CN103197326B - Multi-constellation single base station receiver clock difference estimation method - Google Patents

Abstract

The invention discloses a multi-constellation single base station receiver clock difference estimation method. When multi-constellation data are in fusion process, positions of satellites when signals are emitted cannot be accurately confirmed due to different receiver clock differences among different constellations and the effect of delaying of signal propagation, error terms which are related to the satellite speed and caused by receiver clock differences still can cause changing of errors and affect an actual positioning effect, wherein the maximum error can reach 1m. In the calculation of the positions of the satellites, the receiver clock differences are estimated, the time delaying of the signal propagation is corrected, the receiver clock differences are resolved through a Kalman filtering method, and accordingly the method is practical and can obtain accurate geometrical distance between receivers with corrected receiver clock differences and the satellites. The method can reduce the effect of the receiver clock differences which are related to the satellite speed to a submillimeter level, is suitable for a receiver with clock jumping being one millisecond, and achieves high-accuracy positioning of the multi-constellation fusion.

Description

A kind of single base station receiver clock bias estimation method of many constellations

Technical field

The present invention relates to satnav field, relate in particular to single base station receiver clock bias estimation method of many constellations.

Background technology

GNSS network differential location technology is the hot technology in current satnav field, be widely used in the industries such as mapping and survey of territorial resources, with virtual reference station (VirtualReferenceStation, VRS) the network differential technology that technology is representative is risen, and making to set up reference station formula GPS service system becomes the recent tendency of Current GPS technology application development.VRS technology is as the GPS real-time dynamic positioning technology under many base stations environment, it is the network RTK location technology that integrates Internet technology, wireless communication technique, computer networking technology and GPS technology, also be current application the most extensively, the most successful representative high-tech achievement, VRS technical system has represented the developing direction of location technology of new generation after conventional RTK.

The basic skills of VRS technological orientation is: each reference station continuous acquisition observation data, be real-time transmitted to the database of data processing and control center, and carry out network calculations; The ambiguity of carrier phase value of each individual baseline in the online resolution GPS of control center Reference network; Data processing centre (DPC) utilizes Reference network carrier phase observation data to calculate the two poor composition error on every baseline, and sets up accordingly the spatial parameter model of Range-based error; Movement station user will locate the NMEA(NationalMarineElectronicsAssociation obtaining by single-point, American National maritime affairs Institution of Electronics) rough coordinates of form sends to control center, and control center creates a virtual reference station at this coordinate position; Control center, according to the relative geometrical relation of reference station, user and gps satellite, obtains the space correlation error between movement station and reference station by interpolation computation model, then generates the dummy observation at VRS place according to dummy observation computation model; Control center sends to movement station user using dummy observation as network differential correcting information; User's movement station receives network differential information and VRS forms short baseline, carries out difference resolve by conventional RTK computation model, determines customer location, realizes and fixes and obtain real-time centimetre-sized positioning precision fast, as shown in Figure 1.

In conventional two differential mode types, the receiver clock correction item relevant with the light velocity of each website is eliminated by the mode of difference between satellites in the time building two difference, ignored the impact of the receiver clock correction item relevant with satellite velocities on observation equation.In data handling procedure, for the more stable receiver changing in 1 microsecond of clock, only exist and be less than the error of 1 millimeter and ignore its impact with respect to raw observation.But due to the difference of the designed receiver clock of each manufacturer, part receiver exist larger receiver clock correction even some receiver occur 1ms clock jump, the clock correction value relevant with satellite velocities can maximumly produce and approach the error effect of 1 meter on the geometric distance calculating, and can not be eliminated or weaken in two differences.Therefore, need accurately to estimate each receiver clock correction, the geometric distance of revising between satellite and receiver has obtained correct positioning result.

Summary of the invention

The inventive method receives and launches from signal satellite and the receiver clock correction angle that the clock face moment causes, analyze the generation reason of various constellations different receivers clock correction, the error formula of the receiver clock correction item of having derived in detail relevant with the light velocity and satellite velocities on raw observation impact, a kind of receiver clock correction of estimating in satellite position calculation has been proposed, the practical approach of corrected signal propagation delay, the method can effectively be estimated each constellation receiver clock correction value, and be applicable to exist larger receiver clock correction to utilize the method accurate Calculation unified each constellation coordinate of the satellite position, and carry out comparison correction effect by checking respective satellite and receiver geometric distance variable quantity.The impact of the receiver clock correction item relevant with satellite velocities is attenuated to submillimeter level, and is applicable to the receiver that exists 1 millisecond of clock to jump, and realizes the hi-Fix that many constellations merge.

