Positioning convergence method based on synthetic aperture GNSS

Abstract

The invention provides a positioning convergence method based on a synthetic aperture GNSS, and relates to the technical field of communication, and the method comprises the steps: setting a resolving parameter of a to-be-estimated parameter; constructing a synthetic aperture GNSS mobile platform deck which is used for realizing the circumferential rotation motion or the lifting motion or the combined motion of the circumferential rotation motion and the lifting motion of a GNSS receiver; a satellite ephemeris and observation value file is obtained in real time, data preprocessing is carried out, and satellite signal emission time and a satellite position are calculated; constructing a double-difference observation value by using the original observation value of the satellite, and performing error processing; and based on the double-difference observation value, constraining the motion trail of the antenna of the monitoring station, and resolving the position state of the monitoring station through low-pass filtering and Kalman filtering. According to the method, the problem that the positioning convergence speed is low due to the fact that the multi-path effect is difficult to weaken in real time in a complex multi-path effect region is solved.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to a positioning convergence method based on synthetic aperture GNSS. Background Art

[0002] GNSS (global navigation satellite system) is short for Global Navigation Satellite System. The GNSS system can provide all-weather high-precision positioning, speed measurement, and time service for global users, and has been widely applied in many fields such as engineering practice and scientific research, generating huge economic value and social effects.

[0003] While receiving the direct satellite signals, the GNSS receiver also receives the reflected signals from other objects around the antenna, resulting in systematic deviations in the pseudorange and phase observables. This kind of error is usually called the multipath effect error. The multipath effect error is one of the main error sources affecting the positioning efficiency and accuracy of GNSS, and it must be eliminated or weakened.

[0004] Currently, the methods for weakening the multipath effect mainly include increasing the satellite elevation cut-off angle, installing devices such as choke rings and suppression plates, and using receivers with antenna arrays. Research shows that the current methods for weakening the multipath effect mainly include increasing the satellite elevation cut-off angle, installing devices such as choke rings and suppression plates for the receiver antenna, and using receivers with antenna arrays. Increasing the satellite elevation cut-off angle can, to a certain extent, suppress the influence of the multipath effect. However, since this method shields a certain number of available satellites, changing the satellite geometry configuration may lead to a decrease in positioning accuracy, and even cause GNSS to be unable to work in the case of fewer visible satellites. Installing a choke ring antenna device for the receiver increases the volume and mass of the entire receiver device, and is mostly used in static observation stations. It is too bulky for dynamic measurement situations, not convenient to carry, and the influence of weakening the multipath effect is limited. The receiver device with an antenna array is relatively bulky and costly, which is also the main reason why multi-antenna receivers have not been practically applied in the field of real-time kinematic positioning. Therefore, in the field of Global Navigation Satellite System (GNSS), a set of lightweight and efficient real-time multipath effect weakening methods need to be proposed. Summary of the Invention

[0005] Aiming at the above deficiencies in the prior art, the present invention provides a positioning convergence method based on synthetic aperture GNSS, which solves the problem that in a complex multipath effect area, the multipath effect is difficult to weaken in real time, resulting in a slow positioning convergence speed.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A positioning convergence method based on synthetic aperture GNSS, comprising the following steps:

[0007] S1. Set the solution parameters;

[0008] S2. Start the synthetic aperture GNSS mobile platform for dynamic observation, which is used to realize the circular rotation motion or lifting motion of the GNSS receiver or the combined motion of circular rotation motion and lifting motion;

[0009] S3. Obtain the satellite ephemeris and observation value file in real time, and perform preprocessing. Based on the preprocessing results, calculate the satellite position by calculating the satellite signal emission time, and use the satellite position to construct an observation matrix;

[0010] S4. Use the double-difference observation principle to perform single-difference between stations and double-difference between satellites on the multi-frequency and multi-mode observation values in sequence, construct double-difference observation values, and substitute the double-difference observation values and the observation matrix into the Kalman filter for calculation;

[0011] S5. Based on the double-difference observation values, constrain the movement trajectory of the monitoring station antenna, weaken the multipath effect through low-pass filtering, accurately fix the integer ambiguity through the Kalman filter, and obtain the accurate solution of the position state of the monitoring station to achieve rapid convergence of positioning.

[0012] Further, the S2 is specifically:

[0013] Use the synthetic aperture GNSS mobile platform to realize the circular rotation motion of the GNSS receiver with a radius of one satellite signal wavelength; or

[0014] Use the synthetic aperture GNSS mobile platform to realize the lifting motion of the GNSS receiver with a lifting range from zero to two satellite signal wavelengths; or

[0015] Use the synthetic aperture GNSS mobile platform to realize the combined motion of the circular rotation motion of the GNSS receiver with a radius of one satellite wavelength and the lifting motion with a lifting range from zero to two satellite signal wavelengths.

