CN107229061A

CN107229061A - A kind of star based on low orbit satellite ground difference real-time accurate localization method

Info

Publication number: CN107229061A
Application number: CN201710586437.1A
Authority: CN
Inventors: 王磊; 陈锐志; 李德仁; 潘元进; 李明; 陈亮; 柳景斌
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2017-07-18
Filing date: 2017-07-18
Publication date: 2017-10-03
Anticipated expiration: 2037-07-18
Also published as: CN107229061B

Abstract

The invention belongs to satellite navigation positioning technical field, a kind of with disclosing star based on low orbit satellite difference real-time accurate localization method, this method using low orbit satellite its spaceborne GNSS receiver to terrestrial broadcasting observation data and Real-time orbit data；Ground receiver receives and constitutes double difference observation after the difference information that low orbit satellite is broadcast with local GNSS observations, dynamic base station DGNSS positioning of the progress based on pseudorange or the dynamic base station RTK positioning based on carrier phase.The present invention can realize the real-time accurate Differential positioning service in global range, the distribution independent of ground reference station by the use of the mobile low orbit satellite platform in the whole world as reference station.User is that difference real-time accurate can be achieved to position using single receiver, no operatton scope limitation, without considering data link.

Description

A kind of star based on low orbit satellite ground difference real-time accurate localization method

Technical field

The invention belongs to satellite navigation positioning technical field, more particularly to a kind of star based on low orbit satellite difference it is real-time Precision positioning method.

Background technology

Satellite navigation and location system (GNSS) can provide real-time positioning service, deep change in global range Our life style, and be widely used in many industries of countries in the world.Determine in the whole world of current main flow Position system has GPS, the Russian GLONASS in the U.S., Chinese Beidou systems and the Galileo systems in Europe, India Also in positive Development area navigation system IRNSS.The GNSS location technology precision of current standard is about 5-10 meters.For precision It is required that higher application, it usually needs use the method for precision positioning.The method that precision is positioned at present has Differential positioning method And accurate one-point positioning method.Wherein Differential positioning method includes GPS local area differential's method and wide area differential method again.GPS wide area differential GPS Method and Static Precise Point Positioning are required for calculating various accurate deviation of signal products by the data of ground monitoring net, accurate Track product etc., then is corrected to improve positioning precision in user terminal using these sophisticated products.GPS local area differential method master If the observation data and coordinate of reference station are directly broadcast to user, eliminated in user terminal by way of observation difference respectively The influence of error is planted, high-precision relative positioning is realized.

In summary, the problem of prior art is present be：

GPS wide area differential GPS can provide large-scale precision positioning service, but be due to the accurate ionospheric model branch of current shortage Hold, it usually needs convergence in 20-30 minutes could obtain centimeter-level positioning result.The parametric method that other GPS wide area differential GPS is used is each Differ, it is incompatible between different methods.Form and calculation process are broadcast currently without unified data, is caused different wide Compatible interoperation is unable between the difference product of domain.Further, since understanding not deep enough to new GNSS system signal at present, cause Most of WAAS-Wide Area Augmentation System is only applicable to gps signal.GPS local area differential's method model is simple, and convergence is fast, and real-time is good, positioning accurate Degree is high, is currently based on the real-time dynamic positioning (RTK) of carrier phase and difference GNSS technologies (DGNSS) length based on pseudo range difference All it has been the most widely used precision positioning technology since phase.But differential technique also has the limitation of its own, i.e. user to receive The distance between machine (also referred to as rover station) and reference station are restricted.The distance between receiver user and reference station become long-range guided missile and caused Ionosphere and tropospheric delay correlation between two receivers die down, this influence positioning precision and convergence time.Other base The elongated public visible satellite also resulted between receiver user and reference station of line tails off, thus Long baselines data processing is usual In static data processing.Other long range relative positioning needs to build real-time communication link, uses ground real-time Communication for Power chain Road needs the routing forwarding network of high-power wireless electricity transmitting equipment or complexity, and costly, communication quality is difficult to ensure that.

The content of the invention

The problem of existing for prior art, the invention provides a kind of star based on low orbit satellite ground difference real-time accurate Localization method.

The present invention with being achieved in that a kind of star based on low orbit satellite difference real-time accurate localization method, the base In low orbit satellite star difference real-time accurate localization method by the use of low orbit satellite as reference station, with ground or terrestrial space Receiver carries out Differential positioning；The low orbit satellite carries out ground increasing using the forecast aeronautical satellite ephemeris and clock correction noted on ground Precise autonomous orbit determination or the observation only received using itself carry out autonomous precise orbit determination on strong star；The low orbit satellite The observation of receiver and the satellite-orbit information at correspondence moment on star are earthward broadcast at a certain time interval；Ground receiver Machine will receive difference information and locally received aeronautical satellite distance measuring signal composition double difference observation that low orbit satellite is broadcast, enter RTK or the DGNSS positioning of row mobile base station.As the low orbit satellite of reference station apparently higher than terrestrial user station, it is ensured that distance Have when farther out and enough regard satellite altogether.Remote Real Time Communication Problems are solved using communication link between star ground, simplify user's operation. Low orbit satellite can be global mobile, breaches limitation of the GPS local area differential to operation distance.

Further, the pattern of the Differential positioning includes：

(1) by setting up real time data chain, LEO tracks and observation data are broadcast to receiver user, it is poor in real time to carry out Divide location Calculation；

(2) real time data is connected with setting up star, and LEO observation data and ground receiver observation data are recorded respectively, are entered Act post processing precision LEO orbit determination and Differential positioning is calculated；

(3) real time data is connected with not setting up star, is passed by number or LEO is regularly observed data down transmission by TTC channel, LEO precise orbit determinations are carried out on ground, LEO observations are reused, LEO orbit determination result and ground receiver observation data carry out difference Precision positioning.

Further, the application model of the observation includes：Put down using only the station-keeping mode of Pseudo-range Observations, using phase Slide the station-keeping mode of Pseudo-range Observations, while using pseudorange and the station-keeping mode of carrier phase observation data.

Further, the mode of the LEO autonomous orbit determinations includes:

(1) without using ground enhancement information, entirely autonomous precise orbit determination is carried out using only observation on star；

(2) by uplink communication links between star ground, the enhancement information on ground is uploaded to low orbit satellite, ground enhancing is carried out Star on precise autonomous orbit determination, ground enhancement information include but is not limited to aeronautical satellite prediction orbit, forecast clock correction information；

(3) correction information is broadcast to low orbit satellite by data relay satellite or inter-satellite link, carries out satellite-based enhancing Real-time accurate orbit determination, repeater satellite enhancement information include but is not limited to aeronautical satellite prediction orbit, forecast clock correction information.

Further, observation data of the method for difference precision positioning based on single satellite navigation system, or based on multisystem Observation alignment by union.

The terrestrial user reference coordinate frame of difference precision positioning is included global reference frame or joined using self-defined coordinate Examine framework or the global reference frame Jing Guo encryption.

