阅读说明：本技术 一种基于广播星历的实时数据流中断综合补偿方法 (Real-time data stream interruption comprehensive compensation method based on broadcast ephemeris ) 是由 高旺 赵庆 高成发 潘树国 于 2020-06-30 设计创作，主要内容包括：本发明公开了一种基于广播星历的实时数据流中断综合补偿方法。实时PPP(precise point positioning)需要实时接收轨道和钟差改正数,当实时数据流中断或存在较大时延时,难以保证用户高精度定位的连续性与可靠性。为解决这一问题,本发明基于区域参考站网,利用先前历元的模糊度、卫星FCBs(fractional-cycle biases)以及短时预测的对流层延迟,在当前历元采用广播星历的无电离层组合对包括轨道误差、卫星钟差以及接收机相关误差在内的综合误差进行提取与加权建模,并播发给用户。当实时轨道和钟差改正数存在中断或滞后时,用户仍然可以采用广播星历和综合误差代替,持续实现高精度增强定位。(The invention discloses a real-time data stream interruption comprehensive compensation method based on broadcast ephemeris. Real-time ppp (real-time point position) requires real-time reception of track and clock correction, and when real-time data stream is interrupted or there is a large delay, it is difficult to ensure continuity and reliability of high-precision positioning of a user. In order to solve the problem, the invention is based on a regional reference station network, and utilizes the ambiguity of the previous epoch, the satellite FCBs (fractional-cycle subsystems) and the short-time predicted troposphere delay to extract and weight and model the comprehensive errors including orbit errors, satellite clock errors and receiver related errors by using the ionosphere-free combination of the broadcast ephemeris in the current epoch, and then broadcast the comprehensive errors to the users. When the real-time orbit and the clock error correction number have interruption or lag, the user can still adopt the broadcast ephemeris and the comprehensive error for substitution, and the high-precision enhanced positioning is continuously realized.)

1. A real-time data stream interruption comprehensive compensation method based on broadcast ephemeris is characterized by comprising the following steps:

(1) each reference station performs floating point Precision Point Positioning (PPP) data processing to obtain a PPP floating point solution;

(2) through the single-difference ambiguity fixation between the satellites, each reference station realizes PPP fixed solution;

(3) on the basis of fixed ambiguity, extracting the comprehensive errors of the observed satellites one by one from the reference station;

(4) and the satellites commonly observed by the regional reference station network are subjected to comprehensive error weighting through multiple stations, so that the positioning precision is improved.

2. The broadcast ephemeris-based real-time data stream interruption comprehensive compensation method according to claim 1, wherein the method in step (1) is specifically as follows: constructing a Delaunay triangulation network according to the distribution situation of reference stations, wherein each reference station receives orbit and clock difference correction numbers broadcasted by an analysis center in real time, performing floating point PPP data processing on observation data by adopting a re-parametrization model described by a formula (1), and regarding reference station r and observed satellites s, s-1, …, j, r-1, …, i, i and j as the total number of the reference stations and the satellites, and in a certain epoch t₀Based on combinations without ionosphereThe re-parametrization carrier phase observation equation is as follows:

in the formula, t₀Representing an observation epoch; r and s represent different receivers and satellites, respectively;is t₀A carrier observation of an epoch;

3. The broadcast ephemeris-based real-time data stream interruption comprehensive compensation method according to claim 2, wherein the method of the step (2) is as follows: on the basis of the floating solution in the step (1), firstly, selecting a satellite with a height angle larger than 45 degrees as a reference satellite, eliminating hardware delay at a receiver end by adopting single-difference combination between satellites, then correcting satellite-end wide-lane fractional ambiguity (FCBs) of the floating ambiguity, fixing wide-lane ambiguity by adopting Melboure-Wubsena (MW) combination, finally, calculating narrow-lane floating ambiguity and covariance matrix by using the ionospheric-free ambiguity and the fixed wide-lane ambiguity obtained by the floating PPP in the step (1), correcting the narrow-lane fractional ambiguity at the satellite end, fixing the narrow-lane ambiguity by adopting a least square-reduction correlation algorithm, reconstructing the ionospheric-free ambiguity by using the fixed wide-lane ambiguity and the fixed narrow-lane ambiguity, and updating parameters to be estimated in the formula (1).

