Method for fast repositioning after long time loss of lock of satellite navigation signal

Abstract

After the satellite is recaptured after losing lock, if the losing lock time is less than a losing lock time threshold and the satellite ephemeris is still within a valid period, a satellite navigation signal long-time losing lock fast repositioning method of the application is used for repositioning; the method comprises: dividing a satellite signal transmission time into a bit time above part and a bit time below part; when losing lock, continuously recursively calculating the transmission time locally; when the signal is recaptured and bit synchronization is reached, using a pseudo code period counter to obtain the number of pseudo code periods in the bit time; using a pseudo code and a carrier tracking loop to obtain the value of the real transmission time in a single pseudo code period, which together form the bit time below part of the real transmission time; if there is a bit crossing phenomenon between the recursive transmission time value and the real transmission time value, using the formed bit time below part of the real transmission time to correct the bit time above part in the recursive transmission time value; reconstructing the real transmission time, obtaining the relative pseudo range, and using the relative pseudo range to replace the real pseudo range to perform positioning.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation technology, specifically relating to a method for a receiver to quickly participate in positioning after a satellite navigation signal has been lost for an extended period of time and then reacquired. Background Technology

[0002] In the satellite navigation and positioning process, the receiver must sequentially undergo signal acquisition, carrier tracking, pseudo-code tracking, bit synchronization, subframe synchronization, and ephemeris information parsing and extraction to obtain complete pseudorange information and calculate the correct satellite position before positioning can be completed. Typically, signal acquisition, carrier / pseudo-code tracking, and bit synchronization can be completed within 1 second, while subframe synchronization takes at least 6 seconds. When the satellite signal is lost and reacquired, since the ephemeris information has been saved, it does not need to be parsed again. Following the conventional process, the repositioning time should be no less than 7 seconds. However, in many current application scenarios, the repositioning time is far less than this theoretical value, necessitating modifications to the positioning process to achieve rapid positioning. Furthermore, the loss-of-lock duration of many existing methods is typically short, only tens of seconds. After exceeding a threshold, the conventional positioning process restarts, resulting in a longer processing time. Therefore, how to achieve rapid repositioning after an extremely long loss-of-lock period has become a problem that requires solutions from those skilled in the art. Summary of the Invention

[0003] The purpose of this invention is to provide a method for rapid relocation after a long period of satellite navigation signal loss, thereby solving the problem of rapid relocation after a satellite signal is lost for an extended period and then reacquired.

[0004] To achieve the above objectives, this invention provides a method for rapid repositioning after a prolonged loss of satellite navigation signal lock. A lock-out time threshold is set. After satellite re-acquisition, if the lock-out time is less than the threshold and the satellite ephemeris is still valid, this method is used for repositioning. The method includes: dividing the satellite signal's transmission time into a portion above and below the bit-time; continuously recalculating the transmission time locally when the signal is lost; after the signal is re-acquisition and bit synchronization is achieved, obtaining the number of pseudo-code cycles within the bit-time using a pseudo-code cycle counter; obtaining the value of the true transmission time within a single pseudo-code cycle using a pseudo-code tracking loop and a carrier tracking loop, which together form the portion below the bit-time of the true transmission time; if there is a bit-crossing phenomenon between the recalculated transmission time value and the true transmission time value, using the portion below the bit-time of the true transmission time to correct the portion above the bit-time in the recalculated transmission time value; reconstructing the true transmission time, obtaining the relative pseudorange, and using the relative pseudorange instead of the true pseudorange for positioning.

[0005] The above-mentioned method for rapid repositioning after prolonged loss of satellite navigation signal lock involves setting the lock-out time threshold as follows: after the lock-out, the recursive value of the satellite signal transmission time should not have bit period ambiguity, meaning that the error between the recursive value of the transmission time and the actual value of the transmission time should not exceed half of a single bit period of the navigation message.

