阅读说明：本技术 一种基于glonass广播星历的伪距定位改进方法 (Pseudo-range positioning improvement method based on GLONASS broadcast ephemeris ) 是由 陈俊平 刘姣 张益泽 陈倩 谭伟杰 于超 于 2019-11-22 设计创作，主要内容包括：本发明涉及一种基于GLONASS广播星历的伪距定位改进方法,包括：步骤S1,分析接收机端频间码偏差特性与建模；步骤S2,标定接收机端频间码偏差；步骤S3,确定改进后的定位模型；步骤S4,接收数据,进行伪距动态定位。本发明对接收机端频间码偏差进行了修正,同时在定位方程中引入卫星频间码偏差,大大提高了GLONASS广播星历的伪距定位精度。(The invention relates to a pseudo-range positioning improvement method based on GLONASS broadcast ephemeris, which comprises the following steps: step S1, analyzing the code deviation characteristic between the receiver end frequency and modeling; step S2, calibrating code deviation between receiver end frequencies; step S3, determining an improved positioning model; in step S4, pseudo-range dynamic positioning is performed after receiving the data. The invention corrects the code deviation between the receiver end frequencies, and introduces the code deviation between the satellite frequencies into the positioning equation, thereby greatly improving the pseudo-range positioning accuracy of the GLONASS broadcast ephemeris.)

1. A pseudo-range positioning improvement method based on GLONASS broadcast ephemeris is characterized by comprising the following steps:

step S1, analyzing the code deviation characteristics between the receiver end frequencies based on the historical data and establishing a function model;

step S2, determining the code deviation delta b between adjacent frequencies of the receiver, calibrating the code deviation IFB _ R between adjacent frequencies of the receiver_j ⁱ；

Step S3, the code offset IFB _ R between receiver end frequencies calibrated in step S2_j ⁱIntroducing a function model into a traditional pseudo range positioning model, and simultaneously introducing a satellite inter-frequency code deviation parameter into the positioning model to determine the maximumThe final GLONASS broadcast ephemeris localization model;

and step S4, the observation station receives the observation data and the broadcast ephemeris in real time, acquires the satellite real-time forecast orbit and the satellite clock error, and performs pseudo-range dynamic positioning based on the GLONASS broadcast ephemeris positioning model in the step S3.

2. The pseudorange location fix refinement method according to claim 1, characterized in that said step S1 comprises:

step S11, pseudo-range positioning resolving is carried out by adopting historical observation data, and a survey station coordinate and a survey station clock error are obtained;

step S12, calculating the positioning residual error observed by each satellite on the observation station by using the positioning calculation result in the step S11

Step S13, according to the positioning residual error characteristics in step S12, establishing the code offset IFB _ R between the receiver end frequencies_j ⁱThe functional model of (2).

3. The pseudorange location refinement method according to claim 2, wherein the location solution equation in step S11 is:

wherein the content of the first and second substances,the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j;

4. The pseudorange location refinement method according to claim 2, wherein said step S12 is performed by locating a residual error

wherein the content of the first and second substances,

5. The pseudorange location fix refinement method according to claim 2, characterized in that, in step S13, receiver-side inter-frequency code bias IFB_j ⁱThe functional model of (a) is:

IFB_R_j ⁱ＝k*Δb (6)

where k is the satellite frequency number and Δ b is the code offset between adjacent frequencies.

6. The pseudorange location updating method according to claim 1, wherein the code bias Δ b between adjacent frequencies at the receiver in step S2 is solved according to equation (7):

wherein the content of the first and second substances,

7. The pseudorange location fix refinement method according to claim 1, wherein the final GLONASS broadcast ephemeris location model in step S3 is:

wherein the content of the first and second substances,

Technical Field

The invention relates to a pseudo range single-point positioning technology in the satellite positioning field, in particular to a pseudo range positioning improvement method based on GLONASS broadcast ephemeris.

