Iridium star ira based opportunity signal positioning error compensation method

Abstract

The application relates to an opportunity signal positioning error compensation method based on an iridium star IRA, and relates to the field of opportunity signal positioning. The method is used for solving the problem that in the prior art, an accurate initial solution cannot be obtained in the environment without positioning reference information in the opportunity signal positioning method of a low earth orbit satellite. The method comprises the following steps: connecting a receiver hardware for receiving an iridium star downlink signal; analyzing the iridium star downlink signal; demodulating the iridium star downlink signal to obtain iridium star downlink information; acquiring the projection longitude and latitude of the iridium star relative to the earth's surface, and calculating the average projection position of multiple data; calculating a rough position solution based on a global particle swarm algorithm; acquiring a propagation delay; calculating the satellite position and speed by using the propagation delay; confirming the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the iridium star downlink signal by using a maximum likelihood estimation method; and bringing the initial position, the satellite position and speed of the iridium star downlink signal and the Doppler frequency shift into a Doppler positioning equation to solve the position solution by using the least square method. The method is suitable for the research field of satellite orbit correction algorithms.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of opportunity signal positioning, and in particular to an opportunity signal positioning error compensation method based on Iridium. BACKGROUND

[0002] Low Earth Orbit (LEO) opportunity signal positioning is an emerging positioning technology. Due to its global coverage, high signal strength, fast update frequency and low latency, it is widely used in navigation, timing, monitoring and rescue fields. In the face of complex and variable environment, traditional satellite signal shielding and interference, a single positioning system is limited by the limitedness and reliability of the signal source, and it is difficult to meet the demand of high-precision positioning. At the same time, the cooperative positioning system composed of multiple low-orbit satellites emitting opportunity signals has stronger robustness, higher positioning accuracy and wider coverage, and plays an increasingly important role in unmanned driving, Internet of Things, precision agriculture and other fields.

[0003] Low-orbit satellite opportunity signal positioning is a navigation and positioning problem, which is often coupled with Doppler positioning. At present, scholars at home and abroad have less research on this kind of problem, and its content can be divided into three aspects: signal Doppler solution optimization, satellite orbit estimation optimization, and positioning solution algorithm optimization. Satellite orbit correction algorithm is an error elimination algorithm based on time delay propagation. At present, in the field of low-orbit satellite opportunity signal positioning, there is still no progress in the research on satellite orbit correction algorithm. The traditional low-orbit satellite opportunity signal positioning algorithm focuses on optimizing the Doppler precision of the receiver, and ignores the error of the propagation time delay on the satellite orbit estimation. For the positioning system, in the process of positioning convergence, the acquisition of the initial positioning is very important for the estimation of the propagation time delay and the realization of high-precision positioning results. SUMMARY

[0004] The present application solves the problem that the positioning method based on low-orbit satellite opportunity signal positioning in the prior art is difficult to obtain an accurate initial solution in an environment without positioning reference information, thereby causing a large positioning error, and even failing to converge to a correct solution.

[0005] To solve the above technical problems, the present application is realized by the following technical scheme:

[0006] Scheme one, the present application proposes an opportunity signal positioning error compensation method based on Iridium, which comprises the following steps:

[0007] S1, connecting the receiver hardware for receiving Iridium downlink signals;

[0008] S2, analyzing the received Iridium downlink signals;

[0009] S3, demodulate the received Iridium downlink signal to obtain Iridium downlink information IRA;

[0010] S4, obtaining the projection longitude and latitude of Iridium relative to the earth's surface according to the Iridium downlink information IRA , calculating the average projection position by multiple data ;

[0011] S5, calculating the rough position solution based on the global particle swarm algorithm according to the calculated average projection position and the Iridium visible range ;

[0012] S6, obtaining the propagation delay according to the rough position solution ;

[0013] S7, determining the satellite position by using the TLE file and the SGP4 file, and calculating the satellite position and velocity by using the propagation delay ; ;

[0014] S8, confirming the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal by using the maximum likelihood estimation method ;

[0015] S9, bringing the rough position solution , the satellite position and velocity , and the Doppler frequency shift into the Doppler positioning equation to solve the position solution by least square, and correcting the satellite position by using the Iridium IRA-based opportunity signal positioning error compensation method.