[0006] The aforementioned rapid repositioning method after prolonged loss of satellite navigation signal relies on the constraint that the receiver's signal is only blocked when it is moving on the Earth's surface. Under this constraint, the scenario where the distance between the satellite and the receiver changes most significantly within the same timeframe occurs when, at the time of loss of lock, the satellite is exactly at the horizon in the receiver's field of view and moving towards the zenith; and at the time of reacquisition, the receiver moves along the line where the satellite's orbital plane intersects the Earth's surface towards the satellite's ascending node. The loss-of-lock time threshold is calculated as follows:

[0007]

[0008] Where d0 is the distance between the satellite and the receiver when the lock is lost; R e R is the Earth's radius; s d1 is the satellite's orbital altitude; d1 is the distance between the satellite and the receiver at reacquisition; θ is the angle between the line connecting the receiver to the Earth's center and the line connecting the satellite to the Earth's center; v u T represents the maximum speed of the receiver. d This is the unlocking time threshold; ω s The angular velocity of a satellite orbiting the Earth when its orbit is simplified to a circle; T b δ is the length of a single bit cycle in the navigation message; c is the speed of light; δ is the receiver clock drift.

[0009] The above-mentioned rapid repositioning method after prolonged loss of satellite navigation signal lock involves recording the launch time t of the satellite's last participation in positioning when the signal lock is lost. sr The system uses a receiver crystal oscillator to continuously advance the transmission time: during signal loss of lock, each time the crystal oscillator count reaches the positioning calculation period T, it is reset to 0 and continues counting. Simultaneously, t is... sr =t sr +T, maintain the recursive launch time.

[0010] The above-mentioned rapid relocation method for satellite navigation signals after prolonged loss of lock involves determining the bit synchronization status of the satellite after reacquisition. For GPS satellites, this involves detecting the flip edge of the cumulative value in two adjacent milliseconds (ms). For BeiDou MEO / IGSO satellites, this involves detecting the matching of the cumulative value with the NH code every 20 ms. Using a histogram method, when the cumulative value flips or the NH code matches, the count at that histogram is incremented by 1. The upper limit for synchronization detection is set to 18, and the lower limit is set to 1. If the count of a single histogram exceeds the upper limit and the counts of other histograms are all less than the lower limit, then bit synchronization is determined; otherwise, it is considered asynchronous.

[0011] The above-mentioned rapid relocation method after long-term loss of satellite navigation signal lock involves setting a pseudo-code cycle counter ca in the receiver pseudo-code tracking loop, with a range of 0 to 19. After tracking a complete pseudo-code cycle, a +1 operation is performed. The ca value represents the number of pseudo-code cycles that the tracked satellite has received in the current bit time. When the bits are synchronized, the ca value is initialized and marked as valid.

[0012] The above-mentioned rapid relocation method for satellite navigation signals after prolonged loss of lock-in, wherein, for a satellite that has been reacquired after loss of lock-in, when bit synchronization has been achieved but frame synchronization has not yet been achieved, the following part of the bit time of the satellite's actual launch time is obtained: Where p is the pseudo-code phase obtained from the carrier tracking loop after carrier smoothing, and T c The number of chips in a complete pseudocode cycle.

[0013] The above-mentioned method for rapid relocation after prolonged loss of satellite navigation signal acquisition includes the following part: The part above is used to obtain the bit value of the recursive value of the recapture satellite launch time after the loss of signal acquisition. Where floor represents the floor operation, t sr T is the recursive value for the launch time. b The length of a single bit cycle in the navigation message; the bits used to obtain the recursive value of the satellite launch time are as follows: If there is a bit jump between the lower part of the bit time in the recursive value of the transmission time and the lower part of the bit time in the actual value of the transmission time, then the upper part of the bit time in the recursive value of the transmission time will be corrected as follows:

[0014]

[0015] The aforementioned method for rapid relocation after prolonged loss of satellite navigation signal lock involves reconstructing the actual launch time of the reacquired satellite after the lock loss.

