阅读说明：本技术 一种适用于laas的多径误差模型化方法 (Multi-path error modeling method suitable for LAAS ) 是由 盛传贞 蔚保国 解晶 张京奎 王垚 赵精博 惠沈盈 于 2019-11-04 设计创作，主要内容包括：本发明公开了一种适用局域增强系统(LAAS)的多径误差模型化方法,适用于地面监测站伪距和载波观测量的多径误差修正,它在传统精密单点定位的基础上,采用非组合精密单点模糊度固定处理方法,实现伪距和载波相位的多径误差分离；以精密单点定位伪距和载波相位验后残差为基础,构建高度角/方位角的多径误差模型,基于此,进行监测站伪距和载波相位多径误差的实时补偿,减弱多径误差对LAAS异常检测所带来的不利影响,同时提高差分增强信息生成的精度。(The invention discloses a multipath error modeling method suitable for a Local Area Augmentation System (LAAS), which is suitable for multipath error correction of pseudo range and carrier observed quantity of a ground monitoring station, and realizes multipath error separation of pseudo range and carrier phase by adopting a non-combined precise single-point ambiguity fixing processing method on the basis of traditional precise single-point positioning; and constructing a multipath error model of an altitude angle/an azimuth angle based on the precise single-point positioning pseudo-range and the carrier phase post-test residual error, and performing real-time compensation on the pseudo-range of the monitoring station and the carrier phase multipath error based on the model, so that the adverse effect of the multipath error on LAAS anomaly detection is weakened, and the generation precision of differential enhancement information is improved.)

1. A multi-path error modeling method suitable for LAAS is characterized by comprising the following steps:

(1) under the support of an IGS precision product, determining carrier phase ambiguity, ionosphere delay and troposphere delay information of all satellites by adopting a non-combined precision single-point positioning processing method based on the GNSS pseudo-range of a ground monitoring station and historical observation data of carrier phases;

(2) fitting and smoothing the ionospheric delay and tropospheric delay information of all satellites, taking the fitting and smoothing result as a virtual observed quantity on the basis, adding strong constraint, estimating and determining the ambiguity of the carrier phase again, and simultaneously obtaining the post-test residual errors of pseudo ranges and the carrier phase;

(3) aiming at the post-test residual errors of pseudo ranges and carrier phases of all satellites, constructing a multi-path error model of the pseudo ranges and the carrier phases by taking altitude angles and azimuth angles as characteristic quantities;

(4) aiming at real-time pseudo-range and carrier phase observation data of a monitoring station, a multi-path error model of the pseudo-range and the carrier phase is adopted to compensate the multi-path error; and calculating the basic quantity of the LAAS differential enhanced pseudo range and the carrier phase based on the compensated data.

2. The method for modeling multipath error applicable to LAAS of claim 1, wherein the step (1) is implemented by:

(101) based on historical observation data of a GNSS pseudo-range and a carrier phase of a ground monitoring station, the adopted non-combined precise point positioning observation equation is as follows:

wherein the content of the first and second substances,

(102) the carrier phase ambiguity, ionospheric delay and tropospheric delay estimation method based on the non-combined precise single-point positioning observation equation comprises the following steps:

known quantities were obtained based on IGS precision products: satellite phase deviation

In parameter estimation, for the ionospheric delay parameter IⁱTropospheric delay parameter TⁱAnd receiver carrier phase offset Fcs_b，fCorresponding constraint is added to avoid instability of results caused by equation singularity, and based on the method, carrier phase floating ambiguity of all satellites can be obtained by adopting a Kalman filtering estimation method

3. The method as claimed in claim 2, wherein the step (2) is performed by:

(201) the ionospheric delay and tropospheric delay information of all satellites are respectively removed through fitting smoothing of a time window to eliminate ionospheric delay or tropospheric delay with estimation errors; the method comprises the following steps:

y_s(t)＝p_0，i+p_1，it+p_2，it²

wherein p is_0，i、p_1，iAnd p_2，iAs fitting coefficient, y_s(t) is the corresponding delay observed quantity, if the residual error in the fitting is too large, the corresponding gross error is removed, the fitting is carried out again, the fitting value is used for replacing a field value, and the satellite ionosphere delay information after smoothing is obtainedAnd tropospheric delay information

(202) Ionospheric delay information smoothed based on fitting

wherein

(203) Obtaining pseudo-post-test residuals based on ionospheric delay, tropospheric delay and carrier phase integer ambiguitiesSum carrier phase post-test residualThe following formula is adopted:

4. the method as claimed in claim 3, wherein the step (3) is implemented as follows:

residual error after based on pseudo range test

wherein Sig is a sign function, el and az monitor the elevation angle and azimuth angle of the station and satellite sight respectively, Ns is the summation of the Sig function, N is the number of satellites at time t, t0 is the start time, tN is the end time, elS and azS represent discrete sampling points defined in two dimensions of the elevation angle and azimuth angle respectively, wherein the range of elevation angle is 0 ° to 90 °, the range of azimuth angle is 0 ° to 360 °, and the sampling interval is generally selected to be 5 °.

