阅读说明：本技术 适用于机载的gnss无缝高精度定位和完好性评估方法 (Seamless high-precision positioning and integrity evaluation method of GNSS (Global navigation satellite System) suitable for airborne ) 是由 盛传贞 张京奎 郝青茹 应俊俊 惠沈盈 赵精博 于 2019-11-04 设计创作，主要内容包括：本发明公开了一种适用于机载平台的无缝高精度定位和完好性评估方法,适用于机载平台高精度导航定位以及相关应用领域,它在传统的RAIM算法基础上,采用RTK和RTD双引擎的实时运算结果,实现定位完好性评估,为错误固定模糊度导致的RTK定位异常提供预警；基于GNSS多普勒观测量估计的速度/加速度探测机载运动状态异常,在机载平台运动过程中,以宽巷模糊度作为虚拟观测,实现卫星运动中的短基线和中长基线RTK定位模式的无缝切换,解决机载平台定位模式切换中引擎需要重新初始化问题。(The invention discloses a seamless high-precision positioning and integrity evaluation method suitable for an airborne platform, which is suitable for the high-precision navigation positioning and related application fields of the airborne platform.A real-time operation result of an RTK (real time kinematic) and an RTD (real time kinematic) dual engine is adopted on the basis of the traditional RAIM (random access identity) algorithm to realize the positioning integrity evaluation and provide early warning for RTK positioning abnormity caused by wrong fixing ambiguity; the method is characterized in that the speed/acceleration estimated based on the GNSS Doppler observed quantity is used for detecting the airborne motion state abnormity, in the motion process of an airborne platform, the wide lane ambiguity is used as virtual observation, the seamless switching of the RTK positioning modes of the short base line and the middle and long base line in the satellite motion is realized, and the problem that an engine needs to be reinitialized in the switching of the positioning modes of the airborne platform is solved.)

1. A seamless high-precision positioning and integrity evaluation method for an airborne GNSS (global navigation satellite system) is supported by ground reference station observation data, and provides high-precision positioning and integrity evaluation for an airborne platform on the basis of an airborne platform GNSS carrier phase and a pseudo-range observation value, and is characterized by comprising the following steps:

(1) based on the pseudorange observation value and the carrier phase observation value of the airborne platform, performing single-point positioning, performing RAIM integrity monitoring, detecting possible abnormal satellites, marking and removing the abnormal satellites;

(2) forming pseudo-range double difference values based on the airborne platform pseudo-range observed value and the reference station pseudo-range observed value, performing RTD positioning operation, and calculating the length of a base line; meanwhile, the current position is predicted based on the position, the speed and the acceleration of an epoch on the airborne platform, the RTD positioning operation result and the predicted current position are compared and analyzed, the RTD position precision is evaluated, and the abnormal motion state of the airborne platform is detected;

(3) forming a carrier phase double-difference value based on the carrier phase observed value of the airborne platform and the carrier phase observed value of the reference station; performing RTK calculation by taking the RTD positioning position as an initial coordinate according to the pseudo-range double difference value and the carrier phase double difference value of the reference station and the airborne platform; the RTK calculation specifically comprises the following steps: when the length of the base line is smaller than the threshold value, single-frequency RTK positioning is adopted, when the length of the base line is equal to the threshold value, seamless switching of a positioning mode is carried out, and when the length of the base line is larger than the threshold value, double-frequency deionization layer combined RTK positioning is adopted under the constraint of the ambiguity of a wide lane;

(4) judging the integrity of the RTK positioning result based on the RTD positioning result and the RTK positioning result to obtain an optimal positioning result; and simultaneously estimating the speed and the acceleration of the current epoch of the airborne platform based on the Doppler.

2. The method for seamless high-precision positioning and integrity assessment of GNSS adapted to be onboard as claimed in claim 1, wherein said step (2) comprises the following steps:

(201) forming pseudo-range double difference values based on the pseudo-range observed values of the airborne platform and the pseudo-range observed values of the reference station, wherein the equation is as follows:

()^ijrepresents the single difference between satellite i and satellite j ()_rbRepresenting a single difference between the airborne platform r and the reference station b,

and

(202) Predicting the position coordinate at the current moment based on the position, the speed and the acceleration of an epoch on the airborne platform, wherein the mathematical equation is as follows:

wherein

(203) coordinate of RTD position of airborne platform at current moment

wherein, delta_X1To predict the coordinate deviation between the position coordinates and the RTD position coordinates, δ_pTo discriminate the threshold value, when delta_X1Less than delta_pIf not, the airborne platform has variable speed movement and simultaneously moves according to delta_X1And evaluating the positioning accuracy of the RTD.

