Method and device for improving integrity of positioning service of satellite navigation system

Abstract

The invention provides a method and device for improving the integrity of positioning service of a satellite navigation system, belongs to the technical field of satellite navigation, and can improve the integrity and reliability of user positioning of the satellite navigation system. According to the method, the integrity of the positioning service of the satellite navigation system is improved by processing and resolving the navigation data.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a method and device for improving the integrity of positioning services of a satellite navigation system. Background Art

[0002] During the operation of the Global Navigation Satellite System (GNSS), navigation satellites continuously send signals to ground receiving equipment (i.e. ground monitoring stations). These signals contain the location information, time information, and data for error correction of navigation satellites. Ground control equipment obtains the signals sent by navigation satellites from the monitoring stations and processes the signals for positioning and navigation, such as vehicle positioning and navigation, aviation and marine navigation, and other applications.

[0003] However, since the position of the ground monitoring station is fixed, the signal it receives is limited and is affected by many factors, such as atmospheric delay, multipath effect, satellite orbit error, etc. Therefore, the positioning accuracy may not be high when positioning based on the signal received by the ground monitoring station, resulting in poor integrity of the satellite navigation system's positioning service. Summary of the invention

[0004] The present invention provides a method and device for improving the integrity of a positioning service of a satellite navigation system, which can accurately locate a user and improve the integrity of the positioning service of the satellite navigation system.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for improving the integrity of a positioning service of a satellite navigation system, comprising:

[0007] The main control device acquires the observation data of the navigation satellite from the monitoring device; the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and the monitoring device, and the monitoring device includes at least one ground monitoring station and at least one low-orbit satellite;

[0008] Determining a pseudorange residual between the navigation satellite and the monitoring device; the pseudorange residual is a difference between a pseudorange observation value between the navigation satellite and the monitoring device and a geometric distance between the navigation satellite and the monitoring device after eliminating a common error and a clock error from a receiver of the monitoring device;

[0009] Solving the observation equation constructed when the pseudorange residual is used as the observation value based on the extended Kalman filter algorithm to obtain the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determining the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite; the integrity parameter is used to indicate the integrity of the user positioning service of the satellite navigation system;

[0010] The method and device for improving the integrity of the positioning service of the satellite navigation system provided by the present invention obtains the orbit correction number and clock correction number of the navigation satellite used to locate the user by solving the signal received from the navigation satellite by the combined ground monitoring station and the low-orbit satellite, and then determines the integrity parameter according to the orbit correction number and the clock correction number, and the integrity parameter can be used to more accurately measure the integrity and reliability of the positioning service of the satellite navigation system. Through this technical solution, the low-orbit satellite is used as a monitoring station, and the navigation signal received by the low-orbit satellite is combined to calculate the orbit correction number and clock correction number of the navigation satellite, thereby improving the integrity of the positioning service of the satellite navigation system.

[0011] In an implementation manner of the first aspect, determining a pseudorange residual between the navigation satellite and the monitoring device includes:

[0012] Determine a first pseudorange residual according to the pseudorange observation value and the position of the monitoring device; wherein, when the monitoring device is the low-orbit satellite, the position of the low-orbit satellite is determined based on a single point positioning method and an interpolation method;

[0013] Using a common error correction model, removing the common error in the first pseudorange residual to obtain a second pseudorange residual;

[0014] removing a clock error of a receiver of the monitoring device from the second pseudorange residual to obtain the pseudorange residual;

[0015] In an implementation of the first aspect, a station-by-station estimation method is used to determine a clock error of a receiver of the monitoring device;

[0016] In an implementation of the first aspect, the common error includes at least one of the following: relativistic effect error, differential code bias, time group delay, earth rotation delay, earth gravity delay correction, ionospheric delay, and tropospheric delay;

[0017] In an implementation manner of the first aspect, the satellite navigation system includes a plurality of monitoring devices, one pseudorange residual corresponds to one monitoring device and one navigation satellite, and the method further includes:

[0018] Outliers in the plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites are eliminated.

[0019] In an implementation manner of the first aspect, the removing outliers in a plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites includes:

[0020] Eliminate a first type of pseudorange residual abnormal value from the multiple pseudorange residuals; the first type of pseudorange residual abnormal value is a pseudorange residual corresponding to an unavailable monitoring device; the unavailable monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device is less than a preset number;

[0021] Determine a test statistic of a pseudorange residual corresponding to an available monitoring device; the available monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device being greater than or equal to the preset number;

[0022] When the test statistic follows a chi-square distribution, a test statistic threshold is determined, where in, represents the critical value of the chi-square distribution with k degrees of freedom and α significance level;

[0023] Eliminating a second type of pseudorange residual abnormal value from a plurality of pseudorange residuals after eliminating the first type of pseudorange residual abnormal value; the second type of pseudorange residual abnormal value is a pseudorange residual corresponding to a monitoring device whose test statistic is greater than or equal to the test statistic threshold value among the available monitoring devices;

[0024] In an implementation manner of the first aspect, when the monitoring device is the low-orbit satellite, determining the position of the low-orbit satellite based on a single-point positioning method and an interpolation method includes:

[0025] Determining a clock error of a receiver in the low-orbit satellite based on the navigation data received by the low-orbit satellite;

[0026] Eliminate the clock error of the receiver in the low-orbit satellite from the observation time when the low-orbit satellite receives the signal, so as to obtain the real time when the low-orbit satellite receives the signal;

[0027] Interpolating the positions in the precise ephemeris corresponding to multiple moments of the low-orbit satellite to obtain the position of the low-orbit satellite corresponding to the real moment;

[0028] In an implementation manner of the first aspect, before determining the pseudorange residual between the navigation satellite and the monitoring device, the method further includes:

[0029] The navigation data is preprocessed; the preprocessing method includes cycle slip detection, pseudorange smoothing processing and satellite ephemeris processing.

[0030] In a second aspect, the present invention provides an apparatus for improving the integrity of a positioning service of a satellite navigation system, comprising an acquisition module, a first determination module, and a second determination module;

[0031] The acquisition module is used for the main control device to acquire the observation data of the navigation satellite from the monitoring device; the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and the monitoring device, and the monitoring device includes at least one ground monitoring station and at least one low-orbit satellite;

[0032] The first determination module is used to determine the pseudorange residual between the navigation satellite and the monitoring device; the pseudorange residual is the difference between the pseudorange observation value between the navigation satellite and the monitoring device and the geometric distance between the navigation satellite and the monitoring device after eliminating the common error and the clock error from the receiver of the monitoring device;

[0033] The second determination module is used to solve the observation equation constructed when the pseudorange residual is used as the observation value based on the extended Kalman filter algorithm, obtain the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determine the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite; the integrity parameter is used to indicate the integrity of the user positioning service of the satellite navigation system;

[0034] In an implementation manner of the second aspect, the first determination module is specifically configured to determine the pseudorange residual between the navigation satellite and the monitoring device, including:

[0035] Determine a first pseudorange residual according to the pseudorange observation value and the position of the monitoring device; wherein, when the monitoring device is the low-orbit satellite, the position of the low-orbit satellite is determined based on a single point positioning method;

[0036] Using a common error correction model, removing the common error in the first pseudorange residual to obtain a second pseudorange residual;

[0037] A clock error from a receiver of the monitoring device is removed from the second pseudorange residual to obtain the pseudorange residual.

[0038] In an implementation of the second aspect, the first determination module is specifically configured to determine a clock error of a receiver of the monitoring device by using a station-by-station estimation method;

[0039] In an implementation of the second aspect, the common error includes at least one of the following: relativistic effect error, differential code bias, time group delay, earth rotation delay, earth gravity delay correction, ionospheric delay, and tropospheric delay;

[0040] In an implementation manner of the second aspect, the first determining module is specifically configured to: the satellite navigation system includes a plurality of monitoring devices, one pseudorange residual corresponds to one monitoring device and one navigation satellite, and the method further includes:

[0041] Eliminating abnormal values ​​in a plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites;

[0042] The removing of abnormal values ​​from a plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites comprises:

[0043] Eliminate a first type of pseudorange residual abnormal value from the multiple pseudorange residuals; the first type of pseudorange residual abnormal value is a pseudorange residual corresponding to an unavailable monitoring device; the unavailable monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device is less than a preset number;

[0044] Determine a test statistic of a pseudorange residual corresponding to an available monitoring device; the available monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device being greater than or equal to the preset number;

[0045] When the test statistic follows a chi-square distribution, a test statistic threshold is determined, where in, represents the critical value of the chi-square distribution with k degrees of freedom and α significance level;

[0046] Eliminating a second type of pseudorange residual abnormal value from a plurality of pseudorange residuals after eliminating the first type of pseudorange residual abnormal value; the second type of pseudorange residual abnormal value is a pseudorange residual corresponding to a monitoring device whose test statistic is greater than or equal to the test statistic threshold value among the available monitoring devices;

[0047] In an implementation manner of the second aspect, the first determination module is specifically configured to, when the monitoring device is the low-orbit satellite, determine the position of the low-orbit satellite based on a single point positioning method and an interpolation method, including:

[0048] Determining a clock error of a receiver in the low-orbit satellite based on the navigation data received by the low-orbit satellite;

[0049] Eliminate the clock error of the receiver in the low-orbit satellite from the observation time when the low-orbit satellite receives the signal, so as to obtain the real time when the low-orbit satellite receives the signal;

[0050] Interpolating the positions in the precise ephemeris corresponding to multiple moments of the low-orbit satellite to obtain the position of the low-orbit satellite corresponding to the real moment;

[0051] In an implementation manner of the second aspect, the acquisition module is specifically configured to, before determining the pseudorange residual between the navigation satellite and the monitoring device, the method further includes:

[0052] The navigation data is preprocessed; the preprocessing method includes cycle slip detection, pseudorange smoothing processing and satellite ephemeris processing.