5. The method for modeling multipath error applicable to LAAS according to claim 4, wherein the step (4) is implemented as follows:

(401) pseudoranges received in real time for a monitoring station

(402) the LAAS ground system carries out LAAS differential enhancement information basic quantity according to the real-time pseudo-range and carrier phase measurement value after the correction of the monitoring station

Technical Field

The invention discloses a multipath error modeling method suitable for a Local Area Augmentation System (LAAS), which is suitable for multipath error compensation and correction of pseudo-range and carrier observed quantity of a ground monitoring station.

Background

The system effectively meets the requirements of high precision, safety and continuous landing of civil aircrafts by comprehensively processing and analyzing observation data of uniformly distributed monitoring stations, provides differential enhancement information and integrity information for users, and guides the civil aircrafts to accurately and safely land.

The GNSS signal is influenced by the surrounding environment of the monitoring station to generate reflection and scattering, so that multipath is caused, multipath errors are implicit in the pseudo-range of the monitoring station and the observation quantity of the carrier phase, particularly low elevation angle satellites, the influence of the multipath errors on the LAAS system is mainly reflected in two layers, ① influences the precision of LAAS differential enhancement information, ② influences the resolution of LAAS abnormal detection such as code/carrier deviation degree and phase smoothing abnormal monitoring, and the like.

The invention adopts the current precise single-point positioning ambiguity fixing method according to the multipath error space-time correlation characteristics, realizes the multipath error synchronous separation and modeling of carrier and phase data of the monitoring station based on the ionosphere and troposphere delay time smoothness and strong constraint, and finally solves the continuity and the robustness of the LAAS system service based on the multipath error compensation.

Disclosure of Invention

The invention provides a multi-path error separation and compensation method suitable for LAAS (local area network as), aiming at the problems that the multi-path of a monitoring station restricts the continuity of an LAAS system, reduces the accuracy of differential enhancement information and the like.

The invention is realized by the following technical scheme:

a multi-path error modeling method suitable for LAAS comprises the following steps:

(1) under the support of an IGS precision product, determining carrier phase ambiguity, ionosphere delay and troposphere delay information of all satellites by adopting a non-combined precision single-point positioning processing method based on the GNSS pseudo-range of a ground monitoring station and historical observation data of carrier phases;

(2) fitting and smoothing the ionospheric delay and tropospheric delay information of all satellites, taking the fitting and smoothing result as a virtual observed quantity on the basis, adding strong constraint, estimating and determining the ambiguity of the carrier phase again, and simultaneously obtaining the post-test residual errors of pseudo ranges and the carrier phase;

(3) aiming at the post-test residual errors of pseudo ranges and carrier phases of all satellites, constructing a multi-path error model of the pseudo ranges and the carrier phases by taking altitude angles and azimuth angles as characteristic quantities;

(4) aiming at real-time pseudo-range and carrier phase observation data of a monitoring station, a multi-path error model of the pseudo-range and the carrier phase is adopted to compensate the multi-path error; and calculating the basic quantity of the LAAS differential enhanced pseudo range and the carrier phase based on the compensated data.

Wherein, the specific mode of the step (1) is as follows:

(101) based on historical observation data of a GNSS pseudo-range and a carrier phase of a ground monitoring station, the adopted non-combined precise point positioning observation equation is as follows:

wherein the content of the first and second substances,

and

respectively representing pseudoranges and carrier measurements of the f-frequencies of the i-satellites observed by the ground monitoring station,

and

pseudo range noise and carrier phase noise respectively representing the f-frequencies of the i-satellites observed by the ground monitoring station,

representing the geometric distance, I, between the ground monitoring station and the satellite IⁱAnd gamma_fIonospheric delay and proportionality coefficient, T, respectively representing the reference frequency corresponding to the i satellite observed by the ground monitoring stationⁱAnd M_elRepresenting tropospheric delay and projection function, respectively, deltatⁱAnd δ t represent the satellite clock offset of the i satellite and the receiver clock offset of the ground monitoring station, λ, respectively_fAnd

respectively representing the carrier phase wavelength and the integer ambiguity of the i-satellite,

the pseudorange code phase bias representing the i satellite f frequency,

and

respectively representing pseudo-range multipath and carrier multipath of the frequency of the observation i satellite f of the ground monitoring station,

integer phase offsets representing carrier phases, including satellite phase offsets