3. The method for seamless high-precision positioning and integrity assessment of GNSS adapted to be onboard as claimed in claim 2, wherein said step (3) comprises the following steps:

(301) forming a double difference value of the carrier phase based on the carrier phase observed value of the airborne platform and the carrier phase observed value of the reference station, wherein the equation is as follows:

(302) based on the double difference values of the pseudo range and the carrier phase, when the length of the base line is smaller than a threshold value, single-frequency RTK positioning is adopted, and the realization process is as follows:

when the base length is less than the threshold value L0, the double difference between the double-frequency carrier phase and the pseudo range is adopted, and the ionospheric delay and the tropospheric delay are ignored, and the equation is as follows:

obtaining the position of a real-time airborne platform by adopting a single-frequency RTK positioning mode based on double differences of double-frequency carrier phases and pseudo rangesDetermining carrier phase ambiguity N₁And N₂At the same time obtain

Q_X、

(303) according to the length of a base line, when the RTK is in the L0 critical state transition, seamless switching from a single-frequency RTK positioning mode to dual-frequency deionization layer combined RTK positioning is carried out according to a state conversion matrix D, and a switching equation is as follows:

Q_L3＝D*Q*D^T

wherein I_3×3Is a three-dimensional identity matrix, I_n×nIs an N-dimensional identity matrix, N_wFor the ambiguity of the width lane, Q_L3Is composed of

Q_X、Q_T、

(304) based on the double differences of the pseudo range and the carrier phase, if the base length L is greater than an agreed threshold value L0, the RTK positioning is combined by adopting the double-frequency deionization layer, and the implementation process is as follows:

if the base length is greater than the threshold value L0, the RTK positioning adopts a two-step method; firstly, forming MW combined observed quantity based on double-frequency pseudo range and double-difference value of carrier phase

Then forming pseudo-range dual-frequency ionosphere observed quantity based on dual-difference values of dual-frequency pseudo-range and carrier phase

4. The method for seamless high-precision positioning and integrity assessment of GNSS adapted to be onboard as claimed in claim 3, wherein the step (4) is implemented as follows:

(401) the specific equation for the RTK positioning integrity evaluation is as follows:

wherein

(402) and estimating the speed of the current epoch in real time based on the Doppler information of the current epoch, and estimating and obtaining the acceleration of the current epoch by combining the speed information of the previous epoch moment.

Technical Field

The invention relates to a seamless high-precision positioning and integrity evaluation method based on an airborne GNSS (global navigation satellite system), belonging to the technical field of precision positioning and positioning integrity evaluation in satellite navigation.

Background

The GNSS can provide continuous and real-time navigation, positioning and time services for the airborne platform as an important means for positioning the airborne platform, and with the urgent need of optical imaging such as mapping, reconnaissance and military reconnaissance for high-precision positioning of the airborne platform, the rtk (real time kinematic) technology gradually becomes an important form for high-precision positioning of the airborne platform.

At present, with the gradual increase of the power consumption, size and endurance of airborne platforms, the operation range thereof is expanded from the traditional several kilometers to the present several tens kilometers range, in order to adapt to the operation under different distance conditions, the high-precision positioning method needs to have both short-baseline RTK and medium-baseline RTK positioning, however, the short-baseline RTK and the medium-baseline RTK have certain differences in methods such as observation equation, processing thought, parameter estimation and the like, therefore, under the critical flight state of the airborne platform from the short baseline to the medium-long baseline, the switching of the two processing methods is faced, the convergence time is inevitably increased by the traditional reinitialized switching method, the positioning performance is reduced, therefore, the invention provides a unified method and a seamless switching method suitable for airborne high-precision positioning based on two RTK positioning principles, and solves the problem of seamless switching and high-precision positioning of two RTK positioning methods in a critical state.

In addition, high-precision position information is used as basic data of intelligent control and autonomous navigation of the airborne platform, the reliability and accuracy of the position of the airborne platform are important for reasonable and accurate navigation and control, and compared with GNSS pseudo-range measurement data, carrier phase measurement data are more easily interrupted by environmental changes, so that the reliability of RTK high-precision positioning is reduced.