[0016] The above-mentioned rapid repositioning method after prolonged loss of satellite navigation signal involves solving the following set of relative pseudorange positioning equations to achieve positioning:

[0017]

[0018] Where, ρ i Let be the relative pseudorange of the i-th satellite; c be the speed of light; M be the relative pseudorange of the i-th satellite. i Let be the sum of the group delay, transmit clock error, ionospheric delay, tropospheric delay, satellite position residual, ionospheric and tropospheric model residuals, transmit clock error corrected residuals, and receiver internal noise for the i-th satellite. Let x be the launch time and coordinates of the i-th satellite; u ,y u ,zu () represents the local coordinates to be solved; Let be the launch time of the i-th satellite, obtained through reconstruction, where i = 1, 2, ..., n, and n is the total number of satellites. Let be the integer part of the launch time of the i-th satellite. The fractional part of the launch time of the i-th satellite; taking the first satellite with a precise launch time as the benchmark, if the integer part of the launch times of other satellites is... Integer part of the launch time of the reference satellite If there is a 1-second difference, the decimal part of the launch times of other satellites will be added to or subtracted by 1 second accordingly to eliminate the second difference between the launch times of different satellites and to ensure...

[0019] Compared with the prior art, the beneficial technical effects of the present invention are:

[0020] (1) This invention achieves rapid positioning after signal loss and reacquisition for an extremely long time. The loss time is more than half an hour, which is far longer than the tens of seconds of existing methods.

[0021] (2) The present invention uses relative pseudorange instead of real pseudorange for positioning, which can ignore the maintenance of the receiving time and reduce the complexity of pseudorange calculation after reacquisition.

[0022] (3) By recursively, correcting and reconstructing the transmission time, the present invention omits the frame synchronization link, and can usually locate within 1 second, which greatly shortens the time required for positioning. Attached Figure Description

[0023] The method for rapid relocation after prolonged loss of satellite navigation signal lock according to the present invention is given by the following embodiments and figures.

[0024] Figure 1 This is a schematic diagram illustrating the principle of calculating the unlocking time threshold in this invention.

[0025] Figure 2 This is a flowchart of the rapid relocation method for satellite navigation signals after a long period of signal loss, as described in this invention. Detailed Implementation

[0026] The following will combine Figures 1-2 The rapid relocation method for satellite navigation signal loss after a long period of time is described in further detail below.

[0027] Set a lockout time threshold. After a lockout and reacquisition, check the signal lockout time. If the lockout time is less than the lockout time threshold and the satellite's (referring to the satellite that reacquired the target after a lockout) ephemeris is still valid, then use this method for repositioning. Otherwise, proceed with the conventional positioning process.

[0028] The idea behind setting the unlock time threshold is: after the lock is lost, there should be no bit period ambiguity in the recursive value of the satellite signal transmission time, that is, the error between the recursive value of the transmission time and the actual value of the transmission time should not exceed half of a single bit period of the navigation message.

[0029] The error between the recursive value and the actual value of the launch time is caused by three factors: 1) the satellite's motion around the Earth; 2) the receiver's own motion; the above two motions together cause the distance between the satellite and the receiver to change, resulting in a corresponding difference between the recursive value and the actual value; 3) the clock drift of the receiver's crystal oscillator causes the recursive value to drift.

[0030] Following this line of thought, the receiver's signal is only blocked when it moves across the Earth's surface. Under this constraint, the situation where the distance between the satellite and the receiver changes most significantly within the same time frame occurs: At the moment of loss of lock, the satellite is exactly at the horizon in the receiver's field of view and moving towards the zenith; at the moment of reacquisition, the receiver moves along the line where the satellite's orbital plane intersects the Earth's surface towards the satellite's ascending node. Figure 1 The unlocking time threshold is calculated as follows:

[0031]

[0032] Where d0 is the distance between the satellite and the receiver when the lock is lost; R e R is the Earth's radius; s d1 is the satellite's orbital altitude; d1 is the distance between the satellite and the receiver at reacquisition; θ is the angle between the line connecting the receiver to the Earth's center and the line connecting the satellite to the Earth's center; v u T represents the maximum speed of the receiver. d This is the unlocking time threshold; ω s The angular velocity of a satellite orbiting the Earth when its orbit is simplified to a circle; T b δ is the length of a single bit cycle in the navigation message (i.e., 20ms); c is the speed of light; δ is the receiver clock drift.