Background

The services provided by a Global Navigation Satellite System (GNSS) for a user include positioning, Navigation and time service. The three services are all that the geometric distance between the phase center of the satellite antenna and the phase center of the receiver antenna is used to form a geometric configuration which is enough for solving the position of the user under a fixed coordinate system and a time reference, so that the position and time services are provided for the user by using a certain mathematical model and correction models of various errors. Accurate measurement of distance in satellite navigation positioning relies on accurate determination of time delay. The signal is driven by the satellite clock to begin generating ranging signals, and the total time it takes for the receiver clock to generate a pseudo-random code and successfully acquire the signal, multiplied by the speed of light, is the measured satellite-to-receiver pseudorange. The pseudo range contains errors such as satellite and receiver clock error, channel time delay, troposphere and ionosphere delay, multipath effect and the like.

The channel delay (also called hardware delay) of the satellite refers to the time spent between the start of generating a ranging signal under the driving of a satellite clock pulse and the generation of the signal and the final departure of the signal from the phase center of a satellite transmitting antenna; the channel delay of a receiver refers to the time it takes for a signal to reach the center of the receiver antenna phase to the receiver clock to generate a pseudorandom code and successfully acquire the signal. Because the channels through which different frequency point signals pass are not completely the same, the generated channel delays are different. The difference of the time Delay of different frequency point channels at the satellite end is called The Group Delay (TGD), and the difference of the time Delay of different frequency point channels at the receiver end is called the Differential Code Bias (DCB). For GNSS systems (GPS, BDS, Galileo, etc.) using Code Division Multiple Access (CDMA) technology, since the frequencies of the measurement signals broadcast by the satellites are the same, all satellites only have the difference of channel time delays between several fixed frequency points, and broadcast them through broadcast ephemeris. The GLONASS system transmits signals by using Frequency Division Multiple Access (FDMA), and the Frequency of the signals is different among satellites, so that the channel delay of the GLONASS system also comprises Frequency-dependent Inter-Frequency Bias (IFB), and the difference of the channel delay of the GLONASS system is not broadcast by the satellites.

When a pseudo-range single-point positioning is carried out by using a navigation system broadcast ephemeris, a receiver channel delay common part is usually taken as a part of clock error to be absorbed by the receiver clock error, and the difference of the channel delays of different frequency points needs to be corrected by external parameters. The reference of the broadcast ephemeris satellite clock error is based on a single frequency point (B3 frequency point) except for a Beidou system (BDS), and the broadcast ephemeris and the precise ephemeris clock error of other systems are based on a combined reference without ionosphere delay, wherein GPS and GLONASS are combined by L1/L2, and Galileo is E1/E5a or E1/E5B. Therefore, under the non-ionosphere combination standard, the single frequency user needs to make TGD/DCB correction when using the clock error product.

In real-time single-point positioning based on broadcast ephemeris, channel delay parameters of different frequency points at a satellite end are generally broadcast by the satellite. For the GLONASS system, the inter-frequency code bias can be up to several meters, but the GLONASS broadcast ephemeris does not have TGD and inter-frequency bias IFB parameters for the designed satellites. In this case, the traditional pseudorange location model based on GLONASS broadcast ephemeris has the following problems: (1) GLONASS broadcasts ephemeris space signals with lower accuracy; (2) the code deviation between the receiver end frequencies cannot be absorbed by the receiver clock error, and the influence on positioning is reflected in pseudo-range residual errors; (3) different receiver types or antenna types correspond to unequal hardware delays, which brings difficulty to the determination of the inter-frequency code offset.

Based on the GLONASS broadcast ephemeris, the conventional pseudorange location mathematical model is as follows:

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

the non-ionosphere combined observed value from the satellite i to the observation station j is obtained;

is the geometric distance of the satellite i to the station j,

xⁱ，yⁱ，zⁱfor broadcast ephemeris

The coordinates of the resulting satellite are calculated,x_j,y_j,z_jthe coordinate of the measuring station to be solved is obtained; Δ t_jFor the receiver clock difference to be solved, DCB_j ⁱHardware delay for each satellite for the receiver end; Δ tⁱFor satellite clock error, TGD, calculated from broadcast ephemeris_j ⁱHardware delay for each satellite itself; c is the speed of light and c is the speed of light,

for tropospheric delay, corrections are usually made using models.

