CN101299063A - Method for correcting multiple constellation SBAS system time difference - Google Patents

Abstract

The present invention discloses a method for correcting the time-difference of a multiple-constellation SBAS system, and the method comprises the following steps: a step1, confirming a reference time system, confirming the number of the system time-difference required calculating by the SBAS according to the number of satellite navigation system; a step2, calculating the system time-difference between different satellite navigation system and the reference system; a step3, establishing a time-difference model of the multiple-constellation SBAS system and confirming the broadcast parameter; and a step 4, calculating the wholeness information of the system time-difference. The invention can settle the problem of time-difference resolving of the multiple-constellation SBAS system, and provide a broadcast parameter of the system time-difference and a method for calculating the wholeness information of the system time-difference.

Description

Method for correcting multiple constellation SBAS system time difference

Technical field

The invention belongs to the satellite navigation field, be based on system's time difference correcting method of many constellations satellite-based augmentation system (SBAS).

Background technology

SBAS is a kind of GEO of utilization provides the WAAS-Wide Area Augmentation System of GNSS differential correcting data and integrity information as communication link, and its target is to satisfy the navigational system demand of civil aviaton from the air route mission phase to the vertical guiding precision approach stage.Existing SBAS comprises the WAAS of the U.S., EGNOS, the SNAS of China, the MSAS of Japan and the GAGAN of India in Europe.

Existing SBAS is the distinct area system, only can provide differential correcting data and integrity information for the navigational system of self.Yet along with reaching its maturity of the modern continuous development of GPS, Galileo system and China's dipper system, many constellations satellite navigation system will become the main flow direction of satellite navigation technology.Therefore, in enhancement techniques field, satellite-based, many constellations satellite-based enhancement techniques will become the major subjects of future studies.

Many constellations satellite-based enhancement techniques can be brought significant benefits, for example, owing to can revise the increase of number of satellite, the geometric distributions of available star improves, make the GDOP value correspondingly reduce, further improve the bearing accuracy of all types of user and reduce integrity protection thresholding; Simultaneously, increasing of navigational system makes number of satellite be multiplied, therefore, the ionosphere delay grid is proofreaied and correct required effective sample number and is multiplied, correction accuracy improves, and makes integrity monitoring more accurate, thereby improves the continuity and the availability of system service.

Yet in many constellations SBAS, system's time difference will be present in as unknown term measures in the pseudorange, and the user equivalent range error that is brought by it is very huge.Therefore, resolve the key issue that system becomes the required solution of many constellations SBAS the time difference.After the system that finishes was resolved the time difference, system need set up accurately system's time difference model so that the user can revise the system's time difference in the pseudorange, thereby makes the accurate foundation of system's time difference model become the another key issue of many constellations satellite-based enhancement techniques.Meanwhile, SBAS also answers the control information of broadcast system time difference correction correspondence, and makes this error correcting information satisfy the integrity demand.

At present, still be in the starting stage about the research of many constellations satellite-based enhancement techniques, less about the research document of many constellations SBAS in the world, and most research is conceived to the raising of this technology to system performance, and the correct problems of the still not mentioned system time difference.

Summary of the invention

The invention provides a kind of method for correcting multiple constellation SBAS system time difference, problem is resolved the time difference by the system that this method can solve many constellations SBAS, and provides the mode of broadcasting of system's time difference and the computing method of the integrity information corresponding with system's time difference.

Method for correcting multiple constellation SBAS system time difference provided by the invention may further comprise the steps:

Step 1: determine system's reference time, determine the number of system's time difference of the required calculating of SBAS according to the satellite navigation system number; The number of the described system time difference subtracted one for the satellite navigation system number when reference time, system was identical with the time system of certain satellite navigation system, be the satellite navigation system number when reference time when system is not identical with the time system of arbitrary satellite navigation system;

Step 2: calculate the system's time difference between different satellite navigation systems and reference time system;

(a) calculate SBAS monitoring station receiver clock correction Δ t _{Ref, k}

${\mathrm{\Δt}}_{\mathrm{ref},k}=\frac{1}{\mathrm{cK}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\▿\mathrm{\Δ}{\mathrm{\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}+{\mathrm{\Δt}}_r,$

Wherein, c represents the light velocity, and K represents the number of satellite that base station k and clock synchronization station r look altogether, and K 〉=1, Δ t _rBe the receiver clock correction at clock synchronization station,

For all of base station k and clock synchronization station r are looked the measured value of satellite altogether;

(b) utilize the broadcast ephemeris error of monitoring station data computation correction satellite;

${\mathrm{\δR}}^{\mathrm{sv}}={\mathrm{\ΔR}}^{\mathrm{sv}}-\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}},$

Δ R wherein ^SvBe satellite ephemeris error,

Be satellite broadcasting ephemeris error estimated value;

(c) time difference Δ t of system between calculating navigational system and baseline system ^System

${\mathrm{\Δt}}^{\mathrm{system}}=\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{K}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right),$

Wherein N represents the number at clock synchronization station, and M represents the number of the correction satellite of certain satellite navigation system that the clock synchronization station observes, ${\mathrm{\Δ\ρ}}_k=\mathrm{\Δ}{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}-{\mathrm{\Δt}}_{\mathrm{ref}};$

Step 3: set up many constellations SBAS system time difference model and determine to broadcast parameter;

Step 4: the integrity information of the computing system time difference.

