional wide area differential method such as the current WASS that satisfies the good wide area differential method of real-time such as the U.S. adopts single pseudo range observed quantity and adopts star clock and ephemeris to unify calculation method; There is the bigger shortcoming of stochastic error in pseudo range observed quantity; And star clock and ephemeris unification are resolved, and its geometric dilution of precision is bigger, and the real-time time service precision of satellite is difficult for improving.

Summary of the invention

The technical matters that solves

For fear of the weak point of prior art, the present invention proposes a kind of satellite timing method that strengthens based on GPS wide area differential GPS, can overcome the limitation of traditional wide area differential method aspect time service, utilizes the satellite timing method based on wide area differential method.

Technical scheme

Basic thought of the present invention is: utilize the main difference station of time strict synchronism and time not to set up the difference net in a plurality of secondary station of strict synchronism; In this difference net; Utilize star clock error to carry out the first time at main difference station and separate for the second time and revise, obtain star clock time through twice correction.

The inventive method is characterised in that step is following: the pseudorange observation of code phase and carrier phase is carried out at each difference station simultaneously; And main difference station and satellite navigation system time synchronized; All can record the code phase observed reading and the carrier phase observation data position of pseudorange, concrete steps are following:

Step 1: the pseudo range observed quantity of code phase utilizes the carrier phase observed quantity level and smooth, obtains the pseudo range observed quantity after level and smooth;

Step 2: correct the first time of carrying out star clock error at main difference station, obtains the correction-ρ first time of star clock error _CLK ^k(E), ${\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(E\right)={\mathrm{\ρ}}_1^k-R_1^k\left(E\right);$ Wherein: ρ ₁ ^kBe the pseudorange of satellite k to main difference station, R ₁ ^k(E) be the geometric distance of satellite k to main difference station, E representes the broadcast ephemeris of satellite;

Step 3: carry out the relative separation of ephemeris error at secondary difference station, obtain the relative reduction Δ ρ of this pair difference station ephemeris pseudorange _i ^k-Δ _i ¹:

$\mathrm{\Δ}{\mathrm{\ρ}}_i^k-\mathrm{\Δ}{\mathrm{\ρ}}_i^1={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)-({\mathrm{\ρ}}_1^1-R_1^1\left(E\right))-[({\mathrm{\ρ}}_i^k-R_i^k\left(E\right))-({\mathrm{\ρ}}_i^1-R_i^1\left(E\right))]$

Wherein: Δ ρ _i ^kThe expression satellite k is gone through pseudorange error to the station star of secondary difference station i, Δ ρ _i ¹The expression proper star is gone through pseudorange error, ρ to the station star of secondary difference station i _i ^kThe expression satellite k is to the pseudorange of secondary difference station i, ρ _i ¹The expression proper star is to the pseudorange of secondary difference station i, ρ ₁ ¹The expression proper star is to the pseudorange at main difference station; R ₁ ¹(E) broadcast ephemeris of expression proper star is to the geometric distance at main difference station, R _i ^k(E) broadcast ephemeris of expression satellite k is to the geometric distance of difference station i, R _i ¹(E) broadcast ephemeris of expression proper star is to the geometric distance of difference station i;

Step 4: the relative reduction Δ ρ that utilizes this pair difference station ephemeris pseudorange that the difference station more than three or three obtains _i ^k-Δ ρ _i ¹, adopt three-dimensional user's positioning equation to resolve and obtain the ephemeris correction;

Step 5: correct the second time of carrying out star clock error at main difference station, obtains star clock correction Δ ρ for the second time _CLK ^k,

$\mathrm{\Δ}{\mathrm{\ρ}}_{\mathrm{CLK}}^k=R_1^k\left(S\right)-R_1^k\left(E\right)=\mathrm{\Δ}{t}_u-\mathrm{\Δ}{t}_{u^{\′}},$ R wherein ₁ ^k(S) actual position of expression satellite k is to the geometric distance at main difference station, Δ t _uThe true value of expression user timing results is separated Δ t _{U '}Actual the separating of expression user timing results;

It is Δ t that the true value of said user's timing results is separated for main difference station _u=0;

The actual of said user's timing results separated: star clock correction and the step 4 of utilizing step 2 to obtain multi-satellite obtain the ephemeris correction, and the four-dimensional user's positioning equation of substitution obtains the actual Δ t that separates of the timing results at main difference station _{U '}The actual Δ t that separates with the timing results at main difference station _{U '}As the star clock correction second time;

Step 6: with correction-ρ first time _CLK ^k(E) and star clock correction Δ ρ for the second time _CLK ^kCarry out time service after the star clock error of correction satellite clock.