[0016] Further, an optimal implementation is provided, and the received Iridium downlink signal in S2 is obtained by a Butterworth filter.

[0017] Further, an optimal implementation is provided, and S3 specifically includes:

[0018] S3.1, filtering the received Iridium downlink signal and then performing windowing operation on the filtered signal;

[0019] S3.2, setting a windowing signal strength threshold, and cyclically judging the whole frequency domain signal to capture the pilot information of the windowed signal;

[0020] S3.3, setting the period to 90ms, and capturing the next windowed signal;

[0021] S3.4, demodulating the captured next windowed signal by using BPSK to obtain binary encoding; ​​

[0022] S3.5, decode the windowed signal according to Iridium Star IRA binary encoding rule, the Iridium Star IRA analysis windowed signal contains the projection latitude and longitude LAT, LON of the satellite position on the earth, the satellite number sent by the Iridium Star downlink signal, and the Iridium Star downlink information IRA is obtained.

[0023] Further, a preferred embodiment is provided, and a global particle swarm algorithm is designed in S5 to solve the rough position solution The method is as follows:

[0024] S5.1, initialize the variables of the particle swarm;

[0025] S5.2, according to the calculated average projected position and the radiation range of the Iridium Star downlink signal, the particle boundary is obtained:

[0026]

[0027]

[0028]

[0029] S5.3, the PSO optimization objective function is calculated according to the Doppler shift formula:

[0030]

[0031] Wherein is the target latitude and longitude of the receiver, and in the formula can be obtained by the following formula:

[0032]

[0033] Wherein , is the radius of the earth;

[0034] S5.4, the optimal solution is obtained by traversing the PSO algorithm .

[0035] Further, a preferred embodiment is provided, and the rough position solution is used to obtain the propagation delay in S6. The method is as follows:

[0036] S6.1, according to the calculated propagation delay ;

[0037] S6.2, the satellite position is compensated according to the propagation delay .

[0038] ;

[0039] wherein, , , are the coefficients of cubic interpolation, which are obtained by a cubic interpolation formula.

[0040] Further, a preferred embodiment is provided, in which the propagation delay is calculated in S7. The method for calculating the optimized satellite position estimation to solve the satellite position is as follows:

[0041] S7.1, acquiring the satellite orbit plane inclination and the ascending node right ascension information of the day;

[0042] S7.2, establishing the SGP4 model according to the TLES information of the satellite;

[0043] S7.3, acquiring the satellite position and velocity sequence output according to the SGP4 model and .

[0044] Further, a preferred embodiment is provided, in which the maximum likelihood estimation method is used in S8 to confirm the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal The method is as follows:

[0045] S8.1, using fast Fourier transform on the window where the pilot is located to determine the coarse estimated Doppler .

[0046] S8.2, using the maximum likelihood estimation on the windowed frequency domain signal in the frequency domain to estimate the fine Doppler .

[0047] S8.3, generating a time and Doppler curve according to the windowing and comparing it with the ID of the satellite analyzed in step 2 to complete the confirmation of the Doppler frequency shift of the IRA 11 frequency band signal center frequency in the Iridium downlink signal .

[0048] Further, a preferred embodiment is provided, in which the rough position solution is calculated by the PSODC algorithm.

[0049] Scheme II, a computer device, comprising a memory and a processor, the memory storing a computer program, when the processor runs the computer program stored in the memory, the processor executes the method of any one of scheme I.

[0050] Scheme three, a computer readable storage medium, the computer readable storage medium stores a computer program, the computer program is executed by a processor to realize the steps of the method in any one of the schemes one.

[0051] The present application has the advantages of:

[0052] The present application combines the analysis of the iridium star downlink broadcast signal with the opportunity signal positioning, solves the rough position solution by the PSO algorithm, solves the problem of inaccurate rough position solution by the least square solution of Doppler positioning, and can improve the accuracy of the final positioning convergence and the operation efficiency.