[0053] In a third aspect, the present invention provides an electronic device, comprising a processor and a memory coupled to the processor; the memory is used to store computer instructions, and when the electronic device is running, the processor executes the computer instructions stored in the memory, so that the electronic device performs the method described in the first aspect or any one of its implementations.

[0054] In a fourth aspect, the present invention provides a computer-readable storage medium, comprising computer program instructions, which, when executed by a computer, enable the computer to execute the method as described in the first aspect or any one of its implementations.

[0055] In a fifth aspect, the present invention provides a computer program product, comprising computer program instructions, which, when executed on a computer, enable the computer to execute the method as described in the first aspect or any one of its implementations.

[0056] The technical effects corresponding to the above-mentioned second to fifth aspects and their possible implementations can refer to the above-mentioned description of the technical effects of the first aspect and its possible implementations, and will not be repeated here.

[0057] The beneficial effects of the present invention are:

[0058] The method and device for improving the integrity of the positioning service of the satellite navigation system provided by the present invention obtains the orbit correction number and clock correction number of the navigation satellite used to locate the user by solving the signal received from the navigation satellite by the combined ground monitoring station and the low-orbit satellite, and then determines the integrity parameter according to the orbit correction number and the clock correction number, and the integrity parameter can be used to more accurately measure the integrity and reliability of the positioning service of the satellite navigation system. Through this technical solution, the low-orbit satellite is used as a monitoring station, and the navigation signal received by the low-orbit satellite is combined to calculate the orbit correction number and clock correction number of the navigation satellite, thereby improving the integrity of the positioning service of the satellite navigation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a schematic diagram of the architecture of a global satellite navigation system provided by an embodiment of the present invention;

[0060] Figure 2 is a schematic diagram of the architecture of a satellite-based augmentation system provided by an embodiment of the present invention;

[0061] Figure 3 is a schematic diagram of the architecture of a satellite navigation system provided by an embodiment of the present invention;

[0062] Figure 4 This is one of the flowcharts of a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0063] Figure 5 This is a second flow chart of a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0064] Figure 6 This is a third flow chart of a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0065] Figure 7 This is a fourth flow chart of a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0066] Figure 8 It is a schematic diagram of a pseudorange residual abnormal value processing flow in a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0067] Fig. 9 It is a schematic diagram of an outlier processing framework in a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0068] Fig.10 A schematic diagram of the worst user in the ECEF coordinate system during integrity parameter calculation in a method for improving the integrity of a positioning service of a satellite navigation system provided by an embodiment of the present invention;

[0069] Fig.11 It is a structural schematic diagram of a device for improving the integrity of positioning services of a satellite navigation system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0070] In the description and claims of the present invention, the terms "first" and "second" are used to distinguish different objects rather than to describe a specific order of objects, such as a first pseudorange residual and a second pseudorange residual.

[0071] In the embodiments of the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0072] The embodiments of the present invention relate to positioning services based on a satellite navigation system. Generally, the process of positioning a user (referring to a user device used by the user, such as a mobile phone, a car, etc.) based on a satellite navigation system includes: the user receives a signal sent by a navigation satellite, and obtains the orbit correction number and the clock correction number of the navigation satellite used to position the user, and then determines the user's position according to the navigation signal, and corrects the user's position according to the orbit correction number and the clock correction number of the navigation satellite to obtain the user's precise position. Among them, the orbit correction number and the clock correction number of the navigation satellite are calculated by the main control device in the satellite navigation system based on the navigation data obtained from the monitoring device.

[0073] Combine the following Figure 1 The architecture of the satellite navigation system involved in the embodiments of the present invention and related technical terms are introduced.

[0074] For example, the embodiment of the present invention is described by taking the satellite navigation system as the Global Navigation Satellite System (GNSS) as an example. The GNSS is used to provide accurate location, navigation information and time information of any place on the earth. For example, Figure 1 is a schematic diagram of the architecture of a global satellite navigation system, such as Figure 1 As shown, GNSS can include three parts, namely, a space part, a ground control part and a user equipment part. In the global satellite navigation system, the space part can include multiple navigation satellites 101, the ground control part (i.e., the ground control system) includes a monitoring station 102, a master control station 103 and an injection station 104, and the user equipment part includes a user equipment 105.

[0075] Among them, multiple navigation satellites 101 in the satellite navigation system are distributed on different orbits to ensure continuous coverage around the world. The navigation satellite 101 continuously transmits signals, receives navigation messages and other signals sent by ground stations (such as injection stations 104), and broadcasts navigation messages to users for user positioning. The signals transmitted by the navigation satellite may include a carrier for carrying a modulated signal, a ranging code, and a data code (the navigation message is part of the data code), and ground stations (such as monitoring stations) and user equipment can receive the signals transmitted by the navigation satellite.

[0076] The monitoring station 102 in the ground control system (which has a receiver) is used to monitor the navigation satellite and collect the signals transmitted by the satellite, and process the received signals to obtain the observation data of the navigation satellite, and then send the observation data to the main control station 103. In GNSS, the monitoring stations 102 are distributed in different areas, and the monitoring stations 102 may include multiple, Figure 1 Only one monitoring station is shown.

[0077] Among them, the observation data includes pseudo-range observation values ​​and carrier phase observation values, etc. The monitoring station 102 calculates the product of the time required for the ranging code transmitted by the navigation satellite to reach the monitoring station 102 and the speed of light to obtain the pseudo-range observation value. Due to the existence of various error sources (such as satellite clock, receiver clock error, delay error, etc.), the pseudo-range is not the true geometric distance. The carrier phase observation value is the phase change value of the carrier signal transmitted by the navigation satellite. The carrier phase can be used to smooth the pseudo-range to improve the positioning accuracy.

[0078] The main control station 103 in the ground control system can receive the signals transmitted by the navigation satellite 101 and the satellite observation data sent by the monitoring station 102, and process these data to obtain the position, speed, and clock deviation parameters of the navigation satellite, and then fit the orbital parameters (such as the semi-major axis of the orbit, eccentricity, inclination, etc.) and other information of the navigation satellite based on these parameters. The orbital parameters of the satellite belong to the satellite ephemeris, and the position and speed of the satellite at any time can be calculated based on the satellite ephemeris. The satellite ephemeris includes broadcast ephemeris (predicted ephemeris, satellite orbital parameters obtained in real time) and precise ephemeris (measured ephemeris, accurate satellite orbital parameters obtained by post-calculation).

[0079] The main control station 103 can also calculate the orbit correction number for correcting the orbit parameters of the navigation satellite and the clock correction number for correcting the navigation satellite clock, ionospheric delay and other information based on the satellite observation data and satellite ephemeris. These correction numbers are used to accurately locate the user equipment 105. Therefore, these correction numbers can be collectively referred to as positioning enhancement information.

[0080] The above-mentioned orbit correction number can also be called ephemeris correction number. The orbit correction number is the distance change value (i.e., pseudorange change) caused by the orbit error or ephemeris error of the navigation satellite. The orbit error is the deviation between the orbit parameters given by the satellite ephemeris and the actual orbit parameters of the satellite. Since the position of the satellite can be determined according to the orbit parameters, the orbit error can be used to indicate the difference between the position of the satellite in space determined according to the satellite ephemeris and the actual position of the satellite.

[0081] The clock correction number mentioned above may also be referred to as the satellite clock correction number (i.e., the correction number of the satellite clock), which is the distance change value (i.e., the pseudo-range change, obtained by multiplying time by the speed of light) caused by the satellite clock error (i.e., the error of the satellite clock) of the navigation satellite, and is not limited in the embodiment of the present invention. Among them, the satellite clock error refers to the deviation between the clock on the satellite (such as an atomic clock) and the standard time of the navigation system (i.e., the system time).