4. The broadcast ephemeris-based real-time data stream interruption comprehensive compensation method according to claim 3, wherein the method in step (3) is as follows: on the basis of ambiguity fixing in the step (2), performing single-station comprehensive error extraction by each reference station, randomly selecting one satellite k as a reference satellite, wherein the coordinates of the reference station are known, and once ambiguity is successfully fixed, extracting the high-precision inclined troposphere delay of each satellite by the following formula (2):

in the formula (I), the compound is shown in the specification,is t₀The epoch-fixed single difference ambiguity, which is 0 for the reference star, the oblique troposphere extracted by the above equation is biased, including the non-differential ambiguity of the reference star

real-time track and clock correctionWhen the number has time delay or interruption, at the current epoch t₁Calculating t using broadcast ephemeris₁The comprehensive error formula of the epoch is as follows:

in the formula, t₁＝t₀+ dt, dt represents a time interval;is t₁A carrier observation of an epoch;

in the formula (I), the compound is shown in the specification,

in a continuous observation arc segment without cycle slip, it can be considered that:

in the formula (I), the compound is shown in the specification,

5. The broadcast ephemeris-based real-time data stream interruption comprehensive compensation method according to claim 4, wherein the method of the step (4) is as follows:

after the comprehensive error of a single reference station is obtained in the step (3), weighting is performed through a plurality of reference stations within a preset range, specifically as follows:

where n is the number of reference stations used for weighting, a_iRepresenting a weighting coefficient satisfying the following relation:

in the formula (d)_iRepresents the distance of the user from the reference station i;

and broadcasting the weighted comprehensive error to a user, and when the real-time data stream lags or is interrupted, the user adopts the generated comprehensive error to compensate the orbit error and the clock error based on the broadcast ephemeris so as to improve the positioning accuracy.

Technical Field

The invention relates to a fixed PPP (point-to-point protocol) method for comprehensively compensating interruption of a real-time data stream by adopting a broadcast ephemeris, belonging to the technical field of GNSS (global navigation satellite system) positioning and navigation.

Background

The continuous stability of a real-time precise product is a key factor influencing the positioning continuity and reliability of PPP, the precision of a real-time data stream corrected based on a broadcast ephemeris state domain can meet the positioning precision requirement of the real-time PPP at present, but the continuity and the stability are poor, the information of the real-time data stream has hysteresis and certain uncertainty, and the uncertainty is mainly reflected in data interruption or large data delay caused by temporary fault or network delay of a precise ephemeris generation service system. Although satellite orbit correction has high time domain correlation, satellite clock error changes rapidly with time, the time domain correlation is weak, and positioning using out-of-sync satellite clock error generally only lasts for a few seconds for centimeter-level positioning. When the precise ephemeris is interrupted for tens of seconds to minutes, the real-time performance and reliability of the user terminal positioning can be difficult to guarantee. Therefore, it is necessary to establish an enhanced service system that does not depend on the real-time precision clock error and the track completely, so as to ensure the continuous and reliable positioning of the user under the condition of interruption of the real-time data stream and improve the continuity and reliability of the PPP positioning.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to solve the problem that a user cannot realize continuous high-precision positioning under the condition of lagging or interrupting real-time data flow.

The technical scheme is as follows: the invention adopts the following technical scheme for solving the technical problems: a real-time data stream interruption comprehensive compensation method based on broadcast ephemeris comprises the following steps:

(1) each reference station performs floating point Precision Point Positioning (PPP) data processing to obtain a PPP floating point solution;

(2) through the single-difference ambiguity fixation between the satellites, each reference station realizes PPP fixed solution;

(3) on the basis of fixed ambiguity, extracting the comprehensive errors of the observed satellites one by one from the reference station;

(4) and the satellite observed by the regional reference station network is subjected to comprehensive error weighting through multiple stations, so that the precision and the stability of the satellite are improved.

Further, the method of the step (1) is specifically as follows:

constructing a Delaunay triangulation network according to the distribution situation of reference stations, wherein each reference station receives orbit and clock difference correction numbers broadcasted by an analysis center in real time, performing floating point PPP data processing on observation data by adopting a re-parametrization model described by a formula (1), and regarding reference station r and observed satellites s, s-1, …, j, r-1, …, i, i and j as the total number of the reference stations and the satellites, and in a certain epoch t₀The observation equation of the re-parametrization carrier phase based on the combination without the ionized layer is as follows:

in the formula, t₀Representing an observation epoch; r and s represent different receivers and satellites, respectively;is t₀A carrier observation of an epoch;is t₀Station-to-satellite distance of epochs; c is the speed of light;andis t₀Re-parametrizing receiver clock error and satellite clock error of the epoch respectively absorbs pseudo-range hardware delay of no ionization layer combination at a receiver end and a satellite end;is t₀Tropospheric delay of epoch;

is t₀Non-differential ionospheric combination ambiguity of epochs;b_r(t₀) And b^s(t₀) Are respectively t₀Fractional offset at the receiver end and the satellite end of the epoch.