Further, the star based on low orbit satellite difference real-time accurate localization method specifically include：

1) when the observation time of receiver reading current epoch, pseudorange, carrier phase, Doppler, carrier-to-noise ratio C/N0, locking Between the corresponding navigation message data of observation value information and current epoch；It is the observation time, pseudorange, carrier phase, how general Le, carrier-to-noise ratio C/N0, the observation value information of locking time and the corresponding navigation message data of current epoch are by receiver Portion's PVT algoritic modules output；The observed quantity for being wherein directly used in positioning is pseudorange and carrier phase observation data, and observation model is represented For：

P_i=ρ+δ_orb+c(δt^S-δt^R)+I_i+δ_trop+ε_Pi

φ_i=ρ+δ_orb+c(δt^S-δt^R)-I_i+δ_trop+λ_iN_i+ε_φi

In formula：P_iAnd φ_iRepresent the pseudorange and carrier phase observation data of i-th of frequency (in units of rice)；

ρ represents the geometric distance between satellite and receiver, is expressed as Wherein x^S,y^S,z^SRepresent satellite three-dimensional coordinate, x^R,y^R,z^RRepresent receiver antenna phase center three-dimensional coordinate；δt^SWith δ t^RSatellite With the clock jitter of receiver, unit is the second；

I_iAnd δ_tropRepresent the influence of ionosphere and tropospheric delay；

N_iRepresent the integer ambiguity of i-th of frequency；

ε_PiAnd ε_φiRepresent the receiver observation noise of pseudorange and carrier phase；

C represents the light velocity in vacuum；

λ_iThe carrier wavelength of i-th of frequency is represented, unit is rice；

2) track and clock correction of each aeronautical satellite of calculating signal emission time；Signal emission time calculates that mode includes two Kind：(1) by the precise signal emission time of standard One-Point Location process iterative each aeronautical satellite and corresponding defend The track clock correction of each satellite and the approximate coordinate of ground survey station are calculated after star orbital road and clock correction, successive ignition, (2) utilize puppet Away from observation Approximate Calculation signal emission time, calculate that Principle representation is：

T in formula_s,t_rSignal transmitting and the signal time of reception are represented respectively；

3) information of obtained approximate survey station coordinate and the track clock correction of each aeronautical satellite, meter are calculated according to One-Point Location Survey station is calculated to the geometric distance ρ between each satellite, the information such as elevation of satellite；Further rule of thumb ionospheric model, meter Ionosphere is calculated to carrier phase and the influence I of pseudorange_i, rule of thumb Tropospheric Models, calculate shadow of the troposphere to GNSS signal Ring δ_trop, orbit error δ is also remained in the observation after amendment_orb, receiver clock-offsets δ t^RWith integer ambiguity parameter N_iShadow Ring；

4) in the cycle slip of un-differenced observation aspect detected carrier phase；

5) the difference observation data that the low orbit satellite that processing is received is broadcast；The difference observation packet that low orbit satellite is broadcast Containing signal reception time, the observation that LEO is received low orbit satellite track corresponding with the moment is received, and velocity information；Need first Difference information is decoded, get necessary information；

6) LEO satellite observation moment corresponding navigation satellite signal emission time track and clock correction are calculated；

7) the spaceborne receiver observations of LEO are missed according to the track and clock correction of the track of LEO satellite and aeronautical satellite Poor source correction；

8) un-differenced observation aspect carries out data snooping, cycle slips detection to the carrier phase observation data of the spaceborne receivers of LEO； The observation that cycle slip occurs to detecting is marked；

9) after being pre-processed respectively to the data of ground receiver and the spaceborne receivers of LEO, double difference observation is initially formed Value；Filter out ground receiver and the spaceborne receivers of LEO first regards satellite altogether, and then each navigation system selects a reference Star, for forming difference observation between star；

10) double difference observation is formed；According to step 9) what is determined regards the reference satellite of satellite and each system altogether, constitutes double difference Observation, star the double difference observation of difference be expressed as：

In formulaDouble difference operator is represented, performs after double difference operation, is not disposed in un-differenced observation pretreatment stage Fractional error source be completely eliminated in theory by way of double difference, these error sources include orbit error δ_orb, satellite clock correction δ t^S, receiver clock-offsets δ t^R；Also remained in double difference observation between the double difference geometric distance between the star of station, double difference ionosphere residual effect, star The troposphere influence of difference, carrier phase ambiguity influence and observation noise influence；It is remaining after double difference observation for being formed Error term, the influence of these errors is eliminated by the form of parameter Estimation；

11) cycle slips detection of double difference observation aspect；Using three poor method cycle slips detections；If to the cycle slip of un-differenced observation Detection has enough confidence, can skip this step, directly carries out next step；

12) filter temporal updates；For real-time coordinates estimation, including：A) Sequent least square method and Kalman are used Filter method；Kalman filter model is relevant with observation selection, for Dual Frequency Observation data, there is two kinds of observation models：Based on nothing The model of ionospheric combination observation and the model based on non-combined observation；

A) ionosphere effect is eliminated by Dual-frequency Observations linear combination based on the model without ionospheric combination observation Single order, but the observation quantity without ionospheric combination observation halves, observation noise is 3 times of observation before combination；

B) directly handled using non-combined observation, it is necessary to which every satellite estimates an Ionospheric Parameters；Star of standing is poor The influence in ionosphere can be weakened by dividing, according to non-combined model inference；For non-combined model, filter status vector is chosen for：

X=[Δ r, δ_trop,z, I, N]^T；

Wherein Δ r is 3 × 1 increment of coordinate vector, δ_trop,zFor zenith direction tropospheric delay, each survey station estimates one Parameter；I is each satellite direction of visual lines ionosphere delay, and every visible satellite estimates one, and N joins for double-differential carrier phase fuzziness Number, each signalling channel estimates one；In the case of without ionospheric combination observation, the negligible ionization of filter status vector Layer delay parameter I；For static subscriber's positioning, increment of coordinate Δ r estimates as arbitrary constant；For dynamic positioning, using with Machine walk process is simulated, or the equation of motion of additional external enters row constraint to increment of coordinate parameter；δ_trop,zUse random walk mould Pattern is intended, and realizes direction ionosphere delay I or is initialized using prior information, is then simulated using random walk process；Carrier wave Phase Double difference fuzziness is estimated in continuous tracking using arbitrary constant model, needs parameter to reset when occurring cycle slip；In hair When raw reference star changes star, specially treated is done to all fuzziness parameters；

Filter temporal renewal equation is expressed as：

In formulaP_t ^-Quantity of state and its variance-covariance matrix respectively after the renewal of t time, also referred to as forecast Solution；For t-1 moment customer location state filtering solutions and its variance-covariance matrix；Φ (t, t-1) is t-1 to t State-transition matrix；Q (t) is process noise matrix；For random walk parameter and random constant parameter, state-transition matrix It is set to unit matrix；Diagonal matrix is set to for n independent random walk process Q (t), it is settable for arbitrary constant parameter Q (t) For null matrix；

13) filter measurement updates；According to step 10) analysis, for double difference position pseudorange and carrier phase observation Value linearisation is expressed as：

E (y)=(J, M, Θ, Λ) (Δ r, δ_trop,z,I,N)^T；

E () is mathematic expectaion operator in formula, to f frequency, the observation of s visible double difference satellite, for using For the mathematical modeling of non-combined observation, J be (2*s*f) × 3 Jacobbian matrixes, M for (2*s*f) × 1 row to Amount, the troposphere projection function value of each element correspondence respective satellite；Θ is (2*s*f) × s matrix；Λ be (2*s*f) × (f*s) matrix；For using the observation model without ionospheric combination, except ignoring the corresponding design matrix Θ of Ionospheric Parameters Outside, all observation linear combinations also result in observation number and reduce half than non-combined model；After linearisation, this is non-combined The design matrix of observational equation is defined as：