In the above pseudo-range positioning model, the satellite clock difference in the broadcast ephemeris does not include the satellite-side hardware delay TGD_j ⁱ. Therefore, in the positioning process, the part is delayed by the hardware at the receiver end to delay the DCB_j ⁱAbsorption, thereby locating the mathematical model as:

wherein, ICB_j ⁱFor hardware delays of different satellites after mixing of the two, including the common part ICB₀And the inter-sum deviation part IFB_j ⁱ(including both the station receiver and the satellite), namely: ICB_j ⁱ＝ICB₀+IFB_j ⁱ(ii) a Wherein the common part ICB₀Will be received by the receiver clock difference Δ t_jAbsorption, namely:

thus, the actual positioning mathematical model is:

in the conventional pseudo-range positioning, the parameters to be solved are the coordinate and clock error of the station survey

Ignore IFB_j ⁱPartly, thereby causing a significant increase in positioning error.

Based on the above GLONASS broadcast ephemeris traditional pseudorange positioning model, an obtained dynamic positioning single-day time sequence diagram of 1 month and 10 days in 2018 is shown in fig. 1. The receiver of the selected station KOKV configuration is JAVADTRE _ G3TH DELTA3.6.4 and the antenna is ASH701945G _ MNONE. In the figure, the upper subgraph is the positioning accuracy of east-west and south-north directions, and the lower subgraph is the positioning result time sequence of the elevation direction, so that the following steps can be seen: the positioning accuracy of the east-west direction and the south-north direction is within the range of +/-10 m; the positioning accuracy in the elevation direction is within the range of +/-25 m, and the dispersion of the positioning accuracy in the elevation direction is larger than that in the horizontal direction; the overall positioning error is up to 30 m.

Disclosure of Invention

In order to solve the problem that the traditional pseudo-range positioning accuracy of the GLONASS broadcast ephemeris is poor in the prior art, the invention provides a pseudo-range positioning improvement method based on the GLONASS broadcast ephemeris.

The invention provides a pseudo-range positioning improvement method based on GLONASS broadcast ephemeris, which comprises the following steps:

step S1, analyzing the code deviation characteristics between the receiver end frequencies based on the historical data and establishing a function model;

step S2, determining the code deviation delta b between adjacent frequencies of the receiver, calibrating the code deviation IFB _ R between adjacent frequencies of the receiver_j ⁱ；

Step S3, the code offset IFB _ R between receiver end frequencies calibrated in step S2_j ⁱIntroducing a traditional pseudo-range positioning model into the function model, and introducing a satellite inter-frequency code deviation parameter into the positioning model to determine a final GLONASS broadcast ephemeris positioning model;

and step S4, the observation station receives the observation data and the broadcast ephemeris in real time, acquires the satellite real-time forecast orbit and the satellite clock error, and performs pseudo-range dynamic positioning based on the GLONASS broadcast ephemeris positioning model in the step S3.

The step S1 includes:

step S11, pseudo-range positioning resolving is carried out by adopting historical observation data, and a survey station coordinate and a survey station clock error are obtained;

step S12, calculating the observation result of each satellite on the observation station by using the positioning calculation result in the step S11Positioning residual error

Step S13, according to the positioning residual error characteristics in step S12, establishing the code offset IFB _ R between the receiver end frequencies_j ⁱThe functional model of (2).

The positioning calculation equation in step S11 is:

wherein the content of the first and second substances,

the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j;

the geometric distance from the satellite i to the survey station j is m;

Δt_jfor receiver clock error, DCB₀A common part of the receiver-side hardware delay; IFB _ R_j ⁱFor receiver inter-frequency code bias;

the satellite clock error calculated based on the precise clock error product comprises the hardware delay TGD of the satellite terminal_j ⁱIn the unit of m; c is the speed of light;

is tropospheric delay in m.