[0016] Furthermore, the synthetic aperture GNSS mobile platform for circular rotation motion is a horizontal rotation type GNSS receiver platform device, which includes a tripod, a base set on the tripod, a rotary table motor connected to the base, a rotary table switch and a gear control button respectively connected to the rotary table motor, a rotary table power supply and a horizontal rotary table, and equal-weight weights and a GNSS receiver respectively connected to the horizontal rotary table;

[0017] The horizontal rotation type GNSS receiver platform device is used to make the GNSS receiver do regular circular motion along with the horizontal rotary table.

[0018] Furthermore, the synthetic aperture GNSS mobile carrier platform with lifting motion is a vertical lifting carrier platform device, which includes a tripod, a base arranged on the tripod, a vertical lifting table motor connected to the base, a vertical lifting table switch and a gear control button respectively connected to the vertical lifting table motor, a vertical lifting table power supply, a vertical lifting rod, and a GNSS receiver connected to the vertical lifting rod;

[0019] The vertical lifting carrier platform device is used to make the GNSS receiver do regular vertical lifting motion along with the vertical lifting rod.

[0020] Furthermore, the synthetic aperture GNSS mobile carrier platform combination spiral motion carrier platform device includes a tripod, a base arranged on the tripod, a vertical lifting table motor connected to the base, a vertical lifting table power supply, a vertical lifting rod, a combination spiral moving carrier platform switch and a gear control button, and a rotating table, and a GNSS receiver and an equal weight respectively connected to the rotating table;

[0021] The combination spiral motion carrier platform device is used to make the GNSS receiver do regular combined spiral motion along with the vertical lifting rod and the horizontal rotating table.

[0022] Furthermore, the position state of the monitoring part is solved by low-pass filtering and Kalman filtering, specifically:

[0023] Based on the double-difference observation value, the motion trajectory of the monitoring station antenna is constrained. In the local-level right-handed rectangular coordinate system, the state transition equation and the observation equation of the monitoring point based on Kalman filtering are obtained by the following formula:

[0024]

[0025]

[0026]

[0027] Among them, X t represents the system state vector at time t, L t represents the observation value vector, Φ t,t-1 represents the state transition matrix, C t,t-1 represents the observation design matrix, X t-1 represents the system state vector at time t - 1, W t is the process noise, F t represents the observation noise, N represents the normal distribution, Q t and R t both represent the variance of the normal distribution, Q E and Q N are the state transition noise variances in two directions of the plane respectively, Q Urepresents the variance of the state transition noise in the elevation direction, represents the variance of the ambiguity state transition noise, Q ωb represents the variance of the state transition noise of the reference station zenith troposphere, represents the variance of the state transition noise of the inter-station zenith troposphere, represents the variance of the state transition noise of the ionosphere, and respectively represent the variance matrices of the observation noises of the pseudorange and phase. Among them, the state transition matrix of all parameters to be estimated is obtained by the following formula:

[0028]

[0029] Among them, Φ represents the state transition matrix of all parameters to be estimated, represents the state transition of the double-difference ambiguity, E ωb represents the state transition matrix of the wet delay of the reference station zenith troposphere, represents the state transition matrix of the relative tropospheric wet delay between stations, represents the state transition matrix of the double-difference ionosphere;

[0030] Based on the state transition equation and the observation equation of the monitoring point, by using a low-pass filter to restrict the passage of high-frequency signals, the high-frequency interference is reduced and the multipath effect is weakened;

[0031] Using the Kalman filter to fix the integer ambiguity, the accurate solution of the position state of the monitoring point is obtained, and the rapid convergence of positioning is realized.

[0032] Advantages of the present invention:

[0033] (1) The present invention provides a synthetic aperture GNSS rapid positioning method for real-time weakening of the multipath effect, including a synthetic aperture observation device and a synthetic aperture rapid positioning algorithm. The mobile platform can enable the GNSS receiver to perform circular rotation motion with a radius of one satellite signal wavelength, or the mobile platform can enable the GNSS receiver to perform lifting motion with a lifting range from zero to two satellite signal wavelengths, or the mobile platform can enable the GNSS receiver to perform a combined motion of circular rotation motion with a radius of one satellite signal wavelength and lifting motion with a lifting range from zero to two satellite signal wavelengths. The positioning algorithm realizes rapid weakening of the multipath through antenna trajectory filtering constraints and improves the positioning speed.

[0034] (2) A mobile platform provided by the present invention can perform motions such as single-antenna rotation and lifting, and realizes the equivalent result of virtual array element spatial sampling by signal sampling at different times and positions, thereby realizing real-time weakening of the multipath effect of GNSS synthetic aperture. This device has only one receiver, so it has high portability and mobility.

