A BDS / INS Integrated Navigation and Positioning Method Aided by a Ground-based Long-wave Time Service System

Abstract

The present invention relates to the field of navigation and positioning, and discloses a BDS / INS integrated navigation and positioning method assisted by a ground-based long-wave time service system, including: establishing a mobile experimental platform equipped with a BDS satellite receiver, an inertial navigation device, and a long-wave receiver in a time laboratory; using the ground-based mobile device on the mobile experimental platform to simultaneously receive BDS satellite signals and ground-based long-wave time service signals; monitoring the quality of BDS satellite signals and the number of visible satellites, and based on the monitoring results, selecting a target positioning mode to calculate the absolute position coordinates of the ground-based mobile device; using the absolute position coordinates as initial observation data for integrated navigation and positioning with the INS system, and using an error-state Kalman filter algorithm for integrated navigation and positioning calculation to obtain the final position information of the ground-based mobile device. This method improves the continuity and reliability of navigation and positioning in the case of anomalies or even failures in the BDS satellite system due to external influences.

Description

Technical Field

[0001] The present invention relates to the field of navigation and positioning, and relates to, but is not limited to, a BDS / INS integrated navigation and positioning method assisted by a ground-based long-wave time service system. Background Art

[0002] Global Navigation Satellite Systems (GNSS), represented by the Beidou Navigation Satellite System (BDS), are currently the most important technical means in the field of high-precision position and time services. The BDS system has many advantages such as low cost, high precision, global coverage, and non-accumulative errors, making it provide navigation, positioning, and time service for China's national defense and military and national production. However, due to the natural vulnerability and limitations of the technical characteristics of satellite navigation systems, their ground signals attenuate quickly and have poor signal penetration, and they cannot provide real-time and continuous positioning and time service for users in non-exposed spaces (indoors, tunnels, underground, etc.). Moreover, they are vulnerable to multipath and signal noise interference in complex scenarios such as cities with lush forests and numerous buildings. Therefore, it is necessary to introduce other navigation and positioning systems to assist in improving the availability and reliability of the BDS system. The Inertial Navigation System (INS), as an independent dead reckoning system, can continuously output the position, speed, and attitude information of the carrier without external information input. However, the INS system has the disadvantages of navigation error accumulation and poor long-term positioning accuracy. Therefore, existing integrated positioning systems mostly combine the BDS system with the INS system to achieve continuous positioning services for multi-scenario changes.

[0003] In current research on BDS / INS integrated navigation and positioning systems, the high-precision absolute position information obtained by solving the BDS system is mostly used as the prior value of the initial position of the INS system for filtering and solving. However, when the BDS satellite signal is lost for a long time due to external interference, the entire integrated navigation and positioning system will degrade into a single INS system, and the problem of positioning error accumulation over time still cannot be solved. Based on the above problems, it is necessary to improve the existing technical methods based on BDS / INS integrated navigation and positioning systems to avoid the defect of degraded navigation and positioning accuracy when the BDS satellite signal is interfered. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a BDS / INS integrated navigation and positioning method assisted by a ground-based long-wave time service system, which at least solves the defect problem of degraded navigation and positioning accuracy when the BDS satellite signal is interfered.

[0005] The technical solution of the embodiment of the present invention is specifically as follows:

[0006] An embodiment of the present invention provides a BDS / INS integrated navigation and positioning method assisted by a ground-based long-wave time service system, including:

[0007] Establish a mobile experimental platform equipped with a BDS satellite receiver, an inertial navigation device, and a long-wave receiver in a time laboratory; use the ground-based mobile device on the mobile experimental platform to simultaneously receive BDS satellite signals and ground-based long-wave time service signals; monitor the quality of BDS satellite signals and the number of visible satellites, and select a target positioning mode based on the monitoring results to calculate the absolute position coordinates of the ground-based mobile device; use the absolute position coordinates as initial observation data to perform integrated navigation and positioning with the INS system, and use the error-state Kalman filter algorithm to perform integrated navigation and positioning calculations to obtain the final position information of the ground-based mobile device.

[0008] In some embodiments, the selecting a target positioning mode based on the monitoring results to calculate the absolute position coordinates of the ground-based mobile device includes: when the BDS satellite signals are normal and the number of visible satellites is greater than 4, select at least 4 pieces of BDS satellite raw pseudorange observation data to calculate the absolute position coordinates of the ground-based mobile device; when the BDS satellite signals are abnormal and the number of visible satellites is less than 4, introduce the ground-based long-wave time service signals and the BDS satellite signals to perform integrated calculation of the absolute position coordinates of the ground-based mobile device; when the BDS satellite signals are abnormal and there are no effective visible satellites, introduce 4 long-wave time service signals to replace the BDS system for independent positioning calculation; wherein, the 4 long-wave time service signals have a unified time standard.

