Adaptive fast positioning method and system based on gnss synchronization state

Abstract

The application relates to a GNSS synchronization state-based adaptive fast positioning method and system, and belongs to the technical field of navigation and positioning. The method comprises the following steps: when the ephemeris time synchronization of tracking satellite signals is completed, entering a normal positioning process; otherwise, entering an adaptive time-free positioning process, which comprises the following steps: firstly, dynamically determining a minimum time credible unit and a time search interval according to the synchronization state level of the tracking satellite signals; secondly, determining a relatively accurate local reference time as a local baseline time according to the synchronization state level of the tracking satellite signals and the time search interval; and thirdly, performing fast AGPS iterative calculation after correcting the signal transmission time of the tracking satellite according to the local baseline time and the minimum time credible unit. The method can realize fast positioning of a receiver under a large-range time error.

Description

Technical Field

[0001] This application relates to the field of navigation and positioning technology, and in particular to an adaptive rapid positioning method and system based on GNSS synchronization status. Background Technology

[0002] As the core terminal equipment of GNSS (Global Navigation Satellite System), the positioning speed and stability of the navigation receiver directly determine the application effect of the navigation system. It is widely used in various fields such as the Internet of Things, emergency rescue, and smart terminals. Especially in scenarios requiring high response speed, the rapid positioning capability of the navigation receiver becomes a key indicator. Common GNSS satellite navigation receiver positioning methods in existing technologies include: 1. Traditional cold start positioning: In this mode, the receiver has no prior time information and needs to fully search for GNSS satellite signals, complete bit synchronization and frame synchronization in sequence, and collect key time information such as the second of the week in the message before the position can be calculated. Its first positioning time is usually 30 seconds to several minutes, which is time-consuming and cannot meet the requirements of the scenario for positioning timeliness.

[0003] 2. AGPS (Assisted Global Positioning System) Assisted Positioning: The navigation receiver obtains ephemeris, approximate time and location information through the network to assist in positioning, which can shorten the positioning time. However, this method has strict requirements for the freshness of the approximate time, which usually needs to be controlled within 187 seconds. If the time deviation is too large, the receiver will repeatedly try AGPS positioning and fail, getting stuck in a positioning loop, resulting in positioning abnormalities.

[0004] 3. RTC (Real-Time Clock) Assisted Positioning: This method uses an RTC module to maintain time information, combined with stored ephemeris and approximate location data, to help the receiver quickly locate itself. However, it relies on continuous battery power. For navigation receivers and related equipment stored for extended periods (such as backup positioning terminals and remote IoT sensors), a battery-free design is often used to avoid battery leakage or failure that could damage the equipment. In this case, the RTC module cannot maintain time, and the time information is lost when the device is powered off, rendering this positioning method completely ineffective.

[0005] In summary, existing positioning methods for navigation receivers still suffer from drawbacks such as long processing time, reliance on external networks, stringent requirements for time freshness, and dependence on continuous battery power. Summary of the Invention

[0006] Therefore, it is necessary to provide an adaptive rapid positioning method and system based on GNSS synchronization status that does not require RTC, batteries, or external networks and has high tolerance for time errors, in order to address the above-mentioned technical problems. It is particularly suitable for battery-free application scenarios such as long-term storage devices. By adaptively judging the synchronization status of the tracking satellite signals, it dynamically determines the minimum reliable time unit, thereby determining the AGPS time search range, shortening the positioning time, and significantly improving positioning efficiency and adaptability.

[0007] An adaptive fast positioning method based on GNSS synchronization status, the method comprising: Read the GNSS ephemeris data, approximate location and approximate time stored or injected by the navigation receiver during the last positioning, and after using the approximate time to perform local time pre-calibration, enter the GNSS satellite signal acquisition and tracking stage, and simultaneously latch the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization and completed message time synchronization. If all the tracking satellite signals have completed message time synchronization, it means that the navigation receiver has acquired the signal transmission time of all the tracking satellites. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data. Otherwise, the adaptive time-free positioning process is initiated, which includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracked satellite signal, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracked satellite signal, and then performing fast AGPS iterative solution after correcting the signal transmission time of the tracked satellite based on the local baseline time and the minimum reliable time unit. Determine whether normal positioning or adaptive time-free positioning was successful. If so, perform local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and store the relevant information for this positioning. Otherwise, wait for positioning in the next epoch.