[0035] (3) Without changing the position of the measuring station and the surrounding conditions, by using the synthetic aperture GNSS observation device for real-time weakening of multipath effects proposed in the present invention (mainly including a horizontal rotation platform, a vertical lifting platform, and a combined spiral movement platform), the antenna performs a fast periodic movement with an accurate trajectory relative to the base (including the vertical direction, the horizontal rotation direction, and the combined spiral direction). Moreover, compared with devices such as choke ring antennas and antenna arrays, the device of the present invention has the advantages of being more portable, lower in cost, convenient for installation and movement, etc. By using the device of the present invention to make the antenna perform periodic fast movement and high-frequency sampling, and precisely constraining the dynamic position of the antenna through the designed trajectory, a synthetic aperture GNSS antenna is formed. The synthetic aperture GNSS significantly reduces the temporal correlation of the phase and pseudorange multipath effects, and greatly weakens the multipath effects within a short time through filtering, achieving the purpose of fast and precise positioning. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the principle of multipath effect.

[0037] Figure 2 It is a schematic diagram of the principle of synthetic aperture sampling.

[0038] Figure 3 It is a schematic diagram of the synthetic aperture observation device of the vertical lifting type of the present invention.

[0039] Figure 4 It is a schematic diagram of the synthetic aperture observation device of the horizontal rotation type of the present invention.

[0040] Figure 5 It is a schematic diagram of the synthetic aperture observation device of the combined spiral type of the present invention.

[0041] Figure 6 It is a flowchart of the method of the present invention.

[0042] Figure 7 It is a flowchart of the satellite position calculation of the present invention.

[0043] Figure 8 It is a flowchart for the solution of the integer ambiguity.

[0044] Among them, 1 - tripod, 2 - base horizontal angle screw, 3 - base, 4 - base centering eyepiece, 5 - base level tube, 6 - first threaded hole connecting rod, 7 - rotating table motor, 8 - rotating table power supply, 9 - sixth threaded hole connecting rod, 10 - horizontal rotating table, 11 - equal weight, 12 - second threaded hole connecting rod, 13 - GNSS receiver, 14 - third threaded hole connecting rod, 15 - vertical lifting table motor, 16 - vertical lifting table power supply, 17 - vertical lifting rod, 18 - fourth threaded hole connecting rod, 19 - fifth threaded hole connecting rod, 20 - rotating table switch and gear control button, 21 - vertical lifting table switch and gear control button, 22 - combined screw moving stage switch and gear control button. Detailed implementation manners

[0045] The following describes the detailed implementation manners of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed implementation manners. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0046] Embodiment

[0047] As Figure 6 shown, the present invention provides a positioning convergence method based on synthetic aperture GNSS, and its implementation method is as follows:

[0048] S1. Set the calculation parameters of the parameters to be estimated.

[0049] In this embodiment, the parameters include the motion state parameters of the synthetic aperture GNSS moving stage, the initial equation of the parameters to be estimated in the algorithm process, the state transition noise and other related parameters for subsequent S2 to S5.

[0050] S2. Start the synthetic aperture GNSS moving stage for dynamic observation, which is used to realize the circular rotation motion or lifting motion of the GNSS receiver or the combined motion of the circular rotation motion and the lifting motion. The original data obtained in this step is used for subsequent operations in all steps. Specifically:

[0051] Utilize the synthetic aperture GNSS moving stage to realize the circular rotation motion of the GNSS receiver with a radius of one satellite signal wavelength;

[0052] In this embodiment, the synthetic aperture GNSS mobile platform for circular rotational motion is a horizontal rotational GNSS receiver platform device, which includes a tripod 1, a base 3 disposed on the tripod 1, a rotary table motor 7 connected to the base 3, a rotary table switch and a gear control button 20 respectively connected to the rotary table motor 7, a rotary table power supply 8 and a horizontal rotary table 10, and an equal-weight weight 11 and a GNSS receiver 13 respectively connected to the horizontal rotary table 10; the horizontal rotational GNSS receiver platform device is used to make the GNSS receiver 13 perform regular circular motion along with the horizontal rotary table 10.

[0053] The synthetic aperture GNSS mobile platform is used to realize the lifting motion of the GNSS receiver with a lifting range from zero to two satellite signal wavelengths;

[0054] In this embodiment, the synthetic aperture GNSS mobile platform for lifting motion is a vertical lifting platform device, which includes a tripod 1, a base 3 disposed on the tripod 1, a vertical lifting table motor 15 connected to the base 3, a vertical lifting table switch and a gear control button 21 respectively connected to the vertical lifting table motor 15, a vertical lifting table power supply 16 and a vertical lifting rod 17, and a GNSS receiver 13 connected to the vertical lifting rod 17; the vertical lifting platform device is used to make the GNSS receiver 13 perform regular vertical lifting motion along with the vertical lifting rod 17.

