Single-frequency sbas-based category i precision approach ground augmentation method and apparatus

Abstract

The application discloses a single-frequency SBAS-based ground-based enhancement method and device for category I precision approach, which comprises the following steps: obtaining the centimeter-accuracy position truth value of a ground station master station and a position domain monitoring station; determining the pseudo-range truth value of a satellite based on the position truth value of the ground station master station and the received GNSS navigation signal; obtaining the pseudo-range correction amount and the pseudo-range residual of the satellite according to the pseudo-range truth value and the SBAS enhancement message received by the ground station master station; performing integrity monitoring on the SBAS enhancement message by using the pseudo-range residual, screening effective satellite enhancement parameters and broadcasting; and performing calculation according to the position truth value of the position domain monitoring station and the received effective satellite enhancement parameters to obtain a positioning result. The application solves the problem that the prior art is difficult to meet the requirements of precision approach and low cost at the same time, can meet the strict requirements of civil aviation category I precision approach on positioning accuracy, integrity, continuity and availability, effectively reduces the flight risk in the approach phase, and improves the operation efficiency and flight safety level of the airport.

Description

Technical Field

[0001] This application relates to the field of satellite navigation technology, and in particular to a Class I precision approach ground-based augmentation method and apparatus based on single-frequency SBAS. Background Technology

[0002] Ground-based augmentation systems (GBAS) are a new generation of precision approach and landing navigation systems recommended by the International Civil Aviation Organization (ICAO). Theoretically, it can provide precision approach services from Category I to Category III, meeting the high-precision landing requirements under various weather conditions. Meanwhile, satellite-based augmentation systems (SBAS) broadcast satellite ephemeris, clock bias, and ionospheric delay correction parameters to a wide area via geostationary orbit satellites, achieving meter-level or even sub-meter-level positioning accuracy. Currently, several satellite-based augmentation systems are operational globally, including China's BeiDou-based augmentation system (BDSBAS), the United States' Wide Area Augmentation System (WAAS), and Europe's Geostationary Navigation Overlay Service (EGNOS).

[0003] In existing technologies, standard ground-based augmentation systems typically deploy four or more GNSS (Global Navigation Satellite System) reference receivers and antennas at their ground stations. These, along with complex processing systems and redundant backup equipment, achieve high-precision support during the approach and landing phase through local differential correction and integrity monitoring. In contrast, satellite-based augmentation systems utilize geostationary satellites to broadcast wide-area satellite orbit, clock bias, and ionospheric delay correction information to users within their coverage area. Their single-frequency augmentation service can support APV-I approaches, allowing users to obtain enhanced positioning capabilities without the need to build local reference stations.

[0004] However, both of these systems have significant shortcomings in practical applications. For ground-based augmentation systems, the construction cost of ground stations can reach tens of millions of yuan, and maintenance costs are exorbitant, making them unaffordable for general aviation airports with limited funds. While satellite-based augmentation systems offer wide coverage and require minimal ground infrastructure, their integrity parameters are designed for wide-area applications, often proving overly conservative when used in localized areas, leading to reduced service availability and failing to directly meet the stringent integrity and availability requirements of Category I precision approaches. Therefore, there is an urgent need for a solution that balances high-precision local integrity monitoring with low cost to provide general aviation airports with navigation services that meet Category I precision approach requirements. Summary of the Invention

[0005] This application provides a Type I precision approach ground-based augmentation method and apparatus based on single-frequency SBAS, which solves the problem that existing technologies cannot simultaneously meet the requirements of precision approach and low cost.

[0006] In a first aspect, embodiments of this application provide a Type I precision approach ground-based augmentation method based on single-frequency SBAS, comprising: acquiring centimeter-level accurate true position values ​​of a ground station master station and a position domain monitoring station respectively; determining the pseudorange true value of the corresponding satellite based on the true position value of the ground station master station itself and the received GNSS navigation signal; obtaining the pseudorange correction amount and pseudorange residual of the corresponding satellite according to the pseudorange true value and the SBAS augmentation message received by the ground station master station; using the pseudorange residual to perform pseudorange domain integrity monitoring on the SBAS augmentation message, filtering out effective satellite augmentation parameters, and broadcasting the effective satellite augmentation parameters; and performing positioning calculations based on the true position value of the position domain monitoring station itself and the received effective satellite augmentation parameters to obtain a positioning result.

[0007] In conjunction with the first aspect, in one possible implementation, determining the pseudorange truth value of the corresponding satellite based on the true position value of the ground station master station itself and the received GNSS navigation signal includes: extracting satellite orbital parameters and clock bias parameters from the GNSS navigation signal received by the ground station master station, and calculating the spatial position and satellite clock bias of the corresponding satellite; determining the theoretical propagation time of the electromagnetic wave signal between the satellite and the true position value of the ground station master station based on the spatial position of the satellite and the true position value of the ground station master station; and converting the theoretical propagation time into a distance value after offset compensation using the satellite clock bias to obtain the pseudorange truth value of the corresponding satellite to the ground station master station.

[0008] In conjunction with the first aspect, in one possible implementation, obtaining the pseudorange correction and pseudorange residual for the corresponding satellite based on the true pseudorange value and the SBAS enhancement message received by the ground station master station includes: parsing the SBAS enhancement message received by the ground station master station and extracting the SBAS enhancement parameters for each satellite; wherein, the SBAS enhancement parameters include correction-type correction parameters and integrity correction parameters, and the correction-type correction parameters include satellite ephemeris corrections, clock error corrections, and ionospheric grid corrections; and using the satellite ephemeris corrections to correct the satellite's spatial position. The satellite position deviation introduced by the orbit is determined by the distance difference between the satellite's spatial position before and after correction and the ground station master station; the clock error correction amount of the satellite is obtained using the clock error correction number; the ionospheric delay correction amount at the ground station master station is calculated by bilinear interpolation based on the ionospheric grid correction number; the satellite position deviation, the clock error correction amount, and the ionospheric delay correction amount are combined to generate the pseudorange correction amount of the corresponding satellite; the pseudorange residual of the corresponding satellite is obtained by subtracting the true pseudorange value and the pseudorange correction amount of the corresponding satellite from the satellite observation pseudorange collected in real time by the ground station master station.