[0008] In one embodiment, the GNSS ephemeris data, approximate location, and approximate time stored or injected by the navigation receiver during the previous positioning are read. After local time pre-calibration using the approximate time, the GNSS satellite signal acquisition and tracking phase begins, and the observations and synchronization status levels of the tracked satellite signals are simultaneously latched, including: After the navigation receiver is powered on, it completes hardware self-test and software initialization, and reads the GNSS ephemeris data, approximate time and approximate position stored or injected in the Flash memory. After using the approximate time to pre-calibrate the local time, it enters the GNSS satellite signal acquisition and tracking stage. During the GNSS satellite signal acquisition and tracking phase, signal acquisition is first performed according to the preset GNSS satellite list. After signal acquisition is completed, the system enters the tracking and synchronization state, and the carrier phase and pseudorange observations of the GNSS satellite signals are tracked in real time. Bit synchronization, frame synchronization and message time processing are performed simultaneously until the number of effectively tracked satellites is greater than or equal to 5. At the same time, the observations and synchronization status levels of all tracked satellite signals are latched.

[0009] In one embodiment, normal positioning of the navigation receiver based on observations of the tracked satellite signals and GNSS ephemeris data includes: Based on the observations of the tracking satellite signals and GNSS ephemeris data, the satellite position is calculated and the least squares positioning solution is directly performed to obtain the three-dimensional position and total clock error of the navigation receiver in the ECEF coordinate system.

[0010] In one embodiment, the minimum reliable time unit and time search interval are dynamically determined based on the synchronization status level of the tracked satellite signal, including: Based on the synchronization status level of each tracking satellite signal, the corresponding minimum reliable time unit is obtained, and the minimum reliable time unit of the tracking satellite signal with the lowest synchronization status level among all tracking satellites is selected as the final minimum reliable time unit. The possible values ​​of ; Maximum radial velocity combined with tracking satellite signals , with the speed of light Determine the time search interval , is represented as: .

[0011] In one embodiment, the corresponding minimum reliable time unit is obtained based on the synchronization status level of each tracking satellite signal, including: The value of the minimum reliable time unit for tracking satellite signals increases as the synchronization status level increases.

[0012] In one embodiment, determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracked satellite signal includes: Determine whether at least one tracking satellite signal has reached the synchronization status level of completed message time synchronization; If so, directly obtain the satellite signal transmission time from the message of the tracked satellite signal that has completed message time synchronization, and round up to the nearest second to obtain the local baseline time. ; If not, consider the time search interval. Retrieve the current local latch time Plus As local baseline time ,Right now .

[0013] In one embodiment, correcting the signal transmission time of the tracking satellite based on the local baseline time and the minimum reliable time unit includes: After calculating the satellite positions of each tracked satellite using the GNSS ephemeris data stored or injected in the previous positioning by the navigation receiver, the satellite-to-ground distance between the satellite positions and the approximate positions stored or injected in the previous positioning is calculated. The satellite-to-ground distance is then divided by the speed of light. The time it takes to get the distance between the satellite and the Earth. and to Take the final smallest reliable unit of time. Multiples of integers, to obtain Constant multiples of the distance between Earth and space ; where superscript Indicates the tracking satellite index; Based on the synchronization status level of each tracked satellite signal, the original satellite signal time is calculated using the frame count, bit count, intra-bit count, chip count, and chip phase time obtained from the tracking. , is represented as: ; Among them, the frame count, bit count, and intra-bit count are assigned values ​​according to the synchronization state level reached by each tracked satellite signal, and are 0 when the corresponding synchronization state level is not reached; Using local baseline time and the original satellite signal time Calculate satellite pseudorange duration ; and calculate exist The internal module serves as the smallest unit of internal pseudorange duration. ; use and the duration of pseudorange within the smallest unit The tracking satellite was calculated. The combined signal transmission time is ; Utilizing the time of satellite-to-ground distance Inversely, the tracking satellite was deduced. At local baseline time The signal transmission time is ; against and Construct millisecond integer fuzzy constraint pairs Make corrections to obtain the tracking satellite. Corrected signal transmission time.

[0014] In one embodiment, millisecond integer fuzzy constraint pairs are constructed. Make corrections to obtain the tracking satellite. The corrected signal transmission time includes: The millisecond integer fuzzyness constraint is represented as: ; Among them, superscript As the reference star, For reference star The signal transmission time deduced from the satellite-to-ground distance between the navigation receiver and the ground station. As a reference star The combined signal transmission time; When the inequality for the millisecond integer fuzziness constraint does not hold, by... Addition and subtraction The modification makes the inequality true; After correction, the corrected signal transmission time is obtained. The formula is as follows: .