Beneficial effect

A kind of satellite timing method that strengthens based on GPS wide area differential GPS of the present invention, main effect has two: the satellite time service precision is improved in (1), utilizes this method can make the satellite time service reach 1～3nsec.(2) configuration of simplification ground monitoring system, the construction cost of reduction difference net.

Description of drawings

Fig. 1: the WAAS-Wide Area Augmentation System that the present invention implements

Fig. 2: the one-stop separation principle figure of star clock error

Fig. 3: each difference station and user's timing offset

Fig. 4: the timing synchronous error after each difference station and user's secondary correct

Embodiment

Combine embodiment, accompanying drawing that the present invention is further described at present:

In the present embodiment: the difference net monitoring system on ground comprises main difference station (main website) among Fig. 1, and it is that a plurality of secondary difference station (secondary station) do not require during construction and the system time strict synchronism with the system time strict synchronism of satellite navigation system.Space segment is included in multi-satellite visual in the difference net and forms.

M among Fig. 2 ₁Represent main difference station (main website), S ^kExpression Navsat, wherein S ¹The expression proper star, E ^kThe broadcast ephemeris position of expression Navsat, E ¹The broadcast ephemeris position of expression proper star, E ^IkNavsat is through the correction ephemeris position after radially the ephemeris pseudorange error corrects.R ₁ ^kRepresent main website respectively to the Navsat geometric distance, Δ ρ ₁ ^kRepresent respectively nautical star to the ephemeris pseudorange error of main website in the radially projecting of main website to the broadcast ephemeris direction, i.e. ephemeris pseudorange error, ρ _CLK ^k(S) the star clock pseudorange error true value of expression Navsat (compare with system time, for just, lag behind in advance) to negative, Δ Δ ρ ₁ ^kExpression is with respect to the ephemeris pseudorange reduction of proper star.

The concrete steps of present embodiment:

(1) the one-stop separation of star clock error

Suppose that main website and system time are strict synchronism, the pseudorange of main website observation is through behind double frequency ionosphere corrections and this data preprocessing process of troposphere model tuning, as if the influence of not considering the pseudorange residual error, can think ρ ₁ ^kInclude only the geometric distance R of main website to satellite actual position (S) ₁ ^k(S), star clock pseudorange error ρ _CLK ^k(S), can be expressed as

${\mathrm{\ρ}}_1^k=R_1^k\left(S\right)+{\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)$ (1)

Real star clock errors table is shown

${\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)={\mathrm{\ρ}}_1^k-R_1^k\left(S\right)$ (2)

The radially pseudorange error of supposing broadcast ephemeris is Δ ρ ₁ ^k, the relation according to Fig. 2 satellite broadcasting position and actual position has $R_1^k\left(S\right)=R_1^k\left(E\right)-\mathrm{\Δ}{\mathrm{\ρ}}_1^k,$ Following formula can be rewritten as

${\mathrm{\ρ}}_1^k=R_1^k\left(E\right)-\mathrm{\Δ}{\mathrm{\ρ}}_1^k+{\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)$ (3)

Can be changed into

${\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)-\mathrm{\Δ}{\mathrm{\ρ}}_1^k={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)$ (4)

The summation of star clock and ephemeris error is represented on the left side of equality, and the right of equality is represented with respect to E ^kStar clock pseudorange error, can be expressed as

${\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(E\right)={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)$ (5)

General-ρ _CLK ^k(E) be broadcast to the user as star clock correction, correct the first time of star clock error that Here it is.