Step a: the error of fitting e of etching system time difference during calculating observation _SysT ^r(t),

$e_{\mathrm{sysT}}^r\left(t\right)={\mathrm{\Δt}}_{\mathrm{measure}}^{\mathrm{system}}-\mathrm{\Δ}{\hat{t}}_{\mathrm{est}}^{\mathrm{system}},$

Δ t in the formula _Measure ^SystemBe t system's time difference constantly,

Match value for system's time difference;

Step b: calculate the error sequence in upgrading at interval;

Step c: the statistics limit value of error of calculation sequence,

$E_{\mathrm{sysT}}^r=\left|{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r\right|+\mathrm{\κ}\left(\mathrm{Pr}\right)\·{\mathrm{\σ}}_{\mathrm{sysT}}^r$

In the formula, ${\stackrel{\‾}{e}}_{\mathrm{sysT}}^r=\frac{1}{S}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{e}_{\mathrm{sysT}}^r\left(t_i\right),$ ${\mathrm{\σ}}_{\mathrm{sysT}}^r=\sqrt{\frac{1}{S-1}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{[e_{\mathrm{sysT}}^r\left(t_i\right)-{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r]}^2},$ The fractile of κ (Pr) expression 99.9% fiducial probability correspondence;

Steps d: the absolute error of calculating updated time system's time difference

Step e: computing system TEC time error correction error STCE,

$\mathrm{STCE}={\hat{e}}_{\mathrm{sysT}}+\max \left\{E_{\mathrm{sysT}}^r\right\},$

In the formula, 1≤r≤N.

Method for correcting multiple constellation SBAS system time difference provided by the invention carries out accurate Calculation to many constellations SBAS system's time difference, has reduced user equivalent range error, has improved the bearing accuracy of many constellations SBAS system; Correcting method of the present invention provides the computing method of the integrity information of a kind of system time difference simultaneously, and this method has been eliminated the time difference influence of each time system and receiver time system, for the user provides accurate navigator fix integrity information.

Description of drawings

Fig. 1 represents many constellations SBAS time difference correcting method process flow diagram provided by the invention;

Fig. 2 represents the calculation flow chart of system's time difference among the present invention;

Fig. 3 represents the integrity information calculation flow chart of system's time difference among the present invention;

Fig. 4 represents estimated value and the actual value curve of the system's time difference between GPS that embodiment obtains and reference time system;

Fig. 5 represents the evaluated error curve of the system's time difference between GPS that embodiment obtains and reference time system;

Fig. 6 represents estimated value and the actual value curve of the system's time difference between Galileo system that embodiment obtains and reference time system;

Fig. 7 represents the evaluated error curve of the system's time difference between Galileo system that embodiment obtains and reference time system;

Fig. 8 represents system's TEC time error correction error and fit error curve between GPS that embodiment obtains and reference time system;

Fig. 9 represents system's TEC time error correction error and fit error curve between Galileo system that embodiment obtains and reference time system.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

The present invention is a kind of system's time difference correcting method based on many constellations SBAS, it can for the user provide between different satellite navigation systems and reference time system system's time difference and with corresponding integrity information of system's time difference.The flow process of described method specifically comprises the steps: as shown in Figure 1

Step 1: determine system's reference time, determine the number of system's time difference of the required calculating of SBAS according to the satellite navigation system number.

Suppose that the satellite navigation system number among many constellations SBAS is m, reference time, system was determined according to the time system of central station by SBAS.System's time difference of the required calculating of SBAS is the time difference between different satellite navigation system and reference time system, and difference divides following two kinds of situation analysis during the system of required calculating:

Situation one: reference time, system was identical with the time system of certain satellite navigation system

Because reference time, system only may be identical with the time system of a certain satellite navigation system, therefore, system's time difference number of required calculating for get rid of with system's reference time identical satellite navigation system after, the sum of other satellite navigation system, i.e. m-1.

Situation two: reference time system the time system with any satellite navigation system is not identical

When reference time, system was not identical with the time system of any satellite navigation system, SBAS need calculate the time difference between current all satellite navigation systems and reference time system.Therefore, system's time difference number of required calculating is m.