[0015] In one embodiment, after correcting the signal transmission time of the tracking satellite based on the local baseline time and the minimum time confidence unit, a fast AGPS iterative solution is performed, including: Based on tracking satellites Correction signal transmission time The pseudorange residual equation is constructed and a fast AGPS iterative solution is performed; the AGPS iterative solution process uses least squares iterative solution; the pseudorange residual equation is expressed as: ; in For pseudo-distance residuals, To track satellites Corrected pseudorange, For local latching time, For ionospheric delay, For tropospheric delay, For satellite clock bias, To track satellites exist Satellite position at any given time It is the difference between the current time and the actual time. The above time, As the final, smallest reliable unit of time, This represents the three-dimensional position of the navigation receiver in the ECEF coordinate system. For the local clock bias of the navigation receiver, To track satellites The measurement error; the unknowns in the pseudorange residual equation are , and All other parameters are known values; During the least squares iterative solution, each iteration... The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ; in, For the number of iterations, The total number of iterations. and The first The second iteration and the first The next iteration And it is zero in the first iteration; and respectively tracking satellites In the The second iteration and the first The corrected signal transmission time for the next iteration Initial value ; For each iteration The sum of; The final iterative solution outputs the total clock bias of the navigation receiver. .

[0016] An adaptive rapid positioning system based on GNSS synchronization status, the system comprising: The signal acquisition and tracking module is used to read the GNSS ephemeris data, approximate position and approximate time stored or injected by the navigation receiver in the previous positioning, and after performing local time pre-calibration using the approximate time, it enters the GNSS satellite signal acquisition and tracking stage, and simultaneously latches the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization and completed message time synchronization. The normal positioning module is used to indicate that the navigation receiver has acquired the signal transmission time of all tracked satellites when all the tracking satellite signals have completed message time synchronization. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data. The adaptive time-free positioning module is used to enter the adaptive time-free positioning process when the tracking satellite signal has not been fully synchronized with the message time. This includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracking satellite signal, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracking satellite signal, and after correcting the signal transmission time of the tracking satellite based on the local baseline time and the minimum reliable time unit, performing fast AGPS iterative calculation. The post-positioning processing module is used to determine whether normal positioning or adaptive time-free positioning is successful. If so, it performs local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and stores the relevant information of this positioning. Otherwise, it waits for the positioning of the next epoch.

[0017] The aforementioned adaptive rapid positioning method and system based on GNSS synchronization status, through innovative means such as judging the synchronization status of tracking satellite signals, determining the dynamic minimum reliable time unit and time search interval, and determining the local baseline time search, solves the pain points of existing technologies, such as excessively long initial positioning time in scenarios without RTC / battery, low AGPS time tolerance, and susceptibility to looping. It achieves faster, more stable, and more adaptable rapid positioning capabilities, and is particularly suitable for application scenarios with high reliability and autonomy requirements, such as long-term storage devices and remote IoT sensors. Specifically, this application has the following beneficial effects: 1. It requires no RTC or battery support and does not rely on external networks. It can achieve rapid positioning by relying solely on the positioning information stored or injected by the navigation receiver during the previous positioning, combined with the observation of the tracking satellite signal and the synchronization status level. It is perfectly suited for devices that do not have batteries and require long-term storage.

[0018] 2. When the tracking satellite signal has not been fully synchronized with the message time, partial synchronization status information (such as only bit synchronization or frame synchronization) is used to start the time-free positioning process in advance. The position calculation is completed before the message is fully received. The initial positioning time is significantly shorter than that of traditional positioning. Even in the worst case (without any synchronization information), the positioning time does not exceed that of traditional positioning, which significantly improves positioning efficiency.

[0019] 3. Based on the synchronization status level of the tracked satellite signal, the minimum reliable time unit and time search interval are dynamically determined, and a relatively accurate local reference time is determined as the local baseline time. Combined with the minimum reliable time unit, the signal transmission time is corrected to ensure the convergence of the pseudorange residual equation and avoid falling into the AGPS loop due to excessive time error. This greatly improves the system's tolerance to time error. Regardless of the approximate size of the time error, positioning can be completed according to the adaptive time-free positioning process, ensuring stable and reliable operation of the receiver. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating an adaptive fast positioning method based on GNSS synchronization status in one embodiment; Figure 2 This is a schematic diagram illustrating the implementation process of an adaptive fast positioning method based on GNSS synchronization status in one embodiment; Figure 3 This is a block diagram of an adaptive rapid positioning system based on GNSS synchronization status in one embodiment. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0022] In one embodiment, such as Figure 1 and Figure 2 As shown, an adaptive fast positioning method based on GNSS synchronization status is provided, including the following steps: Step 1: Read the GNSS ephemeris data, approximate location, and approximate time stored or injected by the navigation receiver during the last positioning. After using the approximate time to perform local time pre-calibration, enter the GNSS satellite signal acquisition and tracking stage. Simultaneously latch the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization, and completed message time synchronization.