[0009] In some embodiments, the BDS satellite raw pseudorange observation data is obtained through the following pseudorange observation equation:

[0010] ;

[0011] wherein, is the coordinate of the BDS satellite; is the absolute position coordinate of the ground-based mobile device, which is a parameter to be estimated; P is the BDS satellite pseudorange observation value; c is the speed of light; is the clock error of the BDS receiver, which is a parameter to be estimated; is the clock error of the BDS satellite, which is obtained from the satellite ephemeris; , are the ionospheric delay and the tropospheric delay respectively, which are calculated by an empirical model; is the modelable error and the observation noise.

[0012] In some embodiments, when the number of visible satellites is less than 4, introducing ground-based long-wave timing signals and BDS satellite signals to fuse and solve the absolute position coordinates of the ground-based mobile device includes: when the number of visible satellites is less than 4, using pseudo-range observation values ​​obtained from ground-based long-wave timing signals as supplementary observation information, solving the absolute position coordinates of the ground-based mobile device using a filtering algorithm by simultaneous equations, wherein the equations are as follows:

[0013] ;

[0014] In the formula, is the satellite pseudorange observation value of the i-th BDS; For the The position coordinates of the BDS satellites, is the position coordinate of the long-wave transmitting station; is the absolute position coordinate of the ground-based mobile device, is the parameter to be estimated; c is the speed of light; is the BDS receiver clock error, is the parameter to be estimated; is the pseudorange observation value of the longwave receiver; is the time difference between the long-wave receiver and the long-wave transmitter, obtained through the previous calibration; and represent BDS observation noise and long-wave observation noise respectively.

[0015] In some embodiments, when the BDS satellite signal is abnormal and there are no valid visible satellites, four long-wave timing signals are introduced to replace the BDS system for independent positioning and solving, including: a long-wave receiver simultaneously receives the timing signals of four long-wave transmitters, and uses the timing signals to solve the position coordinates of the ground-based mobile device, and the calculation formula is as follows:

[0016] ;

[0017] In the formula, S 1、 S 2、 S 3、 S4 represents the pseudo-range observations of the four long-wave transmitting stations; ( X 1 ,Y 1 ,Z 1) ( X 2 ,Y 2 ,Z 2) ( X 3 ,Y 3 ,Z 3) ( X 4 ,Y 4 ,Z 4) are the position coordinates of the 1st, 2nd, 3rd and 4th long-wave transmitting stations respectively; c is the speed of light; respectively represent the clock differences between 4 long-wave transmitters and the long-wave receiver, which are parameters to be estimated; respectively represent the observation noises of 4 long-wave transmitters; represents the position coordinates of the ground-based mobile device, which are parameters to be estimated.

[0018] In some embodiments, during the process of performing integrated navigation and positioning calculation using the error-state Kalman filter algorithm, the discretized system state equation and observation equation are as follows:

[0019] ;

[0020] In the formula, and are the state error vectors at the current moment and the previous moment respectively, is the state transition matrix, is the process noise at the previous moment, is the observation error vector at the current moment, which represents the difference between the absolute position coordinates of the ground-based mobile device and the position coordinates calculated by the INS system, is the observation matrix at the current moment, is the observation noise at the current moment.

[0021] The beneficial effects brought by the technical solution provided by the embodiments of the present invention at least include:

[0022] In the embodiments of the present invention, a multi-source integrated navigation and positioning mode is provided, which can select the used navigation and positioning mode according to whether the BDS satellite signal is received normally and the number of visible satellites. When the BDS satellite signal reception is abnormal and the number of visible satellites is less than 4, the ground-based long-wave time signal is used for positioning assistance to realize the calculation of the absolute position information of the carrier, and better integrate the INS system observation values for integrated positioning. The present invention improves the continuity and reliability of navigation and positioning in the case where the BDS satellite system is affected externally and shows abnormalities or even fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings, where:

[0024] Figure 1 is a schematic flowchart of the BDS / INS integrated navigation and positioning method assisted by the ground-based long-wave time system provided by the embodiments of the present invention;

[0025] Figure 2Schematic diagram of the positioning principle of the ground-based long-wave time service system assisting the BDS satellite system provided by the embodiments of the present invention;

[0026] Figure 3 Schematic diagram of the independent positioning principle of the ground-based long-wave time service system provided by the embodiments of the present invention. Specific embodiments

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not intended to limit the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments. However, it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0029] It should be noted that the terms "first / second / third" involved in the embodiments of the present invention are only used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first / second / third" can be interchanged with a specific order or sequence when permitted, so that the embodiments of the present invention described here can be implemented in an order other than that illustrated or described here.