[0009] In conjunction with the first aspect, in one possible implementation, the step of using the pseudorange residuals to perform pseudorange domain integrity monitoring on the SBAS augmentation message, filtering out effective satellite augmentation parameters, and broadcasting the effective satellite augmentation parameters includes: comparing the pseudorange residuals corresponding to each satellite with an integrity threshold one by one, filtering out pseudorange residuals that do not exceed the integrity threshold, and using the SBAS augmentation parameters output by the corresponding satellites as effective satellite augmentation parameters; wherein, the integrity threshold is determined based on the comprehensive error standard deviation of the integrity correction parameters in the SBAS augmentation parameters broadcast in real time by the SBAS augmentation message; after completing the filtering of all pseudorange residuals, the effective satellite augmentation parameters are encapsulated into a standardized differential augmentation message and continuously broadcast outwards.

[0010] In conjunction with the first aspect, in one possible implementation, the step of performing positioning calculation based on the true position value of the location domain monitoring station and the received effective satellite augmentation parameters to obtain the positioning result includes: continuously receiving the effective satellite augmentation parameters broadcast by the ground station master station through the location domain monitoring station, and simultaneously collecting the current satellite observation pseudorange of each satellite; differentially correcting the corresponding satellite observation pseudorange according to the effective satellite augmentation parameters to eliminate ranging deviation; using the true position value of the location domain monitoring station as the calculation benchmark constraint, and jointly performing differential positioning calculation on the differentially corrected satellite observation pseudorange with multiple satellites to obtain the current high-precision positioning result of the location domain monitoring station.

[0011] In conjunction with the first aspect, in one possible implementation, after obtaining the positioning result, the method further includes: comparing the positioning result with the true position value of the location domain monitoring station to obtain a positioning residual; when the positioning residual exceeds the protection level, triggering an alarm and restricting Category I precision approach services.

[0012] In conjunction with the first aspect, in one possible implementation, the centimeter-level accurate positional truth values ​​of the ground station master station and the position domain monitoring station are obtained through high-precision mapping calibration and stored locally.

[0013] Secondly, embodiments of this application provide a Type I precision approach ground-based augmentation device based on single-frequency SBAS, comprising: an acquisition module for acquiring centimeter-level accurate true position values ​​of a ground station master station and a position domain monitoring station, respectively; a pseudorange truth value module for determining the pseudorange truth value of the corresponding satellite based on the true position value of the ground station master station itself and the received GNSS navigation signal; a pseudorange residual module for obtaining the pseudorange correction amount and pseudorange residual of the corresponding satellite based on the pseudorange truth value and the SBAS augmentation message received by the ground station master station; a filtering module for using the pseudorange residual to perform pseudorange domain integrity monitoring on the SBAS augmentation message, filtering out effective satellite augmentation parameters, and broadcasting the effective satellite augmentation parameters; and a positioning calculation module for performing positioning calculation based on the true position value of the position domain monitoring station itself and the received effective satellite augmentation parameters to obtain a positioning result.

[0014] Thirdly, embodiments of this application provide an apparatus comprising: a processor; a memory for storing processor-executable instructions; wherein, when the processor executes the executable instructions, it implements the method as described in the first aspect or any possible implementation of the first aspect.

[0015] Fourthly, embodiments of this application provide a non-volatile computer-readable storage medium, the non-volatile computer-readable storage medium including storage for storing a computer program or instructions that, when executed, cause the method described in the first aspect or any possible implementation of the first aspect to be implemented.

[0016] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: This application's embodiments enhance message parsing and filtering through SBAS to ensure the validity of broadcast parameters; and achieve real-time monitoring of system service status through positioning calculation and residual verification by the position domain monitoring station. The entire solution effectively solves the problem that existing technologies struggle to simultaneously meet the requirements of precision approach and low cost, thereby achieving centimeter-level high-precision positioning. This meets the stringent requirements of Category I precision approach for civil aviation in terms of positioning accuracy, integrity, continuity, and availability, providing stable and reliable ground-based augmentation services for aircraft, effectively reducing flight risks during the approach phase, and improving airport operational efficiency and flight safety. Attached Figure Description

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

[0018] Figure 1 A flowchart of a Type I precision approach ground-based augmentation method based on single-frequency SBAS provided in an embodiment of this application; Figure 2 A schematic diagram of the structure of a Type I precision approach ground-based augmentation device based on a single-frequency SBAS provided in an embodiment of this application; Figure 3 This diagram illustrates an application scenario for the Type I precision approach ground-based augmentation method based on single-frequency SBAS provided in this application embodiment. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] The following description of some technologies involved in the embodiments of this application is provided to aid understanding and should be considered merely exemplary. Therefore, those skilled in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Similarly, for clarity and brevity, some descriptions of well-known functions and structures are omitted in the following description.

[0021] Figure 1 This is a flowchart of a Type I precision approach ground-based augmentation method based on single-frequency SBAS provided in an embodiment of this application, including steps 101 to 105. Wherein, Figure 1 This is merely one execution order shown in the embodiments of this application and does not represent the only execution order of the Type I precision approach ground-based augmentation method based on single-frequency SBAS. Where the final result can be achieved, Figure 1 The steps shown can be performed in parallel or in reverse order.