[0023] Specifically, after the navigation receiver is powered on, it completes hardware self-test and software initialization, and reads the GNSS ephemeris data, approximate time, and approximate position information stored or injected during the last positioning from the Flash memory. After using the approximate time for local time pre-calibration, it enters the GNSS satellite signal acquisition and tracking phase. In the GNSS satellite signal acquisition and tracking phase, it first acquires signals according to the preset GNSS satellite list. After signal acquisition is completed, it enters the tracking and synchronization state, tracks the carrier phase and pseudorange observations of GNSS satellite signals in real time, and performs bit synchronization, frame synchronization, and message time processing simultaneously until the number of effectively tracked satellites is greater than or equal to 5 (meeting the minimum number of satellites required for positioning calculation). At the same time, it latches the observations and synchronization status levels of all tracked satellite signals.

[0024] Step 2: If all the tracking satellite signals have completed message time synchronization, it means that the navigation receiver has acquired the signal transmission time of all the tracking satellites. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data.

[0025] Specifically, the normal positioning process is the traditional satellite navigation positioning process. Based on the observations of the tracked satellite signals and GNSS ephemeris data, the satellite position is calculated and the least squares positioning solution is directly performed to obtain the three-dimensional position and total clock error of the navigation receiver in the ECEF (Earth-centered Earth-fixed) coordinate system. The traditional satellite navigation positioning process is existing technology and will not be described in detail in this application.

[0026] Step 3: If the tracking satellite signals have not been fully synchronized with the message time, the adaptive time-free positioning process is initiated. This includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracking satellite signals, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracking satellite signals, and finally performing fast AGPS iterative calculation after correcting the signal transmission time of the tracking satellites based on the local baseline time and the minimum reliable time unit.

[0027] The minimum reliable time unit is a core parameter in the adaptive time-free positioning process. Its value directly determines the time search range, search efficiency, and positioning accuracy. The determination of the minimum reliable time unit mainly depends on the signal synchronization status of the GNSS tracking satellites. The value is dynamically adjusted by fully considering the differences in satellite synchronization speed and signal stability. The specific rules are as follows: When the number of effectively tracked satellites is ≥5, the minimum reliable time unit is obtained based on the synchronization status level of each tracking satellite signal. The minimum reliable time unit of the tracking satellite signal with the lowest synchronization status level among all tracking satellites is selected as the final minimum reliable time unit. The value of the minimum reliable time unit for each tracked satellite signal increases as its synchronization status level increases; that is, the higher the synchronization status level of the tracked satellite signal, the larger the value of its minimum reliable time unit.

[0028] For example, taking the BeiDou B3 frequency point as an example, the minimum reliable time unit for each tracked satellite signal (including GEO (geostationary orbit satellites) and NGEO (non-geostationary orbit satellites)) is determined as follows: (1) Bit synchronization not completed: At this time, the GEO and NGEO satellite signals are not bit synchronized, and the time information is only reliable within 1ms (the pseudorange period of the GNSS satellite B3 frequency point is 1ms).

[0029] (2) Bit synchronization is completed: At this time, the GEO and NGEO satellites complete bit synchronization and can obtain bit time related information. The duration of one bit of the GEO satellite is 2ms, and the bit synchronization time is about 100ms; the duration of one bit of the NGEO satellite is 20ms, and the bit synchronization time is about 200ms.

[0030] (3) Frame synchronization: GEO satellites take 0.6s-1.2s to complete frame synchronization, and one subframe takes 0.6s; NGEO satellites take 6s-12s to complete frame synchronization, and one subframe takes 6s.

[0031] (4) Complete message time synchronization: According to the GNSS B3 satellite message structure, the GEO satellite obtains the subframe start time from the message, which generally takes 0.6s-3s; the NGEO satellite obtains the subframe start time from the message, which generally takes 6s-12s.

[0032] For the four synchronization states mentioned above, the minimum reliable time unit values ​​corresponding to each tracked satellite signal are shown in Table 1. In Table 1, "Overall available" means that when the synchronization state level of the GEO or NGEO satellite signal is "complete message time synchronization", the message time is available overall, meaning that the accurate satellite signal transmission time can be obtained from the message.

[0033] Table 1. Minimum reliable time unit (ms) for signals from each tracked satellite under GNSS B3 frequency satellite synchronization status.

[0034] Time search interval The determination needs to be combined with the maximum radial velocity of the tracking satellite signal. , with the speed of light Calculations are performed to ensure that the time search interval covers the time errors caused by both types of satellite motion, while avoiding a decrease in positioning accuracy due to an excessively large search interval and a decrease in search efficiency due to an excessively small search interval. The calculation formula is as follows: .