Further, the method of step (2) is as follows: on the basis of the floating solution in the step (1), firstly, selecting a satellite with a height angle larger than 45 degrees as a reference satellite, eliminating hardware delay at a receiver end by adopting single-difference combination between satellites, then correcting satellite-end wide-lane fractional ambiguity (FCBs) of the floating ambiguity, fixing the wide-lane ambiguity by adopting Melboure-Wubbena (MW) combination, finally, calculating the narrow-lane floating ambiguity and a covariance matrix by using the non-ionospheric ambiguity and the fixed wide-lane ambiguity obtained by the PPP in the step (1), correcting the narrow-lane fractional ambiguity at the satellite end, fixing the narrow-lane ambiguity by adopting a least square-reduction correlation algorithm, reconstructing the non-ionospheric ambiguity by using the fixed wide-lane ambiguity and the fixed narrow-lane ambiguity, and updating the parameter to be estimated in the formula (1).

Further, the method of step (3) is as follows:

on the basis of ambiguity fixing in the step (2), each reference station performs single-station comprehensive error extraction, for simplifying the description, one satellite k is randomly selected as a reference satellite, the coordinates of the reference station are known, and once ambiguity is successfully fixed, the high-precision inclined troposphere delay of each satellite can be extracted by the following formula (2):

in the formula (I), the compound is shown in the specification,

is t₀The epoch-fixed single difference ambiguity, which is 0 for the reference star, the oblique troposphere extracted by the above equation is biased, including the non-differential ambiguity of the reference starAnd FCBs at the receiver, namely:

when the real-time orbit and the clock error correction number have time delay or interruption, the current epoch t₁Calculating t using broadcast ephemeris₁The comprehensive error formula of the calendar is as follows:

in the formula, t₁＝t₀+ dt, dt represents a time interval;

is t₁A carrier observation of an epoch;

represents t₁The epoch adopts the station-to-satellite distance calculated by the broadcast ephemeris;is t₁Tropospheric delay of epoch;is t₁Single difference ambiguity with fixed epoch; b^s(t₁) Is t₁As can be seen from equation (4), by correcting the inclined tropospheric delay, the single-difference ambiguity, and the satellite FCBs, the specific expression of the combined error including the orbit error, the satellite clock error, and the receiver clock error can be obtained as follows:

in the formula (I), the compound is shown in the specification,which is indicative of the track error,and

is t₁Re-parameterizing receiver clock error and satellite clock error for the epoch;

considering that the ambiguity is a constant term in the arc of no cycle slip, the troposphere and the FCBs of the satellite change slowly with time, and the short-time prediction can be performed, therefore, in the continuous observation arc of no cycle slip, it can be considered that:

in the formula (I), the compound is shown in the specification,representing the variation of tropospheric delay in dt time interval, which is the main factor affecting the comprehensive error precision, adopting a linear extrapolation model to predict the inclined tropospheric delay in short time, and substituting the formula (6) into the formula (5), thus obtaining the epoch t of a single reference station r₁The composite error of (2).

Further, the method of step (4) is as follows:

after the comprehensive error of a single reference station is obtained in step 3), weighting is performed by a plurality of reference stations within a preset range in order to improve the precision and reliability of the single reference station, specifically as follows:

where n is the number of reference stations used for weighting, which is typically 3 in a delaunay triangulation network; a is_iRepresenting a weighting coefficient satisfying the following relation:

in the formula (d)_iRepresenting the distance of the user from the reference station i.

And broadcasting the weighted comprehensive error to a user, and when the real-time data stream lags or is interrupted, the user can still adopt the generated comprehensive error to compensate the orbit error and the clock error based on the broadcast ephemeris so as to realize continuous high-precision enhanced positioning.

Has the advantages that: compared with the prior art, the technical scheme of the invention has the following beneficial technical effects:

the invention provides a real-time data stream interruption comprehensive compensation method based on broadcast ephemeris, which effectively solves the problems of poor positioning continuity and accuracy of a user under the condition of large or interrupted real-time data stream delay by performing short-time prediction on an inclined troposphere and extracting comprehensive errors from each reference station and broadcasting the comprehensive errors to the user: 1. the troposphere prediction accuracy of the low-altitude angle satellite is improved; 2. the positioning accuracy of the user is improved; 3. the fixed rate of the epoch of the user terminal is improved.