According to the comparison of formula (5) and formula (2), the star clock error ρ that broadcast ephemeris separates _CLK ^k(E) with real star clock error ρ _CLK ^k(s) there is certain deviation (being called for short star clock deviation).Suppose that star clock deviation is Δ ρ _CLK ^k, its value equals geometric distance poor that the main website branch is clipped to broadcast ephemeris and true ephemeris, is expressed as

$\mathrm{\Δ}{\mathrm{\ρ}}_{\mathrm{CLK}}^k={\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(E\right)-{\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)=R_1^k\left(S\right)-R_1^k\left(E\right)$ (6)

The size of this deviation depends on the forecast precision of broadcast ephemeris, in order to reduce this star clock deviation to user's influence regularly, needs further to correct, and this step is called star clock secondary and corrects.

If secondary station also is a time synchronized, except that the numbering difference at difference station, the expression formula of pseudorange is consistent with formula (3), promptly

${\mathrm{\ρ}}_i^k=R_i^k\left(E\right)-\mathrm{\Δ}{\mathrm{\ρ}}_i^k+{\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(S\right)$ (7)

(2) ephemeris error relative separation

Because the actual position of satellite is unknown, thus when correcting with the correction ρ first time of star clock error _CLK ^k(E) replace true star clock error ρ _CLK ^k(S), the pseudorange error of pair station observation is deducted this amount obtain the ephemeris pseudorange error contribution amount of this station, be expressed as this star

$\mathrm{\Δ}{\mathrm{\ρ}}_i^k={\mathrm{\ρ}}_{\mathrm{CLK}}^k-({\mathrm{\ρ}}_i^k-R_i^k\left(E\right))={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)-({\mathrm{\ρ}}_i^k-R_i^k\left(E\right))$ (8)

A plurality of secondary stations simultaneous can be got the ephemeris correction, said process is called the absolute separation of ephemeris pseudorange error here.

If the secondary station asynchronism(-nization) step is selected a proper star (satellite 1), subtract each other through poor other satellite and the pseudorange of observation proper star will observed of interspace list, can eliminate secondary station clock correction, obtain the relative pseudorange error contribution amount of ephemeris at this station, be expressed as

$\mathrm{\Δ\Δ}{\mathrm{\ρ}}_i^k=\mathrm{\Δ}{\mathrm{\ρ}}_i^k-\mathrm{\Δ}{\mathrm{\ρ}}_i^1={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)-({\mathrm{\ρ}}_1^1-R_1^1\left(E\right))-[({\mathrm{\ρ}}_i^k-R_i^k\left(E\right))-({\mathrm{\ρ}}_i^1-R_i^1\left(E\right))]$ (9)

Δ ρ _i ^k-Δ ρ _i ¹Represent the relative error of i station, this amount is distributed to the k station, as the contribution amount of i station the ephemeris pseudorange correction of K satellite to the radially pseudorange error of two satellites.Utilize more than three or three the contribution amount at secondary station, adopt three-dimensional to resolve equation and unite to resolve and to obtain the ephemeris correction, said process is called the relative separation of ephemeris pseudorange error here.

The relative separation method only revised in the pseudorange error radially with respect to proper star different piece, and its publicly-owned part, its value equals the radially pseudorange error R between main website and the proper star ₁ ¹(S)-R ₁ ¹(E), do not correct.This part error regularly can produce droop to the user.Its droop equals user's true value regularly and separates and actual separate poor

$R_1^1\left(E\right)-R_1^1\left(S\right)=c({\mathrm{\Δt}}_u-{\mathrm{\Δt}}_{u^{\′}})$ (10)

Fig. 3 has provided through the star clock and has once corrected the user timing results after correcting with ephemeris error.As can be seen from the figure, each difference station and user's timing offset is equal basically, shows to have a droop, and this droop corrects through star clock secondary.

(3) star clock secondary corrects

Backward inference: if the star clock sum of errors ephemeris error of all satellites all is modified to true value; So according to user's positioning equation; The true ephemeris that utilizes N>=4 satellite can obtain user's timing with true star clock and the true value of positioning result is separated, and main website has known and time synchronized (the Δ t in mapping position (can ignore with the error of actual position) as a special user _u=0) characteristics, this known true value are separated to can be regarded as by true ephemeris and the true value that true star clock is derived and are separated, and can no longer find the solution Δ t like this _uTherefore star clock secondary modification method can be reduced to

$R_1^1\left(E\right)-R_1^1\left(S\right)=-{\mathrm{\Δt}}_{u^{\′}}$ (14)

The differential correcting number of many stars (N >=4) that draw according to the front and the differential timing that user's positioning equation can calculate main difference station are separated, and in main website, this negative value of separating is exactly a star clock secondary correction.