Step 2: calculate the system's time difference between different satellite navigation systems and reference time system

The flow process of this step as shown in Figure 2,

(1) calculates SBAS base station receiver clock correction Δ t _{Ref, k}

The moonscope pseudorange value ρ that satellite-based augmentation system base station receiver is measured _Ref ^SvCan be expressed from the next:

${\mathrm{\ρ}}_{\mathrm{ref}}^{\mathrm{sv}}=R_{\mathrm{ref}}^{\mathrm{sv}}+{\mathrm{c\Δt}}_{\mathrm{ref}}+d_{\mathrm{noise}}+d_{\mathrm{multipath}}+d_{\mathrm{iono}}+d_{\mathrm{tropo}}-{\mathrm{c\Δt}}^{\mathrm{sv}}+{\mathrm{c\Δt}}^{\mathrm{system}}---\left(1\right)$

In the formula (1), c represents the light velocity, R _Ref ^SvThe expression satellite is to the geometric distance of base station, Δ t _RefExpression base station receiver clock is with respect to the time deviation of system's reference time, d _NoiseThe error that expression receiver thermonoise causes, d _MultipathExpression multipath deviation, d _IonoThe expression ionosphere delay, d _TropoThe expression tropospheric delay, Δ t ^SvExpression satellite broadcasting clocking error, Δ t ^SystemSystem's time difference between expression satellite navigation system and reference time system, the situation a period of time in satisfying step 1, Δ t ^System=0.

The pre-service of base station observation pseudo range data process can weaken the influence of receiver thermonoise and multipath, can eliminate ionosphere and tropospheric delay simultaneously, can get formula (2):

${\mathrm{\Δ\ρ}}_{\mathrm{ref}}^{\mathrm{sv}}={\mathrm{\ρ}}_{\mathrm{ref}}^{\mathrm{sv}}-{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}$

(2)

$={\mathrm{\ΔR}}^{\mathrm{sv}}\·l_{\mathrm{ref}}^{\mathrm{sv}}+{\mathrm{c\Δt}}_{\mathrm{ref}}-{\mathrm{c\Δt}}^{\mathrm{sv}}+{\mathrm{c\Δt}}^{\mathrm{system}}+v_{\mathrm{ref}}^{\mathrm{sv}}$

In the formula (2), ${\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}=\sqrt{{(x^s-x_{\mathrm{ref}})}^2+{(y^s-y_{\mathrm{ref}})}^2+{(z^s-z_{\mathrm{ref}})}^2},$ (x ^s, y ^s, z ^s) expression satellite broadcasting ephemeris position, (x _Ref, y _Ref, z _Ref) expression base station position, Δ R ^Sv=(Δ x ^s, Δ y ^s, Δ z ^s) expression satellite broadcasting ephemeris error, l _Ref ^SvRepresent the direction vector of base station to satellite, $v_{\mathrm{ref}}^{\mathrm{sv}}={\mathrm{\δd}}_{\mathrm{noise}}+{\mathrm{\δd}}_{\mathrm{multipath}}+{\mathrm{\δd}}_{\mathrm{iono}}+{\mathrm{\δd}}_{\mathrm{tropo}},$ Wherein, δ d _NoiseExpression thermonoise residual error, δ d _MultipathExpression multipath residual error, δ d _IonoThe expression Ionosphere Residual Error, δ d _TropoExpression troposphere residual error.

In the clock synchronization station of SBAS, receiver clock and system clock maintenance reference time are synchronous, and therefore, its receiver clock correction is known terms.Choose the base station k that looks same satellite with clock synchronization station r altogether, look satellite altogether, utilize formula (2) to get for certain:

${\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}={\mathrm{\ΔR}}^{\mathrm{sv}}\·l_{\mathrm{ref},k}^{\mathrm{sv}}+\mathrm{c\Δ}{t}_{\mathrm{ref},k}-{\mathrm{c\Δt}}^{\mathrm{sv}}+{\mathrm{c\Δt}}^{\mathrm{system}}+v_{\mathrm{ref},k}^{\mathrm{sv}}---\left(3\right)$

${\mathrm{\Δ\ρ}}_r^{\mathrm{sv}}={\mathrm{\ΔR}}^{\mathrm{sv}}\·l_r^{\mathrm{sv}}+c{\mathrm{\Δt}}_r-{\mathrm{c\Δt}}^{\mathrm{sv}}+{\mathrm{c\Δt}}^{\mathrm{system}}+v_r^{\mathrm{sv}}---\left(4\right)$

Doing difference by formula (3) and (4) can get:

${\▿\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}={\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}-{\mathrm{\Δ\ρ}}_r^{\mathrm{sv}}$

(5)

$={\mathrm{\ΔR}}^{\mathrm{sv}}\·(l_{\mathrm{ref},k}^{\mathrm{sv}}-l_r^{\mathrm{sv}})+{\mathrm{c\Δt}}_{\mathrm{ref},k}-{\mathrm{c\Δt}}_r+{\mathrm{\ϵ}}_{\mathrm{ref},k}^{\mathrm{sv}}$

Formula (5) is called " single poor " equation.Formula (3) in (5), Δ ρ _{Ref, k} ^SvWith Δ _r ^SvThe measured value of representing base station k and clock synchronization station r respectively; l _{Ref, k} ^SvWith l _r ^SvRepresent base station k and clock synchronization station r direction vector respectively, Δ t to satellite _{Ref, k}With Δ t _rThe receiver clock correction of representing base station k and clock synchronization station r respectively, ${\mathrm{\ϵ}}_{\mathrm{ref},k}^{\mathrm{sv}}=v_{\mathrm{ref},k}^{\mathrm{sv}}-v_r^{\mathrm{sv}}.$