Drawings

FIG. 1 is a flowchart illustrating an implementation of a method for comprehensive compensation of interruption of real-time data stream based on broadcast ephemeris according to the present invention;

FIG. 2 is a graph comparing the variation of prediction error of a current layer with elevation angle without LEM model and with LEM model (the method of the present invention) under 60s delay;

FIG. 3 is a comparison graph of RMS statistics for prediction error of a flow layer without and with an LEM model (the method of the present invention) versus elevation angle for a 60s delay;

FIG. 4 is a graph of the combined error accuracy distribution corresponding to the use of the LEM model without the LEM model (the method of the present invention) under the 60s delay condition;

fig. 5 is a comparison graph of the user-side PPP fixed solution plane error distributions corresponding to the case of 60s delay without the LEM model and with the LEM model (the method of the present invention);

fig. 6 is a comparison diagram of PPP positioning elevation error distributions of the ue corresponding to the case of 60s delay without the LEM model and with the LEM model (the method of the present invention).

Detailed Description

The invention will be further described with reference to the accompanying drawings and specific examples, it being understood that the description is illustrative only and is not intended to limit the scope of the invention, which is to be given after reading the appended claims, and that modifications in equivalent and expanded forms are intended to fall within the scope of the invention as defined in the appended claims.

The invention provides a broadcast ephemeris-based real-time data stream interruption comprehensive compensation method, which extracts and weights comprehensive errors including orbital errors, satellite clock errors and receiver-related errors through a regional reference station and broadcasts the comprehensive errors to a user, so that the user can still realize continuous high-precision positioning under the condition of large time delay or interruption of real-time data stream.

1) Each reference station performs a floating point Precision Point Positioning (PPP) data processing to obtain a PPP floating point solution

And (3) constructing a Delaunay triangulation network according to the distribution condition of the reference stations, receiving orbit and clock correction numbers broadcasted by an analysis center in real time by each reference station, and performing floating point PPP data processing on the observation data by adopting a re-parametrization model described in a formula (1). For a reference station r (r 1, …, i) and an observed satellite s (s 1, …, j), at some epoch t₀The observation equation of the re-parametrization carrier phase based on the ionosphere-free (IF) combination is as follows:

in the formula, t₀Representing an observation epoch; r and s represent different receivers and satellites, respectively;is t₀A carrier observation of an epoch;is t₀Station-to-satellite distance of epochs; c is the speed of light;and

is t₀Re-parametrizing receiver clock error and satellite clock error of the epoch respectively absorbs pseudo-range hardware delay of no ionization layer combination at a receiver end and a satellite end;is t₀Tropospheric delay of epoch;is t₀Non-differential ionospheric combination ambiguity of epochs; b_r(t₀) And b^s(t₀) Are respectively t₀Fractional offset at the receiver end and the satellite end of the epoch.

2) Through the fixation of single-difference ambiguity among satellites, the fixed solution of PPP is realized by each reference station

On the basis of the floating solution in the step 1), firstly selecting a proper reference satellite (the height angle is larger than 45 degrees), eliminating hardware delay at the receiver end by adopting single difference combination between satellites, then correcting satellite-end wide-lane decimal deviation (fractional-cycle biases, FCBs) of the floating ambiguity, fixing the wide-lane ambiguity by adopting Melboure-Weibena (MW) combination, finally calculating the narrow-lane floating ambiguity and the covariance matrix by using the non-ionospheric ambiguity and the fixed wide-lane ambiguity obtained by the floating point PPP in the step 1), correcting the narrow-lane decimal deviation of the satellite end, and fixing the narrow-lane ambiguity by using a least square reduction correlation algorithm. Reconstructing the ionosphere-free combined ambiguity through the fixed wide lane ambiguity and the narrow lane ambiguity, and updating the parameters to be estimated in the formula (1).

3) On the basis of fixed ambiguity, extracting the comprehensive error of the observed satellite one by one from the reference station