[0022] Step 101: Obtain the centimeter-level accuracy true position values ​​of the ground station master station and the location domain monitoring station respectively. In this embodiment, the centimeter-level accuracy true position values ​​of the ground station master station and the location domain monitoring station are obtained through high-precision surveying and calibration and stored locally.

[0023] Specifically, before the ground-based augmentation system is officially put into operation, static high-precision surveying and mapping operations are carried out respectively for the erection points of the main ground station and the erection points of the position domain monitoring stations. The surveying and mapping operations adopt centimeter-level surveying and mapping equipment to ensure that the accuracy of the finally output coordinate data (i.e., the position true value) reaches the centimeter level. The position true value uniformly adopts three-dimensional spatial coordinate data under the geocentric coordinate system, which completely includes three types of coordinate parameters: the longitude, latitude and altitude of the station. This set of three-dimensional spatial coordinate data is used as the reference position of the corresponding station and will not change throughout the operation of the system.

[0024] After completing the surveying and mapping collection and data calculation, the position true value of the main ground station and the position true value of the position domain monitoring station are respectively written into the local memory of the corresponding station to complete solidified storage. When the ground-based augmentation system subsequently executes all calculation processes such as pseudo-range true value solving and positioning residual verification, this set of position true values can be directly retrieved from the local memory as the calculation reference, without the need for real-time re-surveying and mapping to obtain.

[0025] For example, as Figure 3 shown, in the application scenario of the present application, it consists of one main ground station and one position domain monitoring station. The main ground station is erected near the airport terminal, and the position domain monitoring station is erected at the end of the runway. Before installation, the GNSS (Global Navigation Satellite System) static measurement method is used to accurately measure the antenna phase center coordinates of the main ground station and the position domain monitoring station, so as to obtain the position true value with centimeter-level accuracy under the WGS-84 (the global geocentric geodetic coordinate system supporting GPS) coordinate system, which is pre-stored in the ground data processor and the position domain monitoring processor.

[0026] Further, the main ground station includes: two BDS B1C / GPS L1 (Beidou-3 B1C frequency point signal / GPS system L1 carrier frequency point) compatible GNSS receivers of the same model, each connected to a set of choke ring antennas, and the antennas are installed on the roof with a wide field of view and no obstruction; one industrial-grade ground data processor, which adopts a redundant power supply design, is electrically connected to the two GNSS receivers respectively, and stores the position true value of the main ground station itself inside; a set of VDB (VHF Data Broadcast) transmitting radio station, which works in the 108-117.975 MHz aviation VHF frequency band, adopts D8PSK (octal phase shift keying modulation) modulation mode, has a transmitting power of 50W, and is connected to an omnidirectional transmitting antenna. The main ground station is also deployed with a set of VDB receiving radio station, which is connected to the radio frequency coupler of the VDB transmitting radio station, recovers the VDB messages broadcast outward by the main ground station in real time, and performs decoding and verification on the recovered VDB messages, so as to monitor the correctness of the VDB message broadcast link and the message content in real time.

[0027] The location domain monitoring station includes: an industrial-grade location domain monitoring processor, which stores the true location value of the location domain monitoring station itself, and also integrates a BDS B1C / GPS L1 compatible GNSS receiver module and a VDB receiver module.

[0028] Step 102: Determine the pseudorange true value of the corresponding satellite based on the true position value of the ground station master station and the received GNSS navigation signal. In this embodiment, satellite orbit parameters and clock bias parameters are extracted from the GNSS navigation signal received by the ground station master station, and the spatial position and satellite clock bias of the corresponding satellite are calculated; based on the spatial position of the satellite and the true position value of the ground station master station, the theoretical propagation time of the electromagnetic wave signal between them is determined; after offset compensation of the theoretical propagation time using the satellite clock bias, it is converted into a distance value to obtain the pseudorange true value from the corresponding satellite to the ground station master station.

[0029] Specifically, the ground station master station continuously receives GNSS navigation signals broadcast by visible satellites through its built-in GNSS receiver. These GNSS navigation signals carry complete orbital parameters and clock operation parameters for each satellite in real time. The ground station master station demodulates and analyzes the received GNSS navigation signals, extracts the corresponding satellite orbital parameters and clock bias parameters for each satellite, and accurately calculates the real-time spatial position and clock bias of the satellite in the geocentric coordinate system (WGS-84 coordinate system) at each observation time through fitting calculations using a standard satellite orbit calculation model.

[0030] After obtaining the satellite's spatial position, the pre-fixed true position value of the ground station is retrieved to calculate the geometric straight-line distance between the satellite and the ground station. Based on the principle of the constant speed of light in a vacuum, the calculated geometric straight-line distance is converted into the theoretical propagation time of the electromagnetic wave signal from the satellite to the ground station. Due to errors such as clock drift and clock offset during satellite operation, the directly calculated theoretical propagation time has a slight time deviation. This application utilizes the satellite clock error obtained from the pre-calculated solution to specifically compensate for the deviation in the theoretical propagation time, eliminating the ranging time error caused by satellite clock anomalies. The theoretical propagation time after deviation compensation is then converted back into a distance value by combining the propagation speed of the electromagnetic wave signal (i.e., the speed of light), finally obtaining the pseudorange true value from the satellite to the ground station that is unaffected by satellite clock error interference and possesses the characteristics of the theoretical true value, providing benchmark data for the subsequent accurate calculation of pseudorange correction and pseudorange residual.

[0031] For example, the formula for calculating the true value of the pseudo-distance is as follows: , In the formula, This represents the true value of the satellite's pseudorange. Indicates the satellite's spatial position in the WGS-84 coordinate system. This is the true location of the ground station's main station. At the speed of light, For satellite clock bias, This refers to the receiver clock bias.