Under or the situation that the satellite broadcasting ephemeris error is less not far, all of base station k and clock synchronization station r are looked the measured value of satellite altogether in base station k and clock synchronization station r distance

Do statistical average, can get

${\mathrm{c\Δt}}_{\mathrm{ref},k}-{\mathrm{c\Δt}}_r=\frac{1}{K}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\▿\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}---\left(6\right)$

In the formula (6), K represents the number of satellite that base station k and clock synchronization station r look altogether, and K 〉=1, because the receiver clock correction Δ t at clock synchronization station _rBe known terms, therefore, the receiver clock correction Δ t of base station k _{Ref, k}Can calculate by following formula:

${\mathrm{\Δt}}_{\mathrm{ref},k}=\frac{1}{\mathrm{cK}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\▿\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}+{\mathrm{\Δt}}_r---\left(7\right)$

(2) calculate the satellite broadcasting ephemeris error

At first eliminate the receiver clock correction of base station k and clock synchronization station r, promptly exist

Middle (the Δ t that eliminates _{Ref, k}-Δ t _r), " single poor " equation (5) can turn to then:

${\▿\mathrm{\Δ\ρ}}_k^{\mathrm{sv}}={\▿\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}-c({\mathrm{\Δt}}_{\mathrm{ref},k}-{\mathrm{\Δt}}_r)$

(8)

$={\mathrm{\ΔR}}^{\mathrm{sv}}\·(l_{\mathrm{ref},k}^{\mathrm{sv}}-l_R^{\mathrm{sv}})+{\mathrm{\ϵ}}_{\mathrm{ref},k}^{\mathrm{sv}}$

Same satellite is chosen a plurality of " single poor " equation, resolve satellite broadcasting ephemeris error Δ R ^Sv, wherein, " single poor " equation number should be not less than 3, and the number of promptly treating as the base station of a satellite altogether is not less than 4, and claims this type of satellite for can revise satellite.Suppose that the satellite broadcasting ephemeris error estimated value of resolving out is $\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}}=(\mathrm{\Δ}{\tilde{x}}^s,\mathrm{\Δ}{\tilde{y}}^s,\mathrm{\Δ}{\tilde{z}}^s),$ The correction error δ R of satellite broadcasting ephemeris then ^SvCan be expressed as

${\mathrm{\δR}}^{\mathrm{sv}}={\mathrm{\ΔR}}^{\mathrm{sv}}-\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}}=({\mathrm{\Δx}}^s-\mathrm{\Δ}{\tilde{x}}^s,{\mathrm{\Δy}}^s-\mathrm{\Δ}{\tilde{y}}^s,{\mathrm{\Δz}}^s-\mathrm{\Δ}{\tilde{z}}^s)=(\mathrm{\δ}{\tilde{x}}^s,\mathrm{\δ}{\tilde{y}}^s,\mathrm{\δ}{\tilde{z}}^s)---\left(9\right)$

(3) calculate system's time difference between navigational system and reference time system

To satellite broadcasting ephemeris error Δ R ^SvAfter revising, can get by formula (2):

$\mathrm{\Δ}{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}={\mathrm{\ρ}}_{\mathrm{ref}}^{\mathrm{sv}}-{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}\_\mathrm{est}}^{\mathrm{sv}}$

(10)

$=\mathrm{\δ}{R}^{\mathrm{sv}}\·l_{\mathrm{ref}}^{\mathrm{sv}}+\mathrm{c\Δ}{t}_{\mathrm{ref}}-\mathrm{c\Δ}{t}^{\mathrm{sv}}+\mathrm{c\Δ}{t}^{\mathrm{system}}+v_{\mathrm{ref}}^{\mathrm{sv}}$

In the formula (10), ${\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}\_\mathrm{est}}^{\mathrm{sv}}=\sqrt{{({\tilde{x}}^s-x_{\mathrm{ref}})}^2+{({\tilde{y}}^s-y_{\mathrm{ref}})}^2+{({\tilde{z}}^s-z_{\mathrm{ref}})}^2},$ Expression is through the revised satellite position of ephemeris.

