A combined precise positioning method for GNSS pseudolite combined receiver

Abstract

The application relates to the field of satellite navigation and ground-based enhanced positioning technology, and particularly discloses a combined precise positioning method for a GNSS pseudolite combined receiver, wherein the method comprises the following steps: based on the midline theorem, performing collinear combination processing on observation values of two GNSS antennas to generate virtual observation values from a GNSS satellite to a pseudolite antenna phase center; fusing the virtual observation values with pseudolite original observation values, introducing an inter-system bias representing a difference in receiver clock difference between different systems as an estimated parameter, and constructing a unified combined positioning observation equation; and according to the number of visible pseudolites, adaptively adjusting a positioning strategy: when the number reaches a preset threshold, starting a combined positioning mode to accelerate precise point positioning convergence, otherwise switching to an independent GNSS positioning mode.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation and ground-based augmentation positioning technology, specifically to a combined precise positioning method for a GNSS pseudo-satellite combined receiver. Background Technology

[0002] Global Navigation Satellite Systems (GNSS), as the most widely used absolute positioning technology, can provide positioning accuracy at the meter or even centimeter level in open environments. However, in environments where GNSS signals are blocked or completely blocked, such as urban canyons, indoor spaces, underground spaces, tunnels, and dense forests, GNSS receivers cannot capture a sufficient number of satellite signals, leading to a sharp drop in positioning accuracy or even complete failure. This problem severely restricts the development of emerging fields such as autonomous driving, drone inspection, indoor robots, and underground pipeline maintenance.

[0003] To address the positioning challenges in GNSS-denied environments, existing technologies primarily employ the following solutions, but all have significant limitations: (1) Inertial navigation scheme: This scheme relies on an inertial measurement unit (IMU) to measure the acceleration and angular velocity of the carrier, and obtains position, velocity and attitude information through integration. Pure inertial navigation has the advantages of strong autonomy and no interference from the external environment, but it has the fatal flaw of error accumulation over time. In particular, low-cost MEMS-IMUs, their zero bias error and random walk error will cause the positioning accuracy to deteriorate rapidly within a few seconds, which cannot meet the requirements of long-term high-precision positioning.

[0004] (2) Visual navigation scheme: This scheme extracts visual features in the environment through a camera to achieve simultaneous localization and map building. Visual SLAM has the advantages of low cost and rich information, but it is prone to failure in environments with drastic changes in lighting, lack of texture, and many dynamic objects. It also has scale uncertainty issues, and long-term operation will produce large cumulative errors.

[0005] (3) LiDAR SLAM scheme: This scheme utilizes the three-dimensional point cloud information of the environment measured by LiDAR, which has the advantages of high accuracy and strong resistance to light interference. However, LiDAR is expensive, its performance degrades significantly under adverse weather conditions such as rain, snow and fog, and it is prone to positioning drift in environments with simple geometric features such as long corridors and open squares.

[0006] In summary, there is currently no technical solution that can effectively combine the advantages of GNSS absolute positioning to achieve continuous high-precision positioning in complex and ever-changing environments. This invention addresses these technical problems by proposing a pseudo-satellite / GNSS combined positioning method, aiming to achieve continuous high-precision positioning across all scenarios, from good GNSS signal coverage to complete GNSS rejection, even in situations where GNSS rejection is not possible. Summary of the Invention

[0007] To achieve the objective of this invention, this application provides a combined precise positioning method for a GNSS pseudo-satellite combined receiver, comprising: Step S1: Utilizing the fixed geometric relationship of the space synchronization antenna array, the observations of the two GNSS antennas are collinearly combined based on the median theorem to generate virtual observations from the GNSS satellite to the phase center of the pseudo-satellite antenna; Step S2: The virtual observations are fused with the original pseudo-satellite observations, and the inter-system bias, which characterizes the differences in receiver clock bias between different systems, is introduced as the parameter to be estimated, and a unified combined positioning observation equation is constructed. Step S3: When solving the combined positioning observation equation, the positioning strategy is adaptively adjusted according to the number of visible pseudo-satellites: when the number reaches a preset threshold, the combined positioning mode is activated to accelerate the convergence of precise single-point positioning; otherwise, the independent GNSS positioning mode is switched.