[0053] The present application extracts the initial positioning from the iridium star downlink broadcast signal, calculates the propagation delay through the initial positioning, and applies the propagation delay to compensate for the satellite orbit estimation error, thereby increasing the estimation accuracy of the satellite position and velocity.

[0054] It is also suitable for the research field of satellite orbit correction algorithm. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The iridium-based opportunity signal positioning error compensation method flowchart in the embodiment one.

[0056] Figure 2 The simulation schematic diagram of the iridium-based opportunity signal positioning error compensation method in the embodiment eleven.

[0057] Figure 3 The PSO optimization in the embodiment eleven Schematic diagram.

[0058] Figure 4 The measured Doppler time curve schematic diagram in the embodiment eleven.

[0059] Figure 5 The measured positioning result schematic diagram in the embodiment eleven. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all embodiments of the present application.

[0061] Embodiment one, the present embodiment provides an iridium-based opportunity signal positioning error compensation method, the method comprising the following steps:

[0062] S1. Connect the receiver hardware to receive Iridium downlink signals.

[0063] S2. Analyze the received Iridium downlink signal;

[0064] S3. Demodulate the received Iridium downlink signal to obtain Iridium downlink information IRA;

[0065] S4. Obtain the projection longitude and latitude of the Iridium satellite relative to the earth's surface based on the Iridium downlink information IRA , calculate the average projection position of multiple data ;

[0066] S5, based on the calculated average projection position And the visible range of Iridium, the rough position solution is calculated based on the global particle swarm algorithm ;

[0067] S6, according to the rough position solution Get propagation delay ;

[0068] S7, use TLE file and SGP4 file to determine the position of Iridium downlink signal satellite, using propagation delay Calculating satellite positions and speed ;

[0069] S8. Use the maximum likelihood estimation method to determine the Doppler shift of the IRA 11 band signal center frequency in the Iridium downlink signal. ;

[0070] S9, solve the rough position , Iridium downlink signal satellite position and speed , Doppler shift Substitute it into the Doppler positioning equation and solve the position solution through least squares.

[0071] Implementation method 2: This implementation method further limits the Iridium-based opportunity signal positioning error compensation method described in implementation method 1. In S2, the received Iridium downlink signal is obtained by parsing it through a Butterworth filter.

[0072] Implementation method 3: This implementation method further limits the Iridium-based opportunity signal positioning error compensation method described in implementation method 1. S3 specifically includes:

[0073] S3.1. Filtering the received Iridium downlink signal and performing a windowing operation on it;

[0074] S3.2, set the windowed signal strength threshold, loop to determine the entire frequency domain signal, capture the pilot information of the windowed signal;

[0075] S3.3, set the period to 90ms, capture the next windowed signal;

[0076] S3.4, demodulate the captured next windowed signal using BPSK to obtain binary encoding;

[0077] S3.5, decode the windowed signal according to the Iridium IRA binary encoding rule, the Iridium IRA analysis of the windowed signal includes the projection latitude and longitude LAT, LON of the satellite position on the earth, the satellite number sent by the Iridium downlink signal, and the acquisition of the Iridium downlink information IRA is completed.

[0078] Embodiment four, this embodiment is a further limitation of the Iridium-based opportunity signal positioning error compensation method of embodiment three, the global particle swarm optimization algorithm is designed in S5 to solve the rough position solution The method is:

[0079] S5.1, initialize the variables of the particle swarm;

[0080] S5.2, according to the calculated average projected position and the radiation range of the Iridium downlink signal, the particle boundary is obtained:

[0081]

[0082]

[0083]

[0084] S5.3, calculate the PSO optimization target function according to the Doppler shift formula:

[0085]

[0086] Where is the target latitude and longitude of the receiver, and the formula is which can be obtained by the following formula:

[0087]

[0088] Where , is the radius of the earth;

[0089] S5.4, traverse the optimal solution using the PSO algorithm.

[0090] Embodiment five, this embodiment is a further limitation of the method for compensating for positioning error of opportunistic signal based on Iridium satellite according to embodiment one, in S6, the rough position solution is compensated according to the propagation delay The method for obtaining the propagation delay is:

[0091] S6.1, the calculated propagation delay is compensated according to the calculated propagation delay

[0092] S6.2, the satellite position is compensated according to the propagation delay

[0093]

[0094] Wherein, , , The coefficients of cubic interpolation are obtained by cubic interpolation formula.