For obtaining system's time difference accurately, adopt the observation data at clock synchronization station, because the receiver clock correction Δ t at clock synchronization station _rKnown, formula (10) can be converted into:

${\mathrm{\Δ\ρ}}_k=\mathrm{\Δ}{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}-{\mathrm{c\Δt}}_{\mathrm{ref}}$

(11)

$={\mathrm{\δR}}^{\mathrm{sv}}\·l_{\mathrm{ref}}^{\mathrm{sv}}-{\mathrm{c\Δt}}^{\mathrm{sv}}+{\mathrm{c\Δt}}^{\mathrm{system}}+v_{\mathrm{ref}}^{\mathrm{sv}}$

In the formula (11), because δ R ^SvVery little and δ R ^SvEach component follow Gaussian distribution, the Δ t of different satellites ^SvThe symbol difference.Therefore, at same satellite navigation system, by the Δ ρ at clock synchronization station _kValue can this navigational system and the reference time system between the time difference Δ t of system ^System:

${\mathrm{\Δt}}^{\mathrm{system}}=\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{N}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right)---\left(12\right)$

In the formula (12), N represents the number at clock synchronization station, and M represents the number of the satellite revised of certain satellite navigation system that the clock synchronization station observes.

In like manner, can calculate system's time difference between other satellite navigation system and reference time system.

Step 3: the number of setting up many constellations SBAS system time difference model and determining to broadcast parameter

In many constellations SBAS, system's time difference can be described by system clock initial deviation, frequency departure and frequency drift, adopts following second order polynomial model to carry out match the time difference to system:

Δt ^system＝a ₀+a ₁·(t-t _oc)+a ₂·(t-t _oc) ² (13)

In the formula (13), a ₀Initial time deviation between expression satellite navigation system and reference time system; a ₁The frequency departure coefficient of expression clock; a ₂The frequency drift coefficient of expression clock, t represent that satellite-signal broadcasts constantly t _OcThe reference of expression system time difference corrected parameter constantly.

Hence one can see that, and the system's time difference between each satellite navigation system and reference time system need be broadcast 1 time parameter t _OcAnd 3 time difference model parameter a of system ₀, a ₁, a ₂Therefore, for the situation in the step 1 one, the required number of broadcasting parameter of SBAS is 3 (m-1)+1=3m-2; For the situation in the step 1 two, the number of broadcasting parameter is 3m+1.

Step 4: the integrity information of the computing system time difference

Because t _kSystem's time difference correction constantly will be applied in back one and upgrade the random time t (t of τ at interval _k＜t≤t _k+ τ) in, and its calculating is to finish in previous renewal at interval.Therefore, the integrity information-system's TEC time error correction error with system's time difference is divided into two parts consideration: the error variation in upgrading at interval and the correction error in the tk moment.Calculation process such as Fig. 3, specific as follows:

(1) the error of fitting e of etching system time difference during calculating observation _SysT ^r(t)

The satellite of the same constellation that clock synchronization station r can observe constantly according to t calculates the time difference Δ t of system in this moment _Measure ^SystemSimultaneously, system's time difference of utilizing system to broadcast is corrected the match value of calculation of parameter system's time difference

Therefore, the difference between the two is called error of fitting e _SysT ^r(t), that is:

$e_{\mathrm{sysT}}^r\left(t\right)={\mathrm{c\Δt}}_{\mathrm{measure}}^{\mathrm{system}}-\mathrm{c\Δ}{\hat{t}}_{\mathrm{est}}^{\mathrm{system}}---\left(14\right)$

(2) calculate the error sequence that upgrades in the interval

Suppose that the SBAS base station is t to the turnover rate of central station transmission data _Refresh(unit: second), the renewal of system's time difference correction is spaced apart τ (unit: second), then in upgrading at interval τ, can calculate S=τ/t according to the data of clock synchronization station r _RefreshIndividual e _SysT ^r(t) as a grouping error sequence.

(3) the statistics limit value of error of calculation sequence

Upgrade in the τ of interval at one, calculate the error sequence statistics limit value of clock synchronization station r, promptly

$E_{\mathrm{sysT}}^r=\left|{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r\right|+\mathrm{\κ}\left(\mathrm{Pr}\right)\·{\mathrm{\σ}}_{\mathrm{sysT}}^r---\left(15\right)$

In the formula (15), ${\stackrel{\‾}{e}}_{\mathrm{sysT}}^r=\frac{1}{S}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{e}_{\mathrm{sysT}}^r\left(t_i\right),$ ${\mathrm{\σ}}_{\mathrm{sysT}}^r=\sqrt{\frac{1}{S-1}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{[e_{\mathrm{sysT}}^r\left(t_i\right)-{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r]}^2},$ The fractile of κ (Pr) expression 99.9% fiducial probability correspondence.

(4) absolute error of calculating updated time system's time difference

At t _kConstantly, the absolute error of system's time difference

For:

${\hat{e}}_{\mathrm{sysT}}=c\·|\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{N}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right)-[a_0+a_1\·(t_k-t_{\mathrm{oc}})+a_2\·{(t_k-t_{\mathrm{oc}})}^2\left]\right|---\left(16\right)$

In the formula (16), Δ ρ _kThe same step 2 of represented implication, a ₀, a ₁With a ₂System's time difference correction parameter of representing system broadcasts respectively, t _OcThe reference of expression system time difference corrected parameter constantly.