[0082] The master control station 103 may encapsulate the ephemeris of the navigation satellite and the positioning enhancement information into a navigation message (the navigation message may also include other information, such as time information, etc.) Then, the master control station 103 sends the navigation message to the injection station 104 .

[0083] In the embodiment of the present invention, the master control station 103 may also calculate the integrity parameters of the satellite navigation system according to the calculated orbit correction number and clock correction number, and the integrity parameters are used to measure the integrity of the positioning service of the satellite navigation system.

[0084] The injection station 104 in the ground control system injects the navigation message received from the master control station 103 into the memory of the corresponding navigation satellite. The GNSS may include multiple injection stations 104.

[0085] Furthermore, the above-mentioned navigation satellite 101 can broadcast the injected navigation message to the user device 105. The user device 105 receives signals and navigation messages from multiple navigation satellites 101 and calculates the position of the user device 105 based on this information, that is, locates the user device 105.

[0086] Exemplarily, the user equipment 105 may include various user equipment or terminals with positioning functions, such as mobile phones, transportation equipment (such as cars, airplanes, ships, etc.), cameras, wearable devices, etc.

[0087] In one implementation, in a positioning service scenario, positioning enhancement information may also be calculated and transmitted through a Satellite-Based Augmentation System (SBAS).

[0088] For example, Figure 2 The following is a schematic diagram of the SBAS architecture. The structure of SBAS is similar to that of GNSS. They both share some common equipment. The difference is that SBAS includes geostationary orbit satellites (GEO) 201 for forwarding positioning enhancement information. GEO is a high-orbit satellite. Figure 2The master control station 103 calculates the positioning enhancement information based on the observation data and satellite ephemeris received from the monitoring station 102, and sends the positioning enhancement information to GEO 201. When the user device 105 has a positioning requirement, it can request the positioning enhancement information from GEO 201, and correct the satellite's orbital parameters and the satellite's clock according to the positioning enhancement information, so as to determine the exact position of the user device 105, that is, to achieve accurate positioning of the user device.

[0089] Understandably, SBAS are all regional augmentation systems, including the Wide Area Augmentation System (WAAS) and the European Geosynchronous Navigation Overlay System (EGNOS), which started earlier in development. Their service range can only cover the country and surrounding areas. The Beidou Satellite-Based Augmentation System (BDSBAS) has the same problem as SBAS such as WAAS and EGNOS. Its service range is restricted by the inability to build overseas monitoring stations. It only effectively covers the country and surrounding areas and does not yet have the service capability for the global region. It can be seen that the current SBAS cannot provide effective services in many countries and regions around the world. At the same time. Due to its reliance on the layout of ground monitoring stations, the quality of satellite products provided by SBAS is easily affected by the deterioration of the ground observation geometry when the satellite enters and leaves the country (that is, the ground monitoring station cannot receive the signal transmitted by the navigation satellite), which makes its various performance indicators deteriorate, such as the integrity of the positioning service.

[0090] In order to solve the problem of poor integrity of positioning services in the prior art, an embodiment of the present invention provides a method and device for improving the integrity of positioning services of a satellite navigation system, which obtains the orbit correction number and clock correction number of the navigation satellite used to locate the user by solving the signal received from the navigation satellite by a joint ground monitoring station and a low-orbit satellite, and then determines the integrity parameter based on the orbit correction number and the clock correction number. The integrity parameter can be used to more accurately measure the integrity and reliability of the positioning service of the satellite navigation system. Through this technical solution, a low-orbit satellite is used as a monitoring station, and combined with the navigation signal received by the low-orbit satellite, a more comprehensive and accurate orbit correction number and clock correction number of the navigation satellite are calculated, which has the service capability of the global area, thereby improving the integrity of the positioning service of the satellite navigation system.

[0091] Optionally, the method provided in the embodiment of the present invention may be applied to various satellite navigation systems, such as the Beidou navigation system, the Global Positioning System, the GLONASS satellite navigation and positioning system or the Galileo satellite navigation and positioning system.

[0092] Combination Figure 1 and Figure 2 , Figure 3The schematic diagram of the architecture of a satellite navigation system provided by an embodiment of the present invention includes a plurality of navigation satellites 101, a monitoring station 102, a master control station 103, an injection station 105, a GEO 201 and a low-orbit satellite 301. There may be a plurality of monitoring stations 102 and low-orbit satellites 301 in the satellite navigation system. Figure 3 Only one is shown.

[0093] exist Figure 3 In the satellite navigation system shown, the monitoring station 102 and the low-orbit satellite 301 are used as monitoring equipment to receive signals from the navigation satellite 101, process the signals to obtain the observation data of the navigation satellite, and provide the observation data to the main control station 103. It should be noted that the low-orbit satellite 301 orbits the earth, and the moving low-orbit satellite 301 can receive signals from navigation satellites around the world.

[0094] For detailed introduction of navigation satellite 101, monitoring station 102, master control station 103, injection station 105, and GEO 201, please refer to Figure 1 , Figure 2 and a description of the relevant content.

[0095] Exemplarily, the method for improving the integrity of the positioning service of the satellite navigation system provided by the embodiment of the present invention is as follows: Figure 1 , Figure 2 or Figure 3 The main control station 103 (also referred to as a main control device) is shown to execute, and the main control device may be, for example, a computer, a server, etc. Taking the main control device as a computer as an example, the hardware part of the computer may include: a processor, a memory, a network interface, a user interface, a communication bus, etc.

[0096] The processor is used to control the computer to perform related processing and computing tasks. For example, in the embodiment of the present invention, the processor is used to process the received navigation signal and the satellite observation data to obtain the ephemeris and positioning enhancement information. The processor may include a central processing unit (CPU) or other processors. The processor may be single-core or multi-core. For example, the processor may include multiple CPUs.

[0097] The memory is used to store computer instructions and related data. For example, in an embodiment of the present invention, the memory is used to store satellite observation data, broadcast ephemeris and other data. The memory can be a random access memory (RAM), a read only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory or an optical memory, a disk storage medium or other magnetic storage device, or any other medium that can be used to store program code or data that can be accessed by a computer. Optionally, the memory can be integrated into the processor, and the memory can also be independent of the processor.

[0098] The network interface is used for the computer to communicate with other devices or communication networks, and the network interface can be a transceiver with transceiver functions. For example, in an embodiment of the present invention, the network interface is used to receive signals from navigation satellites, receive observation data of navigation satellites from monitoring stations or low-orbit satellites, and send the ephemeris and positioning enhancement information calculated by the processor to the injection station.

[0099] Optionally, the network interface may include a standard wired interface, a wireless interface (such as a WI-FI interface, a Bluetooth interface, a 5G interface).

[0100] The communication bus is used to realize the connection and communication between different components. For example, the processor, memory, network interface and user interface mentioned above can be interconnected through the communication bus.

[0101] The user interface may include a display screen and an input unit (such as a keyboard). Optionally, the user interface may also include a standard wired interface and a wireless interface.

[0102] Those skilled in the art will appreciate that the above-mentioned computer may also include more or fewer components, or a combination of certain components, or different arrangements of components, which is not limited in the embodiments of the present invention.

[0103] In combination with the above, a method for improving the integrity of positioning services of a satellite navigation system provided by an embodiment of the present invention is described in detail below.

[0104] Combining the above and Figure 3 Satellite navigation systems such as Figure 4 As shown, an embodiment of the present invention provides a method for improving the integrity of positioning services of a satellite navigation system, including the following S101-S103.

[0105] S101, the main control device obtains the observation data of the navigation satellite from the monitoring device;

[0106] In the embodiment of the present invention, the monitoring equipment includes a ground monitoring station (i.e. Figure 3 Monitoring stations 102 in the Figure 3 The low-orbit satellite 301 in the navigation satellite); the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and each monitoring device. The meaning of the pseudo-range observation value can refer to the description in the above embodiment, and the observation data may also include other data;

[0107] Combination Figure 3 The satellite navigation system shown in the figure generally includes a plurality of navigation satellites and a plurality of monitoring devices, each of which can receive signals transmitted by some or all of the navigation satellites;

[0108] For example, take two monitoring devices as an example, one monitoring device is monitoring station A, and the other monitoring device is low-orbit satellite B. If monitoring station A can receive signals transmitted by navigation satellite 1 and navigation satellite 2, and low-orbit satellite B can receive signals transmitted by navigation satellite 3 and navigation satellite 4, then monitoring station A can observe the pseudorange between navigation satellite 1 and monitoring station A (called pseudorange 1), and the pseudorange between navigation satellite 2 and monitoring station A (called pseudorange 2) according to the signals of the navigation satellites, low-orbit satellite B can observe the pseudorange between navigation satellite 3 and low-orbit satellite B (called pseudorange 3), and low-orbit satellite B can observe the pseudorange between navigation satellite 4 and low-orbit satellite B (called pseudorange 4). In this way, the main control device can obtain pseudorange 1 and pseudorange 2 from monitoring station A, and obtain pseudorange 3 and pseudorange 4 from low-orbit satellite B;