A=(J, M, Θ, Λ)；

Then the measurement updaue equation of Kalman filtering is expressed as：

K_t=P_t ^-A(AP_t ^-A^T+R_t)^-1,

K in formula_tFor t filtering gain matrix, R_tFor geometry observation variance-covariance matrix；

14) rear residual test is tested；The rear residual error valuation of testing of filtering equations is expressed as：

χ is constructed according to rear residual error valuation is tested²Inspected numberObey χ²(n-t) it is distributed, wherein n-t represents the free degree；IfThen think to test rear residual error by inspection, otherwise it is assumed that testing rear residual test refusal；In formulaIt is notable Property level be α threshold value；

15) output forecast solution；If testing rear residual test not pass through, then it represents that observation there may be rough error；Use number Rough error is tested according to probe method and rejects or abandons using filter solution, forecast solution is used insteadCarried out as final positioning result defeated Go out；

16) fuzziness is fixed；It is special using the integer of carrier phase ambiguity if filter solution is by testing rear residual test Property obtain centimetre class precision fuzziness fixed solution；Fuzziness fix method using least square drop related algorithm LAMBDA or The mode that width lane ambiguity is decomposed into without ionospheric combination is carried out fuzziness step by step and fixed by person；

By step 13) in state vector merge according to real parameters and the class of numeric parameter two, then observational equation simplifies table It is shown as E (y)=(B, Λ) (b, N)^T, corresponding filter state amountThe corresponding filter solution variance association side of two class parameters Poor matrix is expressed as：

The filter solution of fuzziness parameter is denoted asCommonly referred to as fuzziness real solution, by the real solution of fuzziness parameterAnd its variance-covariance matrix Q_NNAs input, scanned for using LAMBDA methods, the optimal integer for obtaining fuzziness is consolidated Fixed solutionWith the integer fixed solution of suboptimum

17) fuzziness is examined；Being fixed due to the fuzziness of mistake causes positioning result to produce flying spot, and position error compares floating-point Solution is also big, fixes result to fuzziness and tests；Examined using Ratio；

18) float-solution is exported；If the test fails by Ratio, then it is assumed that fuzziness fixed solution is unreliable, it is necessary to use filter Ripple solutionExported as final positioning result；

19) fixed solution is exported；If Ratio upchecks, exported using fuzziness fixed solution as positioning result；Mould Paste degree is fixed as after integer, corresponding real parametersThe condition solution of integer ambiguity is may be updated as, is expressed as：

Corresponding variance-covariance matrix is represented by：

If fuzziness is upchecked, useUsed as last positioning result.

Another object of the present invention is to a kind of with providing star based on low orbit satellite difference real-time accurate alignment system.

Another object of the present invention is to provide a kind of with utilizing the above-mentioned star based on low orbit satellite difference real-time accurate to determine The pelagic region alignment system of position system.

Another object of the present invention is to provide a kind of with utilizing the above-mentioned star based on low orbit satellite difference real-time accurate to determine The alignment system from far-off regions of position system

Another object of the present invention is to provide a kind of with utilizing the above-mentioned star based on low orbit satellite difference real-time accurate to determine The natural calamity disaster area alignment system of position system.

Advantages of the present invention and good effect are：

The present invention provide by the use of low orbit satellite as reference station, realize that difference is determined with the receiver on ground or terrestrial space The method of position.Low orbit satellite earthward broadcasts the satellite at the observation of receiver and correspondence moment on star at a certain time interval Orbit information, ground receiver will receive difference information and locally received aeronautical satellite distance measuring signal that low orbit satellite is broadcast Double difference observation is constituted, RTK or the DGNSS positioning of mobile base station is realized.This method uses low orbit satellite as reference station, real The Differential positioning service of global range is showed, particularly to pelagic region, remote districts and natural calamity disaster area are realized quickly Precision positioning is significant.

The present invention uses the method for GPS local area differential, but the utilization of reference station is improved by mobile reference platform Rate so that reference station service range is not limited to around tens kilometers, and is to provide the differential service of global range.If used The constellation of many LEO satellite compositions can then provide global range continual station star Differential positioning service as reference base station

The present invention can be to be influenceed to cause by natural conditions and economic condition not set up or can not set up earth station Region, such as ocean area, from far-off regions, the region such as earthquake-stricken area provides real-time requiring service.

Star of the present invention Differential positioning algorithm model it is simpler than Static Precise Point Positioning (PPP), can be with by the method for double difference The clock correction and hardware deviation of satellite end and receiver end are voluntarily eliminated, is modified without using external signal deviation product.This Invention utilizes low orbit satellite platform, and the mobile low orbit satellite platform of the reference station of the fixation on ground is replaced.Structure between star ground Into double difference observation to ionosphere delay also have certain weakening effect.

User terminal of the present invention only needs a receiver that can receive LEO difference informations that global model can be achieved Enclose interior precision positioning, star the method for difference help user to break away from the dependence to reference station.Without voluntarily setting up reference station, Real-time communication link need not be set up.Application method is just the same with PPP, but can provide precision and convergence time is all more preferable Real time differential precision positioning is serviced.

Brief description of the drawings

Fig. 1 is the star provided in an embodiment of the present invention based on low orbit satellite ground difference real-time accurate localization method flow chart.

Fig. 2 is the schematic diagram of low orbit satellite provided in an embodiment of the present invention with realizing star difference precision positioning.

Embodiment

In order to make the purpose , technical scheme and advantage of the present invention be clearer, with reference to embodiments, to the present invention It is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, it is not used to Limit the present invention.

The application principle of the present invention is described in detail below in conjunction with the accompanying drawings.

Star provided in an embodiment of the present invention based on low orbit satellite ground difference real-time accurate localization method, it is described to be based on low rail The star of satellite difference real-time accurate localization method by the use of low orbit satellite as reference station, with ground or the receiver of terrestrial space Carry out Differential positioning；The low orbit satellite carries out the enhanced star in ground using the forecast aeronautical satellite ephemeris and clock correction noted on ground Upper precise autonomous orbit determination or the observation only received using itself carry out autonomous precise orbit determination；The low orbit satellite is with certain Time interval earthward broadcast the satellite-orbit information at the observation of receiver on star and correspondence moment；Ground receiver will connect Difference information and locally received aeronautical satellite distance measuring signal composition double difference observation that low orbit satellite is broadcast are received, is moved RTK or the DGNSS positioning of base station.

The Differential positioning includes：

(2) real time data is connected with setting up star, and LEO observation data and ground receiver observation data are recorded respectively, are entered Act post processing LEO precise orbit determinations and Differential positioning is calculated；

The application model of the observation includes：Using only the station-keeping mode of Pseudo-range Observations, use carrier phase smoothed pseudorange The station-keeping mode of observation, while using pseudorange and the station-keeping mode of carrier phase observation data.

The mode of the LEO autonomous orbit determinations includes:

Observation data of the method for difference precision positioning based on single satellite navigation system, or based on multisystem observation connection Close positioning.