Aiming at the problems, the invention provides a seamless high-precision positioning and integrity evaluation method suitable for an airborne platform, which adopts the real-time operation result of RTK and RTD double engines to realize the positioning integrity evaluation and the airborne motion state abnormity detection of the airborne platform, and the designed RTK high-precision positioning unified method and the RTK seamless switching method realize the seamless switching of the RTK positioning mode in the motion process of the airborne platform and solve the problem of the reinitialization of the airborne platform positioning engine.

Disclosure of Invention

The invention provides a seamless high-precision positioning and integrity evaluation method for an airborne GNSS (global navigation satellite system), aiming at the problems of RTK (real-time kinematic) seamless high-precision positioning of an airborne platform in flight from a short baseline to a medium-long baseline, RTK positioning integrity evaluation of the airborne platform, abnormal detection of an airborne motion state and the like.

The invention is realized by the following technical scheme:

a seamless high-precision positioning and integrity evaluation method for an airborne GNSS (global navigation satellite system) is provided, which is supported by ground reference station observation data and based on an airborne platform GNSS carrier phase and a pseudo-range observation value, provides high-precision positioning and integrity evaluation for the airborne platform, and comprises the following steps:

(1) based on the pseudorange observation value and the carrier phase observation value of the airborne platform, performing single-point positioning, performing RAIM integrity monitoring, detecting possible abnormal satellites, marking and removing the abnormal satellites;

(2) forming pseudo-range double difference values based on the airborne platform pseudo-range observed value and the reference station pseudo-range observed value, performing RTD positioning operation, and calculating the length of a base line; meanwhile, the current position is predicted based on the position, the speed and the acceleration of an epoch on the airborne platform, the RTD positioning operation result and the predicted current position are compared and analyzed, the RTD position precision is evaluated, and the abnormal motion state of the airborne platform is detected;

(3) forming a carrier phase double-difference value based on the carrier phase observed value of the airborne platform and the carrier phase observed value of the reference station; performing RTK calculation by taking the RTD positioning position as an initial coordinate according to the pseudo-range double difference value and the carrier phase double difference value of the reference station and the airborne platform; the RTK calculation specifically comprises the following steps: when the length of the base line is smaller than the threshold value, single-frequency RTK positioning is adopted, when the length of the base line is equal to the threshold value, seamless switching of a positioning mode is carried out, and when the length of the base line is larger than the threshold value, double-frequency deionization layer combined RTK positioning is adopted under the constraint of the ambiguity of a wide lane;

(4) judging the integrity of the RTK positioning result based on the RTD positioning result and the RTK positioning result to obtain an optimal positioning result; and simultaneously estimating the speed and the acceleration of the current epoch of the airborne platform based on the Doppler.

Wherein, the step (2) specifically comprises the following steps:

(201) forming pseudo-range double difference values based on the pseudo-range observed values of the airborne platform and the pseudo-range observed values of the reference station, wherein the equation is as follows:

()^ijrepresents the single difference between satellite i and satellite j ()_rbRepresenting a single difference between the airborne platform r and the reference station b,

a double difference of the pseudoranges representing the k frequencies,a double difference value representing the tropospheric delay,

double difference, epsilon, representing ionospheric delay at k frequency_PA residual representing a double difference of the pseudoranges,

the double difference value of the geometric distance between the satellite and the airborne platform is expressed by the following formula:

and

respectively represent the geometrical distances between the airborne platform r and the satellite i, between the reference station b and the satellite i, between the airborne platform r and the satellite j, and between the reference station b and the satellite j, wherein:

and

respectively representing the three-dimensional components of the position of the satellite i,

and

each representing a three-dimensional component, x, of the position j of a satellite_r、y_rAnd z_rA three-dimensional component representing a position of the airborne platform; then RTD positioning operation is carried out, the length of a base line is calculated, and the RTD positioning operation is that the position coordinates of the airborne platform at the current moment are solved based on the pseudo-range double difference value

(x_r，y_r，z_r)；

(202) Predicting the position coordinate at the current moment based on the position, the speed and the acceleration of an epoch on the airborne platform, wherein the mathematical equation is as follows:

whereinFor predicted current time t of airborne platform₁Position coordinates of (2), X₀、v₀And a₀Respectively, at a previous time t₀Estimated position, velocity and acceleration values;