[0109] Exemplarily, the master control device samples the observation data of the navigation satellite at an interval of 30 seconds;

[0110] Due to the influence of comprehensive factors such as the changeable operating state of the navigation satellite, the complex environment and the receiver noise, there are abnormal values ​​in the observation data sent by the monitoring device to the main control device. In the embodiment of the present invention, after the main control device obtains the satellite observation data from the monitoring device, it can perform data preprocessing on the observation data by cycle slip detection, carrier phase smoothing, etc.; data preprocessing can suppress the influence of multipath errors and provide relatively "clean" data for the subsequent pseudorange residual solution;

[0111] Combination Figure 4 ,like Figure 5 As shown, the data preprocessing method is implemented by the following S1011 to S1013;

[0112] S1011, cycle slip detection:

[0113] The cycle slip phenomenon refers to the phenomenon that the ambiguity parameters of the carrier phase observation value change when the satellite is lost or the satellite signal is interrupted, resulting in the discontinuity of the carrier phase observation value. In combination with the process of smoothing the pseudorange in S1012 below, the pseudorange observation value needs to be smoothed using the carrier phase observation value. When a cycle slip occurs, if the ambiguity change is ignored and the pseudorange observation value is continued to be smoothed using the carrier phase observation value, new errors will be introduced, that is, the smoothing result of the pseudorange observation value will have errors.

[0114] S1012, carrier phase smoothed pseudorange:

[0115] Carrier phase smoothed pseudorange uses the change in carrier phase observations to smooth low-precision pseudorange observations. Specifically, the change in carrier phase observations between adjacent epochs is first calculated, and then the pseudorange observations are smoothed using this change to obtain the smoothed pseudorange observations of the current epoch. It should be understood that "epoch" is a time point of an observation; adjacent epochs refer to two observation time points that are consecutive in time.

[0116] In one implementation, when the observation data of multiple epochs are processed, a cumulative calculation may be performed to improve the accuracy of the pseudorange observations;

[0117] Specifically, firstly, the smoothed pseudorange observation value is initialized and assigned, the smoothing factor is set, and then the smoothed pseudorange observation value of the next epoch is calculated;

[0118] For example, taking the observation data of the j-th navigation satellite as an example, during a period of time when the carrier phase does not have a cycle slip, the Hatch filtering method is used, and the calculation formula of the carrier phase smoothing pseudorange is:

[0119]

[0120] In the formula, is the first epoch t in the period of continuous carrier phase 1 The pseudorange observation value of is the smoothed pseudorange observation value of the first epoch. According to the above formula, the smoothed pseudorange observation value of the first epoch is initialized to the pseudorange observation value of the epoch; is the kth (k≥2) epoch t k The smoothed pseudorange observation value at time , t k The pseudorange observation value at the epoch, t k-1 The smoothed pseudorange observations at the epoch, is the smoothing factor, t k-1 Epoch and t kThe difference of the carrier phase observation values ​​of the epoch; the above pseudorange observation values ​​and phase observation values ​​are dual-frequency ionosphere-free observation values;

[0121] Combined with the above carrier phase smoothed pseudorange calculation formula, it can be seen that the smoothing process of pseudorange observations is a cumulative process, and the smoothed pseudorange observations in the later epoch are the cumulative results of the smoothed pseudorange observations in the previous epoch;

[0122] It should be noted that when a cycle slip occurs in the carrier phase, during the pseudorange smoothing process, the smoothed pseudorange observation value of the current epoch needs to be assigned a value according to the initialization method in the above formula (that is, the current epoch is regarded as the first epoch in the new time period), and then the accumulation continues based on the assignment result;

[0123] For example, when a cycle slip occurs in the Nth epoch, the smoothed pseudorange observation value of the Nth epoch is equal to the pseudorange observation value of the epoch. Then, at the N+1th epoch, the smoothed pseudorange value of the Nth epoch is used as the initial value, and the above-mentioned Hatch filter formula is continued to be used for calculation to obtain the smoothed pseudorange observation value of the N+1th epoch.

[0124] S1013, processing the satellite ephemeris of the navigation satellite to obtain the position of the navigation satellite (referred to as the ephemeris position, i.e., the position of the satellite in space determined according to the ephemeris), the distance between each monitoring device and the navigation satellite (referred to as the ephemeris distance), and the deviation value between the true position of the navigation satellite and the ephemeris position of the navigation satellite;

[0125] S102, determining the pseudo-range residual between the navigation satellite and the monitoring device;

[0126] The pseudo-range residual is the difference between the pseudo-range observation value between the navigation satellite and the monitoring device and the true distance between the navigation satellite and the monitoring device after eliminating the common error and the clock error of the receiver from the monitoring device;

[0127] It can be understood that in the global navigation satellite system positioning, due to the existence of various errors, there is a certain difference between the pseudo-range observation value and the true geometric distance. These errors may include the clock error (clock error) of the navigation satellite, the orbit error (ephemeris error) of the navigation satellite, the clock error of the receiver of the monitoring equipment, and the common error;

[0128] In the embodiment of the present invention, the distance difference between the pseudorange observation value between the navigation satellite and the monitoring device and the real distance between the navigation satellite and the monitoring device is first calculated (which may be referred to as a first pseudorange residual), and then the common error and the clock error of the receiver of the monitoring device are eliminated (i.e., the distance deviation caused by the common error and the clock error of the receiver of the monitoring device is removed from the distance difference) to obtain the pseudorange residual between the navigation satellite and the monitoring device; that is, the pseudorange residual in S102 is the distance deviation caused by the clock error of the navigation satellite and the ephemeris error of the navigation satellite;

[0129] Combination Figure 4 ,like Figure 6 As shown, the above S102 is specifically implemented by the following S1021-S1023;

[0130] S1021. Determine a first pseudorange residual according to the pseudorange observation value and the position of the monitoring device;

[0131] In the embodiment of the present invention, the main control device can obtain the position of the monitoring device. When the monitoring device is a ground monitoring station, since the position of the ground monitoring station is fixed, the main control device can pre-store the position of the ground monitoring station; when the monitoring device is a low-orbit satellite, the main control device can determine the position of the low-orbit satellite according to the single-point positioning method and the interpolation method (the single-point positioning process is described in detail below);

[0132] The main control device determines the geometric distance between the navigation satellite and the monitoring device according to the position of the navigation satellite (calculated according to the satellite ephemeris of the navigation satellite) and the position of the monitoring device, and then calculates the difference between the pseudorange observation value between the navigation satellite and the monitoring device and the geometric distance between the two, to obtain a first pseudorange residual;

[0133] In the embodiment of the present invention, the idea of ​​the single-point positioning method and the interpolation method is: by observing the signal transmitted by the GNSS satellite (i.e., the navigation satellite), the clock error of the receiver in the LEO (low-orbit satellite) (i.e., the LEO onboard receiver) is determined; then the clock error of the LEO onboard receiver is deducted from multiple observation times to obtain multiple real times when the LEO receives the GNSS signal; then the positions of the low-orbit satellites at multiple real times in the LEO precise ephemeris are interpolated to obtain the position (precise position) of the LEO at the target time, and the position of the LEO at the target time is used to calculate the first pseudorange residual at the target time;

[0134] The process of the main control device determining the position of the low-orbit satellite using the single-point positioning method and the interpolation method specifically includes S01 to S03:

[0135] S01, the main control device determines the clock error of the receiver in the low-orbit satellite according to the observation data of the navigation satellite received from the low-orbit satellite;

[0136] The observation data of the navigation satellite is obtained by observing the low-orbit satellite. The observation data is the pseudo-range observation value between the navigation satellite and the low-orbit satellite. Then the pseudo-range residual between the navigation satellite and the low-orbit satellite is calculated. The pseudo-range residual is the difference between the pseudo-range observation value between the navigation satellite and the low-orbit satellite and the geometric distance between the two. The calculation formula of the pseudo-range residual can be used to estimate the clock error of the receiver in the low-orbit satellite.