[0030] Those skilled in the art of the present technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the embodiments of the present invention belong. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as here.

[0031] As a high-power land-based radio system, the ground-based long-wave time service system has strong anti-interference ability and diffraction ability for large buildings. Therefore, the long-wave time service system can be used as a backup system for the BDS system. When the BDS satellite is interfered by the outside world and fails for a long time, the time service signal observation value provided by the long-wave time service system can replace the BDS system to provide the initial position information for the INS system. The core of the present invention is to use the observation information of the ground-based long-wave time service system to assist the BDS / INS integrated system to achieve continuous and robust positioning services.

[0032] Figure 1 This is a schematic flowchart of a BDS / INS integrated navigation and positioning method assisted by a ground-based long-wave time service system provided by an embodiment of the present invention. As Figure 1 shown, the method at least includes the following steps:

[0033] Step S110, establish a mobile experimental platform equipped with a BDS satellite receiver, an inertial navigation device, and a long-wave receiver in a time laboratory.

[0034] Here, the time laboratory can be the National Time Service Center of the Chinese Academy of Sciences or other national laboratories. The BDS satellite receiver receives the signals of the Beidou Navigation Satellite System (BDS) to achieve high-precision positioning and time synchronization.

[0035] The inertial navigation device is used to provide navigation information such as the attitude, speed, and position of the carrier (such as the experimental platform). According to the experimental requirements, a platform-type or strapdown inertial navigation device is selected. The platform-type inertial navigation device has high precision and stability, but high cost; the strapdown inertial navigation device has the advantages of small volume, light weight, and low cost.

[0036] The long-wave receiver is used to receive long-wave signals, achieve long-wave communication and navigation backup, and provide a reliable communication means for the experiment. When the satellite navigation signal is unavailable, the long-wave navigation system is used for backup and complementarity.

[0037] Step S120, use the ground-based mobile device on the mobile experimental platform to simultaneously receive BDS satellite signals and ground-based long-wave time service signals.

[0038] Here, the ground-based mobile device, as the carrier, can synchronously receive BDS satellite signals and long-wave time service signals from the ground-based long-wave transmitting station.

[0039] Step S130, monitor the quality of the BDS satellite signals and the number of visible satellites, and select a target positioning mode based on the monitoring results to calculate the absolute position coordinates of the ground-based mobile device.

[0040] Here, the number of visible satellites refers to the number of visible BDS satellites. The target positioning mode is one of the BDS / INS integrated positioning system mode, the long-wave time service signal-assisted positioning mode, and the long-wave time service signal independent positioning mode. In implementation, the least squares algorithm can be used for calculation, and the pseudorange observation equation is linearized at the approximate position of the ground-based mobile device.

[0041] Step S140, use the absolute position coordinates as initial observation data to perform integrated navigation and positioning with the INS system, and use the error state Kalman filter algorithm to perform integrated navigation and positioning calculation to obtain the final position information of the ground-based mobile device.

[0042] Here, when performing fusion, the timestamps of INS data and satellite navigation data should be accurately synchronized. The error state Kalman filter algorithm includes the following processes. Prediction step: Use INS data to predict the state vector at the next moment, including predicted values of position, velocity, and attitude. Update step: When new absolute position coordinates are available, calculate the difference (i.e., the residual) between the predicted value and the observed value, and update the state vector and covariance matrix. Calculate the Kalman gain: Calculate the Kalman gain based on the covariance matrix and observation noise. State update: Use the Kalman gain and the residual to correct the error in the state vector. Covariance update: Update the covariance matrix to reflect the new uncertainty.

[0043] The embodiment of the present invention proposes a BDS / INS integrated navigation and positioning technology method assisted by a ground-based long-wave time service system. This method aims at the problem of reduced positioning service accuracy caused by abnormal satellite signals of the BDS system and long-term failure, and proposes to perform positioning calculation by assisting the BDS system with the ground-based long-wave time service system, solving the continuous calculation of the absolute position information of the integrated positioning system when the BDS system completely fails, and realizing a continuous and reliable positioning service mode in complex scenarios.