And on the basis of the fixed ambiguity in the step 2), each reference station carries out single-station comprehensive error extraction. For simplicity of description, one satellite k is randomly selected as a reference satellite, the coordinates of the reference station are precisely known, and once the ambiguity is successfully fixed, the high-precision inclined tropospheric delay of each satellite can be extracted by equation (2):

in the formula (I), the compound is shown in the specification,is t₀The epoch-fixed single difference ambiguity, which is 0 for the reference star, the oblique troposphere extracted by the above equation is biased, including the non-differential ambiguity of the reference starAnd FCBs at the receiver, namely:

when the real-time orbit and the clock error correction number have time delay or interruption, the current epoch t₁The formula for calculating the comprehensive error by using the broadcast ephemeris is as follows:

in the formula, t₁＝t₀+ dt, dt represents a time interval;

is t₁A carrier observation of an epoch;represents t₁The epoch adopts the station-to-satellite distance calculated by the broadcast ephemeris;

is t₁Tropospheric delay of epoch;is t₁Single difference ambiguity with fixed epoch; b^s(t₁) Is t₁Satellite FCBs of epochs.From equation (4), by correcting the inclined tropospheric delay, the single-difference ambiguity and the satellite FCBs, the specific expression of the combined error including the orbit error, the satellite clock error and the receiver clock error can be obtained as follows:

in the formula (I), the compound is shown in the specification,

represents a track error;and

is t₁The re-parameterization of epochs accounts for receiver clock error and satellite clock error.

Considering that the ambiguity is a constant term in the arc of no cycle slip, the troposphere and the FCBs of the satellite change slowly with time, and the short-time prediction can be performed, therefore, in the continuous observation arc of no cycle slip, it can be considered that:

in the formula (I), the compound is shown in the specification,

representing the variation of the tropospheric delay in dt time intervals, wherein the variation is a main factor influencing the comprehensive error precision, adopting a Linear Extrapolation Model (LEM) to carry out short-time prediction on the inclined tropospheric delay, and substituting a formula (6) into a formula (5) to obtain the epoch t of the single reference station r₁The composite error of (2).

4) The satellite observed by the regional reference station network is subjected to comprehensive error weighting through multiple stations, so that the precision and the stability of the satellite are improved

After the comprehensive error of a single reference station is obtained in the step 3), in order to improve the precision and the reliability of the comprehensive error, weighting is carried out by a plurality of nearby reference stations (within 200 km), and the specific steps are as follows:

where n is the number of reference stations used for weighting, which is typically 3 in a delaunay triangulation network; a is_iRepresenting a weighting coefficient satisfying the following relation:

in the formula (d)_iRepresents the distance of the user from the reference station i;

and broadcasting the weighted comprehensive error to a user, and when the real-time data stream lags or is interrupted, the user can still adopt the generated comprehensive error to compensate the orbit error and the clock error based on the broadcast ephemeris so as to realize continuous high-precision enhanced positioning.

After the technical scheme is adopted, compared with the method without adopting an LEM model, the method has the following beneficial effects: under the condition of real-time data stream delay of 60s, the prediction error of a low-altitude satellite convection layer of an LEM model is not close to 0.6m and obviously deviates from the vicinity of 0, and the corresponding mean value and standard deviation are respectively 0.011m and 0.085m (as shown in figure 2a), but the modeling error of all satellite convection layers of the method is approximate to white noise and fluctuates near 0, the corresponding mean value and standard deviation are respectively 0.002m and 0.023m (as shown in figure 2b), and the standard deviation is reduced by 72.9 percent before and after LEM is adopted; FIG. 3 shows the troposphere prediction error RMS statistical values in different altitude angle intervals, which correspond to low altitude angle satellites of 10-20 degrees, and the RMS value is reduced from 0.195m to 0.038m before and after LEM is adopted, so that the accuracy is improved by 80.5%; FIG. 4 is a comparison graph of the generated comprehensive error precision distribution before and after LEM is adopted, the precision of the comprehensive error is improved from 7.8cm to 1.7cm, and the precision is improved by 78.2%; FIG. 5 is a comparison graph of the distribution of the PPP fixed solution plane positioning errors of the client, which is a relatively dispersed plane positioning error distribution without using an LEM model, and the accuracies of the N direction and the E direction are respectively 0.145m and 0.035m, but the plane positioning error of the method of the present invention is more concentrated near 0, and the accuracies of the N direction and the E direction are respectively 0.014m and 0.015m, which are respectively improved by 90.3% and 57.1%; fig. 6 is a comparison diagram of error distribution in the PPP positioning elevation direction of the user side, without using the LEM model, the error distribution obviously has systematic deviation, but the error of the method of the present invention fluctuates around 0, and according to the statistical result, the accuracy in the elevation direction is improved from 0.230m to 0.041m, the accuracy is improved by 82.2% before and after using the LEM, and meanwhile, the calendar fixing rate is also improved from 11.9% to 98.3%.

The above is the preferred embodiment of the present invention, and it should be noted that: without departing from the principle of the invention, several modifications and refinements of the invention can be made, and these modifications and refinements are deemed to be within the scope of the invention.