[0035] in, To track the maximum radial velocity of satellite signals. For example, combining the motion characteristics of GEO and NGEO satellites, the radial velocity of a GEO satellite is close to 0, while the maximum radial velocity of an NGEO satellite can reach 800 m / s. Therefore 800 m / s is acceptable. The value depends on the minimum reliable time unit of the tracked satellite signal with the lowest synchronization status level. For example, when the GEO satellite has completed frame synchronization and the NGEO has completed bit synchronization, the corresponding minimum reliable time unit should be 20ms. speed of light Taking 299,792,458 m / s, substituting it into the above formula, we can obtain... .

[0036] It should be noted that if the GNSS used is not the BeiDou system, the determination of the minimum reliable time unit and the time search interval shall be handled as if all tracked satellites were NGEO satellites.

[0037] After dynamically determining the minimum reliable time unit and time search interval, a relatively accurate local reference time is further determined as the local baseline time based on the synchronization status level of the tracked satellite signal and the time search interval. The accuracy of the local baseline time directly determines the accuracy of the positioning solution. This application, based on the differences in the synchronization status of GNSS satellites, fully leverages the advantages of satellites and employs two methods for determining the local baseline time to ensure both accuracy and speed, as detailed below: Determine whether at least one tracking satellite signal has reached the synchronization status level of completed message time synchronization; If so, it means that a precise and stable satellite signal transmission time has been obtained. The transmission time of the satellite signal is directly obtained from the message of the tracked satellite signal that has completed message time synchronization, and the transmission time of the satellite signal is rounded up to the nearest second as the local baseline time. ; If no, it means that all tracked satellites have not completed message time synchronization, and time-free positioning is required within the preset time range. In this case, the time search interval should be considered. Retrieve the current local latch time (Local time of sampling) plus As local baseline time ,Right now .

[0038] During the local baseline time determination process, updates are required based on the synchronization status of the tracked satellites, so that... Rapid expansion, time search interval Increase it, and then determine the local baseline time.

[0039] Then, the signal transmission time of the tracking satellite is corrected based on the local baseline time and the minimum reliable time unit. The correction process includes: First, after calculating the satellite positions of each tracked satellite using the GNSS ephemeris data stored or injected in the previous positioning, the satellite-to-ground distance between the satellite positions and the approximate positions stored or injected in the previous positioning is calculated. The satellite-to-ground distance is then divided by the speed of light. The time it takes to get the distance between the satellite and the Earth. and to Take the final smallest reliable unit of time. Multiples of integers, to obtain Constant multiples of the distance between Earth and space ; where superscript Indicates the tracking satellite index; Based on the synchronization status level of each tracked satellite signal, the original satellite signal time is calculated using the frame count, bit count, intra-bit count, chip count, and chip phase time obtained from the tracking. , is represented as: ; Among them, the frame count, bit count, and intra-bit count are assigned values ​​according to the synchronization state level reached by each tracked satellite signal, and are 0 when the corresponding synchronization state level is not reached; Using local baseline time and the original satellite signal time Calculate satellite pseudorange duration ; and calculate exist The internal module serves as the smallest unit of internal pseudorange duration. ; use and the duration of pseudorange within the smallest unit The tracking satellite was calculated. The combined signal transmission time is ; Utilizing the time of satellite-to-ground distance Inversely, the tracking satellite was deduced. At local baseline time The signal transmission time is ; against and Construct millisecond integer fuzzy constraint pairs Make corrections to obtain the tracking satellite. Corrected signal transmission time.

[0040] The process of constructing the millisecond integer fuzzyness constraint is as follows: Due to local baseline time There is an error compared to the actual time (not exceeding) Within this time error, according to Conditions (converted to time units, i.e. ±0.25×) It can be deduced from (ms) that, without considering local clock differences, the local baseline time is used. The error between the proposed combined signal transmission time and the actual signal transmission time should be within ±0.25× Within ms, that is: .

[0041] However, in reality, the transmission time of the combined signal... The middle part includes the local user clock difference In order to eliminate user clock skew By finding a reference star Subtraction can reduce common user clock differences. Eliminating this, we can deduce that the millisecond integer ambiguity constraint is represented as: ; in, For reference star The signal transmission time deduced from the satellite-to-ground distance between the navigation receiver and the ground station. As a reference star The combined signal transmission time.

[0042] When the inequality for the millisecond integer fuzziness constraint does not hold, by... Addition and subtraction The modification makes the inequality true; After correction, the corrected signal transmission time is obtained. The formula is as follows: .