[0055] The synthetic aperture GNSS mobile platform is used to realize the combined motion of the circular rotational motion of the GNSS receiver with a radius of one satellite wavelength and the lifting motion with a lifting range from zero to two satellite signal wavelengths.

[0056] In this embodiment, the synthetic aperture GNSS mobile platform for combined motion is a combined spiral motion platform device, which includes a tripod 1, a base 3 disposed on the tripod 1, a vertical lifting table motor 15 connected to the base 3, a vertical lifting table power supply 16, a vertical lifting rod 17, a combined spiral mobile platform switch and a gear control button 22, and a rotary table 10, and a GNSS receiver 13 and an equal-weight weight 11 respectively connected to the rotary table 10; the combined spiral motion platform device is used to make the GNSS receiver 13 perform regular combined spiral motion along with the vertical lifting rod 17 and the horizontal rotary table 10.

[0057] In this embodiment, the mobile platform of the present invention is used to realize the circular rotational motion of the GNSS receiver with a radius of one satellite signal wavelength, or the lifting motion with a lifting range from zero to two satellite signal wavelengths, or the combined motion of the two.

[0058] In this embodiment, Figures 1 to 5 ( Figure 1where R represents the radius of the antenna's movement, H represents the distance from the antenna to the reflecting surface, ΔS represents the extra distance traveled by the reflected path compared to the direct path, and θ is the incident angle; Figure 2 where the antenna moves in a uniform straight line along the x - direction, reaches x1 at time t1, and reaches x N at time t N (where v represents the speed), the present invention provides a synthetic aperture GNSS mobile platform: including a base 3 and a GNSS receiver 13. The synthetic aperture GNSS mobile platform can achieve the movement synthesized by the circular rotation movement of the GNSS receiver with a radius of one satellite signal wavelength and the lifting movement with a lifting range from zero to two satellite signal wavelengths. The principle is as follows:

[0059] As Figure 1 shown, Figure 1 the schematic diagram of the signal multipath effect of a single reflecting element is shown, from which it can be deduced that:

[0060]

[0061] For a stationary antenna, the change in the multipath phase only depends on the change in the satellite signal incident angle. Since the change in the satellite incident angle is extremely slow (the typical value of the satellite incident angle change rate is 0.00007 radians per second), the period of the multipath effect phase change is very long. If the vertical distance H between the antenna and the reflecting surface is changed periodically and rapidly t , let H t =H + Rsin(2πft), then the multipath effect of the moving antenna is:

[0062]

[0063] where represents the multipath phase of the reflected signal of the moving antenna, represents the deviation of the multipath phase of the reflected signal, in radians, R represents the radius of the antenna's movement (as Figure 1 ), f represents the change frequency of the vertical distance H t , H t represents the vertical distance between the moving antenna and the reflecting surface, t represents time, λ represents the wavelength of the satellite signal, ΔS represents the path length that the reflected signal received by the antenna travels more than the direct signal, H represents the vertical distance between the antenna and the reflecting surface, and θ represents the angle between the direct signal and the reflecting surface.

[0064] In order to make the multipath from the large reflecting element produce a complete periodic phase change, only need to take R = λ / (4sinθ). If the cut - off elevation angle is set above 13 degrees and the distance between the antenna and the tall vertical surface is limited to more than 15 meters, then taking R as the longest observed signal wavelength can meet the requirements.

[0065] Through analysis, it can be obtained that by using the device of the present invention, the antenna performs periodic rapid movement and high-frequency sampling. By designing the trajectory, the dynamic position of the antenna is accurately constrained to form a synthetic aperture GNSS antenna. The synthetic aperture GNSS significantly reduces the temporal correlation of the phase and pseudorange multipath effects. By filtering, the multipath effects are greatly weakened within a short time, achieving the purpose of rapid and precise positioning.