[0008] In some specific embodiments, in step S1, the virtual observation value is determined based on the observation values ​​of the two GNSS antennas and the fixed distance from the two GNSS antennas to the pseudo-satellite antenna.

[0009] In some specific embodiments, in step S2, the inter-system deviation specifically involves estimating the difference between the receiver clock errors of other GNSS systems and pseudo-satellite systems and the GPS receiver clock error using unknown parameters, with the GPS receiver clock error as a reference.

[0010] In some specific embodiments, in step S2, the combined positioning observation equation includes both pseudorange observation equation and carrier phase observation equation; wherein, a dual-frequency ionospheric-free combined model is used to eliminate ionospheric delay error for GNSS observations, and a non-difference non-combined model is used for pseudosatellite observations and ionospheric delay error is ignored.

[0011] In some specific embodiments, step S3, the adaptive adjustment positioning strategy includes: starting the combined positioning mode when the number of visible pseudo-satellites is greater than or equal to 2; using pseudo-satellites to independently provide high-precision coordinate constraints to accelerate convergence when the number is greater than or equal to 4; and prioritizing the selection of pseudo-satellites with the highest signal-to-noise ratio to participate in the solution when the number exceeds 4.

[0012] In some specific embodiments, in step S3, when solving the combined positioning mode, no cutoff elevation angle is set for the pseudo-satellite system, and a signal-to-noise ratio weighting strategy is used to construct a stochastic model.

[0013] In some specific embodiments, a server-side spatial synchronization step is included before step S1: obtaining the three-dimensional coordinates of the pseudo-satellite base station in the International Earth Reference Frame through continuous static precise single-point positioning or real-time dynamic measurement, or measuring the coordinates of the pseudo-satellite base station relative to the calibrated reference station through a total station and converting them to the International Earth Reference Frame.

[0014] In some specific embodiments, in step S3, when the user leaves the pseudo-satellite coverage area and switches to independent GNSS positioning mode, the current positioning result is initialized using the converged ambiguity parameters and coordinate parameters in the combined positioning mode to maintain the positioning accuracy after switching.

[0015] The present invention also provides a GNSS pseudo-satellite combined receiver, comprising: a space synchronization antenna array, consisting of a first GNSS antenna, a second GNSS antenna and a pseudo-satellite antenna located at the midpoint between the two, which are collinearly fixed; The GNSS receiver unit is used to output GNSS observations and second pulse signals; The pseudo-satellite receiving unit is used to output pseudo-satellite observations; The time synchronization module has its input connected to the GNSS receiving unit to receive second pulse signals, and its output connected to the clock pin of the pseudo-satellite receiving unit to achieve nanosecond-level time synchronization. The data processing module adopts an ARM+FPGA heterogeneous architecture, in which the FPGA is used to collect observations and mark timestamps, and the ARM is used to run the above-mentioned combined precise positioning method.