[0043] Finally, based on tracking satellites Correction signal transmission time The pseudorange residual equation is constructed and a fast AGPS iterative solution is performed; the AGPS iterative solution process uses least squares iterative solution; the pseudorange residual equation is expressed as: ; in For pseudo-distance residuals, To track satellites Corrected pseudorange, For local latching time, For ionospheric delay (calculated by the ionospheric delay model). For tropospheric delay (calculated by the tropospheric delay model). This is the satellite clock bias (calculated from ephemeris). To track satellites exist Satellite position at any given time It is the difference between the current time and the actual time. The above time, As the final, smallest reliable unit of time, This represents the three-dimensional position of the navigation receiver in the ECEF coordinate system. For the local clock bias of the navigation receiver, To track satellites The measurement error; the unknowns in the pseudorange residual equation are , and (There are five in total), and the rest of the parameters are known.

[0044] During the least squares iterative solution, each iteration... The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ; in, For the number of iterations, The total number of iterations. and The first The second iteration and the first The next iteration And it is zero in the first iteration; and respectively tracking satellites In the The second iteration and the first The corrected signal transmission time for the next iteration Initial value ; For each iteration The sum of.

[0045] The iteration and iteration exit process is consistent with the traditional least squares solution, and will not be described again in this application. Based on the above formula, iteration can begin after tracking 5 or more satellites, yielding the desired result. , and The final iterative solution outputs the total clock bias of the navigation receiver as follows: .

[0046] Step 4: Determine whether the normal positioning or adaptive time-free positioning was successful. If so, perform local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and store the relevant information for this positioning. Otherwise, wait for the positioning of the next epoch.

[0047] The positioning information includes GNSS ephemeris data, positioning time, and approximate location.

[0048] In summary, the aforementioned adaptive rapid positioning method based on GNSS synchronization status requires no RTC or battery support, nor does it rely on external networks. It achieves rapid positioning solely using the previous positioning information stored in the navigation receiver, combined with observations of the tracking satellite signals and the synchronization status level. This perfectly suits the application requirements of battery-less, long-term storage devices. Even when the tracking satellite signals have not fully completed message time synchronization, this method can utilize partial synchronization status information (such as bit synchronization or frame synchronization) to initiate the adaptive time-free positioning process in advance, completing position calculation before the complete message is received. The initial positioning time is significantly better than traditional positioning methods. Even in the worst-case scenario with no synchronization information, the positioning time does not exceed that of traditional schemes, resulting in a significant improvement in overall positioning efficiency. Simultaneously, this method dynamically determines the minimum reliable time unit and time search interval based on the synchronization status level of the tracked satellite signal, and determines a relatively accurate local reference time as the local baseline time. It also corrects the signal transmission time using the minimum reliable time unit, ensuring the convergence of the pseudorange residual equation and avoiding AGPS loops due to excessive time errors. This significantly improves the system's tolerance to time errors (extending from 187 seconds to over 2 hours). Regardless of the approximate size of the time error, this method can complete positioning using an adaptive time-free positioning process, ensuring stable and reliable receiver operation.

[0049] In one embodiment, such as Figure 3 As shown, an adaptive fast positioning system based on GNSS synchronization status is provided, including: The signal acquisition and tracking module is used to read the GNSS ephemeris data, approximate position and approximate time stored or injected by the navigation receiver in the previous positioning, and after performing local time pre-calibration using the approximate time, it enters the GNSS satellite signal acquisition and tracking stage, and simultaneously latches the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization and completed message time synchronization. The normal positioning module is used to indicate that the navigation receiver has acquired the signal transmission time of all tracked satellites when all the tracking satellite signals have completed message time synchronization. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data. The adaptive time-free positioning module is used to enter the adaptive time-free positioning process when the tracking satellite signal has not been fully synchronized with the message time. This includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracking satellite signal, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracking satellite signal, and after correcting the signal transmission time of the tracking satellite based on the local baseline time and the minimum reliable time unit, performing fast AGPS iterative calculation. The post-positioning processing module is used to determine whether normal positioning or adaptive time-free positioning is successful. If so, it performs local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and stores the relevant information of this positioning. Otherwise, it waits for the positioning of the next epoch.

[0050] Specific limitations regarding the adaptive rapid positioning system based on GNSS synchronization status can be found in the limitations of the adaptive rapid positioning method based on GNSS synchronization status described above, and will not be repeated here. Each module in the aforementioned adaptive rapid positioning system based on GNSS synchronization status can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0052] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application.