[0066] Specifically, as Figure 3 shown, the main function of the vertical lifting stage device is to make the GNSS receiver 13 perform regular vertical lifting movement along with the vertical lifting rod 17 (the range of the vertical lifting movement is h ∈ (0, 51 ± 0.5) cm). While ensuring that the horizontal position of the GNSS receiver 13 remains unchanged and the elevation changes according to the regulations, the influence of multipath in the horizontal direction is weakened. The vertical lifting stage device consists of a tripod 1, a base 3 (including a base horizontal angle screw 2, a base centering eyepiece 4, and a base level tube 5), a third threaded hole connecting rod 14 connecting the base 3 and the vertical lifting stage motor 15, a vertical lifting stage switch and gear control button 21, a vertical lifting stage power supply 16, a vertical lifting rod 17 (with a length of approximately h = 51 ± 0.5 cm), a fourth threaded hole connecting rod 18 connecting the vertical lifting rod 17 and the GNSS receiver 13, and the GNSS receiver 13. Its working principle is as follows:

[0067] The vertical lifting type stage device aligns with the measurement point through the base centering eyepiece 4 of the base 3, and levels and centers by adjusting the base level tube 5 through the base horizontal angle screw 2. Then, the base 3 and the vertical lifting stage motor 15 are connected through the third threaded hole connecting rod 14. The vertical lifting stage switch and gear control button 21, the vertical lifting stage motor 15, and the vertical lifting stage power supply 16 are mainly responsible for controlling the vertical lifting frequency and switch operation of the vertical lifting rod 17. Finally, the vertical lifting rod 17 and the GNSS receiver 13 are connected through the threaded hole connecting rod 18.

[0068] As Figure 4As shown in the figure, the main function of the horizontal rotation type GNSS receiver carrier device is to make the GNSS receiver 13 perform regular circular motion along with the horizontal rotating table 10 (the radius r of the circular motion is 25.5 ± 0.5 cm). Under the condition of ensuring that the elevation remains unchanged and the horizontal position changes according to the regulations, the influence of multipath is weakened in the elevation direction. The horizontal rotation type GNSS receiver carrier device consists of a tripod 1, a base 3 (including a base horizontal angle screw 2, a base centering eyepiece 4, and a base level tube 5), a first threaded hole connecting rod 6 connecting the base 3 and the rotating table motor 7, a rotating table switch and gear control button 20, a rotating table power supply 8, a sixth threaded hole connecting rod 9 connecting the rotating table motor 7 and the rotating table 10, a rotating table 10 (the radius r of the rotating table 10 is 25.5 ± 0.5 cm), a second threaded hole connecting rod 12 connecting the rotating table 10 and the GNSS receiver 13, a GNSS receiver 13, and an equal weight 11. Its working principle is as follows:

[0069] The horizontal rotation type carrier device aligns with the measured point through the base centering eyepiece 4 of the base, and levels the base by adjusting the base level tube 5 through the base horizontal angle screw 2. Then, the base 3 and the rotating motor 7 are connected through the first threaded hole connecting rod 6. The rotating table switch and gear control button 20, the rotating motor 7, and the rotating table power supply 8 are mainly responsible for controlling the horizontal rotation frequency of the rotating table 10 and the operation of the rotating switch of the rotating table 10. Then, the rotating motor 7 and the rotating table 10 are connected through the sixth threaded hole connecting rod 9. Finally, at the left edge of the rotating table 10, the rotating table 10 and the GNSS receiver 13 are connected through the second threaded hole connecting rod 12, and an equal weight 11 is connected at the position centrosymmetric to the second threaded hole connecting rod 12 with respect to the rotating table 10 to maintain the stability of the rotational motion.

[0070] As Figure 5As shown in the figure, the main function of the combined spiral motion stage device is to enable the GNSS receiver 13 to perform a regular combined spiral motion along with the vertical lifting rod 17 and the horizontal rotating table 10 (the horizontal motion is a circular motion with a radius r = 25.5 ± 0.5 cm, and the vertical motion is a vertical lifting motion with a range h ∈ (0, 51 ± 0.5) cm). While ensuring that the horizontal position and elevation of the GNSS receiver 13 change according to the specified trajectory, the influence of multipath is weakened simultaneously in the horizontal and elevation directions, the positioning convergence speed is increased, and high-precision point coordinates are obtained. The combined spiral motion stage device consists of a tripod 1, a base 3 (including a base horizontal angle screw 2, a base centering eyepiece 4, a base level tube 5), a threaded hole connecting rod 14 connecting the base 3 and the vertical lifting stage motor 15, a combined spiral moving stage switch and gear control button 22, a vertical lifting stage power supply 16, a vertical lifting rod 17 (with a length of approximately h = 51 ± 0.5 cm), a fifth threaded hole connecting rod 19 connecting the vertical lifting rod 17 and the rotating table motor 7, a rotating table motor 7, a rotating table power supply 8, a sixth threaded hole connecting rod 9 connecting the rotating table motor 7 and the rotating table 10, a rotating table 10 (the radius of the rotating table 10 is approximately r = 25.5 ± 0.5 cm), a threaded hole connecting rod 12 connecting the rotating table 10 and the GNSS receiver 13, a GNSS receiver 13, and an equal-weight counterweight 11. The working principle is as follows:

[0071] The combined spiral type stage device aligns with the measurement point through the base centering eyepiece 4 of the base 3, levels the base by adjusting the base level tube 5 through the base horizontal angle screw 2, then connects the base 3 and the vertical lifting stage motor 15 through the third threaded hole connecting rod 14, and then connects the vertical lifting rod 17 and the rotating table motor 7 through the fifth threaded hole connecting rod 19. The combined spiral moving stage switch and gear control button 22, the vertical lifting stage motor 15, the vertical lifting stage power supply 16, the rotating table motor 7, and the rotating table power supply 8 are jointly responsible for the movement frequency and switch control in the horizontal and vertical directions of the combined spiral. Finally, at the left edge of the rotating table 10, the rotating table 10 and the GNSS receiver 13 are connected through the second threaded hole connecting rod 12, and an equal-weight counterweight 11 is connected at the position centrosymmetric to the rotating table 10 with respect to the second threaded hole connecting rod 12 to maintain the stability of the rotational motion and make it perform a combined spiral motion.

[0072] S3. Obtain the satellite ephemeris and observation value files in real time, perform preprocessing, and based on the preprocessing results, calculate the satellite position by calculating the satellite signal emission time, and use the satellite position to construct an observation matrix;

[0073] In this embodiment, data preprocessing is used for data quality control, including data preprocessing such as gross error detection. The calculation of the satellite signal emission time and the satellite position provides a basis for subsequent solution. The calculation process of the satellite position is as Figure 7As shown, the direction cosines are further calculated from the calculated satellite positions and placed in the observation matrix. The process is as follows:

[0074] Calculate the average angular velocity n of the satellite's motion;

[0075] Using the average angular velocity n, calculate the mean anomaly M of the satellite at the observation instant;

[0076] Using the mean anomaly M, calculate the eccentric anomaly E;

[0077] Using the eccentric anomaly E, calculate the true anomaly f;

[0078] Using the true anomaly f, calculate the argument of latitude u';

[0079] Using the argument of latitude u', calculate the perturbation correction term;

[0080] Perform perturbation correction processing on u', r', and i0, where u' represents the argument of latitude, r' represents the satellite radius vector, and i0 represents the orbital inclination;

[0081] Calculate the position of the satellite in the orbital plane coordinate system;

[0082] Based on the obtained position, calculate the longitude L of the ascending node at the observation instant;

[0083] Based on the obtained longitude L, obtain the position of the satellite in the conventional terrestrial coordinate system by calculating the position of the satellite in the instantaneous terrestrial coordinate system.

[0084] S4. Using the double-difference observation principle, perform single-difference between stations and double-difference between satellites on the multi-frequency and multi-mode observations in sequence to construct double-difference observations, and substitute the double-difference observations and the observation matrix into the Kalman filter for calculation;

[0085] The original GNSS observations mainly use two types: code pseudorange observations and phase observations, and the mathematical expressions are as follows.

[0086] P = R - c(dt s + B P ) + c(dt r + b P ) + dρ + I + T + M + ε P

[0087]

[0088] In the formula, R represents the geometric distance between the satellite and the receiver at a certain moment, dt s , dt r represent the satellite clock error and the receiver clock error respectively, B P , b P , They respectively correspond to the pseudorange hardware delay and phase hardware delay at the satellite end and the receiver end. \(d\rho\) represents the ephemeris error, \(I\) represents the ionospheric delay, \(T\) represents the tropospheric delay, \(M\) represents the multipath effect, \(\varepsilon\) represents the corresponding measurement noise, and \(P\) represents the code pseudorange observation value. represents the phase observation value.

[0089] On this basis, the pseudorange observation and phase observation are respectively differenced, and the double-difference observation value is used to adjust and solve the displacement change of the monitoring point within a certain period of time. The double-difference observation value is combined by 4 independent observation values, and the inter-station difference and inter-satellite difference are carried out. The following table shows the derivation process of the phase double-difference observation value, and the derivation of the code pseudorange double-difference observation value is similar.

[0090]

[0091] The final double-difference observation value can be expressed by the following formula:

[0092]

[0093] Among them, represents the double-difference observation value, represents the phase observation values of two satellites at the reference station, represents the phase observation values of two satellites at the rover station.