[0044] In some embodiments, selecting a target positioning mode based on the monitoring results to calculate the absolute position coordinates of the ground mobile device includes: when the BDS satellite signal is normal and the number of visible satellites is greater than 4, select at least 4 pieces of original pseudorange observation data of BDS satellites to calculate the absolute position coordinates of the ground mobile device; when the BDS satellite signal is abnormal and the number of visible satellites is less than 4, introduce the ground-based long-wave time service signal and the BDS satellite signal for integrated calculation of the absolute position coordinates of the ground mobile device; when the BDS satellite signal is abnormal and there are no effective visible satellites, introduce 4 long-wave time service signals to perform independent positioning calculation instead of the BDS system; wherein, the 4 long-wave time service signals have a unified time standard.

[0045] Here, when the BDS satellite signal is normal and the number of visible satellites is greater than 4, the integrated positioning system is based on the BDS satellite observations and the INS system observations, and the system time reference is the BDS satellite time, to realize the calculation of the carrier motion state. The observation equation of the integrated positioning system is as follows:

[0046] ;

[0047] In the formula, is the difference between the position calculated by INS and the position observed by BDS, is the BDS position observation vector, which can be represented by and is the position vector of the BDS antenna phase center calculated by inertial navigation. is the transformation matrix.

[0048] When the BDS satellite signal is abnormal and the number of visible satellites is less than 4, a long-wave time service signal is introduced for fusion calculation with the BDS satellite signal to provide the carrier initial position information for the navigation and positioning system.

[0049] In some embodiments, the original pseudo-range observation data of the BDS satellite is obtained through the following pseudo-range observation equation:

[0050] ;

[0051] where, is the coordinate of the BDS satellite; is the absolute position coordinate of the ground-based mobile device, which is a parameter to be estimated; P is the pseudo-range observation value of the BDS satellite; c is the speed of light; is the clock error of the BDS receiver, which is a parameter to be estimated; is the clock error of the BDS satellite, which is obtained from the satellite ephemeris; , are the ionospheric delay and tropospheric delay respectively, which are calculated by the empirical model; is the modelable error and observation noise.

[0052] Here, the parameters to be estimated in the BDS system satellite pseudo-range observation equation considering the above various errors are the three position parameters of the ground-based mobile device and the clock error of the BDS receiver. The position coordinates of the ground-based mobile device can be calculated using the observation data of 4 or more BDS satellites.

[0053] In implementation, the position coordinates of the ground-based mobile device are solved using the least squares algorithm. The pseudo-range observation equation is linearized at the approximate position of the receiver, and can be expressed by the following formula:

[0054] ;

[0055] In the formula, is the pseudo-range residual of the i-th satellite, is the pseudo-range observation value of the i-th BDS satellite, is the geometric distance calculated based on the approximate position of the ground-based mobile device, is the position correction amount of the ground-based mobile device, is the noise error, c is the speed of light, is the clock error of the BDS receiver.

[0056] Taking 4 BDS satellites as an example, 4 observation equations are constructed:

[0057] ;

[0058] The above formula is simplified to: ; Where y is the pseudorange residual, H is the coefficient matrix, is the parameter to be estimated, including the position coordinate correction of the ground-based mobile equipment and BDS receiver clock error , according to the least squares algorithm, the estimated parameter solution is:

[0059] ;

[0060] Finally, the absolute position coordinates of the ground-based mobile equipment are obtained: .

[0061] In some embodiments, when the number of visible satellites is less than 4, introducing ground-based long-wave timing signals and BDS satellite signals to fuse and solve the absolute position coordinates of the ground-based mobile device includes: when the number of visible satellites is less than 4, using pseudo-range observation values ​​obtained from ground-based long-wave timing signals as supplementary observation information, solving the absolute position coordinates of the ground-based mobile device using a filtering algorithm by simultaneous equations, wherein the equations are as follows:

[0062] ;

[0063] In the formula, is the pseudorange observation value of the i-th BDS satellite; For the The position coordinates of the BDS satellites, is the position coordinate of the long-wave transmitting station; is the absolute position coordinate of the ground-based mobile device, is the parameter to be estimated; c is the speed of light; is the BDS receiver clock error, is the parameter to be estimated; is the pseudorange observation value of the longwave receiver; is the time difference between the long-wave receiver and the long-wave transmitter, obtained through the previous calibration; and represent BDS observation noise and long-wave observation noise respectively.

[0064] Here, if Figure 2 The figure shows a schematic diagram of the positioning principle of the ground-based long-wave timing system assisted by the BDS satellite system provided by the implementation case of the present invention. The ground-based long-wave timing signal and three BDS satellite signals are selected for fusion and solution. The absolute position coordinates of the ground-based mobile device can be calculated by combining the pseudo-range observation equations of the long-wave system and the BDS system. This value is used as the initial position information of the INS system to realize fusion navigation positioning.