The terrestrial user reference coordinate frame of difference precision positioning is included global reference frame or joined using self-defined coordinate Examine framework or the global reference frame Jing Guo encryption.Such as ITRF2008, CGCS2000 reference frames.

Star difference precision positioning method be related to aeronautical satellite constellation and include, but are not limited to the existing whole world/regional satellite Navigation system, such as GPS, GLONASS, Beidou, Galileo, IRNSS, QZSS etc..

The application principle of the present invention is further described with reference to specific embodiment.

Star provided in an embodiment of the present invention based on low orbit satellite difference real-time accurate localization method as shown in figure 1, should Algorithm is a real-time location algorithm for being based on extended BHF approach (EKF), be can be used at static and dynamic data Reason.The algorithm can be realized in the firmware algorithm of the inside of GNSS receiver, can also be embodied as post-processing algorithm.In order to full The demand positioned when full, description is using receiver internal firmware algorithm as reference below.Specific implementation steps are as follows：

1) receiver reads the observation time of current epoch, pseudorange, carrier phase, Doppler, carrier-to-noise ratio (C/N0), locking Time etc. observes value information, and the corresponding navigation message data of current epoch, and these information can be by PVT inside receiver Algoritic module is exported.The observed quantity for being wherein directly used in positioning is pseudorange and carrier phase observation data, and its observation model can be with table It is shown as：

P_i=ρ+δ_orb+c(δt^S-δt^R)+I_i+δ_trop+ε_Pi

φ_i=ρ+δ_orb+c(δt^S-δt^R)-I_i+δ_trop+λ_iN_i+ε_φi

ρ represents the geometric distance between satellite and receiver, is represented by Wherein x^S,y^S,z^SRepresent satellite three-dimensional coordinate, x^R,y^R,z^RRepresent receiver antenna phase center three-dimensional coordinate；δt^SWith δ t^RSatellite With the clock jitter (in seconds) of receiver；

I_iAnd δ_tropRepresent the influence of ionosphere and tropospheric delay；

N_iRepresent the integer ambiguity of i-th of frequency；

C represents the light velocity in vacuum；

λ_iRepresent the carrier wavelength of i-th of frequency (in units of rice)；

2) track and clock correction of each aeronautical satellite of calculating signal emission time.Broadcast in view of the correction of low orbit satellite When have the delay that certain data processing and signal are propagated, it is necessary to accurately be calculated to signal emission time.In view of middle height The satellite velocities of rail satellite, it is desirable to which signal emission time calculates error at least below 1 μ s, just can guarantee that calculating orbit error is less than 1cm.Signal emission time calculates that mode has two kinds：(1) standard One-Point Location process iterative each aeronautical satellite is passed through Precise signal emission time and corresponding satellite orbit and clock correction, this method need the track clock of each satellite of successive ignition calculating The approximate coordinate of difference and ground survey station, but signal emission time can be calculated to 100ns after convergence；(2) pseudorange is utilized Observation Approximate Calculation signal emission time, calculates that principle can be expressed as：

T in formula_s,t_rSignal transmitting and the signal time of reception are represented respectively.Contrast pseudorange code P₁Observation model understand, should Formula does not account for ionosphere, the influence of troposphere and receiver clock-offsets.The wherein influence of ionosphere and troposphere to ranging is several Ten meters of magnitudes, the influence calculated to signal emission time is in hundred nanosecond orders.Can the influence of receiver clock-offsets, which be ignored, depends on The model of receiver clock-offsets.The model of receiver clock-offsets has amendment and two kinds of models of millisecond amendment in real time, and real-time correction model connects The stable magnitude in several nanoseconds to hundreds of nanoseconds of receipts machine clock correction, can meet in reckoning demand, millisecond correction model, receiver clock Difference, which has reached 1ms or -1ms, will occur clock jump, if receiver clock uses millisecond correction model, must be fixed using single-point Position method iterative navigation satellite signal emission time.At present major part receiver using or can be configured to clock correction and repair in real time Positive model.Solve after signal emission time, you can the track and clock correction of each satellite are calculated using broadcast ephemeris.

3) information such as obtained approximate survey station coordinate and the track clock correction of each aeronautical satellite, meter are calculated according to One-Point Location Survey station is calculated to the geometric distance ρ between each satellite, the information such as elevation of satellite.Further rule of thumb ionospheric model, such as Klobuchar models, calculate ionosphere to carrier phase and the influence I of pseudorange_i, rule of thumb Tropospheric Models, such as Hopfield models calculate influence δ of the troposphere to GNSS signal_trop, orbit error δ is also remained in the observation after amendment_orb, Receiver clock-offsets δ t^RWith integer ambiguity parameter N_iInfluence.Further, since geometric distance, which is calculated, uses approximate coordinate, repair Influence in observation after just also containing geometric distance residual volume, ionospheric convection layer empirical model can only also correct a part Influence, the residual effect of aeronautical satellite clock correction is also up to nanosecond order, and these error residue amounts can also be retained in revised sight In measured value.

4) in the cycle slip of un-differenced observation aspect detected carrier phase, the with good grounds carrier lock loop of common method (PLL) output locking time come judge loop whether losing lock.Once loop losing lock, carrier phase will be reset, now defeated The carrier phase gone out can produce step signal, it is necessary to be marked.Another situation is exactly that signal is disturbed, signal blocks, or The influence of person's multipath causes carrier loop to be shaken, and such case will not typically cause loop losing lock, but can cause small week Jump, such as half cycle slip or complete cycle are jumped.The situation of half cycle slip can influence PVT bit synchronous and frame synchronization, but do polarity and judge logical The regular hour often is needed, therefore occurs to have a several seconds carrier loops after half cycle slip and PVT can not judge whether to there occurs half Cycle slip, such case Data processing is generally all handled as cycle slip.Jumped for small complete cycle, it is necessary to be sentenced using other method It is disconnected, but the probability that ordinary circumstance occurs is smaller.Judge that small complete cycle jumps conventional method and has free-geometry method, if connect Receipts machine pseudorange tracking noise very little, the method detection cycle slip that MW can also be used to combine.

5) the difference observation data that the low orbit satellite received is broadcast next are handled.The difference observation that low orbit satellite is broadcast Packet contains signal reception time, the observation that LEO is received low orbit satellite track corresponding with the moment is received, and velocity information. Decoded firstly the need of to difference information, get necessary information.

6) LEO satellite observation moment corresponding navigation satellite signal emission time track and clock correction are calculated.Computational methods and That is discussed in step 102 is identical, the difference is that the coordinate of LEO satellite is known, is sent out if using One-Point Location to calculate signal It is to only need to iteration to update co-ordinates of satellite constantly to penetrate, and the coordinate of LEO satellite may be considered true value.In view of the fortune of low orbit satellite Dynamic speed is about 7.6km/s (by taking 500Km orbit altitudes as an example), during the clock face of LEO observations and the actual signal time of reception it Difference should be less than 1 μ s.If the clock correction of the spaceborne receivers of LEO uses real-time correction model, when being received during clock face with actual signal The residual quantity level at quarter is less than hundred nanosecond orders, and the influence to LEO tracks is less than 1cm, can be neglected.The rail that LEO is earthward broadcast Road information should by during clock face to ensure LEO observations of appropriate interpolation or extrapolation process and the actual signal time of reception difference Magnitude is less than 1 μ s.