Locating residuals in the step S12

Calculating according to the formula (5):

wherein the content of the first and second substances,

calculating the geometric distance between the satellite i and the coordinate of the measuring station obtained by positioning calculation, wherein the unit is m;

calculating the obtained station clock error for positioning;

the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j; c is the speed of light;

is tropospheric delay in m.

The code offset IFB between receiver end frequencies in the step S13_j ⁱThe functional model of (a) is:

IFB_R_j ⁱ＝k*Δb (6)

where k is the satellite frequency number and Δ b is the code offset between adjacent frequencies.

The code deviation Δ b between the adjacent frequencies at the receiver end in the step S2 is calculated according to the formula (7):

wherein the content of the first and second substances,

the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j;

the geometric distance from the satellite i to the survey station j is m;

Δt_jfor receiver clock error, DCB₀A common part of the receiver-side hardware delay; k is a satellite frequency number;

Δtⁱ+TGD_j ⁱcalculating the satellite clock error for a precise clock error product; c is the speed of light;

is tropospheric delay in m.

The final GLONASS broadcast ephemeris positioning model in step S3 is:

wherein the content of the first and second substances,

the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j;

the geometric distance from the satellite i to the survey station j is m;

Δt_jfor receiver clock error, DCB₀A common part of the receiver-side hardware delay; k is a satellite frequency number; c is the speed of light;

tropospheric delay in m; Δ tⁱIs the satellite clock error;is the inter-frequency code bias of the satellite terminal.

The method analyzes the positioning residual error characteristics based on the historical data, establishes a receiver end inter-frequency code deviation function model based on the positioning residual error characteristics, and corrects the receiver end inter-frequency code deviation. Meanwhile, the code deviation between satellite frequencies is introduced into a positioning equation, so that the pseudo-range positioning accuracy of the GLONASS broadcast ephemeris is greatly improved.

Drawings

FIG. 1 is a timing diagram of conventional pseudorange dynamic positioning based on GLONASS broadcast ephemeris.

FIG. 2 is a flow diagram of a GLONASS broadcast ephemeris based pseudorange location refinement method in accordance with the present invention.

FIG. 3 is a timing diagram of ephemeris-based pseudorange residuals, in accordance with an embodiment of the invention.

Fig. 4 is a diagram of four station-wide pseudorange residual means versus frequency number according to an embodiment of the invention.

Fig. 5 is a timing diagram of pseudorange residuals based on a receiver inter-frequency bias model in accordance with an embodiment of the invention.

FIGS. 6(a) - (d) are graphs comparing results of different positioning models based on GLONASS broadcast ephemeris.

FIG. 7 is a positioning model verification station selection profile.

FIG. 8 is a comparison of results from different positioning models of globally distributed stations based on GLONASS broadcast ephemeris.

Detailed Description

The following description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will provide a better understanding of the function and features of the invention.

The invention provides a pseudo-range positioning improvement method based on GLONASS broadcast ephemeris, as shown in FIG. 2, comprising:

step S1, analyzing the code bias characteristics between the receiver end frequency based on the historical data and establishing a model, including:

step S11, using historical precise ephemeris and clock error provided by International GNSS Service (IGS) as reference, using historical observation data to perform pseudo-range positioning calculation according to formula (4), to obtain the coordinate and clock error of the survey station:

wherein the content of the first and second substances,

the unit is m, which is the non-ionosphere combined observed value from the satellite i to the observation station j;

is the geometric distance from satellite i to station j (calculated based on the precise satellite orbit and the station's approximate coordinates) in m;

Δt_jfor receiver clock error, DCB₀A common part of the receiver-side hardware delay;

IFB_R_j ⁱignoring IFB _ R for the inter-frequency code bias portion of receiver-side hardware delay when performing positioning solution at this step_j ⁱSo that it is reflected in the positioning residual;

the satellite clock error obtained by calculation for the precise clock error product comprises the hardware delay TGD of the satellite terminal_j ⁱIn the unit of m;

c is the speed of light;

for tropospheric delay, in m, corrections are usually made using a model.