Claims

1. An adaptive fast positioning method based on GNSS synchronization status, characterized in that, The method includes: The system reads the GNSS ephemeris data, approximate location, and approximate time stored or injected by the navigation receiver during the last positioning. After performing local time pre-calibration using the approximate time, it enters the GNSS satellite signal acquisition and tracking stage and simultaneously latches the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization, and completed message time synchronization. If all the tracking satellite signals have completed message time synchronization, it means that the navigation receiver has acquired the signal transmission time of all the tracking satellites. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data. Otherwise, the adaptive time-free positioning process is initiated, which includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracked satellite signal, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracked satellite signal, and then performing fast AGPS iterative solution after correcting the signal transmission time of the tracked satellite based on the local baseline time and the minimum reliable time unit. Determine whether normal positioning or adaptive time-free positioning was successful. If so, perform local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and store the relevant information for this positioning. Otherwise, wait for positioning in the next epoch. Among these, the minimum reliable time unit and time search interval are dynamically determined based on the synchronization status level of the tracked satellite signals, including: Based on the synchronization status level of each tracking satellite signal, the corresponding minimum reliable time unit is obtained, and the minimum reliable time unit of the tracking satellite signal with the lowest synchronization status level among all tracking satellites is selected as the final minimum reliable time unit. The possible values ​​of ; Maximum radial velocity combined with tracking satellite signals , with the speed of light Determine the time search interval , is represented as: ； Among these steps, based on the synchronization status level and time search interval of the tracked satellite signals, a relatively accurate local reference time is determined as the local baseline time, including: Determine whether at least one tracking satellite signal has reached the synchronization status level of completed message time synchronization; If so, directly obtain the satellite signal transmission time from the message of the tracked satellite signal that has completed message time synchronization, and round up to the nearest second to obtain the local baseline time. ; If not, consider the time search interval. Retrieve the current local latch time Plus As local baseline time ,Right now .

2. The adaptive fast positioning method based on GNSS synchronization status according to claim 1, characterized in that, The system reads the GNSS ephemeris data, approximate position, and approximate time stored or injected by the navigation receiver during the previous positioning. After performing local time pre-calibration using the approximate time, it enters the GNSS satellite signal acquisition and tracking phase, and simultaneously latches the observations and synchronization status levels of the tracked satellite signals, including: After the navigation receiver is powered on, it completes hardware self-test and software initialization, and reads the GNSS ephemeris data, approximate time and approximate position stored or injected in the Flash memory. After using the approximate time to pre-calibrate the local time, it enters the GNSS satellite signal acquisition and tracking stage. During the GNSS satellite signal acquisition and tracking phase, signal acquisition is first performed according to the preset GNSS satellite list. After signal acquisition is completed, the system enters the tracking and synchronization state, and the carrier phase and pseudorange observations of the GNSS satellite signals are tracked in real time. Bit synchronization, frame synchronization and message time processing are performed simultaneously until the number of effectively tracked satellites is greater than or equal to 5. At the same time, the observations and synchronization status levels of all tracked satellite signals are latched.

3. The adaptive fast positioning method based on GNSS synchronization status according to claim 2, characterized in that, Based on observations of tracked satellite signals and GNSS ephemeris data, the navigation receiver performs normal positioning, including: Based on the observations of the tracking satellite signals and GNSS ephemeris data, the satellite position is calculated and the least squares positioning solution is directly performed to obtain the three-dimensional position and total clock error of the navigation receiver in the ECEF coordinate system.

4. The adaptive fast positioning method based on GNSS synchronization status according to claim 1, characterized in that, Based on the synchronization status level of each tracked satellite signal, the corresponding minimum reliable time unit is determined, including: The value of the minimum reliable time unit for tracking satellite signals increases as the synchronization status level increases.

5. The adaptive fast positioning method based on GNSS synchronization status according to claim 1, characterized in that, The signal transmission time of the tracking satellite is corrected based on the local baseline time and the minimum reliable time unit, including: After calculating the satellite positions of each tracked satellite using the GNSS ephemeris data stored or injected in the previous positioning by the navigation receiver, the satellite-to-ground distance between the satellite positions and the approximate positions stored or injected in the previous positioning is calculated. The satellite-to-ground distance is then divided by the speed of light. The time it takes to get the distance between the satellite and the Earth. and to Take the final smallest reliable unit of time. Multiples of integers, to obtain Constant multiples of the distance between Earth and space ; where superscript Indicates the tracking satellite index; Based on the synchronization status level of each tracked satellite signal, the original satellite signal time is calculated using the frame count, bit count, intra-bit count, chip count, and chip phase time obtained from the tracking. , is represented as: ； Among them, the frame count, bit count, and intra-bit count are assigned values ​​according to the synchronization state level reached by each tracked satellite signal, and are 0 when the corresponding synchronization state level is not reached; Using local baseline time and the original satellite signal time Calculate satellite pseudorange duration ; and calculate exist The internal module serves as the smallest unit of internal pseudorange duration. ; use and the duration of pseudorange within the smallest unit The tracking satellite was calculated. The combined signal transmission time is ; Utilizing the time of satellite-to-ground distance Inversely, the tracking satellite was deduced. At local baseline time The signal transmission time is ; against and Construct millisecond integer fuzzy constraint pairs Make corrections to obtain the tracking satellite. Corrected signal transmission time.