(203) coordinate of RTD position of airborne platform at current moment(x_r，y_r，z_r) With predicted current time position coordinates

And carrying out comparative analysis, evaluating the RTD position precision and detecting the abnormal motion state of the airborne platform, wherein the process comprises the following steps:

wherein, delta_X1To predict the coordinate deviation between the position coordinates and the RTD position coordinates, δ_pTo discriminate the threshold value, when delta_X1Less than delta_pIf not, the airborne platform has variable speed movement and simultaneously moves according to delta_X1And evaluating the positioning accuracy of the RTD.

Wherein, the step (3) specifically comprises the following steps:

(301) forming a double difference value of the carrier phase based on the carrier phase observed value of the airborne platform and the carrier phase observed value of the reference station, wherein the equation is as follows:

a double difference value representing a carrier phase observation for k frequencies; lambda [ alpha ]_kAnd

wavelength and frequency representing k frequency, respectively;

andsingle difference values representing integer ambiguities of k-frequency satellites i and j, respectively;a residual representing a double difference of the pseudorange and the carrier phase;

(302) based on the double difference values of the pseudo range and the carrier phase, when the length of the base line is smaller than a threshold value, single-frequency RTK positioning is adopted, and the realization process is as follows:

when the base length is less than the threshold value L0, the double difference between the double-frequency carrier phase and the pseudo range is adopted, and the ionospheric delay and the tropospheric delay are ignored, and the equation is as follows:

obtaining the position of a real-time airborne platform by adopting a single-frequency RTK positioning mode based on double differences of double-frequency carrier phases and pseudo ranges

Determining carrier phase ambiguity N₁And N₂At the same time obtain

N₁And N₂A variance matrix Q of parameters, wherein:

and

are respectively as

Variance matrix, N₁Variance matrix and N₂The variance matrix is used to determine the variance of the received signal,

is composed of

And N₁The covariance matrix of (a) is determined,

andare mutually rotated in a mutual way,is composed of

And N₁The covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is N₁And N₂The covariance matrix of (a) is determined,

andare transposed to each other;

(303) according to the length of a base line, when the RTK is in the L0 critical state transition, seamless switching from a single-frequency RTK positioning mode to dual-frequency deionization layer combined RTK positioning is carried out according to a state conversion matrix D, and a switching equation is as follows:

Q_L3＝D*Q*D^T

wherein I_3×3Is a three-dimensional identity matrix, I_n×nIs an N-dimensional identity matrix, N_wFor the ambiguity of the width lane, Q_L3Is composed of

N₁And N_wThe variance matrix of the parameters is then calculated,

for vertical tropospheric delay, Q_L3The meanings of (A) are as follows:

Q_X、Q_T、

andare respectively as

Variance matrix, vertical tropospheric delay

Variance matrix, narrow lane ambiguity N₁Variance matrix and wide lane ambiguity N_wThe variance matrix is used to determine the variance of the received signal,

is composed of

And N₁The covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is composed of

And N_wThe covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is N₁And N_wThe covariance matrix of (a) is determined,

andare transposed to each other, Q_TXIs to beAnd

of the covariance matrix, Q_TXAnd Q_XTAre mutually rotated in a mutual way,is composed of

And N_wThe covariance matrix of (a) is determined,andare mutually rotated in a mutual way,

is composed of

And N₁The covariance matrix of (a) is determined,and

are transposed to each other;

(304) based on the double differences of the pseudo range and the carrier phase, if the base length L is greater than an agreed threshold value L0, the RTK positioning is combined by adopting the double-frequency deionization layer, and the implementation process is as follows:

if the base length is greater than the threshold value L0, the RTK positioning adopts a two-step method; firstly, forming MW combined observed quantity based on double-frequency pseudo range and double-difference value of carrier phase

Its combined equationThenDescribes the observation equation of:

ionospheric delay, ε, combined for MW_P，L5Measurement of noise, widelane ambiguity for MW combinatorial equations

Therein

λ_wWavelength of widelane ambiguity

Due to the ionosphere

And tropospheric delayIs smaller, and therefore, based on the above

Observation equation capable of rapidly determining ambiguity N of wide lane_wSum variance matrix Q_w；