[0137] Optionally, the ephemeris position of the low-orbit satellite can be calculated according to the satellite ephemeris (precise ephemeris) of the low-orbit satellite, and the ephemeris position of the navigation satellite (i.e., the true position of the navigation satellite and the ephemeris position of the navigation satellite obtained in step S1013) can be determined according to the satellite ephemeris (precise ephemeris) of the navigation satellite, and then, the geometric distance between the navigation satellite and the low-orbit satellite can be determined according to the ephemeris position of the low-orbit satellite and the ephemeris position of the navigation satellite;

[0138] In one implementation, the clock bias of each low-orbit satellite is estimated by using a station-by-station estimation method. For each low-orbit satellite, the pseudo-range residual between the navigation satellite and the low-orbit satellite is expressed as:

[0139]

[0140] In formula (1), is the pseudorange residual between the j-th navigation satellite and the i-th low-orbit satellite, Expressed as The transpose of is the orbit correction number of the j-th navigation satellite obtained based on the observation data of the j-th navigation satellite by the i-th low-orbit satellite (the distance unit reflecting the orbit error), for The unit direction vector, b i is the clock correction number of the i-th low-orbit satellite (reflecting the distance unit of the clock error), is the clock correction number of the jth navigation satellite (reflecting the distance unit of the clock error), is the residual error (distance unit);

[0141] In the above formula (1), in order to facilitate the solution, Considered as random error, The variance of j , the clock correction number of the low-orbit satellite can be calculated by weighted least square method;

[0142] The clock correction number b of the low-orbit satellite obtained by the least squares method i The estimated value of is:

[0143]

[0144] In the formula, for The variance of N is the number of visible satellites of the low-orbit satellite; Visible Satellites refers to navigation satellites that can be captured by the receiver of the monitoring equipment and successfully receive signals;

[0145] S02, eliminating the clock error of the receiver in the low-orbit satellite from the observation time of the low-orbit satellite receiving signal, so as to obtain the real time when the low-orbit satellite receives the signal;

[0146] S03, interpolating the positions of the low-orbit satellites corresponding to multiple real moments to obtain the positions of the low-orbit satellites;

[0147] In the embodiment of the present invention, the main control device obtains the precise ephemeris of the low-orbit satellite, the precise ephemeris of the low-orbit satellite determines multiple positions of the low-orbit satellite corresponding to multiple real moments, and interpolates the multiple positions of the low-orbit satellite to obtain the position of the low-orbit satellite at the target moment;

[0148] Specifically, the above interpolation method is:

[0149] First, determine the interpolation interval and select the interpolation interval from the above real time series. The interpolation interval should cover the time period required for prediction (including the target time), and use the existing time nodes in the interpolation interval as interpolation nodes.

[0150] Secondly, for each interpolation node, the corresponding position data is extracted from the precise ephemeris of the low-orbit satellite. The position data is usually the coordinates (X, Y, Z) in the Earth-centered Earth-fixed coordinate system.

[0151] Then, a polynomial is constructed based on the interpolation nodes and the corresponding position data using the Lagrange interpolation formula. The order of the polynomial depends on the number of interpolation nodes, but a high order may lead to numerical instability.

[0152] Finally, for the target time that needs to be predicted, the target time is substituted into the Lagrange interpolation polynomial to calculate the position of the low-orbit satellite at the target time;

[0153] Exemplarily, the Lagrange interpolation polynomial P(t) satisfies:

[0154]

[0155] Where t is the target time, y i is the coordinate of the low-orbit satellite of the i-th interpolation node, n is the total number of points in the interpolation node (i.e., the interpolation order); l i (t) is the basis function of the i-th interpolation node;

[0156] l i(t)Satisfy:

[0157]

[0158] Where, t i is the i-th interpolation node, t j is the time of the jth interpolation node, j≠i and 0≤j <n; It is the product of all terms starting from j=0 and ending at j=n, excluding j=i. The basis function represents that each basis function takes the value of 1 at its corresponding interpolation node and takes the value of 0 at other interpolation nodes, ensuring that the value at each interpolation node matches the given function value;

[0159] Substituting the target time t to be predicted into the above P(t), the satellite position P(t) value corresponding to time x can be obtained;

[0160] The position of the low-orbit satellite P(t) = {X(t), Y(t), Z(t)}. The position of the low-orbit satellite at the target time can be expressed as:

[0161]

[0162] S1022, using a common error correction model to remove the common error in the first pseudorange residual to obtain a second pseudorange residual;

[0163] The common error includes at least one of the following: relativistic effect error, differential code deviation, time group delay, earth rotation delay, earth gravity delay correction, ionospheric delay and tropospheric delay;

[0164] In one implementation, the embodiment of the present invention may use a tropospheric model to perform correction to deduct the common error in the first pseudorange residual, and obtain the second pseudorange residual;

[0165] It can be understood that the common error model is a model for correcting data, which can remove the common error in the data; in the embodiment of the present invention, the first pseudorange residual is processed using the common error model, which can remove the common error in the first pseudorange residual; the detailed process of removing the common error in the data using the common error model can refer to the description of the prior art materials, and the embodiment of the present invention will not be described in detail;

[0166] S1023, removing the clock error of the receiver in the monitoring device from the second pseudorange residual, to obtain a pseudorange residual between the navigation satellite and the monitoring device, where the pseudorange residual is caused by the clock error of the navigation satellite and the ephemeris error of the navigation satellite;

[0167] In the embodiment of the present invention, the monitoring equipment includes a ground monitoring station and a low-orbit satellite. The clock errors of the receivers in the ground monitoring station and the low-orbit satellite can be determined by using a single-point positioning method. For the process of determining the ground monitoring station and the low-orbit satellite by using the single-point positioning method, reference can be made to the relevant description of S01 in the above embodiment, which will not be repeated here.

[0168] Taking the i-th monitoring device and the j-th navigation satellite as an example, after deducting the common error and the clock error of the receiver in the monitoring device from the first pseudorange residual between the j-th navigation satellite and the i-th monitoring device, the pseudorange residual is satisfy:

[0169]

[0170] In formula (2), Expressed as The transpose of is the orbit correction number of the j-th navigation satellite obtained based on the observation data of the j-th navigation satellite by the i-th low-orbit satellite, for The unit direction vector of is the clock correction number of the jth navigation satellite (in distance units), is the residual error;

[0171] Generally, for a ground monitoring station with a fixed position, the satellite common view method is used to determine the clock error of its receiver, that is, the error between the clock of the monitoring station's receiver and the navigation satellite system time is determined by a common view satellite (i.e., a satellite that can be observed by the ground monitoring station); in the embodiment of the present invention, when a low-orbit satellite is used as a monitoring device, due to the high-speed movement of the low-orbit satellite, it is difficult for the navigation system to determine the common view satellite that can be observed by both the ground monitoring station and the low-orbit satellite, so the satellite common view method is no longer applicable; in this case, the embodiment of the present invention adopts a single-point positioning method, which can smoothly determine the clock deviation of the receiver in the ground monitoring station and the low-orbit satellite;

[0172] Optionally, after obtaining the pseudorange residuals through S102, in order to control the data quality of the pseudorange residuals, the embodiment of the present invention further provides a method for removing abnormal values ​​(gross errors and large system errors) in the pseudorange residuals; Figure 6 ,like Figure 7 As shown, the method further includes S104;

[0173] S104, eliminating abnormal values ​​in a plurality of pseudorange residuals between a plurality of monitoring devices and a plurality of navigation satellites;

[0174] It should be understood that the satellite navigation system includes multiple monitoring devices, and there is one pseudo-range residual between one monitoring device and one navigation satellite, so there are multiple pseudo-range residuals between multiple monitoring devices and multiple navigation satellites;

[0175] In an embodiment of the present invention, the abnormal values ​​of the pseudorange residuals can be divided into two categories, namely, the first category of pseudorange residual abnormal values ​​and the second category of pseudorange residual abnormal values; specifically, the pseudorange residuals calculated according to the data of the unavailable monitoring device are classified as the first category of pseudorange residual abnormal values, and the unavailable monitoring device is a monitoring device whose number of visible satellites is less than a preset number among multiple monitoring devices; the pseudorange residuals calculated according to the monitoring device whose test statistic is greater than or equal to the test statistic threshold among the available monitoring devices are classified as the second category of pseudorange residuals; the available monitoring device is a monitoring device whose number of visible satellites is greater than or equal to the preset number among multiple monitoring devices;

[0176] Exemplarily, the preset number of visible satellites may be 5, or other values ​​selected according to requirements;

[0177] Therefore, in one implementation, combining Figure 7 ,like Figure 8 As shown, the first type of pseudorange residual abnormal values ​​and the second type of pseudorange residual abnormal values ​​of the pseudorange residual are eliminated through S1041-S1043;

[0178] S1041, eliminating the first type of pseudorange residual abnormal values ​​from multiple pseudorange residuals; the first type of pseudorange residual abnormal values ​​are pseudorange residuals corresponding to unavailable monitoring equipment;

[0179] Combination Figure 8 ,like Fig. 9 As shown, taking the preset number of visible satellites as 5 as an example, it is determined whether the number of visible satellites of the monitoring device is greater than or equal to 5. If not (i.e., the number of visible satellites of the monitoring device is less than 5), it means that the data received by the monitoring device for positioning is insufficient, so the data obtained by these monitoring devices should be removed; if yes (i.e., the number of visible satellites of the monitoring device is greater than or equal to 5), it means that the number of navigation satellite data obtained by the monitoring device is sufficient, so it is retained;