[0033] The present invention provides a method for rapid repositioning of satellite navigation signals after prolonged signal loss. The method divides the satellite signal transmission time into a portion above the bit time and a portion below the bit time. When the signal is lost, the transmission time is continuously recursively calculated locally. After the signal is reacquired and bit synchronization is achieved, the number of pseudo-code cycles within the bit time is obtained using a pseudo-code cycle counter. The true transmission time within a single pseudo-code cycle is obtained using a pseudo-code tracking loop and a carrier tracking loop, which together form the portion below the bit time of the true transmission time. If there is a bit-crossing phenomenon between the recursed transmission time value and the true transmission time value, the portion above the bit time in the recursed transmission time value is corrected using the portion below the bit time of the true transmission time. The true transmission time is reconstructed. After obtaining the relative pseudorange, positioning is performed.

[0034] This invention uses relative pseudorange instead of true pseudorange in positioning calculation. After signal loss, there is no need to focus on maintaining the accuracy of local reception time. The relative pseudorange can be obtained by reconstructing the transmission time of the satellite signal, thus reducing the complexity of pseudorange calculation after reacquisition.

[0035] In the conventional positioning process, the pseudorange of each satellite can be expressed as:

[0036]

[0037] Among them, t R t represents the time of satellite signal reception. s The time of satellite signal transmission; (x u ,y u ,z u (x) represents the local coordinates to be solved (i.e., the receiver coordinates to be solved); (x) represents the coordinates to be solved. s ,y s ,z s ) represents the satellite coordinates at the time the satellite signal was transmitted; T G Group delay; δt s For the transmission clock bias; δt R T represents the receiver clock error to be solved. iono With T trno These are the ionospheric delay and the tropospheric delay, respectively; n r It is the sum of satellite position residual, residual after transmission clock error correction, residual of ionospheric and tropospheric models, and receiver internal noise.

[0038] From the pseudorange formula (i.e., formula (2)), the positioning equations can be expressed as:

[0039]

[0040] in, Let be the satellite signal transmission time of the i-th satellite, where i = 1, 2, ..., n, and n is the total number of satellites; M represents the satellite coordinates at the time the i-th satellite transmitted its signal; i The group delay T of the i-th satellite G , transmission clock bias δt s Ionospheric delay T iono tropospheric delay T trno and n r The sum; the right side of the positioning equations represents the actual distance between each satellite and the receiver, although it includes unknowns (x). u ,y u ,z u However, the specific value is uniquely determined; left side With M i All are known terms; tR With δt R Treating the whole as an unknown, even if t is changed R or δt R The actual receiving time t r =t R -δt R It remains the only certainty.

[0041] The launch time of each satellite is divided into integer and fractional parts, measured in seconds:

[0042]

[0043] in, The integer part of the launch time of the i-th satellite; It represents the fractional part of the launch time of the i-th satellite.

[0044] Based on the first satellite whose precise launch time is obtained, if the integer part of the launch time of other satellites is... Integer part of the launch time of the reference satellite The 1-second difference indicates that the launch times of these two satellites spanned a full second. By adding or subtracting 1 second from the decimal part of the launch times of other satellites, the potential second-spanning differences between launch times can be eliminated, and... Ignore the receiving time and directly use Formula (3) can then be rewritten in the following form:

[0045]

[0046] Formula (5) is defined as the relative pseudorange positioning equation set, as shown in Formula (5), where the relative pseudorange ρ of each satellite is... i The receiving time t is no longer included. R The relative pseudorange value depends only on the satellite's launch time. Get Then the system of equations can be solved to complete the location calculation.