(5) computing system TEC time error correction error STCE

In the next one upgraded at interval, making the maximal value of the error sequence statistics limit value at all clock synchronization stations was max{E _SysT ^r, but system's TEC time error correction error STCE through type (17) calculates:

$\mathrm{STCE}={\hat{e}}_{\mathrm{sysT}}+\max \left\{E_{\mathrm{sysT}}^r\right\}---\left(17\right)$

In the formula (17), 1≤r≤N.The error of fitting of system's time difference in STCE can upgrade at interval so that 99.9% probability envelope is next.

Utilize method provided by the invention, following specific embodiment arranged:

Embodiment: utilize satellite-based augmentation system-SNAS monitoring gps satellite and the Galileo satellite of China, choose 30 base stations and constitute the SNAS monitoring network, 5 clock synchronization stations are wherein arranged, simulation time is 2400 seconds.Reference time, system was the Big Dipper time system that SNAS follows, and SNAS will provide the integrity information that system's time difference correction between GPS, Galileo system and baseline system and system's time difference correct for user in the service area.

Step 1: determine system's reference time, determine the number of system's time difference of the required calculating of SBAS according to the satellite navigation system number.

Determine that reference time, system was the time system of the Big Dipper, it is 2 that satellite navigation system is counted m, is respectively GPS and Galileo system.Because GPS, Galileo time system and reference time system all inconsistent, therefore, according to circumstances two as can be known, difference is 2 during the system of required calculating, is respectively the system's time difference between GPS, Galileo system and reference time system.

Step 2: calculate the system's time difference between different satellite navigation systems and reference time system.

(1) calculates SBAS base station receiver clock correction At _{Ref, k}

In emulation, during t=1500s, calculate SNAS base station k (1≤k≤25) and look number of satellite K altogether apart from its nearest clock synchronization station r (1≤r≤5).According to formula (7), can get the receiver clock correction Δ t of base station k _{Ref, k}:

${\mathrm{\Δt}}_{\mathrm{ref},k}=\frac{1}{\mathrm{cK}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{\▿\mathrm{\Δ\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}+{\mathrm{\Δt}}_r$

(2) calculate the satellite broadcasting ephemeris error

SBAS only can provide the differential correcting data of ephemeris for revising satellite.During t=1500s, can revise the satellite number and be: 20, can revise satellite and look every the base station number that can revise star altogether as shown in table 1.

Table 1 can be revised satellite and look every the base station number that can revise satellite altogether

Can revise satellite	A2	B1	B2	C1	C2	D3	E1	E2	E4	G2
											The base station number	30	30	27	30	21	30	14	27	8	20
Can revise satellite	G3	G4	G5	G10	G11	G17	G18	G21	G22	G23
											The base station number	30	30	25	30	30	12	30	14	25	12

A2, B1, B2, C 1, C2, D3, E1, E2, E4 represent the satellite revised of GPS in the table 1, and G2, G3, G4, G5, G10, G11, G17, G18, G21, G22, G23 represent the satellite revised of Galileo system.The base station data of a satellite are treated as in utilization altogether, resolve satellite broadcasting ephemeris error estimated value according to formula (8) and are $\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}}=(\mathrm{\Δ}{\tilde{x}}^s,\mathrm{\Δ}{\tilde{y}}^s,\mathrm{\Δ}{\tilde{z}}^s),$ Thereby the broadcast ephemeris that can revise satellite is revised.

(3) the system's time difference between calculating navigational system and baseline system

The satellite the revised number that clock synchronization station r (1≤r≤5) observes is as shown in table 2.

The number of satellite revised that table 2 clock synchronization station observes

According to ${\mathrm{\Δt}}^{\mathrm{system}}=\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{N}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right),$ N represents the number at clock synchronization station, and M represents to revise number of satellite, can get the system's time difference between GPS, Galileo system and baseline system thus, and is as shown in table 3.

System's time difference between table 3 GPS, Galileo system and baseline system (unit: meter)

System's time difference	Calculated value	Actual value	Difference
				GPS and baseline system	17.7121	18.0921	-0.3800
Galileo and baseline system	16.7299	17.0287	-0.2988

Step 3: set up many constellations SBAS system time difference model and determine to broadcast parameter

Choose with reference to moment t _Oc=1500s is according to second order polynomial model Δ t ^System=a ₀+ a ₁(t-t _Oc)+a ₂(t-t _Oc) ²The calculated value of system's time difference in the last time interval of match, the system that obtains between GPS, Galileo system and baseline system broadcasts parameter the time difference, and is as shown in table 4.

System between table 4 GPS, Galileo system and baseline system broadcasts parameter the time difference

As shown in table 4 since reference time system and gps time system, Galileo time system all inequality, therefore, the required number of parameters of broadcasting is 3m+1=3 * 2+1=7.