And receiver phase deviation Fcs_b，fThe expression is as follows:

(102) the carrier phase ambiguity, ionospheric delay and tropospheric delay estimation method based on the non-combined precise single-point positioning observation equation comprises the following steps:

known quantities were obtained based on IGS precision products: satellite phase deviation

Pseudorange code bias

And satellite clock difference deltatⁱSubstituting the obtained data into a non-combined precise single-point positioning observation equation, and accurately obtaining the data under the known precise coordinates of the ground monitoring station and the support of the IGS precise ephemerisTherefore, the estimation parameters of the equation comprise receiver clock difference deltat and receiver carrier phase deviation Fcs_b，fIonospheric delay parameter IⁱTropospheric delay parameter TⁱAnd carrier phase integer ambiguity

In parameter estimation, for the ionospheric delay parameter IⁱTropospheric delay parameter TⁱAnd receiver carrier phase offset Fcs_b，fCorresponding constraint is added to avoid instability of results caused by equation singularity, and based on the method, carrier phase floating ambiguity of all satellites can be obtained by adopting a Kalman filtering estimation method

Then, the integer ambiguity of each satellite can be obtained by adopting an LAMBDA method

So as to obtain the ionospheric delay parameter I after ambiguity fixing solutionⁱAnd tropospheric delay Tⁱ。

Wherein, the specific mode of the step (2) is as follows:

(201) the ionospheric delay and tropospheric delay information of all satellites are respectively removed through fitting smoothing of a time window to eliminate ionospheric delay or tropospheric delay with estimation errors; the method comprises the following steps:

y_s(t)＝p_0，i+p_1，it+p_2，it²

wherein p is_0，i、p_1，iAnd p_2，iAs fitting coefficient, y_s(t) is the corresponding delay observed quantity, if the residual error in the fitting is too large, the corresponding gross error is removed, the fitting is carried out again, the fitting value is used for replacing a field value, and the satellite ionosphere delay information after smoothing is obtainedAnd tropospheric delay information

(202) Ionospheric delay information smoothed based on fitting

And tropospheric delay information

As a virtual observed quantity, adding strong constraint information; ionospheric delay information

And tropospheric delay information

The virtual observation equation of (a) is as follows:

wherein

And

matrices representing ionospheric delay and convective delay, respectively,. epsilon_I，iAnd ε_T，iRespectively representing the observation deviation of the ionosphere and the troposphere, and performing parameter estimation and ambiguity fixation again based on a virtual observation equation and the non-combined precise single-point positioning observation equation in the step (101) to obtain a receiver clock error delta t and a receiver carrier phase deviation Fcs_b，fIonospheric delay parameter IⁱTropospheric delay parameter TⁱAnd carrier phase integer ambiguity

(203) Obtaining pseudo-post-test residuals based on ionospheric delay, tropospheric delay and carrier phase integer ambiguities

Sum carrier phase post-test residualThe following formula is adopted:

the specific implementation manner of the step (3) is as follows:

residual error after based on pseudo range test

Sum carrier phase post-test residual

Constructing pseudo-range multi-path error model MP by using altitude angle and azimuth angle as characteristic quantities_fMultipath error model of sum carrier phase

The model adopts the following formula:

wherein Sig is a sign function, el and az monitor the elevation angle and azimuth angle of the station and satellite sight respectively, Ns is the summation of the Sig function, N is the number of satellites at time t, t0 is the start time, tN is the end time, elS and azS represent discrete sampling points defined in two dimensions of the elevation angle and azimuth angle respectively, wherein the range of elevation angle is 0 ° to 90 °, the range of azimuth angle is 0 ° to 360 °, and the sampling interval is generally selected to be 5 °.

The specific implementation manner of the step (4) is as follows:

(401) pseudoranges received in real time for a monitoring station

And carrier phase measurements

Using multipath models for compensation, the complement of whichThe compensation method comprises the following steps:

(402) the LAAS ground system carries out LAAS differential enhancement information basic quantity according to the real-time pseudo-range and carrier phase measurement value after the correction of the monitoring stationAnd

the following formula is adopted for the calculation of (1):

the geometric distance between the monitoring station and the satellite is obtained based on the precise coordinates known to the monitoring station and the broadcast ephemeris parameters.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a multi-path error separation and compensation method suitable for LAAS (local area network applications), which is used for designing a pseudo-range and carrier phase multi-path error synchronous separation method based on precise single-point positioning ambiguity fixing and information constraint aiming at the problem that pseudo-range and carrier phase multi-path errors cannot be separated simultaneously, and constructing a multi-path error model of an elevation angle and an azimuth angle aiming at the monitoring station multi-path compensation requirement of an LAAS system, so that the compensation of real-time multi-path errors of a monitoring station is met, the smoothing time of carrier phase smooth pseudo-range of the monitoring station of the LAAS system is reduced, the resolution of the LAAS system abnormal detection is improved, and the precision of differential enhanced information is improved.