[0032] Step 103: Based on the pseudorange true value and the SBAS enhancement message received by the ground station master station, obtain the pseudorange correction amount and pseudorange residual of the corresponding satellite. In this embodiment, the SBAS enhancement message received by the ground station master station is parsed, and the SBAS enhancement parameters of each satellite are extracted from it. The SBAS enhancement parameters include correction parameters and integrity correction parameters. The correction parameters include satellite ephemeris corrections, clock bias corrections, and ionospheric grid corrections. The satellite's spatial position is corrected using the satellite ephemeris corrections, and the orbital-induced satellite position deviation is determined by the distance difference between the satellite's spatial position before and after correction and the ground station master station. The clock bias correction amount of the satellite is obtained using the clock bias correction amount. The ionospheric delay correction amount at the ground station master station is calculated using bilinear interpolation based on the ionospheric grid correction amount. The satellite position deviation, clock bias correction amount, and ionospheric delay correction amount are combined to generate the pseudorange correction amount for the corresponding satellite. The pseudorange residual for the corresponding satellite is obtained by subtracting the true pseudorange value and pseudorange correction amount from the satellite observation pseudorange collected in real time by the ground station master station.

[0033] Specifically, the ground station master station continuously receives SBAS enhancement messages broadcast from the airspace and decodes them to separate the SBAS enhancement parameters unique to each visible satellite. SBAS enhancement parameters include correction parameters and integrity correction parameters. Correction parameters include satellite ephemeris corrections, clock error corrections, and ionospheric grid corrections; integrity correction parameters include UDRE (User Differential Range Error) and GIVE (Grid Ionospheric Vertical Error).

[0034] From the SBAS enhancement parameters corresponding to each satellite, correction parameters specifically targeting satellite pseudorange errors are extracted. These correction parameters are generated by the satellite-based augmentation system based on satellite orbital deviations, clock deviations, and ionospheric delay errors. Simultaneously, the ground station master station uses its built-in GNSS receiver to conduct real-time signal observations of each visible satellite, acquiring real-time satellite observation pseudoranges. These pseudoranges are measured distance values ​​that include various space propagation errors and equipment observation errors.

[0035] Furthermore, error correction calculations are performed for each satellite. First, the corresponding satellite ephemeris correction values ​​are retrieved, and the spatial positions of the satellites obtained from previous calculations based on GNSS navigation signals are corrected and compensated to obtain the accurate spatial position of the satellite after correction. The geometric straight-line distances between the satellite's spatial position before and after correction and the true position value of the ground station master station are calculated separately. The difference between the two sets of geometric straight-line distances is calculated, and the resulting distance difference is the ranging deviation introduced by the satellite orbit error, denoted as the satellite position deviation.

[0036] Secondly, the clock correction values ​​corresponding to each satellite are extracted. The clock correction values ​​directly represent the time errors caused by the satellite's on-orbit clock offset and clock drift. Combined with the conversion of time quantities to distance quantities at the speed of light, the clock correction values ​​of the corresponding satellites are accurately obtained, which are used to offset the pseudorange observation errors caused by satellite clock anomalies.

[0037] Subsequently, correction calculations were performed on the ionospheric grid corrections. Since the SBAS enhanced message only broadcasts the correction parameters (i.e., ionospheric grid corrections) for globally discrete ionospheric grid points, it cannot directly meet the fixed-point observation requirements of the ground station master station. Therefore, this embodiment employs a bilinear interpolation algorithm. Based on the latitude and longitude coordinates of the ground station master station, the ionospheric grid region where it is located is determined. The ionospheric grid corrections at the four vertices of the grid are retrieved, and the ionospheric delay correction on the observation satellite signal path of the ground station master station is solved through two-dimensional planar interpolation.

[0038] Finally, the satellite position deviation, clock error correction, and ionospheric delay correction obtained from the above calculations are algebraically superimposed to obtain the pseudorange correction. This pseudorange correction is used to compensate for the main systematic errors in the satellite observation process. Simultaneously, the ground station master station acquires the original satellite observation pseudoranges of each visible satellite in real time using its built-in GNSS receiver. The original satellite observation pseudoranges contain systematic errors and random observation noise. Using a single satellite as an independent calculation unit, based on the currently acquired real-time satellite observation pseudoranges, the true pseudorange value of the corresponding satellite and the integrated pseudorange correction are subtracted sequentially. This completely eliminates the theoretical reference distance error and the correctable errors of the ground-based augmentation system, ultimately obtaining the pseudorange residual that retains only residual random errors. This provides core data support for subsequent accurate pseudorange domain integrity monitoring and selection of effective satellite augmentation parameters.

[0039] Those skilled in the art should understand that, due to the large pseudorange noise (meter level) of satellite observations, it is impossible to meet the sub-meter accuracy requirements of Category I precision approach, and it is also impossible to effectively monitor pseudorange residuals. Therefore, it is necessary to smooth it first. This application uses 100-second carrier smoothing pseudorange technology to smooth the satellite observation pseudorange.

[0040] Step 104: Utilize pseudorange residuals to perform pseudorange domain integrity monitoring on SBAS augmentation messages, screen out effective satellite augmentation parameters, and broadcast the effective satellite augmentation parameters. In this embodiment, the pseudorange residuals corresponding to each satellite are compared one by one with the integrity threshold, and pseudorange residuals that do not exceed the integrity threshold are screened out. The SBAS augmentation parameters output by the corresponding satellites are taken as effective satellite augmentation parameters. The integrity threshold is determined based on the comprehensive error standard deviation of the integrity correction parameters in the SBAS augmentation parameters broadcast in real time in the SBAS augmentation messages. After screening all pseudorange residuals, the effective satellite augmentation parameters are encapsulated into standardized differential augmentation messages and continuously broadcast.