6. The adaptive fast positioning method based on GNSS synchronization status according to claim 5, characterized in that, Constructing millisecond integer fuzzy constraint pairs Make corrections to obtain the tracking satellite. The corrected signal transmission time includes: The millisecond integer fuzziness constraint is expressed as follows: ； Among them, superscript As the reference star, For reference star The signal transmission time deduced from the satellite-to-ground distance between the navigation receiver and the ground station. As a reference star The combined signal transmission time; When the inequality for the millisecond integer fuzziness constraint does not hold, by... Addition and subtraction The modification makes the inequality true; After correction, the corrected signal transmission time is obtained. The formula is as follows: 。 7. The adaptive fast positioning method based on GNSS synchronization status according to claim 6, characterized in that, After correcting the signal transmission time of the tracking satellites based on the local baseline time and the minimum reliable time unit, a fast AGPS iterative solution is performed, including: Based on tracking satellites Correction signal transmission time The pseudorange residual equation is constructed and a fast AGPS iterative solution is performed; the AGPS iterative solution process uses least squares iterative solution; the pseudorange residual equation is expressed as: ； in For pseudo-distance residuals, To track satellites Corrected pseudorange, For local latching time, For ionospheric delay, For tropospheric delay, For satellite clock bias, To track satellites exist Satellite position at any given time It is the difference between the current time and the actual time. The above time, As the final, smallest reliable unit of time, This represents the three-dimensional position of the navigation receiver in the ECEF coordinate system. For the local clock bias of the navigation receiver, To track satellites The measurement error; the unknowns in the pseudorange residual equation are , and All other parameters are known values; During the least squares iterative solution, each iteration... The correction signal transmission time needs to be updated for the next iteration, as expressed by the formula: ； in, For the number of iterations, The total number of iterations. and The first The second iteration and the first The next iteration And it is zero in the first iteration; and respectively tracking satellites In the The second iteration and the first The corrected signal transmission time for the next iteration Initial value ; For each iteration The sum of; The final iterative solution outputs the total clock bias of the navigation receiver. .

8. An adaptive rapid positioning system based on GNSS synchronization status, characterized in that, The system includes: The signal acquisition and tracking module is used to read the GNSS ephemeris data, approximate position and approximate time stored or injected by the navigation receiver in the previous positioning, and after performing local time pre-calibration using the approximate time, it enters the GNSS satellite signal acquisition and tracking stage, and simultaneously latches the observations and synchronization status levels of the tracked satellite signals. The synchronization status levels are sorted from low to high as follows: incomplete bit synchronization, completed bit synchronization, completed frame synchronization and completed message time synchronization. The normal positioning module is used to indicate that the navigation receiver has acquired the signal transmission time of all tracked satellites when all the tracking satellite signals have completed message time synchronization. At this time, the navigation receiver can directly perform normal positioning based on the observation of the tracking satellite signals and GNSS ephemeris data. The adaptive time-free positioning module is used to enter the adaptive time-free positioning process when the tracking satellite signal has not been fully synchronized with the message time. This includes first dynamically determining the minimum reliable time unit and time search interval based on the synchronization status level of the tracking satellite signal, then determining a relatively accurate local reference time as the local baseline time based on the synchronization status level and time search interval of the tracking satellite signal, and after correcting the signal transmission time of the tracking satellite based on the local baseline time and the minimum reliable time unit, performing fast AGPS iterative calculation. The post-positioning processing module is used to determine whether normal positioning or adaptive time-free positioning is successful. If so, it performs local time synchronization again based on the total clock difference of the navigation receiver obtained from the positioning calculation and stores the relevant information of this positioning. Otherwise, it waits for the positioning of the next epoch. Among these, the minimum reliable time unit and time search interval are dynamically determined based on the synchronization status level of the tracked satellite signals, including: Based on the synchronization status level of each tracking satellite signal, the corresponding minimum reliable time unit is obtained, and the minimum reliable time unit of the tracking satellite signal with the lowest synchronization status level among all tracking satellites is selected as the final minimum reliable time unit. The possible values ​​of ; Maximum radial velocity combined with tracking satellite signals , with the speed of light Determine the time search interval , is represented as: ； Among these steps, based on the synchronization status level and time search interval of the tracked satellite signals, a relatively accurate local reference time is determined as the local baseline time, including: Determine whether at least one tracking satellite signal has reached the synchronization status level of completed message time synchronization; If so, directly obtain the satellite signal transmission time from the message of the tracked satellite signal that has completed message time synchronization, and round up to the nearest second to obtain the local baseline time. ; If not, consider the time search interval. Retrieve the current local latch time Plus As local baseline time ,Right now .

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