Step 4: the integrity information of the computing system time difference

(1) error of fitting of etching system time difference during calculating observation

The number of satellite revised that clock synchronization station r (1≤r≤5) observes when t=1500s is as shown in table 2.Data according to clock synchronization station r can calculate the t gps system time difference constantly:

${\mathrm{\Δt}}_r^{\mathrm{GPS}-\mathrm{BD}}=\frac{1}{\mathrm{cK}}\underset{l=1}{\overset{K}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_l$

Wherein, K represents to revise the gps satellite number.Simultaneously, utilize system's time difference correction parameter of system broadcasts can get the match value of the gps system time difference:

$\mathrm{\Δ}{\hat{t}}^{\mathrm{GPS}-\mathrm{BD}}=a_0+a_1\·(t-t_{\mathrm{oc}})+a_2\·{(t-t_{\mathrm{oc}})}^2$

The two subtracts each other can get error of fitting:

$e_{\mathrm{sysTGPS}}^r\left(t\right)={\mathrm{c\Δt}}_r^{\mathrm{GPS}-\mathrm{BD}}-\mathrm{c\Δ}{\hat{t}}^{\mathrm{GPS}-\mathrm{BD}}$

In like manner, can calculate the error of fitting of the Galileo system time difference.

(2) calculate the error sequence that upgrades in the interval

Setting the SNAS base station is 6s to the turnover rate of central station transmission data, and the renewal of system's time difference correction τ at interval is 60s, and then in last one upgraded at interval, clock synchronization station r can calculate 10 e _SysT ^r(t _x) (1≤x≤10) as a grouping error sequence, the error sequence value is shown in table 5,6.

The GPS error sequence value at table 5 clock synchronization station (unit: rice)

The Galileo error sequence value at table 6 clock synchronization station (unit: rice)

(3) the statistics limit value of error of calculation sequence

In this upgrades at interval, according to formula $E_{\mathrm{sysT}}^r=\left|{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r\right|+\mathrm{\κ}\left(\mathrm{Pr}\right)\·{\mathrm{\σ}}_{\mathrm{sysT}}^r$ Calculate the statistics limit value of each clock synchronization station error sequence; The error of fitting of system's time difference in can upgrading at interval so that 99.9% probability envelope is next according to STCE is tabled look-up and is determined that fractile κ (Pr) value is 3.29, error sequence statistics limit value result of calculation such as table 7.

The error sequence statistics limit value (unit: rice) at table 7 clock synchronization station

(4) absolute error of calculating updated time system's time difference

System's time difference absolute error when calculating updated time t=1500s according to formula (16) is as shown in table 8.

Table 8 system time difference absolute error (unit: rice)

(5) computing system TEC time error correction error

As shown in Table 7, the maximal value of the error sequence of GPS that the clock synchronization station obtains and Galileo system statistics limit value is respectively 2.4196 and 2.0872, according to $\mathrm{STCE}={\hat{e}}_{\mathrm{sysT}}+\max \left\{E_{\mathrm{sysT}}^r\right\}$ Computing system TEC time error correction error, result will be applied in next the renewal in the interval (1500,1560), and the result is as shown in table 9.

Table 9 system TEC time error correction error (STCE) (unit: rice)

GPS in the simulation time section and the estimated value of the system's time difference between baseline system and actual value as shown in Figure 4, evaluated error is as shown in Figure 5.The estimated value of system's time difference between Galileo and baseline system and actual value as shown in Figure 6, evaluated error is as shown in Figure 7.By Fig. 4 to Fig. 7 as can be known, system's time difference between GPS and dipper system estimates that the mistake value is (in the scope of 1m～0.8m), system's time difference evaluated error between Galileo and dipper system is (in the scope of 0.6m～0.6m), as seen, utilize correcting method provided by the invention can accurately calculate system's time difference between navigational system and reference time system.

System's TEC time error correction error and error of fitting are shown in Fig. 8,9 between GPS, Galileo system and baseline system.By Fig. 8,9 as can be known, the error of fitting of the system's time difference in the GPS, the Galileo that calculate of each updated time and the system's TEC time error correction error between dipper system can envelope is next be upgraded at interval.Hence one can see that, uses method provided by the invention and can obtain system's time difference integrity information accurately.

Claims (3)

1, a kind of method for correcting multiple constellation SBAS system time difference is characterized in that, comprises the steps:

Step 1: determine system's reference time, determine the number of system's time difference of the required calculating of SBAS according to the satellite navigation system number; The number of the described system time difference subtracted one for the satellite navigation system number when reference time, system was identical with the time system of certain satellite navigation system, be the satellite navigation system number when reference time when system is not identical with the time system of arbitrary satellite navigation system;

Step 2: calculate the system's time difference between different satellite navigation systems and baseline system;

(a) calculate SBAS monitoring station receiver clock correction Δ t _{Ref, k}

${\mathrm{\Δt}}_{\mathrm{ref},k}=\frac{1}{\mathrm{cK}}\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\▿\mathrm{\Δ}{\mathrm{\ρ}}_{\mathrm{ref},k}^{\mathrm{sv}}+\mathrm{\Δ}{t}_r,$

Wherein, c represents the light velocity, and K represents the number of satellite that base station k and clock synchronization station r look altogether, and K 〉=1, Δ t _rBe the receiver clock correction at clock synchronization station,