[0041] Specifically, the ground station master station has a locally pre-stored integrity threshold adapted to the Civil Aviation Category I Precision Approach Safety Specifications (exemplarily set to three times). This integrity threshold, corresponding to the 1e-7 false alarm rate required by civil aviation (a mandatory standard for Category I precision approaches), is calculated and calibrated in conjunction with the maximum allowable ranging error for airport operations and the system's centimeter-level positioning accuracy margin. It is used to uniformly determine the error level of the SBAS enhancement parameters for a single satellite. The process involves iterating through all visible satellites in the current airspace, retrieving the pseudorange residual calculated for each satellite in the previous steps, and comparing this pseudorange residual with the locally stored integrity threshold for each satellite.

[0042] If the pseudorange residual of a satellite is less than the integrity threshold, it means that the residual error of the SBAS enhancement parameters associated with the satellite is within a safe and controllable range. The complete SBAS enhancement parameters of the satellite are retained and marked as valid satellite enhancement parameters. If the pseudorange residual of the satellite is greater than or equal to the integrity threshold, it means that the SBAS enhancement parameters of the satellite have a large deviation and cannot meet the integrity requirements of Category I precision approach. The satellite enhancement parameters are marked as invalid satellite enhancement parameters, and the complete set of SBAS enhancement parameters corresponding to the satellite is removed. The SBAS enhancement parameters of the satellite can only be re-added to the broadcast queue if they are determined to be valid satellite enhancement parameters for 5 to 10 consecutive message cycles.

[0043] Furthermore, the composite error standard deviation of the integrity correction parameter in the SBAS enhancement parameters of this application is calculated using a synthesis algorithm based on the square root of the sum of squares of independent errors, as shown in the following formula: , In the formula, The comprehensive error standard deviation of the integrity correction parameter in the SBAS enhancement parameters is used for integrity threshold determination and pseudorange residual over-limit judgment. The user differential distance error represents the residual satellite-end ranging error remaining after the satellite orbit and satellite clock error have been corrected by the SBAS enhancement parameters. The parameters are directly broadcast by the SBAS enhancement message signal. The vertical error of the ionosphere is represented by the residual ionospheric delay error after SBAS ionospheric grid interpolation correction. is the standard deviation of the tropospheric delay error, and is the residual ranging error remaining after the tropospheric delay is compensated using an empirical model. The standard deviation of the multipath error is the ranging error at the receiver caused by the superposition of the direct navigation signal and the reflected environmental signal. These four types of errors are independent of each other, and are synthesized according to the error propagation law to obtain the comprehensive error standard deviation.

[0044] Those skilled in the art should understand that the above The standard deviation of the comprehensive error of the integrity correction parameter in the SBAS enhancement parameters fully characterizes the comprehensive error level between the SBAS pseudorange correction and the measured pseudorange. After solving for the pseudorange residual in step 104, its value is used as the integrity threshold to verify whether the pseudorange residual obtained based on the SBAS enhancement parameters is compliant and valid.

[0045] After filtering all pseudorange residuals, all valid satellite augmentation parameters are compiled and uniformly encoded and encapsulated according to the common data format of ground-based augmentation systems to generate standardized differential augmentation messages. The ground station master station continuously broadcasts the encapsulated standardized differential augmentation messages through its supporting radio frequency transmitting equipment, which are then synchronously captured and parsed by the location domain monitoring stations and airborne receiving equipment within the airport.

[0046] Specifically, the selected effective satellite augmentation parameters are uniformly encoded and encapsulated according to the RTCA DO-246E (Local Augmentation System Space Signal Interface Control File for Precision Approach Based on Global Navigation Satellite System) standard to generate standardized differential augmentation messages conforming to civil aviation specifications, specifically GBAS VDB (Very High Frequency Differential Data Broadcast Link for Ground-Based Augmentation System). The generated standardized differential augmentation messages include three core message types: MT1, MT2, and MT4. The MT1 message stores the pseudorange correction amount, correction rate of change, and corresponding error standard deviation for each satellite. The MT2 message records the unique identifier of the ground station, the current operational service type, and the real-time system status. The MT4 message contains a built-in FASDB (Final Approach Segment Data Block), which fully describes the approach procedure geometric parameters such as runway azimuth, glide slope angle, and runway threshold coordinates. The broadcast frequency of each type of message strictly adheres to standard constraints. For MT1 messages, the minimum broadcast frequency is once per frame for all measurement blocks, and the maximum broadcast frequency is once per time slot for all measurement blocks. For MT2 messages, the minimum broadcast frequency is once every 20 consecutive frames, and the maximum broadcast frequency is once per frame. For MT4 messages, the minimum broadcast frequency is once every 20 consecutive frames, and the maximum broadcast frequency is once per frame for all FAS data blocks. After encoding and encapsulation, the ground station master station continuously broadcasts this set of standardized differential enhanced messages through the supporting VDB radio frequency transmission equipment (i.e., the VDB transmitting radio deployed at the ground station master station), for synchronous reception and parsing by the airport position domain monitoring station and the airborne GBAS equipment.

[0047] In addition, this application can also collect satellite observation data synchronously through multiple GNSS receivers, calculate the pseudorange residuals corresponding to each visible satellite separately, and then conduct consistency comparison and verification of the pseudorange residuals of the same visible satellite output by multiple GNSS receivers, and eliminate GNSS receiver faults based on the comparison results.

[0048] Step 105: Perform positioning calculation based on the true position value of the location domain monitoring station and the received effective satellite augmentation parameters to obtain the positioning result. In this embodiment, the location domain monitoring station continuously receives effective satellite augmentation parameters broadcast by the ground station master station and simultaneously collects the current satellite observation pseudorange of each satellite; differential correction is performed on the corresponding satellite observation pseudorange based on the effective satellite augmentation parameters to eliminate ranging bias; using the true position value of the location domain monitoring station as the calculation reference constraint, differential positioning calculation is performed on the differentially corrected satellite observation pseudorange using multiple satellites to obtain the current high-precision positioning result of the location domain monitoring station.