Technical scheme of the present invention is:

Many constellations clock correction is analyzed:

For receiver moment t _kreceive satellite emission signal, this moment receiver clock correction is δ _k, t during with respect to GPS:

t=t _k-δ _k

The station star distance of this t moment receiver and satellite can be expressed as

${\mathrm{\ρ}}_k^i=\mathrm{c\τ}$

$=|r_k\left(t\right)-r^i(t-\mathrm{\τ})|$

Wherein c is the light velocity, and τ is signal propagation time, r _k(t) the receiver vector position while being signal reception time t, r ⁱsatellite vector position when (t-τ) is signal x time t-τ, r ⁱ(t-τ) can be expressed as again:

$r^i(t-\mathrm{\τ})=r^i\left(t\right)-{\stackrel{\·}{r}}^i\left(t\right)\mathrm{\τ}$

Utilize above-mentioned formula, we can solve signal propagation time τ:

$(c^2-{\stackrel{\·}{r}}^i\left(t\right)\·{\stackrel{\·}{r}}^i\left(t\right)){\mathrm{\τ}}^2-2{\stackrel{\·}{r}}^i\left(t\right)(r_k\left(t\right)-r^i\left(t\right))\mathrm{\τ}$

$-(r_k\left(t\right)\·r_k\left(t\right)-2r_k\left(t\right)\·r^i\left(t\right)+r^i\left(t\right)\·r^i\left(t\right))=0$

For many constellation systems, various constellations system the clock error correction value of corresponding master station not identical, between each system, corrected value precision is to be determined by each master station clock accuracy, separate.For the satellite of same constellation, itself and receiver clock correction can be merged to estimation, and for many constellations, each constellation should have its independent receiver clock correction value and estimate its precision.So the receiver clock correction value of each constellation is actual be here:

${\mathrm{\δt}}_k=\mathrm{\δ}{\hat{t}}_k+\mathrm{\δ}{t}_{G/R/C/E}^i$

Here refer to the clock error correction value of various constellations (corresponding to GPS, GLONASS, the Big Dipper, GALILEO) master station, for the corrected value of the clock of receiver own.

Kalman filtering method is estimated receiver clock correction:

1) adopt satellite pseudorange guestimate satellite-signal transmission time τ ₀=P/c; Suppose initial receiver clock correction δ t _kbe 0, utilize initial observation epoch and signal transmission time τ ₀obtain the instantaneous coordinate (X of satellite ⁱ, Y ⁱ, Z ⁱ) and initial satellite clock correction correction δ t ⁱ ₀, due in regional reference station network network (moving continuously satnav service colligate system, ContinuousOperational ReferenceSystem, CORS), base station coordinates is known, can calculate the geometric distance of initial satellite position and receiver , and recalculate signal transmission time .

${\mathrm{\ρ}}_k^i=\sqrt{{(X^i-X_k)}^2+{(Y^i-Y_k)}^2+{(Z^i-Z_k)}^2}$

${\mathrm{\τ}}_k^i=\frac{1}{c}{\mathrm{\ρ}}_k^i$

2) build receiver clock bias estimation equation, solve various constellations receiver clock correction value separately single epoch, and wherein n is the population of satellite, δ t _k(G), δ t _k(R), δ t _k(C), δ t _k(E) be respectively the corresponding receiver clock correction value of GPS, GLONASS, the Big Dipper, GALILEO, δ t ⁱrepresent the initial satellite clock correction correction of corresponding satellite

BX=L

For CORS base station, because its coordinate is known, only need to estimate receiver clock correction, can estimate by list least square epoch, for its coordinate the unknown of rover station, still need to set it as unknown parameter, build Kalman filter and solve:

X ^T=[δX,δY,δZ,δt _k(G),δt _k(R),δt _k(C),δt _k(E)]

Wherein, δ X, δ Y, δ Z is base station coordinate correction value, δ t _k(G), δ t _k(R), δ t _k(C), δ t _k(E) be respectively the corresponding receiver clock correction value of GPS, GLONASS, the Big Dipper, GALILEO, n is the population of satellite, for coefficient after equation linearization.

Use experience model is determined observed reading weight and initial parameter value, if receiver does not exist clock to jump, can adopt white noise to carry out the variation of analog receiver clock correction, for the receiver that exists clock to jump, sets corresponding receiver clock correction dynamic noise matrix and is , σ _t=3.0e5, unit is rice, jumps and is caused pseudorange maximum changing value by 1ms clock.

3) utilize the receiver clock correction value that second step obtains to calculate corresponding moment satellite position, obtains accurate receiver and the satellite geometry distance of corrected received machine clock correction.

In the computation process of above-mentioned satellite position and receiver clock correction, also need to consider the impact of earth rotation and relativistic effect, and the relevant atmosphere convection layer of modelling and ionosphere delay error item, to obtain correct receiver clock correction and satellite position information.