Drawings

FIG. 1 is a diagram illustrating the movement of the airborne platform from a short baseline to a medium-long baseline;

Detailed Description

For better illustrating the objects and advantages of the present invention, the technical solution of the present invention will be further described with reference to fig. 1. In the present embodiment, the method is described by taking four LAAS ground monitoring stations (A, B, C, D) as an example. The equipment of the invention comprises: an LAAS system ground GNSS monitoring station, a schematic diagram of which is shown in FIG. 1, receives GNSS signals, tracks and captures the GNSS signals to obtain carrier phase measurement data and pseudo-range measurement data, and then sends the carrier phase measurement data and the pseudo-range measurement data to an LAAS ground processing center, the center executes multi-path error difference separation and modeling based on accumulated historical data of each monitoring station, and carries out LAAS difference enhancement information and integrity processing according to observation data of each monitoring station received in real time, wherein the whole processing comprises the following steps:

1. under the support of an IGS precision product, determining carrier phase ambiguity, ionosphere delay and troposphere delay information of all satellites by adopting a non-combined precision single-point positioning processing method based on the GNSS pseudo-range of a ground monitoring station and historical observation data of carrier phases;

(101) based on historical observation data of a GNSS pseudo-range and a carrier phase of a ground monitoring station, the adopted non-combined precise point positioning observation equation is as follows:

wherein the content of the first and second substances,

andrespectively representing pseudoranges and carrier measurements of the f-frequencies of the i-satellites observed by the ground monitoring station,

and

pseudo range noise and carrier phase noise respectively representing the f-frequencies of the i-satellites observed by the ground monitoring station,

representing the geometric distance, I, between the ground monitoring station and the satellite IⁱAnd gamma_fIonospheric delay and proportionality coefficient, T, respectively representing the reference frequency corresponding to the i satellite observed by the ground monitoring stationⁱAnd M_elRepresenting tropospheric delay and projection function, respectively, deltatⁱAnd δ t represent the satellite clock offset of the i satellite and the receiver clock offset of the ground monitoring station, λ, respectively_fAndrespectively representing the carrier phase wavelength and the integer ambiguity of the i-satellite,

the pseudorange code phase bias representing the i satellite f frequency,and

respectively representing pseudo-range multipath and carrier multipath of the frequency of the observation i satellite f of the ground monitoring station,

integer phase offsets representing carrier phases, including satellite phase offsets

And receiver phase deviation Fcs_b，fThe expression is as follows:

(102) the carrier phase ambiguity, ionospheric delay and tropospheric delay estimation method based on the non-combined precise single-point positioning observation equation comprises the following steps:

known quantities were obtained based on IGS precision products: satellite phase deviation

Pseudorange code bias

And satellite clock difference deltatⁱSubstituting the obtained data into a non-combined precise single-point positioning observation equation, and accurately obtaining the data under the known precise coordinates of the ground monitoring station and the support of the IGS precise ephemeris

Therefore, the estimation parameters of the equation comprise receiver clock difference deltat and receiver carrier phase deviation Fcs_b，fIonospheric delay parameter IⁱTropospheric delay parameter TⁱAnd carrier phase integer ambiguity

In parameter estimation, for the ionospheric delay parameter IⁱTropospheric delay parameter TⁱAnd receiver carrier phase offset Fcs_b，fCorresponding constraint is added to avoid instability of results caused by equation singularity, and based on the method, carrier phase floating ambiguity of all satellites can be obtained by adopting a Kalman filtering estimation method

Then, the integer ambiguity of each satellite can be obtained by adopting an LAMBDA methodSo as to obtain the ionospheric delay parameter I after ambiguity fixing solutionⁱAnd tropospheric delay Tⁱ。

2. Fitting and smoothing the ionospheric delay and tropospheric delay information of all satellites, taking the fitting and smoothing result as a virtual observed quantity on the basis, adding strong constraint, estimating and determining the ambiguity of the carrier phase again, and simultaneously obtaining the post-test residual errors of pseudo ranges and the carrier phase;