[0094] S5. Based on the double-difference observation value, the movement trajectory of the monitoring station antenna is constrained to establish an accurate state transition equation and its corresponding noise for the subsequent filtering process, and the multipath effect is weakened by low-pass filtering. The integer ambiguity is accurately fixed through Kalman filtering to obtain an accurate solution of the position state of the monitoring station, realizing the fast convergence of positioning. Specifically:

[0095] Based on the double-difference observation value, the movement trajectory of the monitoring station antenna is constrained. In the local north-east-down (NED) coordinate system with the station as the origin, the state transition equation and observation equation of the monitoring point based on Kalman filtering are obtained by using the following formula:

[0096]

[0097]

[0098]

[0099] Among them, \(X\) t represents the system state vector at time \(t\), \(L\) t represents the observation value vector, \(\varPhi\) t,t-1 represents the state transition matrix, \(C\) t,t-1 represents the observation design matrix, \(X\) t-1 represents the system state vector at time \(t - 1\), \(W\) t process noise, \(F\) tdenotes the observation noise, N denotes the normal distribution, Q t and R t both denote the variances of the normal distribution, Q E and Q N respectively represent the state transition noise variances in two directions of the plane, Q U represents the state transition noise variance in the elevation direction, represents the state transition noise variance of the ambiguity, Q ωb represents the state transition noise variance of the zenith troposphere of the reference station, represents the state transition noise variance of the inter-station zenith troposphere, represents the state transition noise variance of the ionosphere, and respectively represent the variance matrices of the observation noises of the pseudorange and the phase. Among them, the state transition matrix of all parameters to be estimated is obtained by the following formula:

[0100]

[0101] where, Φ represents the state transition matrix of all parameters to be estimated, represents the state transition of the double-difference ambiguity, E ωb represents the state transition matrix of the wet delay of the zenith troposphere of the reference station, represents the state transition matrix of the relative tropospheric wet delay between stations, represents the state transition matrix of the double-difference ionosphere;

[0102] A low-pass filter, abbreviated as a low-pass filter, is an electronic circuit or algorithm used for signal processing. Its basic function is to allow signal components with frequencies lower than a certain set threshold to pass through smoothly, while attenuating or blocking high-frequency signals beyond this threshold to varying degrees. This filtering characteristic enables the low-pass filter to effectively remove unwanted high-frequency noise or other undesired high-frequency signals in various applications. As an effective signal processing tool, the low-pass filter has important applications in weakening the multipath effect. The multipath effect of a synthetic aperture antenna usually causes interference of high-frequency components, and the first-order low-pass filter can effectively reduce the influence of these high-frequency interferences by restricting the passage of high-frequency signals, thereby quickly weakening the multipath effect.

[0103] Such as Figure 8As shown, in the carrier phase observation system, the integer property of the integer ambiguity parameter has a decisive influence on the measurement accuracy. There are undetermined integer ambiguity parameters in the observation data, and the ambiguity parameters in the real solution domain must be converted into integer solutions through integer constraints to achieve precise calculation of the distance from the satellite to the ground receiver. Affected by the observation system error, the actually calculated ambiguity parameters often deviate from the ideal integer state. Based on the state transition equation and the observation equation of the monitoring point, according to the integer property of the ambiguity, the ambiguity is fixed from a real number to an integer, which is called the solution of the integer ambiguity. The Kalman filter is used to quickly fix the integer ambiguity to obtain the precise solution of the position state of the monitoring point and achieve rapid convergence of positioning.

[0104] In this embodiment, according to the motion state of the synthetic aperture observation device of the present invention, reasonable state transition noise variances are given in the elevation and plane directions according to the motion speed of the antenna to achieve antenna trajectory constraint filtering; the low-pass filter, as an effective signal processing tool, has an important application in weakening the multipath effect. The multipath effect of the synthetic aperture antenna usually causes interference of high-frequency components, and the first-order low-pass filter can effectively reduce the influence of these high-frequency interferences by restricting the passage of high-frequency signals, thereby quickly weakening the multipath effect. Therefore, the present invention uses a first-order low-pass filter combined with the Kalman filter to filter and weaken the multipath effect with high-frequency characteristics, and finally improves the convergence speed of positioning.

[0105] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A positioning convergence method based on synthetic aperture GNSS, characterized in that, Including the following steps: S1. Set the solution parameters; S2. Start the synthetic aperture GNSS mobile platform for dynamic observation, which is used to realize the circular rotation motion or lifting motion of the GNSS receiver or the combined motion of circular rotation motion and lifting motion; S3. Obtain the satellite ephemeris and observation value file in real time, and perform preprocessing. Based on the preprocessing results, calculate the satellite position by calculating the satellite signal emission time, and use the satellite position to construct an observation matrix; S4. Use the double-difference observation principle to perform single-difference between stations and double-difference between satellites on the multi-frequency and multi-mode observation values in sequence to construct double-difference observation values, and substitute the double-difference observation values and the observation matrix into the Kalman filter for calculation; S5. Based on the double-difference observation values, constrain the movement trajectory of the monitoring station antenna, weaken the multipath effect through low-pass filtering, accurately fix the integer ambiguity through the Kalman filter, obtain the accurate solution of the position state of the monitoring station, and achieve rapid convergence of positioning.