For all of base station k and clock synchronization station r are looked the measured value of satellite altogether;

(b) calculate the satellite broadcasting ephemeris error; Suppose that the satellite broadcasting ephemeris error estimated value of being resolved out by single eikonal equation is $\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}}=(\mathrm{\Δ}{\tilde{x}}^s,\mathrm{\Δ}{\tilde{y}}^s,\mathrm{\Δ}{\tilde{z}}^s),$ The correction error δ R of satellite broadcasting ephemeris then ^SvFor:

${\mathrm{\δR}}^{\mathrm{sv}}={\mathrm{\ΔR}}^{\mathrm{sv}}-\mathrm{\Δ}{\tilde{R}}^{\mathrm{sv}},$

Δ R wherein ^SvBe satellite ephemeris error;

(c) calculate the time difference Δ t of system between navigational system and reference time system ^System

${\mathrm{\Δt}}^{\mathrm{system}}=\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{N}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right),$

Wherein N represents the number at clock synchronization station, and M represents the number of the correction satellite of certain satellite navigation system that the clock synchronization station observes, ${\mathrm{\Δ\ρ}}_k=\mathrm{\Δ}{\widetilde{\mathrm{\ρ}}}_{\mathrm{ref}}^{\mathrm{sv}}-{\mathrm{\Δt}}_{\mathrm{ref}};$

Step 3: the number of setting up many constellations SBAS system time difference model and determining to broadcast parameter;

Step 4: the integrity information of the computing system time difference;

Step a: the error of fitting e of etching system time difference during calculating observation _SysT ^r(t),

$e_{\mathrm{sysT}}^r\left(t\right)=\mathrm{c\Δ}{t}_{\mathrm{measure}}^{\mathrm{system}}-\mathrm{c\Δ}{\hat{t}}_{\mathrm{est}}^{\mathrm{system}},$

Δ t in the formula _Measure ^SystemThe estimated value of the etching system time difference during for each clock synchronization station t, Match value for system's time difference;

Step b: calculate the error sequence in upgrading at interval; Described error sequence is meant in upgrading at interval τ, the S=τ/t that goes out according to the data computation of clock synchronization station r _RefreshIndividual e _SysT ^r(t);

Step c: the statistics limit value of error of calculation sequence,

$E_{\mathrm{sysT}}^r=\left|{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r\right|+\mathrm{\κ}\left(\mathrm{Pr}\right)\·{\mathrm{\σ}}_{\mathrm{sysT}}^r$

In the formula, ${\stackrel{\‾}{e}}_{\mathrm{sysT}}^r=\frac{1}{S}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{e}_{\mathrm{sysT}}^r\left(t_i\right),$ ${\mathrm{\σ}}_{\mathrm{sysT}}^r=\sqrt{\frac{1}{S-1}\underset{i=1}{\overset{S}{\mathrm{\Σ}}}{[e_{\mathrm{sysT}}^r\left(t_i\right)-{\stackrel{\‾}{e}}_{\mathrm{sysT}}^r]}^2},$ The fractile of κ (Pr) expression 99.9% fiducial probability correspondence;

Steps d: the absolute error of calculating updated time system's time difference

${\hat{e}}_{\mathrm{sysT}}=c\·|\frac{1}{\mathrm{cN}}\underset{r=1}{\overset{N}{\mathrm{\Σ}}}\left(\frac{1}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\Δ\ρ}}_k\right)-[a_0+a_1\·(t_k-t_{\mathrm{oc}})+a_2\·{(t_k-t_{\mathrm{oc}})}^2\left]\right|,$

In the formula, a ₀, a ₁With a ₂System's time difference correction parameter of representing system broadcasts respectively, t _OcThe reference of expression system time difference corrected parameter constantly;

Step e: computing system TEC time error correction error STCE,

$\mathrm{STCE}={\hat{e}}_{\mathrm{sysT}}+\max \left\{E_{\mathrm{sysT}}^r\right\},$

In the formula, 1≤r≤N, max{E _SysT ^rIt is the maximal value of the error sequence statistics limit value at all clock synchronization stations.

2, method for correcting multiple constellation SBAS system time difference according to claim 1 is characterized in that, the described system of step 3 time difference model is

Δt ^system＝a ₀+a ₁·(t-t _oc)+a ₂·(t-t _oc) ²

In the formula, a ₀Initial time deviation between expression satellite navigation system and reference time system; a ₁The frequency departure coefficient of expression clock; a ₂The frequency drift coefficient of expression clock, t represent that satellite-signal broadcasts constantly t _OcThe reference of expression system time difference corrected parameter constantly.

3, method for correcting multiple constellation SBAS system time difference according to claim 1 is characterized in that, the number that step 3 is described broadcasts parameter is 3 (m-1)+1=3m-2 when reference time when system is identical with the time system of certain satellite navigation system; Is 3m+1 when reference time when system is not identical with the time system of arbitrary satellite navigation system.

Images