[0180] After the first type of pseudorange residual anomalies are screened out, there may still be some error terms in the remaining pseudorange residuals that need to be further removed, see S1042-S1044 for details;

[0181] S1042, determining a test statistic of a pseudorange residual corresponding to an available monitoring device;

[0182] Optionally, the test statistic is Where V represents the pseudorange residual, V Tis the transpose of the pseudorange residual V, P is the unit weight matrix, represents the variance of pseudorange residuals;

[0183] S1043. When the test statistic obeys a chi-square distribution, determine a test statistic threshold;

[0184] In the embodiment of the present invention, the test statistic threshold (σ T )for in, represents the critical value of the chi-square distribution with k degrees of freedom and α significance level;

[0185] S1044, removing the second type of pseudorange residual abnormal values ​​from the plurality of pseudorange residuals after removing the first type of pseudorange residual abnormal values;

[0186] The second type of pseudorange residual abnormal value is the pseudorange residual corresponding to the monitoring device whose test statistic is greater than or equal to the test statistic threshold among the available monitoring devices;

[0187] In the embodiment of the present invention, according to the test statistic threshold σ T To determine whether the test statistic is out of range, if the test statistic is greater than or equal to the test statistic threshold, it means that one or more pseudorange residuals in the pseudorange residuals are significantly different from the rest of the pseudorange residuals, and these pseudorange residuals are considered to be outliers, so they need to be removed; if the test statistic is less than the test statistic threshold, it means that the pseudorange residual values ​​are all within the normal range, so they are retained as normal values;

[0188] Through the above S1021 to S1023 and S104, the pseudorange residual is processed with common error removal, clock error removal of the receiver of the monitoring device and outlier removal in sequence, so as to obtain a pseudorange residual affected only by the orbit error of the navigation satellite, the clock error of the navigation satellite and the preset residual error. Further, the following S103 is executed to solve the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite from the pseudorange residual;

[0189] S103, solving the observation equation constructed when the pseudorange residual is used as the observation value based on the extended Kalman filter algorithm, obtaining the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determining the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite;

[0190] Among them, the integrity parameter is used to indicate the integrity of the positioning service of the satellite navigation system;

[0191] Based on the above S102, it can be known that the clock error of the receiver of the monitoring device is removed (i.e., the clock correction number b is used to correct the clock error of the receiver). iThe observation equation established by using the pseudo-range residual after clock synchronization of the monitoring equipment as the observation value is as follows: As shown; it should be understood that since the orbit error of the navigation satellite includes the orbit radial error, the orbit tangential error and the orbit normal error, these three errors together cause the error in the calculation of the navigation satellite position. Generally speaking, the radial error of the satellite orbit will be absorbed into the clock error and is difficult to separate. Therefore, in the embodiment of the present invention, the clock correction number of the navigation satellite and the radial correction number of the orbit of the navigation satellite are firstly equivalent to an equivalent clock correction number for estimation to obtain the equivalent clock correction number;

[0192] The above equivalent clock correction number can be expressed as:

[0193] pcor j =δ orb_j +δ satclk_j

[0194] Where, pcor j represents the equivalent clock correction number of navigation satellite j; δ orb_j represents the radial correction of the orbit of navigation satellite j (i.e. Distance deviation caused by radial error in satclk_j represents the clock correction number of navigation satellite j;

[0195] Combining equation (2) with the above equivalent clock correction formula, the pseudorange residual can be expressed as:

[0196]

[0197] In combination with the above, the solution process of the embodiment of the present invention includes the following first step, second step and third step;

[0198] Step 1: first use the extended Kalman filter algorithm to solve the equivalent clock correction number and its covariance matrix in formula (3) through the specific steps of the following S1031, and use the equivalent clock correction number as the clock correction number of the navigation satellite, and use the covariance matrix of the equivalent clock correction number as the covariance matrix of the clock correction number of the navigation satellite;

[0199] Step 2: Substitute the calculated equivalent clock correction number into equation (2) to calculate the residual error The residual error in formula (3) After removing the residual error, we get the pseudorange residual formula (3-1):

[0200] Step 3: Substitute the equivalent clock correction number into formula (3-1), and then use the extended Kalman filter algorithm to solve the residual orbit error using the specific steps of S1032 below to obtain the residual orbit correction number and its covariance matrix, and use the residual orbit correction number as the orbit correction number of the navigation satellite, and use the covariance matrix of the residual orbit correction number as the covariance matrix of the orbit correction number of the navigation satellite;

[0201] S1031, calculating the clock correction number of the navigation satellite and the covariance matrix of the clock correction number of the navigation satellite;

[0202] Based on the above content, the equivalent clock correction number pcor is j In the process of solving the problem, it is necessary to use the observation equation and the state equation to perform the estimated calculation. The observation model provides the relationship between the existing pseudo-range observation value of the navigation satellite and the corresponding state of the navigation satellite, and the state transfer equation can predict the future value of the state. Therefore, the observation model and the state transfer equation are combined, that is, the historical observation value and the historical state information can be used to estimate the current state. (That is, the state transfer equation is used to predict the state at the next moment, and the observation model is used to correct the prediction to make it closer to the actual observation value.)

[0203] Exemplarily, the process of using extended Kalman filtering to calculate the clock correction number of the navigation satellite and the orbit radial correction number of the navigation satellite includes:

[0204] First, set the number of monitoring devices to M j , establish t i The equivalent clock correction number pcor of navigation satellite j at time j The Kalman filter observation equation and state transfer equation (also called clock correction number) are as follows:

[0205] Observation equation:

[0206]

[0207] In the formula, Z(t i ) is the observed quantity, Z(t i ) is the pseudorange residual, X(t i ) is the state transfer equation; H(t i ) is the design matrix, t i The measurement noise at each moment; The covariance matrix of i ), For the Mth j The pseudorange residual between the monitoring device and the jth satellite;

[0208]

[0209] H(t i )satisfy:

[0210]

[0211] State transfer equation:

[0212]

[0213] Where F(t) is the state transfer matrix, F(t i ,t i-1 ) is t i-1 Time to t i The state transfer matrix at time , t i-1 The noise of the state transition process at the moment, The covariance matrix of i-1 );

[0214] The state transfer matrix F(t i ,t i-1 ):

[0215]

[0216] Measurement noise satisfy:

[0217]

[0218] in, is the residual error of the pseudorange residual between the navigation satellite j and the first monitoring device and the pseudorange residual between the navigation satellite j and the first monitoring device geometric distance, is the navigation satellite j and the Mth j The pseudorange between the monitoring devices and the navigation satellite j and the Mth j The residual error of the pseudo-range residual between the geometric distances of the monitoring devices;

[0219] Based on the above formula, t can be completed by the following equations 1 and 2 i The equivalent clock correction number pcor of navigation satellite j at time j and the covariance matrix of the clock corrections The estimation process:

[0220] Equation 1: Estimation of navigation satellite clock corrections:

[0221]

[0222] in, is the estimated value of the state, is the state prediction value, K(t i) is the gain matrix;

[0223] Equation 2. Calculate the covariance matrix of the clock corrections:

[0224] P(t i )=[IK(t i )H(t i )]P(t i ,t i-1 )

[0225] Among them, P(t i ,t i-1 ) is t i-1 Time to t i The variance-covariance matrix of the prediction at time K(t i ) is the gain matrix;

[0226] satisfy:

[0227]

[0228] P(t i ,t i-1 )satisfy:

[0229] P(t i ,t i-1 )=F(t i ,t i-1 )P(t i-1 )F T (t i ,t i-1 )+Q(t i-1 )

[0230] K(t i )satisfy:

[0231] K(t i )=P(t i ,t i-1 )H T (t i )[H(t i )P(t i ,t i-1 )H T (t i )+R(t i )] -1

[0232] The clock correction number of the navigation satellite obtained The covariance matrix of the navigation satellite clock correction number is

[0233]

[0234] in, for The first row and first column of the element; P 1,1 (t i ) is P(t i )'s first row and first column;

[0235] S1032, calculating the remaining orbit correction number of the navigation satellite and the remaining orbit correction number covariance matrix of the navigation satellite;

[0236] The equivalent clock error pcor is calculated j Substituting it into the above formula (3-1), that is, eliminating the pseudorange change caused by the radial orbit error of the navigation satellite and the clock error of the navigation satellite in formula (2), the new pseudorange residual is obtained: Using the new pseudorange residuals The observation equation is established as follows (4), and the remaining orbit corrections are calculated (i.e., the navigation satellite orbit corrections other than the radial direction are calculated);

[0237] The observation equation is:

[0238]

[0239] In the formula, is the pseudorange residual in formula (3), pcor j is the equivalent clock correction calculated by S1031 (i.e. the clock correction of the navigation satellite), is the new pseudorange residual, Expressed as The transpose of is the orbit correction number of the jth navigation satellite obtained based on the observation data of the jth navigation satellite by the i-th low-orbit satellite, [dx j dy j dz j ] is the three-dimensional orbit error component of the j-th navigation satellite; It is the residual error of the pseudo-range residual after removing the radial orbit error and the clock error of the navigation satellite;