7) the spaceborne receiver observations of LEO are missed according to the track and clock correction of the track of LEO satellite and aeronautical satellite Poor source correction.The step implementation procedure and step 3) it is similar, the difference is that not being that ground connects because LEO belongs to spacecraft Receipts machine, its ionosphere being subject to and tropospheric influencing characterisitic have difference with ground receiver.Troposphere influence is often referred to ground To the near-earth atmosphere of 30Km height, therefore it is generally acknowledged that influence of the troposphere to the spaceborne receiver observations of LEO can be neglected, place Tropospheric delay is not corrected during reason.Other ionosphere is smaller than ground to the observation of the spaceborne receivers of LEO, according to Chapman is theoretical, and the ionosphere effect that the spaceborne receiver observation of low orbit satellite is subject to is about the 30%-50% on ground.To star The ionosphere correction model for carrying receiver observation is also multiplied by a certain scale factor as spaceborne usually using ground empirical model The ionosphere correction empirical model of receiver observation.Because atmospheric density section curve and temperature profile curve can not be surveyed accurately Fixed, Chapman models are also approximate empirical model, it is impossible to influence of the ionosphere to observation is completely eliminated.

8) un-differenced observation aspect carries out data snooping, cycle slips detection to the carrier phase observation data of the spaceborne receivers of LEO. Processing method is identical with step 104, the receiver the difference is that movement velocity of LEO satellite is above the ground level, using some and geometry , it is necessary to the selection of special consideration threshold value during the method detection cycle slip of distance correlation.The observation that cycle slip occurs to detecting is carried out Mark.

9) after being pre-processed respectively to the data of ground receiver and the spaceborne receivers of LEO, double difference observation is initially formed Value.Double difference observation typically first carries out difference between survey station, then carries out inter-satellite difference.For star baseline in the case of, first Filter out ground receiver and the spaceborne receivers of LEO regards satellite altogether, and then each navigation system selects a reference star, for shape Difference observation between Cheng Xing.The observation quality of reference star directly affects the quality of all double difference observations, it is therefore desirable to as far as possible The preferable satellite of observation quality is chosen as reference star, normal conditions use elevation angle highest satellite or signal carrier-to-noise ratio Best satellite is used as reference satellite.On the other hand, reference star, which changes, can cause all double difference fuzziness parameters discontinuous. When changing reference star, fuzziness parameter needs specially treated to avoid fuzziness parameter from continually resetting, therefore during selection reference star Also as far as possible reference star can be kept constant, to ensure the continuity of fuzziness parameter.When multisystem combined positioning, it is necessary to Each satellite system selects reference star respectively, because hardware delay has a different between the signal of different navigation system, and this Individual difference can not be eliminated using the inter-satellite difference of different system.Deviation can be disappeared by the method for parameter Estimation between this system Remove, more general way is that each navigation system chooses reference satellite and carrys out cancellation receiver clock correction (contain system between deviation) respectively Influence.

10) double difference observation is formed；According to step 9) what is determined regards the reference satellite of satellite and each system altogether, constitutes double difference Observation, star the double difference observation of difference can be expressed as：

In formulaDouble difference operator is represented, performs after double difference operation, is not disposed in un-differenced observation pretreatment stage Fractional error source can be completely eliminated in theory by way of double difference, these error sources include aeronautical satellite orbit error δ_orb, aeronautical satellite clock correction δ t^S, receiver clock-offsets δ t^R.The double difference geometric distance between the star of station, double difference electricity are also remained in double difference observation The troposphere influence (assuming that LEO observations are not influenceed by tropospheric delay) of difference, carrier phase mould between absciss layer residual effect, star Paste degree influences and observation noise influence.For forming error term remaining after double difference observation, it is necessary to give in function model Consider, the influence of these errors is eliminated by the form of parameter Estimation.Consideration star differential signal propagation delay of arriving at a station causes between station When single poor LEO observation moment and earth station's observation moment can not close alignment, this can give double difference observation to introduce time irreversibility Error.Consider delay of data processing etc. on star communication bandwidth limitation of arriving at a station, star, amount of star Differencing communication of the standing delay up to the several seconds Level.Time in-synchronization error mainly results in the orbit error of aeronautical satellite in double difference observation, clock correction and ionospheric error it is residual Remaining error influence becomes big.Processing strategy was counted respectively according to LEO and ground receiver observation moment in non-difference data processing stage Aeronautical satellite track and clock correction are calculated, is then corrected.

11) cycle slips detection of double difference observation aspect.As the supplement of non-poor aspect cycle slips detection, double difference observation is formed After cycle slips detection can also be carried out in double difference observation aspect, typical method has three poor method cycle slips detections.The week of double difference aspect The not necessary step of detection is jumped, if having enough confidence to the cycle slips detection of un-differenced observation, this step is can skip, directly Carry out next step.

12) filter temporal updates.Complete the data processing of double difference observation, you can the process of start parameter estimation. For real-time coordinates estimation, Sequent least square method and Kalman filtering method can be used.Kalman filtering method be adapted to it is static and Dynamic data processing, Sequent least square method eliminates process by introducing parameter and prior information constraint can also be realized and blocked Kalman Filtering effect of equal value.This step illustrates Differential positioning parameter between the star of station so that Kalman filtering solves coordinate parameters as an example The method of estimation.Kalman filter model is relevant with observation selection, for Dual Frequency Observation data, there is two kinds of representative observation moulds Type：Based on the model without ionospheric combination observation and the model based on non-combined observation.Based on being observed without ionospheric combination The model of value can eliminate the single order of ionosphere effect by Dual-frequency Observations linear combination, but without ionospheric combination observation The observation quantity of value halves, and observation noise is about 3 times of observation before combination.Another method is directly to use non-group Close observation to be handled, but need every satellite to estimate an Ionospheric Parameters.Consideration star difference of arriving at a station can weaken electricity The influence of absciss layer, part is according to non-combined model inference below.For non-combined model, filter status vector is chosen for：

X=[Δ r, δ_trop,z, I, N]^T；

Wherein Δ r is 3 × 1 increment of coordinate vector, δ_trop,zFor zenith direction tropospheric delay, each survey station estimates one Parameter.I is each satellite direction of visual lines ionosphere delay, and every visible satellite estimates one (except reference satellite), and N is carrier wave phase Position double difference fuzziness parameter, each signalling channel estimates one.In the case of without ionospheric combination observation, filter status The negligible ionosphere delay parameter I of vector.For static subscriber's positioning, increment of coordinate Δ r can be right as arbitrary constant estimation In dynamic positioning, random walk process can be used to simulate, can also the equation of motion of additional external increment of coordinate parameter is entered Row constraint.δ_trop,zUsually using random walk modeling, realize that direction ionosphere delay I can use prior information initial Change, then simulated using random walk process.Double-differential carrier phase fuzziness is estimated in continuous tracking using arbitrary constant model Meter, needs parameter to reset when occurring cycle slip.Occurring when reference star changes star, it is necessary to do special place to all fuzziness parameters Reason, it is to avoid fuzziness parameter is reset.Filter temporal renewal equation is represented by：

In formulaP_t ^-Quantity of state and its variance-covariance matrix respectively after the renewal of t time, also commonly referred to as Forecast solution.For t-1 moment customer location state filtering solutions and its variance-covariance matrix.Φ (t, t-1) is t-1 to t The state-transition matrix at moment.Q (t) is process noise matrix.For random walk parameter and random constant parameter, state transfer Matrix can be set to unit matrix.Diagonal matrix can be set to for n independent random walk process Q (t), for arbitrary constant parameter Q (t) it may be configured as null matrix.