[0016] The beneficial effects of the above technical solution are as follows: Compared with existing technologies, the present invention provides a combined precise positioning method for GNSS pseudo-satellite combined receivers. Through an integrated hardware architecture, it achieves nanosecond-level time synchronization and millimeter-level spatial unification of GNSS and pseudo-satellite observations. Based on this, it uses the median theorem to generate virtual observations and introduces inter-system deviation parameters to construct a unified observation equation. Then, it combines the number of visible pseudo-satellites to adaptively adjust the positioning strategy. Thus, in complex environments where GNSS signals are blocked or denied, it significantly improves positioning accuracy and convergence speed, greatly reduces the deployment cost and threshold of pseudo-satellite systems, and ensures continuous, stable, and highly reliable positioning from open environments to completely denied environments. It has good compatibility and wide engineering applicability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a combined precise positioning method for a GNSS pseudo-satellite combined receiver, provided as an embodiment of the present invention; Figure 2 A schematic diagram of a pseudo-satellite / GNSS combined system for a combined precise positioning method for a GNSS pseudo-satellite combined receiver is provided as an embodiment of the present invention; Figure 3 This is a schematic diagram of pseudo-satellite / GNSS time synchronization for a combined precise positioning method for a GNSS pseudo-satellite combined receiver, provided as an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0021] Example 1 One embodiment of the present invention provides a combined precise positioning method for a GNSS pseudo-satellite combined receiver, referring to... Figure 1 As shown, it includes: Step S1: Utilizing the fixed geometric relationship of the space synchronization antenna array, the observations of the two GNSS antennas are collinearly combined based on the median theorem to generate virtual observations from the GNSS satellite to the phase center of the pseudo-satellite antenna; In a specific embodiment of the present invention, in step S1, the virtual observation value is determined based on the observation values ​​of the two GNSS antennas and the fixed distance from the two GNSS antennas to the pseudo-satellite antenna.

[0022] By utilizing the fixed geometric relationships of a space-synchronous antenna array, virtual observations are generated from the GNSS satellite to the pseudo-satellite receiving antenna, achieving spatial unification at the user end. Suppose that the observations of two GNSS receiving antennas for the same GNSS satellite are respectively and (Pseudorange or carrier phase observations are applicable), the distances from both GNSS antennas to the pseudosatellite antenna are... ; According to the median theorem, the virtual observations from the GNSS satellite to the pseudo-satellite receiving antenna... for: but, The virtual observations are fused with the pseudo-satellite observations output by the pseudo-satellite receiving unit to construct a unified observation equation.

[0023] Step S2: The virtual observations are fused with the original pseudo-satellite observations, and the inter-system bias, which characterizes the differences in receiver clock bias between different systems, is introduced as the parameter to be estimated, and a unified combined positioning observation equation is constructed. In a specific embodiment of the present invention, in step S2, the inter-system deviation specifically involves estimating the difference between the receiver clock errors of other GNSS systems and pseudo-satellite systems and the GPS receiver clock error using unknown parameters, with the GPS receiver clock error as a reference.

[0024] In a specific embodiment of the present invention, in step S2, the combined positioning observation equation includes both pseudorange observation equation and carrier phase observation equation; wherein, a dual-frequency ionospheric-free combined model is used to eliminate ionospheric delay error for GNSS observations, and a non-difference non-combined model is used for pseudosatellite observations and ionospheric delay error is ignored.

[0025] In pseudosatellite / GNSS integrated positioning, the ISB can be estimated as an unknown parameter. Since the ISB represents the difference in receiver clock bias between each system and a reference system, assuming the GPS receiver clock bias is used as a reference, the ISB of GLONASS, Galileo, BDS, and pseudosatellite systems relative to the GPS system can be expressed by the following formula: In the formula, different subscripts represent different systems. , , and These represent the inter-system deviations of GLONASS, Galileo, BDS, and pseudosatellite systems relative to the GPS system, respectively. , , , and These represent the receiver clock biases for the GPS, Galileo, GPS, GLONASS, and BDS systems, respectively.

[0026] The pseudo-satellite / GNSS combined positioning observation equation for ISB considering inter-system bias is as follows: In the formula, Indicates the satellite's PRN number. Indicates the satellite's frequency; and They represent frequencies respectively. The pseudorange and carrier phase observations are in meters. This represents the geometric distance from the receiver reference point to the satellite's center of mass, expressed in meters (m). The speed of light is expressed in m / s. This indicates the receiver clock bias, expressed in seconds (s). This indicates the relativistic correction, expressed in meters (m). This represents tropospheric delay, expressed in meters (m). Represents frequency The ionospheric delay on the surface, in meters; Represents frequency The wavelength, measured in meters per cycle (m / Hz); Indicates ambiguity; This indicates the phase winding error, expressed in cycles. and They represent frequencies respectively. Other errors (including multipath error, antenna phase center deviation, solid tide, ocean tide, polar tide, etc.) and pseudorange and phase observation noise are measured in meters.