2. The positioning convergence method based on synthetic aperture GNSS according to claim 1, wherein The synthetic aperture GNSS mobile platform in S2 includes: Using the synthetic aperture GNSS mobile platform to realize the circular rotation motion of the GNSS receiver with a radius of one satellite signal wavelength; or Using the synthetic aperture GNSS mobile platform to realize the lifting motion of the GNSS receiver with a lifting range from zero to two satellite signal wavelengths; or Using the synthetic aperture GNSS mobile platform to realize the combined motion of the circular rotation motion of the GNSS receiver with a radius of one satellite wavelength and the lifting motion with a lifting range from zero to two satellite signal wavelengths.

3. The positioning convergence method based on synthetic aperture GNSS according to claim 2, characterized in that, The synthetic aperture GNSS mobile platform for circular rotation motion is a horizontal rotation type GNSS receiver platform device, which includes a tripod (1), a base (3) arranged on the tripod (1), a rotary table motor (7) connected to the base (3), a rotary table switch and gear control button (20) respectively connected to the rotary table motor (7), a rotary table power supply (8) and a horizontal rotary table (10), and equal weight weights (11) and a GNSS receiver (13) respectively connected to the horizontal rotary table (10); The horizontal rotation type GNSS receiver platform device is used to make the GNSS receiver (13) perform regular circular motion along with the horizontal rotary table (10).

4. The positioning convergence method based on synthetic aperture GNSS according to claim 2, wherein The synthetic aperture GNSS mobile platform for lifting motion is a vertical lifting platform device, which includes a tripod (1), a base (3) arranged on the tripod (1), a vertical lifting table motor (15) connected to the base (3), a vertical lifting table switch and gear control button (21) respectively connected to the vertical lifting table motor (15), a vertical lifting table power supply (16) and a vertical lifting rod (17), and a GNSS receiver (13) connected to the vertical lifting rod (17); The vertical lifting platform device is used to make the GNSS receiver (13) perform regular vertical lifting motion along with the vertical lifting rod (17).

5. The positioning convergence method based on synthetic aperture GNSS according to claim 2, wherein The combined spiral motion carrier platform device of the synthetic aperture GNSS mobile carrier for the synthetic motion includes a tripod (1), a base (3) arranged on the tripod (1), a vertical lifting table motor (15) connected to the base (3), a vertical lifting table power supply (16), a vertical lifting rod (17), a combined spiral mobile carrier platform switch and gear control button (22), and a rotating table (10), and a GNSS receiver (13) and an equal-weight counterweight (11) respectively connected to the rotating table (10); The combined spiral motion carrier platform device is used to make the GNSS receiver (13) perform a regular combined spiral motion along with the vertical lifting rod (17) and the horizontal rotating table (10).

6. The positioning convergence method based on synthetic aperture GNSS according to claim 1, characterized in that, Solve the position state of the monitoring station, specifically as follows: Based on the double-difference observations, constrain the movement trajectory of the monitoring station antenna. In the local-level coordinate system (ENU), use the following formula to obtain the state transition equation and observation equation of the monitoring point based on the Kalman filter: Among them, X t represents the system state vector at time t, L t represents the observation value vector, Φ t,t-1 represents the state transition matrix, C t,t-1 represents the observation design matrix, X t-1 represents the system state vector at time t - 1, W t process noise, F t represents the observation noise, N represents the normal distribution, Q t and R t both represent the variances of the normal distribution, Q E and Q N are respectively the state transition noise variances in two directions of the plane, Q U represents the state transition noise variance in the elevation direction, represents the ambiguity state transition noise variance, Q ωb represents the reference station zenith troposphere state transition noise variance, represents the inter-station zenith troposphere state transition noise variance, represents the ionosphere state transition noise variance, and respectively represent the variance matrices of the observation noises of the pseudorange and phase. Among them, the state transition matrix of all parameters to be estimated is obtained by the following formula: Among them, Φ represents the state transition matrix of all parameters to be estimated, represents the state transition of double-difference ambiguity, E ωb represents the state transition matrix of the zenith tropospheric wet delay of the reference station, represents the state transition matrix of the relative tropospheric wet delay between stations, represents the state transition matrix of double-difference ionosphere; Based on the state transition equation and observation equation of the monitoring point, use a low-pass filter to reduce high-frequency interference and weaken the multipath effect by restricting the passage of high-frequency signals; Use the Kalman filter to fix the integer ambiguity and obtain the precise solution of the position state of the monitoring point, realizing the rapid convergence of positioning.

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