13) filter measurement updates；According to step 10) analysis, for double difference position pseudorange and carrier phase observation Value can be linearized and is expressed as：

E (y)=(J, M, Θ, Λ) (Δ r, δ_trop,z,I,N)^T；

E () is mathematic expectaion operator in formula, to f frequency, observation (total visible star of s visible double difference satellite Number subtracts reference star number), for the mathematical modeling using non-combined observation, J is (2*s*f) × 3 Jacobbian matrixes, M is the column vector of (2*s*f) × 1, the troposphere projection function value of each element correspondence respective satellite.Θ For (2*s*f) × s matrix.Λ is (2*s*f) × (f*s) matrix.For using the observation model without ionospheric combination, remove Outside negligible Ionospheric Parameters corresponding design matrix Θ, all observation linear combinations also result in observation number than non-group The model of conjunction reduces half.After linearisation, the design matrix of non-combined model observational equation is defined as：

A=(J, M, Θ, Λ)；

Then the measurement updaue equation of Kalman filtering is represented by：

K_t=P_t ^-A(AP_t ^-A^T+R_t)^-1,

P_t ⁺=(I-K_tA)P_t ^-,

K in formula_tFor t filtering gain matrix, R_tFor geometry observation variance-covariance matrix.

14) rear residual test is tested；The rear residual error valuation of testing of filtering equations is represented by：

χ can be constructed according to rear residual error valuation is tested²Inspected numberObey χ²(n-t) it is distributed, wherein n-t represents the free degree. IfThen think to test rear residual error by inspection, otherwise it is assumed that testing rear residual test refusal.In formulaIt is aobvious The threshold value that work property level is α.

15) output forecast solution；If testing rear residual test not pass through, then it represents that observation there may be rough error.It can be used Data snooping is tested rejecting to rough error, can also abandon using filter solution, uses forecast solution insteadTied as final positioning Fruit is exported.

16) fuzziness is fixed；If filter solution is by testing rear residual test, it can attempt to utilize carrier phase ambiguity Integer characteristic obtains the fuzziness fixed solution of centimetre class precision.Due to star difference baseline group into double difference observation, it was positioned Journey is equivalent to Long baselines relative positioning.Fuzziness fix method can use least square drop related algorithm (LAMBDA) or The mode for being decomposed into width lane ambiguity without ionospheric combination is carried out into fuzziness step by step to fix.By step 13) in state to Amount merges according to real parameters and the class of numeric parameter two, then observational equation can be simplified shown as E (y)=(B, Λ) (b, N)^T, Corresponding filter state amountThe corresponding filter solution variance-covariance matrix of two class parameters is represented by：

The filter solution of fuzziness parameter is denoted asCommonly referred to as fuzziness real solution, by the real solution of fuzziness parameterAnd its variance-covariance matrix Q_NNAs input, scanned for using LAMBDA methods, the optimal whole of fuzziness can be obtained Number fixed solutionWith the integer fixed solution of suboptimum

17) fuzziness is examined；Because the fuzziness fixation of mistake may cause positioning result to produce flying spot, position error ratio Float-solution is also big, therefore fuzziness fixation result is tested.Examined usually using Ratio.Ratio is examined and is defined as：

In formulaFor the suboptimal solution of integer ambiguity.For the norm of Euclid two.μ is that ratio examines threshold value, generally Take 2-5.Think if above formula is set upBy examining, otherwise it is assumed that examining refusal.

18) float-solution is exported；If the test fails by Ratio, then it is assumed that fuzziness fixed solution is unreliable, it is necessary to use filter Ripple solutionExported as final positioning result.

19) fixed solution is exported；If Ratio upchecks, exported using fuzziness fixed solution as positioning result.Mould Paste degree is fixed as after integer, corresponding real parametersThe condition solution of integer ambiguity is may be updated as, is expressed as：

Corresponding variance-covariance matrix is represented by：

If fuzziness is upchecked, useUsed as last positioning result.

Above-mentioned steps can realize the difference real-time accurate positioning between ground receiver and low orbit satellite.

The principle of low orbit satellite provided in an embodiment of the present invention with realizing star difference precision positioning is as shown in Figure 2.In figure GEO/IGSO/MEO refer to it is existing the whole world or region satellite navigation system satellite, including but not limited to GPS, GLONASS, Beidou, Galileo, IRNSS and QZSS navigational satellite system.LEO refers to be equipped with double frequency GNSS signal receiver, with height Precision autonomous orbit determination ability, and with the low orbit satellite for earthward broadcasting information capability.Ground reference station refers to be laid in the earth The CORS on surface, the monitoring net (IGS) that such as world GNSS is serviced, many GNSS try nets (MGEX) etc..Ground distributor Analysis center is to refer to the observation data by each ground reference station of Network Capture, can calculate or forecast that in real time navigation is defended The track and clock correction of star, and can be by ground centre data of the note to low orbit satellite on the aeronautical satellite track and clock correction of forecast Processing center.User refers to GNSS signal receive capabilities, and can receive, the difference letter that parsing low orbit satellite is broadcast Breath, determines the receiving device of itself precision coordinate by way of Differential positioning.As shown in Fig. 2 GEO/IGSO/MEO is led in figure Boat satellite it is lasting navigation signal is earthward broadcast with low orbit satellite, navigation signal is by low orbit satellite, user and ground reference station Receive.Ground reference station sends the observation received to Ground analysis center, and Ground analysis is each centrally through COMPREHENSIVE CALCULATING The observation data of individual earth station, it is determined that the accurate GEO/IGSO/MEO tracks and clock correction information with forecast in real time.In view of low rail Satellite TT length of window is limited, it usually needs the track and clock correction of forecast a few hours, then by prediction orbit and clock correction information Data compression is carried out, in observing and controlling window, the data after compression are uploaded to low orbit satellite.Low orbit satellite uses spaceborne receiver Observation data and the ground enhancement information that receives carry out real-time accurate track determination.Then by the track of itself and with for the moment Carve corresponding observation data to be encoded, broadcast to ground.Terrestrial user using the GEO/IGSO/MEO satellites received observation Value, and the difference information that low orbit satellite is broadcast, with forming star difference baseline, complete double difference positioning.Although star parallax range compared with It is long, thousands of kilometers are generally had hundreds to, but the double difference observation formed remains able to effectively cancellation receiver clock correction, satellite Clock correction, weakens ionosphere effect, effectively simplifies the complexity of precision positioning, improves location efficiency and precision.In addition, this articles and opinions The star stated differential system can also be run in autonomous mode, i.e., without Ground analysis center support pattern.There is no ground ginseng Examine station and supported with Ground analysis center, autonomous orbit determination can also reach 0.5m or so result on star.Directly using autonomous fixed The result of rail with entering planet difference, still can obtain the Real-Time Positioning better than 1 meter.Ground analysis center and low orbit satellite it Between direct communication link can also indirectly be set up by modes such as data relay satellite or inter-satellite links.