Then, based on double-frequency pseudo range and carrier phase, double-difference composition is carried outPseudo-range dual-frequency ionosphere-eliminating observation quantity

Dual-frequency ionospheric observations of sum-carrier

The combination equation is as follows:

and

then

And

the equation of (1) is expressed as follows:

and ε_P，L3Representative pseudorange dual-frequency ionospheric elimination observations

Dual-frequency ionospheric observations of noise and carrierNoise, M_FAnd

respectively representing the projection function and the vertical tropospheric delay; determining the ambiguity N of the wide lane determined in the above steps_wAs a virtual observation, i.e. a prior variance matrix, of Q_wIn combination with the above

And

observing equations, estimating vertical tropospheric delay in real time

And airborne platform position

I.e. x_r、y_rAnd z_rDetermining narrow lane ambiguity N₁And a wide lane ambiguity N_wWhile obtaining the current epochN₁And N_wVariance matrix Q of parameters_L3。

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

(401) the specific equation for the RTK positioning integrity evaluation is as follows:

wherein

Airborne platform current time t obtained for RTD positioning₁The position coordinates of the (c) and (d),

airborne platform current time t acquired for RTK positioning₁Is delta is a discrimination threshold when delta is_rtkWhen the value is smaller than delta, the RTK does not have larger positioning deviation, otherwise, the RTK positioning result has larger deviation, and meanwhile, the value is based on delta_rtkEvaluating the positioning integrity of the RTK;

(402) and estimating the speed of the current epoch in real time based on the Doppler information of the current epoch, and estimating and obtaining the acceleration of the current epoch by combining the speed information of the previous epoch moment.

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

the invention provides a seamless high-precision positioning and integrity evaluation method suitable for an airborne platform, aiming at the problem of RTK switching of the airborne platform from a short baseline to a medium-long baseline, realizing seamless switching of state parameters and a random model of the airborne platform based on a state transition matrix and pseudo observed quantity of wide lane ambiguity, solving the problem of reinitialization of a positioning engine in RTK positioning mode switching of the airborne platform, and designing a mutual verification method by adopting position prediction and real-time operation results of RTK and RTD engines to realize positioning integrity evaluation and airborne motion state anomaly detection of the airborne platform.

Drawings

FIG. 1 is a drawing of the movement process 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 process of moving from the short baseline to the medium-long baseline along the working route using the airborne platform will be described as an example (the baseline refers to the horizontal distance between the reference station and the airborne platform). The equipment of the invention comprises: a schematic diagram of a ground GNSS reference station and an airborne GNSS high-precision positioning device is shown in FIG. 1, the reference station receives GNSS signals in real time, tracks and captures carrier phase measurement and pseudo-range measurement data, and then sends the carrier phase measurement data and the pseudo-range measurement data to the airborne GNSS high-precision positioning device in real time, and based on the above, the GNSS high-precision positioning device executes airborne platform high-precision positioning and integrity evaluation, and the method comprises the following steps:

1. based on the pseudorange observation value and the carrier phase observation value of the airborne platform, performing single-point positioning, performing RAIM integrity monitoring, detecting possible abnormal satellites, marking and removing the abnormal satellites;

(101) and performing single-point positioning operation based on the airborne pseudo-range observed value and the satellite ephemeris data to obtain the approximate airborne platform position and the post-test residual error, and executing a receiver RAIM algorithm if the post-test residual error exceeds a specified threshold and the number of observed satellites is more than 5.

(102) The receiver RAIM algorithm is specifically executed as follows: and circularly eliminating the single-point positioning after the satellite at a certain moment, marking the satellite as an abnormal satellite when the residual error is obviously reduced after the satellite is deleted, and not using the satellite in the subsequent processing.

2. Forming pseudo-range double difference values with the pseudo-range observed values of the reference station based on the airborne pseudo-range observed values, performing RTD positioning operation, and calculating the length of a base line; and meanwhile, carrying out comparison analysis (based on the position, the speed and the acceleration of the last epoch) with the predicted current position, evaluating the RTD position precision and detecting the abnormal motion state of the airborne platform.