[0049] Specifically, the location domain monitoring station is equipped with a dedicated signal receiving module that continuously listens to the standardized differential augmentation messages broadcast by the ground station master station around the clock. It captures and decodes these messages in real time, extracts effective satellite augmentation parameters, and stores them according to satellite numbers, providing a data source for subsequent observation data correction. Simultaneously, the GNSS receiving antenna built into the location domain monitoring station synchronously collects satellite signals transmitted by all visible satellites in the sky, calculating the satellite observation pseudorange for each satellite in real time. This raw pseudorange data is superimposed with multiple ranging interference biases, including satellite orbital errors, satellite clock errors, and ionospheric and tropospheric propagation delays.

[0050] The location domain monitoring station retrieves the effective satellite augmentation parameters cached locally. Using the satellite number as the matching index, it performs differential correction calculations on the original data of the satellite observation pseudoranges of the corresponding satellites one by one. It uses various error compensation quantities in the effective satellite augmentation parameters to offset the ranging deviations such as orbit, clock, and atmospheric propagation contained in the original data of the satellite observation pseudoranges, and generates a clean satellite observation pseudorange after correction.

[0051] Before performing the positioning calculation, the centimeter-level precision true position values, pre-stored locally at the location domain monitoring station, are read and used as constraints for this positioning calculation to improve the convergence accuracy of the results. Then, the pseudoranges of satellite observations from multiple visible satellites, after differential correction, are integrated and substituted into the standard differential positioning model for simultaneous solution, eliminating random errors caused by pseudoranges from individual satellites. Finally, the complete three-dimensional spatial coordinates of the location domain monitoring station at the current moment are output. These coordinates represent the real-time high-precision positioning result of the location domain monitoring station, used for subsequent system integrity verification.

[0052] The position domain monitoring processor connects to the GNSS choke antenna and the VDB omnidirectional receiving antenna via the chassis RF interface. Utilizing its own precisely known true position, the position domain monitoring processor receives GNSS navigation signals and SBAS augmentation messages (including SBAS augmentation parameters) through the GNSS receiving module, and receives standardized differential augmentation messages broadcast by the ground station master station through the VDB receiving module. It calculates the positioning result and compares it with its own precisely known true position to assess the system service level.

[0053] In this embodiment of the application, after obtaining the positioning result, the positioning result can be compared with the true position value of the location domain monitoring station to obtain the positioning residual; when the positioning residual exceeds the protection level, an alarm is triggered and the Class I precision approach service is restricted.

[0054] For example, the preset horizontal alarm threshold (HAL) for Category I precision approach in civil aviation is 40 meters, and the vertical alarm threshold (VAL) is 10 meters. The system calculates the horizontal protection level (HPL) and vertical protection level (VPL) in real time. If the calculated HPL is greater than HAL, or the VPL is greater than VAL, it is also determined that the system service does not meet the operating standards, triggering an alarm and terminating the external broadcast of Category I precision approach service.

[0055] Specifically, after obtaining the real-time high-precision positioning result, the location domain monitoring station initiates a location domain integrity self-check process to verify the overall service accuracy and safety performance of the entire ground-based augmentation system. The location domain monitoring station retrieves the locally pre-stored true location value as an absolute benchmark, compares the real-time calculated positioning result with this true location value dimension by dimension, calculates the position deviations in longitude, latitude, and altitude, and combines these multi-dimensional deviations to obtain the overall positioning residual at the current moment. This positioning residual directly reflects the actual error level of the current ground-based augmentation system's enhanced positioning.

[0056] The ground-based augmentation system has locally pre-stored protection level thresholds adapted to the Category I precision approach operation standards of civil aviation. These protection level thresholds represent the maximum permissible positioning error limit to ensure aircraft approach and landing safety. The calculated positioning residuals are compared with the protection level thresholds in real time to determine the service status of the ground-based augmentation system.

[0057] When the positioning residual is within the protection level threshold, the positioning accuracy and integrity indicators of the current ground-based augmentation system are deemed to meet the requirements for Category I precision approach operations, and the ground-based augmentation system maintains normal service status. However, if satellite anomalies, SBAS augmentation parameter deviations, or environmental interference occur, causing the real-time positioning residual to exceed the protection level threshold, the service accuracy of the current ground-based augmentation system is deemed substandard, failing to guarantee Category I precision approach flight safety. In this case, the ground-based augmentation system immediately triggers built-in audible and visual alarms and background alarm prompts, simultaneously restricting the external use of the airport's Category I precision approach service to prevent unqualified augmented positioning services from being used for aircraft approach operations. This provides a safety net at the position domain level, ensuring the safety of civil aviation flight operations.

[0058] This application's embodiments construct a complete Category I precision approach ground-based augmentation scheme based on single-frequency SBAS by accurately calculating the pseudorange truth value, effectively extracting the pseudorange residual, and establishing a collaborative monitoring mechanism between the pseudorange and position domains. The scheme first obtains the pseudorange truth value with theoretical true value characteristics through satellite clock bias compensation, providing a reliable basis for subsequent correction and residual calculations. Then, it ensures the validity of broadcast parameters through the parsing and filtering of SBAS-enhanced messages. Finally, it achieves real-time monitoring of the ground-based augmentation system's service status through positioning calculation and residual verification by position domain monitoring stations. The entire scheme solves problems such as satellite clock drift, orbital deviation, and multipath interference in traditional ground-based augmentation systems, achieving centimeter-level high-precision positioning. It fully meets the stringent requirements of Category I precision approach for civil aviation in terms of positioning accuracy, integrity, continuity, and availability, providing stable and reliable ground-based augmentation services for aircraft, effectively reducing flight risks during the approach phase, and improving airport operational efficiency and flight safety.