The present invention can improve the utilization rate at ground reference station, and Differential positioning service range is extended into the whole world.

The present invention can provide the Differential positioning service of global range, particularly in ocean area, remote districts, earthquake disaster Area etc. sets up the region at ground reference station without condition.

Star of the present invention Differential positioning algorithm model it is simpler than Static Precise Point Positioning (PPP), can be with by the method for double difference The clock correction and hardware deviation of satellite end and receiver end are voluntarily eliminated, thus is repaiied without using external signal deviation product Just.Based on star differential position system positioning convergence time and positioning precision in terms of be better than Static Precise Point Positioning.

The present invention can provide the high accuracy positioning service towards active user, and precise single-point positioning technology will rely on a variety of External precision data product is corrected observation data, and portioned product has certain delay, and this causes Static Precise Point Positioning Technology is more applied in the not high scene of post processing and real-time.The method of the present invention is adapted to real-time high-precision positioning application.

The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all essences in the present invention Any modifications, equivalent substitutions and improvements made within refreshing and principle etc., should be included in the scope of the protection.

Claims

1. a kind of star based on low orbit satellite ground difference real-time accurate localization method, it is characterised in that described to be based on low orbit satellite Star difference real-time accurate localization method by the use of low orbit satellite as reference station, carried out with the receiver of ground or terrestrial space Differential positioning；The low orbit satellite is connect using precise autonomous orbit determination on ground or the enhanced star of repeater satellite or only using itself The observation received carries out autonomous precise orbit determination；The low orbit satellite earthward broadcasts receiver on star at a certain time interval Observation and correspondence the moment satellite-orbit information；Ground receiver will receive difference information and the sheet that low orbit satellite is broadcast The aeronautical satellite distance measuring signal composition double difference observation that machine is received, moves RTK or the DGNSS positioning of base station.

2. the star based on low orbit satellite as claimed in claim 1 ground difference real-time accurate localization method, it is characterised in that described The pattern of Differential positioning includes：

(1) by setting up real time data chain, LEO tracks and observation data is broadcast to receiver user, real time differential is carried out and determines Position is calculated；

(2) real time data is connected with setting up star, records LEO observation data and ground receiver observation respectively by ground receiver Data, carry out processing LEO precise orbit determinations afterwards and Differential positioning is calculated；

(3) real time data is connected with not setting up star, is passed by number or LEO is regularly observed data down transmission by TTC channel, on ground Face carries out LEO precise orbit determinations, reuses LEO observations, it is accurate that LEO orbit determination result and ground receiver observation data carry out difference Positioning.

3. the star based on low orbit satellite as claimed in claim 1 ground difference real-time accurate localization method, it is characterised in that described The application model of observation includes：Using only the station-keeping mode of Pseudo-range Observations, the positioning using carrier phase smoothed pseudorange observation Pattern, while using pseudorange and the station-keeping mode of carrier phase observation data.

4. the star based on low orbit satellite as claimed in claim 2 ground difference real-time accurate localization method, it is characterised in that described The mode of LEO autonomous orbit determinations includes:

(2) by uplink communication links between star ground, the enhancement information on ground is uploaded to low orbit satellite, the enhanced star of ground is carried out Upper precise autonomous orbit determination, ground enhancement information includes but is not limited to aeronautical satellite prediction orbit, forecasts the information of clock correction；

(3) correction information is broadcast to low orbit satellite by data relay satellite or inter-satellite link, carries out the enhanced reality in satellite-based When precise orbit determination, repeater satellite enhancement information include but is not limited to aeronautical satellite prediction orbit, forecast clock correction information.

5. the star based on low orbit satellite as claimed in claim 2 ground difference real-time accurate localization method, it is characterised in that difference Observation data of the method for precision positioning based on single satellite navigation system, or based on multisystem observation alignment by union.

The terrestrial user reference coordinate frame of difference precision positioning includes global reference frame or uses self-defined coordinate reference frame Frame or the global reference frame Jing Guo encryption.

6. the star based on low orbit satellite as claimed in claim 1 ground difference real-time accurate localization method, it is characterised in that described Star based on low orbit satellite difference real-time accurate localization method specifically include：

1) receiver reads the observation time of current epoch, pseudorange, carrier phase, Doppler, carrier-to-noise ratio C/N0, locking time Observe value information and the corresponding navigation message data of current epoch；The observation time, pseudorange, carrier phase, Doppler, load Make an uproar than C/N0, the observation value information of locking time and the corresponding navigation message data of current epoch by PVT inside receiver Algoritic module is exported；The observed quantity for being wherein directly used in positioning is pseudorange and carrier phase observation data, and observation model is expressed as：

P_i=ρ+δ_orb+c(δt^S-δt^R)+I_i+δ_trop+ε_Pi

φ_i=ρ+δ_orb+c(δt^S-δt^R)-I_i+δ_trop+λ_iN_i+ε_φi

In formula：P_iAnd φ_iRepresent the pseudorange and carrier phase observation data of i-th of frequency (in units of rice)；ρ represents satellite and connect Geometric distance between receipts machine, is expressed asWherein x^S,y^S,z^SRepresent satellite Three-dimensional coordinate, x^R,y^R,z^RRepresent receiver antenna phase center three-dimensional coordinate；

δt^SWith δ t^RThe clock jitter of satellite and receiver, unit is the second；

I_iAnd δ_tropRepresent the influence of ionosphere and tropospheric delay；

N_iRepresent the integer ambiguity of i-th of frequency；

C represents the light velocity in vacuum；

λ_iThe carrier wavelength of i-th of frequency is represented, unit is rice；

2) track and clock correction of each aeronautical satellite of calculating signal emission time；Signal emission time calculates that mode includes two kinds： (1) the precise signal emission time and corresponding satellite rail of standard One-Point Location process iterative each aeronautical satellite are passed through The track clock correction of each satellite and the approximate coordinate of ground survey station are calculated after road and clock correction, successive ignition, (2) are seen using pseudorange Measured value Approximate Calculation signal emission time, calculates that Principle representation is：

3) information of obtained approximate survey station coordinate and the track clock correction of each aeronautical satellite is calculated according to One-Point Location, calculates and surveys The geometric distance ρ stood between each satellite, the information such as elevation of satellite；Further rule of thumb ionospheric model, calculates electricity Absciss layer is to carrier phase and the influence I of pseudorange_i, rule of thumb Tropospheric Models, calculate influence of the troposphere to GNSS signal δ_trop, orbit error δ is also remained in the observation after amendment_orb, receiver clock-offsets δ t^RWith integer ambiguity parameter N_iInfluence；

5) the difference observation data that the low orbit satellite that processing is received is broadcast；The difference observation packet that low orbit satellite is broadcast is containing letter Number receive time, the observation that LEO is received low orbit satellite track corresponding with the moment is received, and velocity information；Firstly the need of right Difference information is decoded, and gets necessary information；

6) LEO satellite observation moment corresponding each aeronautical satellite track of signal emission time and clock correction are calculated；

7) error source is carried out to the spaceborne receiver observations of LEO according to the track and clock correction of the track of LEO satellite and aeronautical satellite Correction；