Advantage of the present invention and beneficial effect:

Many constellations reference station satellite clock correction method of estimation, from signal receives and the transmitting clock face moment causes satellite and receiver clock correction angle, analyze the generation reason of various constellations different receivers clock correction, the error formula of the receiver clock correction item of having derived in detail relevant with the light velocity and satellite velocities on raw observation impact, and the difference of having compared different vendor's receiver clock, a kind of receiver clock correction of estimating in satellite position calculation has been proposed, the practical approach of corrected signal propagation delay, the method can effectively be estimated each constellation receiver clock correction value, and be applicable to exist larger receiver clock correction to utilize the method accurate Calculation unified each constellation coordinate of the satellite position, and carry out comparison correction effect by checking respective satellite and receiver geometric distance variable quantity.Analyze by a large amount of measured datas, by revising accurate satellite position, can calculate correct many constellations blur level result and relevant atmosphere delay error.Show with the experiment of Big Dipper laboratory reference station data based on the GPS of Southeast China University: the impact of the receiver clock correction item relevant with satellite velocities is attenuated to submillimeter level by the method, and be applicable to the receiver that exists 1 millisecond of clock to jump, realize the hi-Fix that many constellations merge.

Brief description of the drawings

Fig. 1 is VRS and Reference network graph of a relation;

Fig. 2 is the each base station receiver GPS of baseline LIXI-JLHU clock correction;

Fig. 3 is the each base station receiver Big Dipper of baseline LIXI-JLHU clock correction;

Fig. 4 is that baseline LIXI-JLH satellite carrier changes (G19 satellite) with station star apart from difference;

Fig. 5 is that baseline LIXI-JLH satellite carrier changes (C06 satellite) with station star apart from difference;

Fig. 6 is that the two poor atmosphere errors that add clock correction correction of baseline LIXI-JLH satellite postpone;

Fig. 7 is that the two poor atmosphere errors that do not add clock correction correction of baseline LIXI-JLH satellite postpone;

Fig. 8 is certain brand three system receiver receiver clock correction;

Fig. 9 is IGSHofn website receiver GPS clock correction;

Figure 10 is IGSHofn website receiver Big Dipper clock correction;

Figure 11 is that IGSohi2 website is received machine GPS clock correction;

Figure 12 is IGSwuhn website receiver GPS clock correction.

Embodiment

Adopt one group of GPS of Southeast China University and Big Dipper laboratory reference station data, comprise Big Dipper double frequency B1, B2 carrier wave pseudorange observation data, the L1 of GPS, L2 carrier wave pseudorange observation data, the gift west wing LIXI of Southeast China University binary-star system (GPS and the Big Dipper) reference station and lake, Kowloon JLHU binary-star system reference station are selected in laboratory reference station, and base length is 19.7km, receiver model is and the logical U240 of core star that data sampling is spaced apart 1 second.Fig. 2 is two website receiver GPS clock correction values, Fig. 3 is two website receiver Big Dipper clock correction values, wherein LIXI website is jumped at the 3522nd receiver clock that occurs 1 millisecond epoch, and the generation that clock is jumped is caused by receiver itself, therefore the clock correction value of GPS and the Big Dipper produces and jumps at synchronization.

For double difference observation, the carrier wave of two differences and station star distance difference reflects be fixing blur level and two poor tropospheric delay and two poor ionospheric delay values, wherein the less variation of length of delay in short baseline of rear two atmosphere errors is slow, can ignore that it is right impact.

$\mathrm{\Δ}\▿(\mathrm{\λ\φ}-\mathrm{\ρ})=\mathrm{\Δ}\▿N+\mathrm{\Δ}\▿T-\mathrm{\Δ}\▿I$

Utilize said method, relatively the two poor carrier waves of this baseline and station star distance difference change, analysis receiver clock is jumped the impact on double difference observation.The results are shown in Figure 4,5.Fig. 4 is that the two differences of GPS19 satellite change, and Fig. 5 is that the two differences of Big Dipper C06 satellite change.

In upper figure, elevation of satellite is less, the station star that its product of being jumped by radial velocity and receiver clock causes is larger apart from error hop value, simultaneously, utilize the method for correction mentioned in this article station star distance, can effectively solve the error that receiver clock correction causes station star distance, to obtain the correct blur level result of baseline.