[0059] While this application provides the method operation steps as described in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-inventive labor. The order of steps listed in this embodiment is merely one possible execution order among many and does not represent the only execution order. In actual device or client product execution, the methods shown in this embodiment or the accompanying drawings can be executed sequentially or in parallel (e.g., in a parallel processor or multi-threaded processing environment).

[0060] like Figure 2 As shown in the figure, this application embodiment also provides a Type I precision approach ground-based augmentation device 200 based on single-frequency SBAS. The device includes: an acquisition module 201, a pseudorange true value module 202, a pseudorange residual module 203, a filtering module 204, and a positioning calculation module 205, as detailed below.

[0061] The acquisition module 201 is used to acquire the true position values ​​with centimeter-level accuracy of the ground station master station and the position domain monitoring station, respectively.

[0062] The pseudorange truth module 202 is used to determine the pseudorange truth value of the corresponding satellite based on the ground station master station's own position truth value and the received GNSS navigation signal.

[0063] The pseudorange residual module 203 is used to obtain the pseudorange correction amount and pseudorange residual of the corresponding satellite based on the pseudorange true value and the SBAS enhancement message received by the ground station master station.

[0064] The filtering module 204 is used to monitor the pseudorange domain integrity of SBAS augmented messages using pseudorange residuals, filter out effective satellite augmentation parameters, and broadcast the effective satellite augmentation parameters.

[0065] The positioning calculation module 205 is used to perform positioning calculation based on the true position value of the position domain monitoring station and the received effective satellite augmentation parameters to obtain the positioning result.

[0066] Some modules in the apparatus described in this application can be described in the general context of computer-executable instructions that are executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, classes, etc., that perform a specific task or implement a specific abstract data type. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0067] The apparatus or module described in the above embodiments can be implemented by a computer chip or physical entity, or by a product with a certain function. For ease of description, the above apparatus is described by dividing it into various modules according to their functions. When implementing the embodiments of this application, the functions of each module can be implemented in one or more software and / or hardware. Of course, a module that implements a certain function can also be implemented by combining multiple sub-modules or sub-units.

[0068] The methods, apparatus, or modules described in this application can be implemented in a computer-readable program code manner. The controller can be implemented in any suitable manner, such as a microprocessor or processor and a computer-readable medium storing computer-readable program code (e.g., software or firmware) executable by the (micro)processor, logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers. Examples of controllers include, but are not limited to, the following microcontrollers: ARC 625D, Atmel AT91SAM, Microchip PIC18F26K20, and Silicon Labs C8051F320. A memory controller can also be implemented as part of the control logic of a memory. Those skilled in the art will also recognize that, in addition to implementing the controller in purely computer-readable program code manner, the same functionality can be achieved by logically programming the method steps to make the controller take the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the means included within it for implementing various functions can also be considered as structures within the hardware component. Alternatively, the device used to implement various functions can be viewed as either a software module that implements the method or a structure within a hardware component.

[0069] This application also provides an apparatus, the apparatus comprising: a processor; a memory for storing processor-executable instructions; wherein, when the processor executes the executable instructions, it implements the method described in this application.

[0070] This application also provides a non-volatile computer-readable storage medium storing a computer program or instructions thereon, which, when executed, enables the method described in this application embodiment to be implemented.

[0071] Furthermore, in the various embodiments of the present invention, each functional module can be integrated into a processing module, or each module can exist independently, or two or more modules can be integrated into a single module.

[0072] The aforementioned storage media include, but are not limited to, Random Access Memory (RAM), Read-Only Memory (ROM), Cache, Hard Disk Drive (HDD), or Memory Card. The memory can be used to store computer program instructions.

[0073] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary hardware. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product, or it can be embodied in the process of data migration. The computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, mobile terminal, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0074] The various embodiments described in this specification are presented in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. All or part of this application can be used in numerous general-purpose or special-purpose computer system environments or configurations. Examples include: personal computers, server computers, handheld or portable devices, tablet devices, mobile communication terminals, multiprocessor systems, microprocessor-based systems, programmable electronic devices, network PCs, minicomputers, mainframe computers, and distributed computing environments including any of the above systems or devices, etc.

[0075] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A Type I precision approach ground-based augmentation method based on single-frequency SBAS, characterized in that, include: Obtain the true position values ​​with centimeter-level accuracy from both the ground station master station and the position domain monitoring station; Determining the pseudorange truth value of the corresponding satellite based on the true position value of the ground station master station and the received GNSS navigation signal includes: extracting satellite orbit parameters and clock bias parameters from the GNSS navigation signal received by the ground station master station, and calculating the spatial position and satellite clock bias of the corresponding satellite; determining the theoretical propagation time of the electromagnetic wave signal between the satellite and the true position value of the ground station master station based on the satellite's spatial position and the true position value of the ground station master station; and converting the theoretical propagation time into a distance value after offset compensation using the satellite clock bias to obtain the pseudorange truth value of the corresponding satellite from the ground station master station. Based on the true pseudorange value and the SBAS enhancement message received by the ground station master station, the pseudorange correction amount and pseudorange residual of the corresponding satellite are obtained, including: parsing the SBAS enhancement message received by the ground station master station and extracting the SBAS enhancement parameters of each satellite; wherein, the SBAS enhancement parameters include correction-type correction parameters and integrity correction parameters, and the correction-type correction parameters include satellite ephemeris corrections, clock error corrections, and ionospheric grid corrections; the satellite's spatial position is corrected using the satellite ephemeris corrections, and the satellite's position is compared with the position before and after the correction. The distance difference between the spatial location and the ground station master station determines the satellite position deviation introduced by the orbit; the clock error correction amount of the satellite is obtained using the clock error correction number; the ionospheric delay correction amount at the ground station master station is calculated by bilinear interpolation based on the ionospheric grid correction number; the satellite position deviation, the clock error correction amount, and the ionospheric delay correction amount are combined to generate the pseudorange correction amount of the corresponding satellite; the pseudorange residual of the corresponding satellite is obtained by subtracting the true pseudorange value and the pseudorange correction amount of the corresponding satellite from the satellite observation pseudorange collected in real time by the ground station master station. The pseudorange residual is used to monitor the pseudorange domain integrity of the SBAS enhanced message, and effective satellite enhancement parameters are screened and broadcast. The positioning result is obtained by performing positioning calculations based on the true position value of the location domain monitoring station and the received effective satellite augmentation parameters.