[0240] Exemplarily, using an extended Kalman filter to solve the residual orbit error of a navigation satellite includes:

[0241] First, set the number of monitoring devices to M j , establish t i Satellite orbit correction number of navigation satellite j at time The Kalman filter observation equation and state transfer equation, the observation equation is as shown in the above equation (5), and the state transfer equation is as shown in the above equation (6):

[0242] Observation equation:

[0243]

[0244] In the formula, Z(t i ) is the observed quantity, Z(t i ) is the pseudorange residual, X(t i ) is the state transfer equation; H(t i ) is the design matrix, t i The measurement noise at each moment; The covariance matrix of i ), For the Mth j The pseudorange residual between the monitoring device and the jth satellite;

[0245] Among them, Z(t i )satisfy:

[0246]

[0247] H(t i )satisfy:

[0248]

[0249] State transfer equation:

[0250]

[0251] The state transfer matrix F(t i ,t i-1 )for:

[0252]

[0253] Right now:

[0254] In the formula, is the orbit correction number of the navigation satellite, is the velocity correction number of the navigation satellite;

[0255] Measurement noise satisfy:

[0256]

[0257] in, is the residual error of the pseudorange residual between the navigation satellite j and the first monitoring device and the geometric distance between the navigation satellite j and the first monitoring device (excluding the clock error), is the navigation satellite j and the Mth jThe pseudorange between the monitoring devices and the navigation satellite j and the Mth j The residual error of the pseudorange residual (minus the clock error) between the geometric distances of the monitoring devices;

[0258] Based on the above formula, t can be completed by the following equations 3 and 4 i The remaining orbit correction number of navigation satellite j at time and the covariance matrix of the residual orbit corrections The estimation process;

[0259] Equation 3. Estimate the remaining satellite orbit corrections:

[0260]

[0261] in, is an estimated value, is the state prediction value, K(t i ) is the gain matrix;

[0262] Equation 4. Calculate the covariance matrix of the residual orbit corrections:

[0263] P(t i )=[IK(t i )H(t i )]P(t i ,t i-1 )

[0264] Among them, P(t i ,t i-1 ) is t i-1 Time to t i The variance-covariance matrix of the prediction at time K(t i ) is the gain matrix;

[0265] satisfy:

[0266]

[0267] P(t i ,t i-1 )satisfy:

[0268] P(t i ,t i-1 )=F(t i ,t i-1 )P(t i-1 )F T (t i ,t i-1 )+Q(t i-1 )

[0269] K(t i)satisfy:

[0270] K(t i )=P(t i ,t i-1 )H T (t i )[H(t i )P(t i ,t i-1 )H T (t i )+R(t i )] -1

[0271] in,

[0272]

[0273] Where P 12 for and The covariance matrix, P 22 for The covariance matrix of is the variance of the residual orbit corrections;

[0274] The remaining orbit correction number of the navigation satellite is obtained as for The elements of the first row and first column of the navigation satellite are the covariance matrix of the residual orbit correction number P 1,1 (t i ), P 1,1 (t i )for The element in the first row and first column of ;

[0275] Through the above-mentioned extended Kalman filter algorithm, the covariance matrix of the residual orbit error (i.e., orbit correction number) of the navigation satellite and the orbit correction number of the navigation satellite, and the covariance matrix of the clock error (clock correction number) of the navigation satellite and the clock correction number of the navigation satellite are solved; the orbit information received by the user is corrected by using the orbit correction number of the navigation satellite, and the clock information of the navigation satellite is corrected by using the clock correction number of the navigation satellite;

[0276] Furthermore, the covariance matrix of the navigation satellite orbit correction number can be used to calculate the integrity-related parameters. The calculation of the integrity-related parameters can reflect the comprehensive correction accuracy of the above correction numbers, thereby improving the early warning capability, the positioning accuracy, integrity and reliability of the navigation system;

[0277] S1033, integrity parameter calculation;

[0278] In the actual process, in addition to the above-mentioned orbit correction number of the navigation satellite and the clock correction number of the navigation satellite, there are still some errors that cannot be completely eliminated. In order to clearly reflect these errors, these errors can be solved and estimated again to obtain the corrected error estimate (i.e., integrity parameter). The integrity parameter provides the uncertainty measurement of the correction information itself, helping users understand the possible error range when using these correction information for positioning;

[0279] In the embodiment of the present invention, the integrity parameter is a dual-frequency error; the dual-frequency error DFRE (Dual-FrequencyRangeError) refers to a dual-frequency ranging error integrity parameter calculated for each satellite in a dual-frequency multi-constellation satellite-based augmentation system; the user can use DFRE to calculate the integrity protection level, and then determine whether the service performance of the dual-frequency multi-constellation satellite-based augmentation system meets the integrity requirements of the current stage; if the DFRE value of a satellite is small, it means that the satellite is relatively healthy and has high observation quality, thereby ensuring the safety of the user; on the contrary, if the DFRE value is large, it may mean that the satellite may be at the edge of the service area and it is difficult to provide sufficiently accurate positioning information, which is unacceptable in safety-critical applications;

[0280] In the embodiment of the present invention, the covariance matrix of the navigation satellite orbit correction number and the covariance matrix of the navigation satellite clock correction number are projected along a certain worst user position direction to obtain an error confidence limit (DFRE value) in the worst user position direction; specifically, this can be achieved through the following steps ①-③;

[0281] ① Based on the orbit information correction number and clock information correction number of the navigation satellite calculated in S103, the pseudorange residual is corrected;

[0282] The correction error generated during the correction process is shown in the following formula:

[0283]

[0284] ② Obtain the projection of the above correction error within the service area;

[0285] First, assume that the maximum projection direction of the correction error in the service area (the user position located in the maximum projection direction is called the worst user position, WUL), and the projection of the correction error in the service area satisfies the following formula:

[0286]

[0287] in, To correct the error ε j The transpose of is the unit direction vector from satellite j to the worst user position, and is the unit direction vector from the navigation satellite to the user, and

[0288] Then use the covariance matrix of the navigation satellite orbit correction number and the navigation satellite clock correction number The distribution of the correction error is described by the value of . The reason is that the true value of the satellite orbit and clock error is actually unknown, so the correction error of the correction number cannot be calculated directly. The correction error of follows a normal distribution with zero mean. The expression is as follows:

[0289]

[0290] In the above formula, is the covariance matrix composed of orbit correction and clock correction, is the covariance matrix of the orbit corrections, is the covariance matrix of the clock corrections;

[0291] Based on the projection of the correction error in the service area and the distribution of the correction error, the correction error ε j The variance of the projection on the worst user position is expressed as:

[0292]

[0293] In the formula, is the variance of the correction error of the orbit information correction number and the clock information correction number of navigation satellite j projected on the worst user position, is the unit direction vector from navigation satellite j to the worst user position;

[0294] ③Use the result obtained in step ② is the variance of the correction error of the navigation satellite j orbit information correction number and the clock information correction number projected on the worst user position, and DFRE can be calculated. DFRE satisfies the following formula:

[0295]

[0296] Among them, DFRE envelops the maximum projection of the residual error of the correction number in the service area with a probability of 99.9%, and 3.29 in the formula is the quantile corresponding to the confidence probability of 99.9%;

[0297] For example, based on the above content, it can be known that in step ②, the unit direction vector from the navigation satellite to the worst user position needs to be obtained. The solution method is as follows:

[0298] Find within satellite signal coverage area Make To reach the maximum Solving method to optimize:

[0299] Since the covariance matrix of the orbit correction number is is a real symmetric matrix, there exists an orthogonal unit matrix C such that:

[0300]

[0301] Among them, λ 1 , 2 and λ 3 for The eigenvalue of (assuming λ 1 ≥λ 2 ≥λ 3 >0); the column vector of matrix C is About Lambda i Eigenvector of (i=1, 2, 3);

[0302] The ECEF coordinate system can be transformed into a new coordinate system through the matrix C, the origin of which is located at satellite j, and the x-axis, y-axis and z-axis are the directions pointed by the column vectors of C respectively; as follows Fig.10 As shown;

[0303] According to the method of mathematical analytic geometry, we can get The expression is as follows;

[0304]

[0305] In the formula, α is the zenith angle, β is The angle with the x-axis, x WUL ,y WUL , z WUL The calculation of is as follows:

[0306]

[0307] In the formula, r e is the radius of the Earth, r s is the distance from the satellite to the center of the earth, δ = 90°-α-ε, ε is the altitude angle of the satellite relative to the receiver; [x 1 y 1 z 1 ] T =X 0 / |X 0 |, X 0 is the coordinate of the origin of the ECEF coordinate system in the new coordinate system,

[0308] Since, formula (15) calculates y WUL When the formula is ±a 0, we can get two positions, so There will be two directions, choose the one that makes Reach a maximum direction, denoted by Where η is The angle between the DFRE and the x-axis, so the value of DFRE can be expressed as follows:

[0309]

[0310] In summary, the embodiments of the present invention provide a method and device for improving the integrity of the positioning service of a satellite navigation system, which obtains the orbit correction number and clock correction number of the navigation satellite used to locate the user by jointly calculating the signal received from the navigation satellite by the ground monitoring station and the low-orbit satellite, and then determines the integrity parameter according to the orbit correction number and the clock correction number, and the integrity parameter can be used to more accurately measure the integrity and reliability of the positioning service of the satellite navigation system. Through this technical solution, the low-orbit satellite is used as a monitoring station, and combined with the navigation signal received by the low-orbit satellite, the orbit correction number and clock correction number of the navigation satellite are calculated to be more comprehensive and accurate, thereby improving the integrity of the positioning service of the satellite navigation system.