Step S12, using the positioning result in step S11 to calculate the positioning residual error observed by each satellite on the observation station according to the formula (5)

Wherein the content of the first and second substances,the geometric distance to satellite i calculated using the station coordinates obtained by the positioning solution,

and resolving the obtained station clock error for positioning.

Step S13, according to the positioning residual error characteristics, establishing the code offset IFB _ R between the receiver end frequencies_j ⁱAnd a model of the satellite frequency number. The method specifically comprises the following steps: first determining a positioning residualAs a function of the frequency number, and then will locate the residual errorSubstitution to receiver end inter-frequency code bias IFB _ R_j ⁱ。

For example, by analyzing the characteristics of the positioning residual error, the positioning residual error is obtainedThe function relationship with the satellite frequency number is a linear function, so that

Where k is the satellite frequency number, and Δ b is the code offset between adjacent frequencies, i.e., the difference between the GLONASS satellite frequency numbers is 1. Then, the function relationship between the code deviation between the receiver end frequencies and the satellite frequency number is obtained as follows:

IFB_R_j ⁱ＝k*Δb (6)

of course, the functional relationship obtained by analyzing the characteristics of the localization residuals may be other functions, such as quadratic function, inverse function, etc.

Step S2, determining the code deviation delta b between adjacent frequencies of the receiver end, and calibrating the code deviation function model between adjacent frequencies of the receiver end.

The code deviation Δ b between adjacent frequencies can be obtained by residual fitting in step S13, but the accuracy of the parameter values obtained based on this method is limited. Therefore, in order to improve the parameter modeling precision, the code deviation function model between the receiver end frequencies is substituted into the formula (4), and the delta b value is obtained through positioning calculation. For example, substituting equation (6) into equation (4) results in a new positioning solution equation:

the value of code deviation delta b between adjacent frequencies of the receiver can be calculated by formula (7) when the code deviation between the adjacent frequencies of the receiver and the satellite frequency number are in a linear function relationship, so that a function model of the code deviation between the adjacent frequencies of the receiver can be calibrated.

And step S3, introducing the receiver-end inter-frequency code bias function model calibrated in the step S2 into a traditional pseudo-range positioning model, and correcting the receiver inter-frequency code bias. Meanwhile, a satellite inter-frequency code deviation parameter is introduced into the positioning model, and a finally improved GLONASS broadcast ephemeris positioning model is obtained.

The conventional pseudorange location model is shown in equation (1), where the hardware delay DCB is at the receiver end and at the satellite end_j ⁱ，TGD_j ⁱBoth contain a common part and an inter-frequency bias part, i.e.: DCB_j ⁱ＝DCB₀+IFB_R_j ⁱ，TGD_j ⁱ＝TGD₀+IFB_S_j ⁱ(ii) a Wherein the common part DCB₀,TGD₀Will be measured the clock error Δ t_jAbsorption, i.e.

Then the formula (1) is rewritten as:

then, substituting the receiver inter-frequency code bias function model calibrated in step S2 into equation (8), for example, substituting equation (6) into equation (8), the final improved GLONASS broadcast ephemeris positioning model is:

the coordinate and clock error of the measuring station can be calculated by the formula (10)And satellite side inter-frequency code deviation parametersThe functional form of the code deviation between the satellite end frequencies can be a piecewise constant and the like, and the function can be estimated simultaneously with the coordinate of the survey station and the clock error of the survey station by adopting a least square method, a filtering method and the like.

And step S4, the observation station receives the observation data and the broadcast ephemeris in real time, acquires the satellite real-time forecast orbit and the satellite clock error, and performs pseudo-range dynamic positioning based on the GLONASS broadcast ephemeris positioning model in the step S3.

Compared with the traditional pseudo-range positioning mathematical model of the formula (1), the pseudo-range positioning method corrects the code deviation between the frequencies of the receiver, estimates the code deviation between the frequencies of the satellite clock difference broadcasted by the broadcast ephemeris and improves the positioning precision.

The present invention will be further described with reference to the following embodiments of a method for improving pseudorange positioning based on GLONASS broadcast ephemeris.