2. The method according to claim 1, characterized in that, The process of using the pseudorange residual to perform pseudorange domain integrity monitoring on the SBAS enhanced message, filtering out effective satellite enhancement parameters, and broadcasting the effective satellite enhancement parameters includes: The pseudorange residuals corresponding to each satellite are compared with the integrity threshold one by one, and the pseudorange residuals that do not exceed the integrity threshold are selected. The SBAS enhancement parameters output by the corresponding satellite are used as effective satellite enhancement parameters. The integrity threshold is determined based on the comprehensive error standard deviation of the integrity correction parameters in the SBAS enhancement parameters broadcast in real time by the SBAS enhancement message. After screening all pseudorange residuals, the effective satellite augmentation parameters are encapsulated into standardized differential augmentation messages and continuously broadcast.

3. The method according to claim 1, characterized in that, The positioning result is obtained by performing positioning calculation based on the true position value of the location domain monitoring station and the received effective satellite augmentation parameters, including: The location domain monitoring station continuously receives the effective satellite augmentation parameters broadcast by the ground station master station, and simultaneously collects the current satellite observation pseudorange of each satellite; Differential correction is performed on the corresponding satellite observation pseudorange based on the effective satellite augmentation parameters to eliminate ranging bias; Using the true position value of the location domain monitoring station as the solution benchmark constraint, differential positioning solution is performed on the differentially corrected satellite observation pseudorange by multiple satellites to obtain the current high-precision positioning result of the location domain monitoring station.

4. The method according to claim 1, characterized in that, After obtaining the location result, the process also includes: The positioning result is compared with the true position value of the location domain monitoring station to obtain the positioning residual; When the positioning residual exceeds the protection level, an alarm is triggered and Category I precision approach services are restricted.

5. The method according to claim 1, characterized in that, The centimeter-level accurate position values ​​of the ground station master station and the position domain monitoring station are obtained through high-precision mapping and calibration, and stored locally.

6. A Type I precision approach ground-based augmentation device based on single-frequency SBAS for implementing the method described in any one of claims 1-5, characterized in that, include: The acquisition module is used to acquire the true position values ​​with centimeter-level accuracy from the ground station master station and the position domain monitoring station, respectively. The pseudorange truth value module is used to determine the pseudorange truth value of the corresponding satellite based on the true position value of the ground station master station itself and the received GNSS navigation signal. This includes: extracting satellite orbital parameters and clock bias parameters from the GNSS navigation signal received by the ground station master station, and calculating the spatial position and clock bias of the corresponding satellite; determining the theoretical propagation time of the electromagnetic wave signal between the satellite and the true position value of the ground station master station based on the satellite's spatial position and the true position value of the ground station master station; and converting the theoretical propagation time into a distance value after offset compensation using the satellite clock bias, thus obtaining the pseudorange truth value from the corresponding satellite to the ground station master station. The pseudorange residual module is used to obtain the pseudorange correction and pseudorange residual for the corresponding satellite based on the true pseudorange value and the SBAS enhancement message received by the ground station master station. This includes: parsing the SBAS enhancement message received by the ground station master station and extracting the SBAS enhancement parameters for each satellite; wherein the SBAS enhancement parameters include correction-type correction parameters and integrity correction parameters, and the correction-type correction parameters include satellite ephemeris corrections, clock error corrections, and ionospheric grid corrections; correcting the satellite's spatial position using the satellite ephemeris corrections, and then correcting the satellite's position using satellite correction... The distance difference between the satellite's position directly before and after the ground station and the master station determines the satellite position deviation introduced by the orbit; the clock error correction is obtained using the clock error correction; the ionospheric delay correction at the master station is calculated using bilinear interpolation based on the ionospheric grid correction; the satellite position deviation, the clock error correction, and the ionospheric delay correction are combined to generate the pseudorange correction for the corresponding satellite; the pseudorange residual for the corresponding satellite is obtained by subtracting the true pseudorange value and the pseudorange correction from the satellite observation pseudorange collected in real time by the master station. The filtering module is used to perform pseudorange domain integrity monitoring on the SBAS augmented message using the pseudorange residual, filter out effective satellite augmentation parameters, and broadcast the effective satellite augmentation parameters. The positioning calculation module is used to perform positioning calculation based on the true position value of the location domain monitoring station and the received effective satellite augmentation parameters to obtain the positioning result.

7. An apparatus for performing a Type I precision approach ground-based augmentation method based on single-frequency SBAS, characterized in that, include: processor; Memory used to store processor-executable instructions; When the processor executes the executable instructions, it implements the method as described in any one of claims 1 to 5.

8. A non-volatile computer-readable storage medium, characterized in that, Includes storage of computer programs or instructions that, when executed, cause the method as described in any one of claims 1 to 5 to be implemented.

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