[0047] By applying the relative pseudorange positioning method described above, after the satellite signal is lost and reacquired, there is no need to consider the maintenance accuracy of the local reception time; it is only necessary to reconstruct the transmission time of each satellite.

[0048] To determine the bit synchronization status of a satellite after reacquisition, for GPS satellites, the flip edge of the cumulative value in two adjacent milliseconds (ms) is detected; for BeiDou MEO / IGSO satellites, the matching status of the cumulative value every 20ms with the NH code is detected. Specifically, the histogram method is used. When the cumulative value flips or the NH code matches, the count at that histogram is incremented by 1. The upper limit of the cumulative detection is set to 18, and the lower limit is set to 1. If the count of a single histogram exceeds the upper limit and the counts of other histograms are all less than the lower limit, then the bit is considered synchronized; otherwise, it is considered asynchronous.

[0049] A pseudocode cycle counter ca is set in the receiver pseudocode tracking loop, with a range of 0 to 19. After tracking a complete pseudocode cycle, an increment operation is performed. The ca value represents the number of pseudocode cycles that the tracked satellite has received in the current bit time. When the bits are synchronized, the ca value is initialized and marked as valid.

[0050] When the signal lock is lost, record the launch time t when the satellite last participated in positioning. sr The system uses a receiver crystal oscillator to continuously advance the transmission time: during signal loss of lock, each time the crystal oscillator count reaches the positioning calculation period T, it is reset to 0 and continues counting. Simultaneously, t is... sr =t sr +T, maintain the recursive launch time. t sr This is a recursive value for the launch time.

[0051] For a satellite that has been recaptured after losing lock-on, when bit synchronization has been achieved but frame synchronization has not yet been achieved, the following part of the bit sequence of the satellite's actual launch time is obtained: Where p is the pseudo-code phase obtained from the carrier tracking loop after carrier smoothing, and T c The number of chips in a complete pseudocode cycle;

[0052] The above part is used to obtain the bits of the recursive value of the satellite launch time: Where floor represents the floor operation;

[0053] The following part is used to obtain the bits of the recursive value of the satellite launch time:

[0054] If there is a bit jump between the lower part of the bit time in the recursive value of the transmission time and the lower part of the bit time in the actual value of the transmission time, then the upper part of the bit time in the recursive value of the transmission time will be corrected, as follows:

[0055]

[0056] The actual launch time of the satellite was reconstructed:

[0057] Using the reconstructed actual launch time, the positioning solution is calculated according to formula (5).

[0058] For BeiDou GEO satellites, since their frame synchronization time is much shorter than that of other types of satellites, this method is unnecessary, and conventional positioning procedures can be used directly. This invention is applicable to GPS satellites, BeiDou MEO satellites, and BeiDou IGSO satellites.

[0059] Example:

[0060] Taking BeiDou MEO satellites as an example, the first step is to determine the time threshold for loss of lock:

[0061] Let the satellite orbital altitude R s Approximately 21,528 km, Earth's radius R e The distance is approximately 6371 km. According to formula (1), we have:

[0062] d0 = 27161822m;

[0063]

[0064] Assume the receiver's maximum speed is v u The speed is 100 m / s. The orbital speed of BeiDou MEO satellites around the Earth is approximately 12 hours per revolution, i.e., ω s =0.00833333° / s, θ=(76.79949569-0.00923266T d )°;

[0065] The receiver clock drift δ typically does not exceed 0.5 ppm, and the speed of light c = 299,794,258 m / s and the navigation message bit period T b Substituting 0.02s into the system of equations in formula (1), and after simplification, we obtain T. d Equations with variables:

[0066] 22470T d 2 +7244336620T d

[0067] +355489058000000cos(76.79949569-0.00923266T d )

[0068] -235049875445596=0

[0069] The equation has no analytical solution, so the bisection method is used to solve it. Assuming the accuracy of the closed interval is 2s, the final result is T. d =2621s;