Taking the data of the IGS stations AREG, RDSD, KOKV and WIND as an example, the GLONASS broadcast ephemeris is utilized for data processing, and the practical application effect of the positioning new model provided by the invention is verified. The station receiver and antenna configuration is shown in table 1.

TABLE 1 survey station receiver and antenna conditions

First, based on step S1, a receiver-side inter-frequency code bias characteristic is obtained using historical data (precision orbit, clock error, and observation data for 7 consecutive days from 1/7/2018), as shown in fig. 3. The pseudorange residuals for each satellite in fig. 3 show a non-zero mean behavior. Taking three satellites of R01, R02 and R03 as examples, the pseudo-range residual error mean values of the AREG and RDSD two stations to the three satellites are-0.20 m, -1.1m and 1.6m respectively; -0.75m, -0.61m, 1.68 m. Fig. 4 is a graph of the mean of all four station-survey pseudoranges residuals versus all satellite frequency numbers, where the frequencies of each satellite are shown in table 2. As can be seen from the figure, the pseudorange residual mean value of each satellite has a very strong linear correlation with the corresponding frequency number, that is, a very strong linear correlation exists between the code bias and the frequency number between the frequencies at the receiver.

TABLE 2 satellite PRN number to frequency number correspondence (each frequency number corresponds to two satellites)

On the basis, based on step S2, the receiver-end inter-frequency code bias is calibrated by using a linear model. The average values of 7 days for obtaining the code deviation delta b between the adjacent frequencies of the 4 measuring stations are respectively as follows: 0.233m, 0.216m, 0.148m, -0.174m, and standard deviations of 1.8cm, 1.1cm, 1.2cm, and 1.2cm, respectively. The delta b values of all days are close, which indicates that the inter-frequency deviation of the receiver shows the characteristic of long-term stability, so that the historical calibration result can be forecasted for later positioning.

At this time, the system difference existing in the pseudo-range residual is greatly reduced. As an example, fig. 5 shows a pseudo-range residual time series of three satellites R01, R02, R03 of AREG and RDSD stations. Compared with the figure 3, the non-zero mean characteristic of the pseudo-range residuals of 3 satellites is greatly eliminated, particularly R02 and R03, the mean values of the pseudo-range residuals of the AREG station are reduced to 0.1m and 0.6m from-1.1 m and 1.6m, and the mean values of the pseudo-range residuals of the RDSD station are reduced to 0.2m and 0.8m from-0.6 m and 1.7 m.

Based on the results obtained in steps S3-S4, Δ b estimated based on historical data is used to correct inter-receiver end-frequency bias, and a GLONASS broadcast ephemeris positioning model is used to perform pseudo-range dynamic positioning on the observed data of the four stations 2018 in 1 month and 10 days. Figure 6 shows a dynamic positioning time series of the broadcast ephemeris pseudorange location model for both the conventional model and the improved model. The positioning accuracy obtained by the improved model in the graph is obviously better than that of the traditional model, the dynamic positioning error is relatively concentrated, and the existing deviation value is small.

Further, to verify the reliability of the GLONASS broadcast ephemeris positioning improvement model, 25 stations distributed globally are selected for positioning verification, and the stations are distributed as shown in fig. 7. The related receivers are mainly of two types, namely TRIMBLE NETR9 and JAVADTRE _ G3TH DELTA, and pseudo-range positioning processing is carried out by adopting a dynamic positioning mode.

And respectively adopting a traditional model and an improved model to perform data analysis. The improved model corrects the inter-frequency deviation of the observation station on the basis of the traditional model and estimates the inter-frequency difference of each satellite. The RMS values of the dynamic positioning results of 25 substations 2018 in 1, 10 days in north and south N, east and west E and elevation U are shown in fig. 8, and the average positioning accuracy in N, E, U is improved from 3.89m, 3.87m and 11.02m to 1.89m, 2.23m and 5.77m in the three directions, wherein the average improvement percentages are 51.1%, 41.7% and 48.3%, respectively.

The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.