In network RTK (Real-TimeKinematic, real-time dynamic positioning), utilize the exact position of website to generate in real time two poor troposphere, the ionosphere delay of each baseline.After the two poor blur leveles of fixed base, adopt without geometric model and estimate ionospheric delay values, clock relevant to satellite velocities jumped the saltus step that can not cause ionosphere delay, and for two poor tropospheric delay value, adopt without ionosphere combination and obtain accurately two poor tropospheric delay value, now the receiver clock correction error relevant with satellite velocities can affect on causing the saltus step of tropospheric delay value the generation of atmosphere errors, as shown in Figure 6,7.

In Fig. 6,7, do not consider that the receiver clock correction relevant with satellite velocities can obtain wrong tropospheric delay value and jump the moment at clock causing the saltus step of tropospheric delay value, ionospheric delay values adopts and calculates without geometric model, used herein is that correct blur level result is calculated the ionospheric delay values on L1, L2, it should be noted that, do not consider the correction of receiver clock correction, clock is jumped the moment and can be caused satellite ambiguity resolution result incorrect and affect the correct generation of ionospheric delay values.

Receiver clock jumping meeting is to producing the error (relevant with elevation of satellite) that approaches 1 meter on geometric distance between satellite and receiver, this part error can not be eliminated in two differences, and affect the fixing and difference positioning precision of blur level.Method of estimation to many constellations satellite clock correction in this paper, can effectively determine satellite orbital position and estimate the geometric distance between satellite and receiver, solve receiver clock and jump the impact on data processing, the time reference of each constellation in unified many constellations data anastomosing algorithm, has engineering significance simultaneously.

The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make the some improvements and modifications that can expect, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (1)

1. the list of constellation more than a base station receiver clock bias estimation method, comprises the following steps:

(1), each base station continuous acquisition observation data, and be real-time transmitted to central server to receive each base station Satellite Observations, described each base station Satellite Observations comprises satellite L1, L2 carrier phase observation data and P1, P2 pseudorange observation information, and carry out real time data pre-service, described pre-service comprises gross error and cycle slip detection;

(2), adopt receiver to observe the satellite pseudorange guestimate satellite-signal transmission time τ obtaining ₀=P/c; Suppose initial receiver clock correction δ t _kbe 0, utilize initial observation epoch and signal transmission time τ ₀obtain the instantaneous coordinate (X of satellite ⁱ, Y ⁱ, Z ⁱ) and the initial satellite clock correction correction δ t that utilizes ephemeris file to obtain ⁱ ₀, due in regional reference station network network, base station coordinates is known, can calculate the geometric distance of initial satellite position and receiver and recalculate signal transmission time wherein P is actual measurement Pseudo-range Observations, and c is light velocity value,

${\mathrm{\ρ}}_k^i=\sqrt{{(X^i-X_k)}^2+{(Y^i-Y_k)}^2+{(Z^i-Z_k)}^2}$

${\mathrm{\τ}}_k^i=\frac{1}{c}{\mathrm{\ρ}}_k^i$

(3), build receiver clock bias estimation equation, solve various constellations receiver clock correction value separately single epoch, wherein n is the population of satellite, δ t _k(G), δ t _k(R), δ t _k(C), δ t _k(E) be respectively the corresponding receiver clock correction value of GPS, GLONASS, the Big Dipper, GALILEO, δ t ⁱrepresent the initial satellite clock correction correction of the corresponding satellite of institute, ε is for comprising tropospheric delay, ionosphere delay and be correlated with not modeled residual error item, noise item,

BX＝L

For continuous operation satnav service colligate system CORS base station, because its coordinate is known, only need to estimate receiver clock correction, can estimate by list least square epoch, for its coordinate the unknown of rover station, still need to set it as unknown parameter, build Kalman filter and solve:

X ^T＝[δX,δY,δZ,δt _k(G),δt _k(R),δt _k(C),δt _k(E)]

Wherein, δ X, δ Y, δ Z is base station coordinate correction value, δ t _k(G), δ t _k(R), δ t _k(C), δ t _k(E) be respectively the corresponding receiver clock correction value of GPS, GLONASS, the Big Dipper, GALILEO, n is the population of satellite, for coefficient after equation linearization;

Use experience model is determined observed reading weight and initial parameter value, if receiver does not exist clock to jump, can adopt white noise to carry out the variation of analog receiver clock correction, for the receiver that exists clock to jump, sets corresponding receiver clock correction dynamic noise matrix and is σ _t=3.0e5, unit is rice, jumps and is caused pseudorange maximum changing value by 1ms clock;

(4), utilize the receiver clock correction value that second step obtains to calculate corresponding moment satellite position, obtains accurate receiver and the satellite geometry distance of corrected received machine clock correction,

In the computation process of above-mentioned satellite position and receiver clock correction, also need to consider the impact of earth rotation and relativistic effect, and the relevant atmosphere convection layer of modelling and ionosphere delay error item, finally obtain correct receiver clock correction and satellite position information.