[0027] It is important to note that GNSS systems can receive dual-frequency observations, eliminating ionospheric delay errors through the ionospheric-free combination of the two frequencies. In contrast, pseudosatellite systems can currently only receive single-frequency observations, but since pseudosatellite systems are typically deployed on the ground or at low altitudes, ionospheric delay errors do not need to be considered.

[0028] Step S3: When solving the combined positioning observation equation, the positioning strategy is adaptively adjusted according to the number of visible pseudo-satellites: when the number reaches a preset threshold, the combined positioning mode is activated to accelerate the convergence of precise single-point positioning; otherwise, the independent GNSS positioning mode is switched.

[0029] In a specific embodiment of the present invention, step S3, the adaptive adjustment positioning strategy includes: when the number of visible pseudo-satellites is greater than or equal to 2, starting the combined positioning mode; when the number is greater than or equal to 4, using pseudo-satellites to independently provide high-precision coordinate constraints to accelerate convergence; when the number exceeds 4, prioritizing the selection of pseudo-satellites with the highest signal-to-noise ratio to participate in the solution.

[0030] In a specific embodiment of the present invention, in step S3, when solving the combined positioning mode, no cutoff elevation angle is set for the pseudo-satellite system, and a signal-to-noise ratio weighting strategy is used to construct a stochastic model.

[0031] In a specific embodiment of the present invention, in step S3, when the user leaves the pseudo-satellite coverage area and switches to independent GNSS positioning mode, the current positioning result is initialized using the converged ambiguity parameters and coordinate parameters in the combined positioning mode to maintain the positioning accuracy after switching.

[0032] Since the elevation angle of pseudosatellite systems is usually low or even negative, no cutoff elevation angle was set for pseudosatellite systems, and the random model uses signal-to-noise ratio (SNR) for weighting. Other error handling methods are shown in Table 1 below.

[0033] Table 1. PPP Positioning Processing Strategy for Pseudo-Satellite / GNSS Combination Based on the number of visible pseudosatellites and the augmentation time, the positioning mode is adaptively adjusted: when the number of visible pseudosatellites is ≥2, combined positioning is initiated; when the number is ≥4, pseudosatellites can independently provide high-precision coordinate constraints, accelerating PPP convergence; after more than 4, the marginal effect of accuracy improvement decreases, and pseudosatellites with high signal-to-noise ratio are selected first to participate in the solution; if the user leaves the pseudosatellite coverage area, the system switches to GNSS independent PPP mode, using the converged ambiguity and coordinate parameters to maintain positioning accuracy.

[0034] In one specific embodiment of the present invention, a server-side spatial synchronization step is included before step S1: the three-dimensional coordinates of the pseudo-satellite base station under the International Earth Reference Frame are obtained by continuous static precise single-point positioning or real-time dynamic measurement, or the coordinates of the pseudo-satellite base station relative to the calibrated reference station are measured by a total station and converted to the International Earth Reference Frame.

[0035] This application employs a rigid, fixed array of dual GNSS antennas and a single pseudosatellite antenna, combined with a hardware-level PPS time synchronization module, to achieve nanosecond-level time synchronization and millimeter-level spatial unification of GNSS and pseudosatellite signals from different frequency bands. Furthermore, a GNSS virtual observation generation method based on the median theorem solves the problem of tightly coupled positioning caused by the incompatibility between pseudosatellites and GNSS frequency bands, enabling the fusion of two types of observations without modifying existing receiver hardware. Additionally, an adaptive pseudosatellite enhancement strategy clarifies the impact of the number of pseudosatellites and enhancement time on positioning accuracy; only two pseudosatellites are needed to achieve an 85% improvement in GNSS PPP accuracy, and after 16 seconds of enhancement, independent GNSS PPP still maintains centimeter-level accuracy.