[0070] Assuming the receiver is currently blocked and a loss of lock occurs, taking a BeiDou MEO satellite as an example, the time of loss of lock is 432422.524581327s. The recursive value t for the transmission time is initialized with this value. sr If the receiver observation sampling period is 0.1s, then t is set for each sampling. sr =t sr +0.1, to maintain the recursion of the satellite launch time;

[0071] Assuming this satellite is the first to be reacquired by the receiver and quickly achieve bit synchronization, its recursive transmission time t is... sr The duration of the lockout is 433546.724581327s, and the duration of the lockout can be roughly estimated as 1124s, which is less than the threshold of 2621s. Figure 2 The positioning process does not require waiting for subframe synchronization; it directly reconstructs the actual launch time according to the present invention.

[0072] Assume that the number of integer cycles of pseudocode received in a single bit read from the pseudocode counter is 16, and the pseudocode phase p after carrier smoothing read from the carrier tracking loop is 3518.425.

[0073] Number of chips per pseudo-code cycle for BeiDou satellites (T) c The value is 10230. When obtaining the bit information for the satellite's launch time, the following portion is used:

[0074] The above part is used to obtain the bits of the recursive value of the satellite launch time:

[0075]

[0076] The following part is used to obtain the bits of the recursive value of the satellite launch time:

[0077]

[0078] Check if there is a bit-cycle jump between the recursive value and the actual value at the transmission time:

[0079] The presence of a bit-crossing period indicates that the satellite and receiver moved towards each other during the period of loss of lock, therefore... Make corrections, adjust forward by 20ms:

[0080]

[0081] The actual launch time of the satellite was reconstructed:

[0082]

[0083] Determine if the ephemeris is still valid. If invalid, wait for subframe synchronization to extract the ephemeris; if valid, the relative pseudorange can be directly assembled for positioning according to the procedure of this invention.

[0084] Assuming the currently stored ephemeris of this satellite has a reference time t oe The ephemeris is 432000s, and the effective time is 433546-432000=1546s. The ephemeris validity period is usually 2 hours, so its ephemeris is still within the validity period. It can be used to directly form a relative pseudorange for positioning according to the process of this invention.

[0085] Based on the satellite's launch time, the receiving time... The relative pseudo-distance ρ = c(t) R -t s )=c(433546-433546-0.716343932);

[0086] When the number of satellites with the actual launch time is greater than 4, the positioning result can be calculated using formula (5).

Claims

1. A method for rapid repositioning after prolonged loss of satellite navigation signal lock, characterized in that, Set a time threshold for loss of lock. If the time of loss of lock is less than the time threshold and the satellite ephemeris is still valid after the satellite loses lock and is re-acquired, this method shall be used for relocation. This method includes: The transmission time of satellite signals is divided into the portion above bit time and the portion below bit time; When the signal is lost, the transmission time is continuously recursively calculated locally. Once the signal is reacquired and bit synchronization is achieved, the number of pseudo-code cycles within the bit time is obtained using the pseudo-code cycle counter; the value of the actual transmission time within a single pseudo-code cycle is obtained using the pseudo-code tracking loop and the carrier tracking loop, which together constitute the following part of the bit time of the actual transmission time; If there is a bit jump between the recursive value of the transmission time and the actual value of the transmission time, the lower part of the bit time in the recursive value of the transmission time is used to correct the upper part of the bit time in the recursive value of the transmission time. Reconstruct the actual launch time, obtain the relative pseudorange, and use the relative pseudorange to replace the actual pseudorange for positioning. For satellites that have reacquired after losing lock-on, when bit synchronization has been achieved but frame synchronization has not yet been achieved, the following part of the bits representing the satellite's actual launch time is obtained: ,in, The pseudo-code phase obtained from the carrier tracking loop after carrier smoothing. The number of chips in a complete pseudocode cycle; The above part is used to obtain the bits of the recursive value of the satellite launch time after the loss of lock: ， in, This is a round-down operation. This is a recursive value for the launch time. The length of a single bit cycle in a navigation message; The following part is used to obtain the bits of the recursive value of the satellite launch time: ； If there is a bit jump between the lower part of the bit time in the recursive value of the transmission time and the lower part of the bit time in the actual value of the transmission time, then the upper part of the bit time in the recursive value of the transmission time will be corrected as follows: ； The actual launch time of the satellite after it was recaptured was reconstructed: .

2. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 1, characterized in that, The idea behind setting the unlock time threshold is: after the lock is lost, there should be no bit period ambiguity in the recursive value of the satellite signal transmission time, that is, the error between the recursive value of the transmission time and the actual value of the transmission time should not exceed half of a single bit period of the navigation message.

3. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 2, characterized in that, The receiver's signal is only blocked when it moves across the Earth's surface. Under this constraint, the situation where the distance between the satellite and the receiver changes the most within the same time period occurs when: at the moment of loss of lock, the satellite is exactly at the horizon in the receiver's field of view and moving towards the zenith; at the moment of reacquisition, the receiver moves along the line where the satellite's orbital plane intersects the Earth's surface towards the satellite's ascending node. The loss-of-lock time threshold is calculated as follows: （1） in, This represents the distance between the satellite and the receiver when the lock is lost. The radius of the Earth; This refers to the satellite's orbital altitude. This refers to the distance between the satellite and the receiver during recapture. The angle between the line connecting the receiver to the Earth's center and the line connecting the satellite to the Earth's center; This is the maximum speed of the receiver. This is the unlocking time threshold; The angular velocity of a satellite orbiting the Earth when its orbit is simplified to a circle; The length of a single bit cycle in a navigation message; The speed of light; This is due to receiver clock drift.

4. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 1, characterized in that, When signal lock is lost, record the launch time of the last time the satellite participated in positioning. The system continuously recursively calculates the transmission time using a receiver crystal oscillator: during signal loss of lock, the crystal oscillator count is reset to 0 after each time it reaches the positioning calculation period T, and the counting continues. Simultaneously, it makes... The launch time is maintained through recursion.

5. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 1, characterized in that, To determine the bit synchronization status of a satellite after reacquisition, for GPS satellites, the flip edge of the cumulative value in two adjacent milliseconds (ms) is detected; for BeiDou MEO / IGSO satellites, the matching status of the cumulative value every 20ms with the NH code is detected. Using the histogram method, when the cumulative value flips or the NH code matches, the count at that histogram is incremented by 1. The upper limit for synchronization detection is set to 18, and the lower limit is set to 1. If the count of a single histogram exceeds the upper limit and the counts of other histograms are all less than the lower limit, then the bit is considered synchronized; otherwise, it is considered asynchronous.

6. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 5, characterized in that, A pseudo-code period counter is set in the receiver pseudo-code tracking loop. The range is 0~19, and an +1 operation is performed after tracking a complete pseudocode cycle. The value represents the number of pseudo-code integer cycles that the tracked satellite has received in the current bit time; after bit synchronization, it will... The value is initialized and marked as valid.

7. The rapid repositioning method after prolonged loss of satellite navigation signal lock as described in claim 1, characterized in that, To complete the positioning, solve the following set of relative pseudorange positioning equations: in, For the first The relative pseudorange of the satellites; The speed of light; For the first The sum of the group delay of each satellite, the transmit clock error, the ionospheric delay, the tropospheric delay, the satellite position residual, the ionospheric and tropospheric model residuals, the residuals after transmit clock error correction, and the receiver internal noise. For the first Launch time and satellite coordinates of each satellite; The local coordinates to be solved; , For the first The launch times of the satellites were obtained through reconstruction. , The total number of satellites For the first The integer part of the launch time of each satellite. For the first The decimal part of the launch time of each satellite; Based on the first satellite whose precise launch time is obtained, if the integer part of the launch time of other satellites is... Integer part of the launch time of the reference satellite If there is a 1-second difference, the decimal part of the launch times of other satellites will be added to or subtracted by 1 second accordingly to eliminate the second difference between the launch times of different satellites and to ensure... = , .

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