(4) with correction-ρ first time _CLK ^k(E) and star clock correction Δ ρ for the second time _CLK ^kCarry out time service after the star clock error of correction satellite clock.

Find out that by Fig. 3 expression adopts user's timing results of correction of star clock and ephemeris correction, the result shows the timing offset at each difference station and user after the difference among the figure, can find out droop of existence.

Fig. 4 has provided the result that star clock secondary corrects; As can beappreciated from fig. 4, Wuhan is after the interior user's of two nets in Chengdu the timing synchronous error process star clock secondary correction; User's timing results is controlled within 1～3nsec, has explained that indirectly the satellite time service precision can reach 1～3nsec.This explains that this method is very effective.

Claims (1)

1. satellite timing method that strengthens based on GPS wide area differential GPS; It is characterized in that: the pseudorange observation of code phase and carrier phase is carried out at each difference station simultaneously; And main difference station and satellite navigation system time synchronized; All can record the code phase observed reading and the carrier phase observation data position of pseudorange, concrete steps are following:

Step 1: the pseudo range observed quantity of code phase utilizes the carrier phase observed quantity level and smooth, obtains the pseudo range observed quantity after level and smooth;

Step 2: correct the first time of carrying out star clock error at main difference station, obtains the correction first time of star clock error

${\mathrm{\ρ}}_{\mathrm{CLK}}^k\left(E\right)={\mathrm{\ρ}}_1^k-R_1^k\left(E\right);$ Wherein:

Be the pseudorange of satellite k to main difference station,

Represent the geometric distance that main difference station is arrived in the position that resolves of satellite k, E representes to utilize the broadcast ephemeris of satellite to resolve the satellite position of acquisition, is called for short the position of resolving of satellite;

Step 3: carry out the relative separation of ephemeris error at secondary difference station, obtain the relative reduction of this pair difference station ephemeris pseudorange

$\mathrm{\Δ}{\mathrm{\ρ}}_i^k-\mathrm{\Δ}{\mathrm{\ρ}}_i^1={\mathrm{\ρ}}_1^k-R_1^k\left(E\right)-({\mathrm{\ρ}}_1^1-R_1^1\left(E\right))-[({\mathrm{\ρ}}_i^k-R_i^k\left(E\right))-({\mathrm{\ρ}}_i^1-R_i^1\left(E\right))]$

Wherein: expression satellite k is gone through pseudorange error to the station star of secondary difference station i;

expression proper star is gone through pseudorange error to the station star of secondary difference station i;

expression satellite k is to the pseudorange of secondary difference station i;

expression proper star is to the pseudorange of secondary difference station i, and expression proper star is to the pseudorange at main difference station;

representes the geometric distance that main difference station is arrived in the position that resolves of proper star; What

expression utilized satellite k resolves the position to the geometric distance of secondary difference station i,

expression proper star resolve the geometric distance of position to secondary difference station i;

Step 4: utilize the relative reduction

of this pair difference station ephemeris pseudorange that the difference station more than three or three obtains to adopt three-dimensional user's positioning equation to resolve and obtain the ephemeris correction;

Step 5: correct the second time of carrying out star clock error at main difference station, obtains star clock correction for the second time

$\mathrm{\Δ}{\mathrm{\ρ}}_{\mathrm{CLK}}^k=R_1^k\left(S\right)-R_1^k\left(E\right)=\mathrm{\Δ}{t}_u-\mathrm{\Δ}{t}_{u^{\′}},$ Wherein

The actual position of expression satellite k is to the geometric distance at main difference station, Δ t _uThe true value of expression user timing results is separated Δ t _{U '}Actual the separating of expression user timing results;

It is Δ t that the true value of said user's timing results is separated for main difference station _u=0;

The actual of said user's timing results separated: star clock correction and the step 4 of utilizing step 2 to obtain multi-satellite obtain the ephemeris correction, and the four-dimensional user's positioning equation of substitution obtains the actual Δ t that separates of the timing results at main difference station _{U '}The actual Δ t that separates with the timing results at main difference station _{U '}As the star clock correction second time;

Step 6: Taking the first correction

and the second satellite clock corrections

Fixed satellite clock satellite clock error after timing.

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