[0095] Embodiment six, this embodiment is a further limitation of the method for compensating for positioning error of opportunistic signal based on Iridium satellite according to embodiment one, in S7, the propagation delay The method for calculating the optimized satellite position estimation to solve the satellite position And velocity Is:

[0096] S7.1, obtain the satellite orbit plane inclination and the ascending node right ascension information on the same day;

[0097] S7.2, establish SGP4 model according to TLES information of satellite;

[0098] S7.3, obtain the satellite position and velocity sequence output by SGP4 model And .

[0099] Embodiment seven, this embodiment is a further limitation of the method for compensating for positioning error of opportunistic signal based on Iridium satellite according to embodiment one, in S8, the method for confirming the Doppler shift of the center frequency of IRA 11 frequency band signal in Iridium satellite downlink signal by maximum likelihood estimation is:

[0100] S8.1, use fast Fourier transform to determine the coarse estimated Doppler

[0101] S8.2, windowing in frequency domain, and using maximum likelihood estimation to estimate fine Doppler​​​​​​ ;

[0102] S8.3, according to the windowed generation time and Doppler profile and with the step 2 in the analysis of iridium downlink signal satellite ID comparison, the completion of the iridium downlink signal IRA 11 frequency band signal center frequency Doppler shift confirmation.

[0103] Embodiment eight, this embodiment is further limited to the iridium-based opportunity signal positioning error compensation method described in embodiment one, the rough position solution in S9 Is calculated by the PSODC algorithm.

[0104] Embodiment nine, this embodiment proposes a computer device, comprising a memory and a processor, the memory has stored a computer program, when the processor runs the computer program stored in the memory, the processor executes the method described in any one of embodiments one to eight.

[0105] Embodiment nine, this embodiment proposes a computer readable storage medium, the computer readable storage medium stores a computer program, the computer program is executed by the processor to realize the steps of the method described in any one of embodiments one to eight.

[0106] Embodiment eleven, this embodiment proposes an embodiment for explaining the above-mentioned embodiments one to ten, which is specifically:

[0107] See Figures 1 to 5 This embodiment, this embodiment iridium downlink signal error compensation positioning method, the method comprises the following steps:

[0108] Step 1, connect hardware for receiving signal such as Figure 2 As shown in table 1;

[0109] Step 1.1, set clock synchronization using high-precision clock for synchronization, set the receiver parameters as shown in table 1;

[0110] Step 1.2, using C++ to write gnuradio receiver code, including usrp source, bandpass filter, file writing;

[0111] Step 2, parse the received signal, use Butterworth filter to the signal, window operation, set the window power threshold, traverse the signal to determine the signal pilot;

[0112] Step 2.1, after locking the pilot, using BPSK to demodulate the pilot and the signal in the window to obtain digital signal;

[0113] ​Step 2.2, the bit stream is decoded using the Viterbi algorithm for convolutional code;

[0114] Step 2.3, find the start of the frame in the continuous bit stream according to the synchronization sequence;

[0115] Step 2.4, remove the bit padding according to the protocol specification, and assemble into a data packet according to the protocol;

[0116] Step 3, get the Doppler shift by using the pilot;

[0117] Step 3.1, use fast Fourier transform to determine the coarse Doppler estimation of the window where the pilot is located ;

[0118] Step 3.2, windowing in the frequency domain, and using maximum likelihood estimation to estimate the fine Doppler

[0119] Step 3.3, generate a time-Doppler graph according to the windowing and compare it with the signal satellite ID parsed in step 2 to determine the source of the signal Doppler.

[0120] Step 4, match the satellite Doppler with the satellite ID, and determine the position and speed of the satellite corresponding to the ID according to the satellite ID.

[0121] Step 4.1, find the corresponding Two-Line Element Sets (TLES) according to the satellite ID to obtain the satellite orbit plane inclination, ascending node right ascension, etc. information on the same day;

[0122] Step 4.2, establish the SGP4 model according to the satellite TLES information, and set the sampling rate to 60ms for windowing

[0123] Step 4.3, get the satellite position and speed sequence output by the SGP4 model and .