[0311] Accordingly, an embodiment of the present invention provides a device for improving the integrity of positioning services, such as Figure 5 As shown, it includes an acquisition module 501, a first determination module 502 and a second determination module 503;

[0312] The acquisition module 501 is used for the main control device to acquire the observation data of the navigation satellite from the monitoring device; the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and the monitoring device, and the monitoring device includes at least one ground monitoring station and at least one low-orbit satellite; for example, the acquisition module 501 is used to implement S101 in the above-mentioned method for improving the integrity of the positioning service;

[0313] The first determination module 502 is used to determine the pseudorange residual between the navigation satellite and the monitoring device; the pseudorange residual is the difference between the pseudorange observation value between the navigation satellite and the monitoring device and the geometric distance between the navigation satellite and the monitoring device after eliminating the common error and the clock error of the receiver from the monitoring device; for example, the first determination module 502 is used to implement S102 in the above method for improving the integrity of the positioning service, and specifically, can implement the above S1021-S1023;

[0314] The second determination module 503 is used to solve the observation equation constructed when the pseudo-range residual is used as the observation value based on the extended Kalman filter algorithm, obtain the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determine the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite; the integrity parameter is used to indicate the integrity of the user positioning service of the satellite navigation system. For example, the second determination module 503 is used to implement S103 in the above method for improving the integrity of the positioning service.

[0315] Optionally, the first determination module 502 is specifically used to: determine a first pseudorange residual according to the pseudorange observation value and the position of the monitoring device; wherein, when the monitoring device is the low-orbit satellite, the position of the low-orbit satellite is determined based on a single-point positioning method; adopt a common error correction model to remove the common error in the first pseudorange residual to obtain a second pseudorange residual; remove the clock error of the receiver from the monitoring device in the second pseudorange residual to obtain the pseudorange residual. For example, the first determination module 502 is specifically used to implement S102 in the above-mentioned method for improving the integrity of positioning services, and specifically includes S1021-S1023.

[0316] Each module of the above-mentioned device for improving the integrity of positioning services can also be used to execute other steps in the above-mentioned method embodiment. The relevant contents involved in the above-mentioned method embodiment can all be referred to the functional description of the corresponding functional modules, which will not be repeated here.

[0317] The embodiment of the present invention further provides a main control device, including: a processor and a memory coupled to the processor; the memory is used to store computer instructions, and when the electronic device is running, the processor executes the computer instructions stored in the memory, so that the electronic device executes the method described in the above embodiment. The processor can implement the above-mentioned acquisition module 501, the first determination module 502 and the second determination module 503.

[0318] An embodiment of the present invention further provides a computer-readable storage medium, which includes a computer program. When the computer program runs on a computer, the method described in the above embodiment is executed.

[0319] An embodiment of the present invention further provides a computer program product, which includes computer program instructions. When the computer program instructions are run on a computer, the method described in the above embodiment is executed.

[0320] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0321] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving the integrity of a positioning service of a satellite navigation system, characterized in that: include: The main control device acquires the observation data of the navigation satellite from the monitoring device; the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and the monitoring device, and the monitoring device includes at least one ground monitoring station and at least one low-orbit satellite; Determining a pseudorange residual between the navigation satellite and the monitoring device; The pseudorange residual is the difference between the pseudorange observation value between the navigation satellite and the monitoring device and the geometric distance between the navigation satellite and the monitoring device after eliminating the common error and the clock error of the receiver from the monitoring device; Solving the observation equation constructed with the pseudorange residual as the observation value based on the extended Kalman filter algorithm to obtain the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determining the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite; The integrity parameter is used to indicate the integrity of the user positioning service of the satellite navigation system.

2. The method according to claim 1, characterized in that The determining of the pseudorange residual between the navigation satellite and the monitoring device comprises: Determine a first pseudorange residual according to the pseudorange observation value and the position of the monitoring device; wherein, when the monitoring device is the low-orbit satellite, the position of the low-orbit satellite is determined based on a single point positioning method and an interpolation method; Using a common error correction model, removing the common error in the first pseudorange residual to obtain a second pseudorange residual; A clock error from a receiver of the monitoring device is removed from the second pseudorange residual to obtain the pseudorange residual.

3. The method according to claim 2, characterized in that The method further comprises: The clock error of the receiver of the monitoring device is determined by using a station-by-station estimation method.

4. The method according to claim 2, characterized in that The common error includes at least one of the following: relativistic effect error, differential code bias, time group delay, earth rotation delay, earth gravity delay correction, ionospheric delay and tropospheric delay.

5. The method according to claim 2, characterized in that The satellite navigation system includes a plurality of monitoring devices, one pseudorange residual corresponds to one monitoring device and one navigation satellite, and the method further includes: Outliers in the plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites are eliminated.

6. The method according to claim 5, characterized in that The removing of abnormal values ​​from a plurality of pseudorange residuals between the plurality of monitoring devices and the plurality of navigation satellites comprises: Eliminate a first type of pseudorange residual abnormal value from the multiple pseudorange residuals; the first type of pseudorange residual abnormal value is a pseudorange residual corresponding to an unavailable monitoring device; the unavailable monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device is less than a preset number; Determine a test statistic of a pseudorange residual corresponding to an available monitoring device; the available monitoring device is a monitoring device among the multiple monitoring devices, the number of visible satellites of the monitoring device being greater than or equal to the preset number; When the test statistic follows a chi-square distribution, a test statistic threshold is determined, where in, represents the critical value of the chi-square distribution with k degrees of freedom and α significance level; From the multiple pseudorange residuals after eliminating the first type of pseudorange residual abnormal values, eliminate the second type of pseudorange residual abnormal values; the second type of pseudorange residual abnormal values ​​are the pseudorange residuals corresponding to the monitoring devices whose test statistic is greater than or equal to the test statistic threshold among the available monitoring devices.

7. The method according to claim 2, characterized in that When the monitoring device is the low-orbit satellite, determining the position of the low-orbit satellite based on a single-point positioning method and an interpolation method includes: Determining a clock error of a receiver in the low-orbit satellite based on the navigation data received by the low-orbit satellite; Eliminate the clock error of the receiver in the low-orbit satellite from the observation time when the low-orbit satellite receives the signal, so as to obtain the real time when the low-orbit satellite receives the signal; Interpolate the positions in the precise ephemeris corresponding to multiple moments of the low-orbit satellite to obtain the position of the low-orbit satellite corresponding to the real moment.

8. The method according to any one of claims 1 to 7, characterized in that Before determining the pseudorange residual between the navigation satellite and the monitoring device, the method further includes: The navigation data is preprocessed; the preprocessing method includes cycle slip detection, pseudorange smoothing processing and satellite ephemeris processing.

9. A device for improving the integrity of positioning services of a satellite navigation system, characterized in that: It includes an acquisition module, a first determination module and a second determination module; The acquisition module is used for the main control device to acquire the observation data of the navigation satellite from the monitoring device; the observation data of the navigation satellite includes the pseudo-range observation value between each navigation satellite and the monitoring device, and the monitoring device includes at least one ground monitoring station and at least one low-orbit satellite; The first determination module is used to determine the pseudorange residual between the navigation satellite and the monitoring device; The pseudorange residual is the difference between the pseudorange observation value between the navigation satellite and the monitoring device and the geometric distance between the navigation satellite and the monitoring device after eliminating the common error and the clock error of the receiver from the monitoring device; The second determination module is used to solve the observation equation constructed when the pseudorange residual is used as the observation value based on the extended Kalman filter algorithm, obtain the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite used to locate the user, and determine the integrity parameter of the satellite navigation system according to the orbit correction number of the navigation satellite and the clock correction number of the navigation satellite; The integrity parameter is used to indicate the integrity of the user positioning service of the satellite navigation system.

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