8) un-differenced observation aspect carries out data snooping, cycle slips detection to the carrier phase observation data of the spaceborne receivers of LEO；To inspection The observation for occurring cycle slip is measured to be marked；

9) after being pre-processed respectively to the data of ground receiver and the spaceborne receivers of LEO, double difference observation is initially formed；It is first First filter out ground receiver and the spaceborne receivers of LEO regards satellite altogether, and then each navigation system selects a reference star, is used for Form difference observation between star；

10) double difference observation is formed；According to step 9) what is determined regards the reference satellite of satellite and each system, composition double difference observation altogether Value, star the double difference observation of difference be expressed as：

In formulaDouble difference operator is represented, is performed after double difference operation, the portion not disposed in un-differenced observation pretreatment stage Error source is divided to be completely eliminated in theory by way of double difference, these error sources include orbit error δ_orb, satellite clock correction δ t^S, connect Receipts machine clock correction δ t^R；Difference between the double difference geometric distance between the star of station, double difference ionosphere residual effect, star is also remained in double difference observation Troposphere influence, carrier phase ambiguity influence and observation noise influence；For forming error remaining after double difference observation , the influence of these errors is eliminated by the form of parameter Estimation；

11) cycle slips detection of double difference observation aspect；Using three poor method cycle slips detections；If to the cycle slips detection of un-differenced observation There is enough confidence, can skip this step；

12) filter temporal updates；For real-time coordinates estimation, including：A) Sequent least square method and Kalman filtering are used Method；Kalman filter model is relevant with observation selection, for Dual Frequency Observation data, there is two kinds of observation models：Based on without ionization The model of layer combination observation and the model based on non-combined observation；

A) the single order Xiang Ying in ionosphere is eliminated by Dual-frequency Observations linear combination based on the model without ionospheric combination observation Ring, but the observation quantity without ionospheric combination observation halves, observation noise is 3 times of observation before combination；

B) directly handled using non-combined observation, it is necessary to which every satellite estimates an Ionospheric Parameters；Stand star difference energy Weaken the influence in ionosphere, according to non-combined model inference；For non-combined model, filter status vector is chosen for：

X=[Δ r, δ_trop,z, I, N]^T；

Wherein Δ r is 3 × 1 increment of coordinate vector, δ_trop,zFor zenith direction tropospheric delay, each survey station estimates a parameter； I is each satellite direction of visual lines ionosphere delay, and every visible satellite estimates one, and N is double-differential carrier phase fuzziness parameter, often Individual signalling channel estimates one；In the case of without ionospheric combination observation, the negligible ionosphere of filter status vector is prolonged Slow parameter I；For static subscriber's positioning, increment of coordinate Δ r estimates as arbitrary constant；For dynamic positioning, random trip is used Process simulation is walked, or the equation of motion of additional external enters row constraint to increment of coordinate parameter；δ_trop,zUse random walk pattern die Intend, realize direction ionosphere delay I or initialized using prior information, then simulated using random walk process；Carrier phase Double difference fuzziness is estimated in continuous tracking using arbitrary constant model, needs parameter to reset when occurring cycle slip；Joining When examining star and changing star, specially treated is done to all fuzziness parameters；

Filter temporal renewal equation is expressed as：

In formulaP_t ^-Quantity of state and its variance-covariance matrix respectively after the renewal of t time, also referred to as forecast solution；For t-1 moment customer location state filtering solutions and its variance-covariance matrix；Φ (t, t-1) is that t-1 arrives t State-transition matrix；Q (t) is process noise matrix；For random walk parameter and random constant parameter, state-transition matrix is set For unit battle array；Diagonal matrix is set to for n independent random walk process Q (t), be may be configured as arbitrary constant parameter Q (t) Null matrix；

13) filter measurement updates；According to step 10) analysis, for double difference position pseudorange and carrier phase observation data line Property is expressed as：

E (y)=(J, M, Θ, Λ) (Δ r, δ_trop,z,I,N)^T；

E () is mathematic expectaion operator in formula, to f frequency, the observation of s visible double difference satellite, for using non-group For the mathematical modeling for closing observation, J is the Jacobbian matrixes of (2*s*f) × 3, and M is the column vector of (2*s*f) × 1, often The troposphere projection function value of individual element correspondence respective satellite；Θ is (2*s*f) × s matrix；Λ is (2*s*f) × (f*s) Matrix；For using the observation model without ionospheric combination, in addition to ignoring the corresponding design matrix Θ of Ionospheric Parameters, institute There is observation linear combination to also result in observation number and reduce half than non-combined model；After linearisation, the non-combined observation The design matrix of equation is defined as：

A=(J, M, Θ, Λ)；

Then the measurement updaue equation of Kalman filtering is expressed as：

K_t=P_t ^-A(AP_t ^-A^T+R_t)^-1,

P_t ⁺=(I-K_tA)P_t ^-,

15) output forecast solution；If testing rear residual test not pass through, then it represents that observation there may be rough error；Visited using data Survey method is tested to rough error and rejects or abandon using filter solution, uses forecast solution insteadExported as final positioning result；

16) fuzziness is fixed；If filter solution is by testing rear residual test, obtained using the integer characteristic of carrier phase ambiguity Obtain the fuzziness fixed solution of centimetre class precision；The method that fuzziness is fixed drops related algorithm LAMBDA using least square or will The mode for being decomposed into width lane ambiguity without ionospheric combination carries out fuzziness step by step and fixed；

By step 13) in state vector merge according to real parameters and the class of numeric parameter two, then observational equation is simplified shown as E (y)=(B, Λ) (b, N)^T, corresponding filter state amountThe corresponding filter solution variance-covariance matrix of two class parameters It is expressed as：

The filter solution of fuzziness parameter is denoted asCommonly referred to as fuzziness real solution, by the real solution of fuzziness parameterAnd its Variance-covariance matrix Q_NNAs input, scanned for using LAMBDA methods, obtain the optimal integer fixed solution of fuzziness With the integer fixed solution of suboptimum

17) fuzziness is examined；Being fixed due to the fuzziness of mistake causes positioning result to produce flying spot, and position error is than float-solution also Greatly, result is fixed to fuzziness to test；Examined using Ratio；

18) float-solution is exported；If the test fails by Ratio, then it is assumed that fuzziness fixed solution is unreliable, it is necessary to use filter solutionExported as final positioning result；

19) fixed solution is exported；If Ratio upchecks, exported using fuzziness fixed solution as positioning result；Fuzziness It is fixed as after integer, corresponding real parametersThe condition solution of integer ambiguity is may be updated as, is expressed as：

Corresponding variance-covariance matrix is represented by：

If fuzziness is upchecked, useUsed as last positioning result.

7. it is a kind of as claimed in claim 1 the star based on low orbit satellite difference real-time accurate localization method based on low orbit satellite Star ground difference real-time accurate alignment system.

8. the star of low orbit satellite described in a kind of utilization claim 7 difference real-time accurate alignment system ocean real-time accurate determine Position system.

9. the star of low orbit satellite described in a kind of utilization claim 7 difference real-time accurate alignment system remote districts in real time essence Close alignment system.

10. a kind of star using low orbit satellite as claimed in claim 7 difference real-time accurate alignment system natural calamity calamity Area's real-time accurate alignment system.