[0124] Step 5, use the Iridium-based IRA opportunity signal positioning error compensation method to correct the satellite position

[0125] Step 5.1, initialize the variables of the particle swarm;

[0126] Step 5.2, according to the projection latitude and longitude and the radiation range of the Iridium downlink signal, the particle boundary is calculated:

[0127]

[0128]

[0129]

[0130] Step 5.3, the PSO optimization objective function form is obtained according to the Doppler shift formula as follows:

[0131]

[0132] Wherein is the receiver target latitude and longitude, wherein can be obtained by the following formula:

[0133]

[0134] Wherein , is the radius of the earth.

[0135] Step 5.4, the optimal solution is obtained by using PSO algorithm ;

[0136] Step 5.5, the estimated propagation delay is calculated according to the calculation ;

[0137] Step 5.6, the satellite position is compensated according to the propagation delay ;

[0138] ;

[0139] Wherein , , are the coefficients of cubic interpolation, which are obtained by cubic interpolation formula.

[0140] Step 6, all the obtained Doppler and satellite position and velocity rough position solution are brought into the Doppler positioning formula to solve.

[0141] Step 6.1, the Doppler formula is simplified according to the relationship between the receiver and the transmitter position;

[0142] Step 6.1.1, the basic Doppler shift formula is as follows, wherein is the measured Doppler shift, is the rate of change of the distance between the satellite and the receiver, is the speed of light, is the carrier frequency

[0143]

[0144] Step 6.1.2, in the Earth-Centered, Earth-Fixed coordinate system (ECEF), which can be expressed as follows, where are the corrected position of the satellite at the kth sampling time and the position of the receiver, respectively, and are the corrected velocity of the satellite at the kth sampling time and the received motion velocity, respectively;

[0145]

[0146] Step 6.1.3, when the receiver motion velocity is slow or static and can be ignored relative to the transmitter velocity, the formula can be simplified as follows:

[0147]

[0148] Step 6.1.4, when the receiver receives multiple satellite signals, the multiple satellite positions and corresponding Doppler shifts are solved, and the formula is modified as follows, where is the Doppler error caused by the common clock difference between the satellite and the receiver, which can be solved and eliminated in subsequent iterations:

[0149]

[0150] Step 6.2, the above formula is linearized using the Levenberg–Marquardt algorithm and is solved iteratively;

[0151] Step 6.2.1, after linearizing the formula, its differential expression is as follows:

[0152]

[0153] where , is the linearized Jacobian matrix

[0154] Step 6.2.2, solve its Jacobian matrix J, and its Jacobian matrix expression is as follows:

[0155]

[0156] Step 6.2.3, through the Levenberg–Marquardt algorithm, the rough position solution is brought in, and the equation is iterated, which is expressed as follows:

[0157]

[0158] where is the differential form of the receiver position vector, is the Jacobian matrix, is the weight matrix (usually the identity matrix), is the damping parameter, is the identity matrix, is the differential form of the observation vector of Doppler shift.

[0159] Step 6.2.2: Iterate and update the receiver position using the above formula , until the residual converges.

[0160] Table 1 Receiver parameters

[0161]

[0162] The present embodiment will be further described below with reference to specific examples.

[0163] Example:

[0164] Build a receiving device consisting of USRP, host computer and receiving antenna. Set the center frequency to 1626.25, bandwidth to 1MHZ, and sampling rate to 2MHz.

[0165] The traditional Doppler positioning algorithm and the Iridium IRA-based opportunity signal positioning error compensation algorithm are simulated and compared under the same environment. The parameters are shown in Table 2. The results are as follows: Figure 2 As shown in the figure, the simulation cannot simulate the signal error very well. The same set of data collected under the same environment is compared using the traditional Doppler positioning algorithm and the method adopted by the present invention. The positioning is performed using partial sampling and repeated positioning, full sampling and positioning, and the Iridium IRA-based opportunity signal positioning error compensation algorithm. The useful information parsed from the downlink signal is shown in Table 3. The optimization result is shown in the figure Figure 3 As shown, its time Doppler map is as follows Figure 4 As shown, the results are Figure 5 As shown in Table 7, the positioning results errors of the two algorithms for the same data are shown in Table 7.