[0036] Example 2 The present invention also provides a GNSS pseudo-satellite combined receiver, comprising: a space synchronization antenna array, consisting of a first GNSS antenna, a second GNSS antenna and a pseudo-satellite antenna located at the midpoint between the two, which are collinearly fixed; The GNSS receiver unit is used to output GNSS observations and second pulse signals; The pseudo-satellite receiving unit is used to output pseudo-satellite observations; The time synchronization module has its input connected to the GNSS receiving unit to receive second pulse signals, and its output connected to the clock pin of the pseudo-satellite receiving unit to achieve nanosecond-level time synchronization. The data processing module adopts an ARM+FPGA heterogeneous architecture, in which the FPGA is used to collect observations and mark timestamps, and the ARM is used to run the above-mentioned combined precise positioning method.

[0037] In a specific embodiment of the present invention, step S1 includes: The time synchronization module receives the second pulse signal output by the GNSS receiving unit, uses its rising edge as the time reference to correct the crystal oscillator frequency of the pseudo-satellite receiving unit, and simultaneously latches two types of observations and marks them with a unified timestamp at each second pulse moment to achieve nanosecond-level time synchronization.

[0038] In a specific embodiment of the present invention, in step S1, the phase center distance between the first GNSS antenna and the second GNSS antenna is fixed at 25cm, and the phase centers of all antennas are coplanar and collinear.

[0039] The integrated receiver of this invention adopts an integrated design, mainly including a GNSS receiving unit, a pseudo-satellite receiving unit, a time synchronization module, a space synchronization antenna array, a data processing module, and a power supply module. Each unit is connected via an internal bus, and the specific structure is as follows: Space Synchronous Antenna Array: It adopts a rigid, fixed, linear layout, including two GNSS receiving antennas and one pseudo-satellite receiving antenna; the pseudo-satellite receiving antenna is located at the midpoint of the two GNSS receiving antennas, and the phase center distance between the two GNSS receiving antennas is fixed at 25cm; the phase centers of all antennas are coplanar and collinear, ensuring that the relative positional relationship remains unchanged during movement.

[0040] GNSS receiver unit: Supports GPS L1 / L2 and BDS B1 / B2 dual-frequency signal reception, with a sampling rate of 10Hz, and outputs pseudorange, carrier phase observations and pulse-per-second (PPS) signals; Pseudo-satellite receiving unit: Supports reception of pseudo-satellite signals in the 2.4G ISM band, with a sampling rate of 10Hz, and outputs pseudorange and carrier phase observation values; Time synchronization module: a hardware-level synchronization unit, with its input end connected to the PPS signal of the GNSS receiver unit and its output end connected to the clock pin of the pseudo-satellite receiver unit; it calibrates the temperature-compensated quartz crystal frequency of the pseudo-satellite receiver unit through the PPS signal, and achieves nanosecond-level time alignment between the pseudo-satellite and GNSS observations within a continuous PPS period; Data processing module: It adopts an ARM+FPGA heterogeneous architecture. The FPGA is responsible for the real-time acquisition and timestamp marking of observations, while the ARM is responsible for running the combined positioning algorithm and outputting the final positioning result. Power module: Provides stable DC power to each unit, supporting both lithium battery and external power supply.

[0041] When deploying a pseudosatellite system, the first step is to unify the spatial coordinates of the server: If the pseudo-satellite base station is equipped with a GNSS receiver, its three-dimensional coordinates under the ITRF (International Earth Reference Frame) can be obtained through continuous 24-hour static PPP or RTK measurements, with an accuracy better than 1 cm. If the pseudo-satellite base station is not equipped with a GNSS receiver, a GNSS reference station is first set up in the experimental area and its coordinates are calibrated. Then, the coordinates of each pseudo-satellite base station relative to the reference station are measured using a total station and converted to the ITRF frame.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0043] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The embodiments of the present invention are described with reference to flowchart illustrations and / or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing terminal equipment to cause a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the functions specified in one or more boxes. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the invention. Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0044] The methods and apparatus provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0045] In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "a specific embodiment" or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A combined precise positioning method for a GNSS pseudo-satellite combined receiver, characterized in that, include: Step S1: Utilizing the fixed geometric relationship of the space synchronization antenna array, the observations of the two GNSS antennas are collinearly combined based on the median theorem to generate virtual observations from the GNSS satellite to the phase center of the pseudo-satellite antenna; Step S2: The virtual observations are fused with the original pseudo-satellite observations, and the inter-system bias, which characterizes the differences in receiver clock bias between different systems, is introduced as the parameter to be estimated, and a unified combined positioning observation equation is constructed. Step S3: Solve the combined positioning observation equation and adaptively adjust the positioning strategy according to the number of visible pseudo-satellites, wherein: when the number reaches a preset threshold, the combined positioning mode is activated to accelerate the convergence of precise single-point positioning; otherwise, switch to independent GNSS positioning mode.

2. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, In step S1, the virtual observation value is determined based on the observation values ​​of the two GNSS antennas and the fixed distance between the two GNSS antennas and the pseudo-satellite antenna.

3. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, In step S2, the inter-system deviation specifically refers to: using the receiver clock bias of the GPS system as a reference, estimating the difference between the receiver clock biases of other GNSS systems and pseudo-satellite systems and the GPS receiver clock bias through unknown parameters.

4. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 3, characterized in that, In step S3, the combined positioning observation equation includes both pseudorange observation equation and carrier phase observation equation; wherein, a dual-frequency ionospheric-free combined model is used to eliminate ionospheric delay error for GNSS observations, and a non-difference non-combined model is used for pseudosatellite observations and ionospheric delay error is ignored.

5. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, Step S3, the adaptive adjustment positioning strategy includes: when the number of visible pseudo-satellites is greater than or equal to 2, the combined positioning mode is activated; when the number is greater than or equal to 4, pseudo-satellites are used to independently provide high-precision coordinate constraints to accelerate convergence; when the number exceeds 4, pseudo-satellites with the highest signal-to-noise ratio are selected first to participate in the solution.

6. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, In step S1, the phase center distance between the first GNSS antenna and the second GNSS antenna is fixed at 25cm, and the phase centers of all antennas are coplanar and collinear.

7. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, In step S3, when solving the combined positioning mode, no cutoff elevation angle is set for the pseudo-satellite system, and a signal-to-noise ratio weighting strategy is used to construct a stochastic model.

8. The combined precise positioning method for a GNSS pseudo-satellite combined receiver according to claim 1, characterized in that, Before step S1, there is also a server-side spatial synchronization step: obtaining the three-dimensional coordinates of the pseudo-satellite base station in the International Earth Reference Frame through continuous static precise single-point positioning or real-time dynamic measurement, or measuring the coordinates of the pseudo-satellite base station relative to the calibrated reference station through a total station and converting them to the International Earth Reference Frame.

9. The combined precise positioning method for a GNSS pseudosatellite combined receiver according to claim 1, characterized in that, In step S3, when the user leaves the pseudo-satellite coverage area and switches to independent GNSS positioning mode, the current positioning result is initialized using the converged ambiguity parameters and coordinate parameters in the combined positioning mode to maintain the positioning accuracy after the switch.

10. A GNSS pseudo-satellite combination receiver for implementing the method of any one of claims 1 to 9, characterized in that, include: The space-synchronous antenna array consists of a first GNSS antenna, a second GNSS antenna, and a pseudo-satellite antenna located at the midpoint between them, all fixed together in a collinear manner. The GNSS receiver unit is used to output GNSS observations and second pulse signals; The pseudo-satellite receiving unit is used to output pseudo-satellite observations; The time synchronization module has its input connected to the GNSS receiving unit to receive second pulse signals, and its output connected to the clock pin of the pseudo-satellite receiving unit to achieve nanosecond-level time synchronization. The data processing module adopts an ARM+FPGA heterogeneous architecture, wherein the FPGA is used to collect observation values ​​and mark timestamps, and the ARM is used to run the combined precise positioning method according to any one of claims 1 to 10.

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