(201) the ionospheric delay and tropospheric delay information of all satellites are respectively removed through fitting smoothing of a time window to eliminate ionospheric delay or tropospheric delay with estimation errors; the method comprises the following steps:

y_s(t)＝p_0，i+p_1，it+p_2，it²

wherein p is_0，i、p_1，iAnd p_2，iAs fitting coefficient, y_s(t) is the corresponding delay observed quantity, if the residual error in the fitting is too large, the corresponding gross error is removed, the fitting is carried out again, the fitting value is used for replacing a field value, and the satellite ionosphere delay information after smoothing is obtained

And tropospheric delay information

(202) Ionospheric delay information smoothed based on fitting

And tropospheric delay information

As a virtual observed quantity, adding strong constraint information; ionospheric delay information

And tropospheric delay information

The virtual observation equation of (a) is as follows:

whereinAnd

matrices representing ionospheric delay and convective delay, respectively,. epsilon_I，iAnd ε_T，iRespectively representing the observation deviation of the ionosphere and the troposphere, and performing parameter estimation and ambiguity fixation again based on a virtual observation equation and the non-combined precise single-point positioning observation equation in the step (101) to obtain a receiver clock error delta t and a receiver carrier phase deviation Fcs_b，fIonospheric delay parameter IⁱTropospheric delay parameter TⁱAnd carrier phase integer ambiguity

(203) Obtaining pseudo-post-test residuals based on ionospheric delay, tropospheric delay and carrier phase integer ambiguities

Sum carrier phase post-test residual

The following formula is adopted:

3. and constructing a multi-path error model of the pseudo-range and the carrier phase by taking the altitude angle and the azimuth angle as characteristic quantities according to the post-test residuals of the pseudo-range and the carrier phase of all satellites.

In the post-pseudorange-a-test residuals and the carrier-phase-a-test residuals, the principal component thereof is a multipath error, and therefore, the post-pseudorange-a-test residuals are based thereon

Sum carrier phase post-test residualConstructing pseudo-range multi-path error model MP by using altitude angle and azimuth angle as characteristic quantities_fMultipath error model of sum carrier phase

The model adopts the following formula:

wherein Sig is a sign function, el and az monitor the elevation angle and azimuth angle of the station and satellite sight respectively, Ns is the summation of the Sig function, N is the number of satellites at time t, t0 is the start time, tN is the end time, elS and azS represent discrete sampling points defined in two dimensions of the elevation angle and azimuth angle respectively, wherein the range of elevation angle is 0 ° to 90 °, the range of azimuth angle is 0 ° to 360 °, and the sampling interval is generally selected to be 5 °.

4. Aiming at real-time pseudo-range and carrier phase observation data of a monitoring station, a multi-path error model of the pseudo-range and the carrier phase is adopted to compensate the multi-path error; and calculating the basic quantity of the LAAS differential enhanced pseudo range and the carrier phase based on the compensated data.

(401) The pseudo range and carrier phase multi-path error real-time compensation of the monitoring station adopts the following method:

pseudoranges received in real time for a monitoring station

And carrier phase measurements

The multi-path model is adopted for compensation, and the compensation method comprises the following steps:

(402) the LAAS ground system carries out LAAS differential enhancement information basic quantity according to the real-time pseudo-range and carrier phase measurement value after the correction of the monitoring stationAndthe following formula is adopted for the calculation of (1):

the geometric distance between the monitoring station and the satellite is obtained based on the precise coordinates known to the monitoring station and the broadcast ephemeris parameters. Based on the above obtaining

And

the multi-path error is greatly weakened, and the LAAS abnormal risk distinguishing efficiency and the information generation enhancing precision are improved.

In summary, the invention provides a multi-path error separation and compensation method suitable for LAAS, aiming at the problem that pseudo-range and carrier phase multi-path errors can not be separated simultaneously, the invention designs a pseudo-range and carrier phase multi-path error synchronous separation method based on precise single-point positioning ambiguity fixing and information constraint, and simultaneously constructs a multi-path error model of a height angle and an azimuth angle aiming at the multi-path error compensation requirement of a monitoring station of the LAAS system, thereby meeting the real-time compensation requirement of the monitoring station, reducing the time required by LAAS pseudo-range smoothing, improving the integrity monitoring resolution of the LAAS system and improving the precision of differential enhanced information.

The invention solves the problems of multipath error separation, modeling and real-time compensation of the pseudo range and carrier phase observed quantity of the LAAS monitoring station, greatly weakens the adverse effect of the multipath error on the continuity and the availability of the LAAS system, is particularly suitable for multipath error compensation of GNSS data of a CORS station, and has important engineering practical application value.