[0166] Table 2 Simulation parameters

[0167]

[0168] Table 3 Analytical data of some measured Iridium downlink signals

[0169] Time (ms) from start time ID Beam ID Satellite projected longitude Satellite projected latitude 000017798.8167 050 44 +38.50 +131.93 000327702.7871 048 28 +52.59 +128.83 000332022.7479 048 28 +45.23 +125.19 000340662.6774 048 28 +44.71 +125.32 000393582.4155 048 31 +45.69 +126.99

[0170] Table 4. Positioning results of traditional algorithm and proposed algorithm

[0171]

[0172] In combination with the above data and Figure 5 It can be seen that the positioning accuracy of the traditional Doppler positioning algorithm is 126.6618m and 48.431m respectively, and the root mean square error is 126.662m. According to the algorithm of the patent, the north-east error is-100.767m and 31.554m respectively, and the root mean square error is 105.592m. Compared with the traditional Doppler positioning algorithm, the root mean square error of the positioning accuracy obtained by the algorithm is reduced by 24.56m. Therefore, the improved algorithm has higher positioning accuracy.

[0173] In summary, the algorithm proposed in the application realizes Iridium opportunity signal positioning. Moreover, while realizing Doppler positioning, the algorithm can estimate the rough position solution by the PSODC algorithm to correct the satellite position and speed, reduce the estimation error of the satellite position and speed, and improve the accuracy of the low-orbit satellite opportunity signal positioning.

[0174] Figure 1Any processes or methods described in the flowcharts or otherwise described herein can be understood as representing code modules, segments, or portions of code which include one or more executable instructions for implementing specific logic functions (or steps) of the application, and / or that the various embodiments of the application can include other implementations that are not strictly a software routine or code module. It is therefore intended that the embodiments of the application should not be limited to the particular combinations of hardware and software routines or code modules set forth herein, but should include all functions in accordance with the purpose and principles of the application. The flows presented in the flowcharts and the described herein can also represent code modules, segments, or portions of code which include one or more executable instructions for implementing specific logic functions (or steps) or the various embodiments of the application. It should also be understood that, in some alternative implementations, the functions noted in the boxes can occur out of the order noted in the figures, including

[0175] Those skilled in the art will understand that the above description is merely illustrative of the preferred embodiments of the application and the present application can be practiced in other ways. Consequently, the various embodiments and / or features described herein can be combined with one another, as techniques of the application are not limited to any particular combinations described. It is therefore intended that the application be construed broadly, and be limited only by the spirit and scope of the appended claims, including equivalents thereof.

[0176] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the foregoing description without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims be interpreted as including all such variations and modifications as fall within the spirit and scope of the application. It is further intended that the disclosure of all such modifications and variations be included within the scope of the application, the terms used herein being defined solely for purposes of the description being applied thereto unless otherwise indicated.

Claims

1. A method for compensating for the error in the position fix based on the opportunity signals of the IRAs, characterized in that, The method comprises the following steps: S1, connect the receiver hardware for receiving Iridium downlink signal; S2, analyze the received Iridium downlink signal; S3, demodulate the received Iridium downlink signal to obtain Iridium downlink information IRA; S4, get the projection longitude and latitude of the iridium star relative to the earth surface according to the iridium star downlink information IRA Calculate the average projection position by averaging multiple data ; S5. Calculate the average projected position based on the calculated average projected position and the iridium star visual range, calculate a coarse position solution based on a global particle swarm algorithm ; S6, obtaining a coarse position solution obtaining a propagation delay ; S7, determine the position of the satellite using the TLE file and the SGP4 file, using the propagation delay Calculate satellite position With speed ; S8, confirming the doppler shift of the center frequency of the IRA 11 band signal in the iridium satellite downlink signal using maximum likelihood estimation ; S9, the coarse position solution , satellite position and velocity , Doppler shift into the Doppler positioning equation to solve the position solution by least squares, and correct the satellite position based on the Iridium IRA opportunity signal positioning error compensation method.