(201) Forming pseudo-range double difference values based on the pseudo-range observed values of the airborne platform and the pseudo-range observed values of the reference station, wherein the equation is as follows:

()^ijrepresents the single difference between satellite i and satellite j ()_rbRepresenting a single difference between the airborne platform r and the reference station b,a double difference of the pseudoranges representing the k frequencies,

a double difference value representing the tropospheric delay,

double difference, epsilon, representing ionospheric delay at k frequency_PA residual representing a double difference of the pseudoranges,

the double difference value of the geometric distance between the satellite and the airborne platform is expressed by the following formula:

and

respectively represent the geometrical distances between the airborne platform r and the satellite i, between the reference station b and the satellite i, between the airborne platform r and the satellite j, and between the reference station b and the satellite j, wherein:

and

respectively representing the three-dimensional components of the position of the satellite i,

and

each representing a three-dimensional component, x, of the position j of a satellite_r、y_rAnd z_rA three-dimensional component representing a position of the airborne platform; then RTD positioning operation is carried out, the length of a base line is calculated, and the RTD positioning operation is that the position coordinates of the airborne platform at the current moment are solved based on the pseudo-range double difference value

(x_r，y_r，z_r)；

(202) Predicting the position coordinate at the current moment based on the position, the speed and the acceleration of an epoch on the airborne platform, wherein the mathematical equation is as follows:

wherein

For predicted current time t of airborne platform₁Position coordinates of (2), X₀、v₀And a₀Respectively, at a previous time t₀Estimated position, velocity and acceleration values;

(203) coordinate of RTD position of airborne platform at current moment

(x_r，y_r，z_r) With predicted current time position coordinatesAnd carrying out comparative analysis, evaluating the RTD position precision and detecting the abnormal motion state of the airborne platform, wherein the process comprises the following steps:

wherein, delta_X1To predict the coordinate deviation between the position coordinates and the RTD position coordinates, δ_pTo discriminate the threshold value, when delta_X1Less than delta_pIf not, the airborne platform has variable speed movement and simultaneously moves according to delta_X1And evaluating the positioning accuracy of the RTD.

3. And performing RTK calculation (adopting single-frequency RTK positioning if the length of the base line is less than a certain threshold value, or adopting double-frequency deionization layer combined RTK positioning under the limitation of wide lane ambiguity) based on the RTD position coordinates as initial coordinate information according to the double differences of the pseudo range and the carrier phase of the base station and the airborne station, and performing seamless switching of the positioning mode according to the length of the base line.

(301) Forming a double difference value of the carrier phase based on the carrier phase observed value of the airborne platform and the carrier phase observed value of the reference station, wherein the equation is as follows:

a double difference value representing a carrier phase observation for k frequencies; lambda [ alpha ]_kAndwavelength and frequency representing k frequency, respectively;and

single difference values representing integer ambiguities of k-frequency satellites i and j, respectively;

a residual representing a double difference of the pseudorange and the carrier phase;

(302) based on the double difference values of the pseudo range and the carrier phase, when the length of the base line is smaller than a threshold value, single-frequency RTK positioning is adopted, and the realization process is as follows:

when the base length is less than the threshold value L0, the double difference between the double-frequency carrier phase and the pseudo range is adopted, and the ionospheric delay and the tropospheric delay are ignored, and the equation is as follows:

obtaining real time by adopting a single-frequency RTK positioning mode based on double differences of double-frequency carrier phase and pseudo rangeAirborne platform location

Determining carrier phase ambiguity N₁And N₂At the same time obtain

N₁And N₂A variance matrix Q of parameters, wherein:

Q_X、

and

are respectively as

Variance matrix, N₁Variance matrix and N₂The variance matrix is used to determine the variance of the received signal,is composed of

And N₁The covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is composed of

And N₁The covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is N₁And N₂The covariance matrix of (a) is determined,

and

are transposed to each other;

(303) according to the length of a base line, when the RTK is in the L0 critical state transition, seamless switching from a single-frequency RTK positioning mode to dual-frequency deionization layer combined RTK positioning is carried out according to a state conversion matrix D, and a switching equation is as follows:

Q_L3＝D*Q*D^T

wherein I_3×3Is a three-dimensional identity matrix, I_n×nIs an N-dimensional identity matrix, N_wFor the ambiguity of the width lane, Q_L3Is composed of

N₁And N_wThe variance matrix of the parameters is then calculated,

for vertical tropospheric delay, Q_L3The meanings of (A) are as follows:

Q_X、Q_T、

and

are respectively as

Variance matrix, vertical tropospheric delay

Variance matrix, narrow lane ambiguity N₁Variance matrix and wide lane ambiguity N_wThe variance matrix is used to determine the variance of the received signal,

is composed ofAnd N₁The covariance matrix of (a) is determined,and

are mutually rotated in a mutual way,

is composed of

And N_wThe covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is N₁And N_wThe covariance matrix of (a) is determined,

and

are transposed to each other, Q_TXIs to beAnd

of the covariance matrix, Q_TXAnd Q_XTAre mutually rotated in a mutual way,is composed ofAnd N_wThe covariance matrix of (a) is determined,

and

are mutually rotated in a mutual way,

is composed of

And N₁The covariance matrix of (a) is determined,and

are transposed to each other;

(304) based on the double differences of the pseudo range and the carrier phase, if the base length L is greater than an agreed threshold value L0, the RTK positioning is combined by adopting the double-frequency deionization layer, and the implementation process is as follows:

if the base length is greater than the threshold value L0, the RTK positioning adopts a two-step method; firstly, forming MW combined observed quantity based on double-frequency pseudo range and double-difference value of carrier phase

Its combined equation

Then

Describes the observation equation of:

ionospheric delay, ε, combined for MW_P，L5Measurement of noise, widelane ambiguity for MW combinatorial equations

Therein λ_wWavelength of widelane ambiguity

Due to the ionosphere

And tropospheric delay

Is smaller, and therefore, based on the above

Observation equation capable of rapidly determining ambiguity N of wide lane_wSum variance matrix Q_w；

Then forming pseudo-range dual-frequency ionosphere observed quantity based on dual-difference values of dual-frequency pseudo-range and carrier phaseDual-frequency ionospheric observations of sum-carrierThe combination equation is as follows:

and

then

And

the equation of (1) is expressed as follows:

and ε_P，L3Double-frequency power-eliminating device for representing pseudo rangeObserved amount of separation

Dual-frequency ionospheric observations of noise and carrier

Noise, M_FAnd

respectively representing the projection function and the vertical tropospheric delay; determining the ambiguity N of the wide lane determined in the above steps_wAs a virtual observation, i.e. a prior variance matrix, of Q_wIn combination with the above

Andobserving equations, estimating vertical tropospheric delay in real timeAnd airborne platform position

I.e. x_r、y_rAnd z_rDetermining narrow lane ambiguity N₁And a wide lane ambiguity N_wWhile obtaining the current epoch

N₁And N_wVariance matrix Q of parameters_L3。

4. Judging the integrity of the RTK positioning result based on the RTD positioning result and the RTK positioning result to obtain an optimal positioning result; while current epoch velocity and acceleration are estimated based on doppler.

(1) The specific equation for the RTK positioning integrity evaluation is as follows:

whereinAirborne platform current time t obtained for RTD positioning₁The position coordinates of the (c) and (d),

airborne platform current time t acquired for RTK positioning₁Is delta is a discrimination threshold when delta is_rtkWhen the positioning deviation is smaller than delta, the RTK does not have larger positioning deviation, otherwise, the RTK positioning result has larger deviation, and delta simultaneously_rtkThe positioning integrity of RTK is reflected to a certain extent.

(2) And estimating the speed of the current epoch in real time based on the Doppler information of the current epoch, and estimating and obtaining the acceleration information of the current epoch by combining the speed information at the previous epoch moment to obtain the estimation of the speed and the acceleration of the airborne platform at the current epoch moment.

In a word, the seamless high-precision positioning and integrity evaluation method suitable for the airborne platform, provided by the invention, aims at the RTK switching problem of the airborne platform from a short baseline to a medium-long baseline, realizes seamless switching of state parameters and a random model of the airborne platform based on a state transition matrix and pseudo observed quantity of wide lane ambiguity, solves the problem of reinitialization of a positioning engine in the RTK positioning mode switching of the airborne platform, and designs a mutual verification method by adopting position prediction, RTK and RTD dual-engine real-time operation results to realize positioning integrity evaluation and airborne motion state anomaly detection of the airborne platform.

The method solves the problem of seamless switching of the airborne platform from a short baseline to a medium-long baseline in a critical flight state, improves the positioning precision, integrity and reliability, is particularly suitable for high-precision navigation of the airborne platform under a large operation radius, and has important engineering practical application value.