2. The Iridium Star (IRA) based opportunity signal positioning error compensation method according to claim 1, characterized in that, The analysis of the received Iridium downlink signal in S2 is obtained by a Butterworth filter.

3. The Iridium Star (IRA) based opportunity signal positioning error compensation method according to claim 1, wherein, S3 specifically includes: S3.1, after filtering the received Iridium downlink signal, windowing operation is performed on it; S3.2, set the windowing signal strength threshold, loop to judge the whole frequency domain signal, capture the pilot information of the windowing signal; S3.3, set the period to 90ms, capture the next windowing signal; S3.4, demodulate the captured next windowing signal using BPSK to obtain binary encoding; S3.5, decode the windowing signal according to the Iridium IRA binary encoding rule, and the Iridium IRA analysis of the windowing signal includes the projection latitude and longitude LAT, LON of the satellite position on the earth, the satellite number of the Iridium downlink signal, and the completion of obtaining the Iridium downlink information IRA.

4. The Iridium Star (IRA) -based opportunity signal positioning error compensation method according to claim 3, characterized in that, A global particle swarm optimization algorithm is designed in S5 to solve the coarse position solution The method is as follows: S5.1, initialize the variables of the particle swarm; S5.

2. Calculating the average projected position from the calculated average position and the range of the Iridium satellite downlink signal to find the particle boundary: S5.3, calculate the PSO optimization target function according to the Doppler shift formula: wherein is the receiver target latitude, is the measured Doppler shift, is the carrier frequency, where may be obtained from the equation: wherein , is the radius of the earth; S5.4, traverse to get the optimal solution by PSO algorithm .

5. The Iridium Star (IRA) based opportunity signal positioning error compensation method of claim 1, wherein, S6 coarse position solution acquiring the propagation delay The method is: S6.

1. Calculate the propagation delay according to the calculated propagation delay ; S6.2, satellite position according to propagation delay Compensation is made ； wherein, is the corrected velocity of the satellite at the kth sampling time, , , are the coefficients of the cubic interpolation, respectively, obtained from the cubic interpolation formula.

6. The Iridium Star (IRA) based opportunity signal positioning error compensation method of claim 1, wherein, S7 employs propagation delay Computing optimized satellite position estimates to solve for satellite position With velocity The method is: S7.1, obtain the satellite orbit plane inclination and the ascending node right ascension information; S7.2, establish the SGP4 model according to the satellite TLES information; S7.3, obtaining satellite position and velocity sequence output according to SGP4 model with .

7. The Iridium Star (IRA) based opportunity signal positioning error compensation method of claim 1, wherein, The method for confirming the Doppler frequency shift of the signal center frequency of the IRA 11 frequency band signal in the iridium satellite downlink signal in S8 utilizes the maximum likelihood estimation method The method is as follows: S8.

1. Use a fast Fourier transform on the window in which the pilot lies to determine a coarse estimate of the Doppler ; S8.2, windowing in frequency domain uses maximum likelihood estimation method to determine fine Doppler within the window ; S8.3, according to the windowed generation time and Doppler profile and with step 2 in the analysis of Iridium downlink signal satellite ID to compare, complete the Iridium downlink signal in the IRA 11 frequency band signal center frequency of the Doppler shift confirmation. S8.3, according to the windowed generation time and Doppler profile and with step 2 in the analysis of Iridium downlink signal satellite ID to compare, complete the Iridium downlink signal in the IRA 11 frequency band signal center frequency of the Doppler shift confirmation. S8.3, according to the windowed generation time and Doppler profile and with step 2 in 8. The Iridium Star (IRA) based opportunity signal positioning error compensation method of claim 1, wherein, Coarse position solution in S9 Calculated by PSODC algorithm.

9. Computer device comprising a memory and a processor, characterized in that The memory stores a computer program, and when the processor runs the computer program stored in the memory, the processor executes the method of any one of claims 1 to 8.

10. A computer readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by the processor to realize the steps of the method of any one of claims 1 to 8.

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