[0065] In some embodiments, when the BDS satellite signal is abnormal and there are no valid visible satellites, four long-wave timing signals are introduced to replace the BDS system for independent positioning and solving, including: a long-wave receiver simultaneously receives the timing signals of four long-wave transmitters, and uses the timing signals to solve the position coordinates of the ground-based mobile device, and the calculation formula is as follows:

[0066] ;

[0067] In the formula, S 1、 S 2、 S 3、 S4 represents the pseudo-range observations of the four long-wave transmitting stations; ( X 1 ,Y 1 ,Z 1) ( X 2 ,Y 2 ,Z 2) ( X 3 ,Y 3 ,Z 3) ( X 4 ,Y 4 ,Z 4) are the position coordinates of the 1st, 2nd, 3rd and 4th long-wave transmitting stations respectively; c is the speed of light; They represent the clock differences between the four long-wave transmitters and the long-wave receivers, which are parameters to be estimated; They represent the observation noise of four long-wave transmitting stations respectively; Represents the position coordinates of the ground-based mobile equipment, which is the parameter to be estimated.

[0068] Here, when the BDS satellite signal is abnormal and there is no effective observation satellite, four long-wave timing signals are introduced to replace the BDS system to solve the absolute position of the carrier. It is worth noting that when using four long-wave timing signals to solve the position coordinates of ground-based mobile equipment, it is necessary to ensure a unified time standard. my country's long-wave timing system broadcasts the national standard time.

[0069] like Figure 3 The figure is a schematic diagram of the independent positioning principle of the ground-based long-wave timing system provided by the embodiment of the present invention. The long-wave receiver receives the absolute time signals of four long-wave transmitting stations, and the absolute position coordinates of the ground-based mobile device are obtained by combining the above equations. , and the clock difference between the long-wave receiver and the long-wave transmitting station . And use the absolute position coordinate information as auxiliary information for the fusion navigation and positioning system.

[0070] In some embodiments, in the process of using the error state Kalman filter algorithm to perform fusion navigation positioning solution, the discretized system state equation and observation equation are as follows:

[0071] ;

[0072] In the formula, and are the state error vectors at the current moment and the previous moment respectively, is the state transition matrix from the (k - 1)th moment to the kth moment, is the process noise at the previous moment, is the observation error vector at the current moment, representing the difference between the absolute position coordinates of the ground moving device and the position coordinates calculated by the INS system, is the observation matrix at the current moment, is the observation noise at the current moment.

[0073] The iterative process of the error state Kalman filter can be represented by the following formula:

[0074] Calculate the gain matrix : , in the formula, is the predicted value of the variance - covariance matrix at the current moment, is the observation matrix, is the measurement noise variance matrix.

[0075] Update the state at the current moment : , in the formula, is the predicted value of the state vector at the current moment, is the observation vector at the current moment.

[0076] Update the variance - covariance matrix at the current moment : , in the formula, is the identity matrix, and the meanings of the other symbols are the same as above.

[0077] State prediction and covariance prediction:

[0078] ;

[0079] In the formula, is the state transition matrix from the kth moment to the (k + 1)th moment, is the state noise variance matrix, is the predicted value of the variance - covariance matrix at the (k + 1)th moment, is the state prediction value at the (k + 1)th moment, and the meanings of the other symbols are the same as above.

[0080] In an embodiment of the present invention, a multi-source fusion navigation and positioning mode is provided, which can select the navigation and positioning mode to be used according to whether the BDS satellite signal is received normally and the number of visible satellites. When the BDS satellite signal reception is abnormal and the number of visible satellites is less than 4, the ground-based long-wave time signal is used for positioning assistance to realize the calculation of the absolute position information of the carrier, and the INS system observation values are better fused for fusion positioning. The present invention improves the continuity and reliability of navigation and positioning in the case where the BDS satellite system is affected by external factors and appears abnormal or even fails.

[0081] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present invention. Therefore, the "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present invention, the sequence numbers of the above processes do not mean the order of execution, and the order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention. The serial numbers of the embodiments of the present invention above are only for description and do not represent the advantages or disadvantages of the embodiments.

[0082] It should be noted that in this article, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, the element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0083] In several embodiments provided by the present invention, it should be understood that the disclosed method can be implemented in other ways. The methods disclosed in several method embodiments provided by the present invention can be combined arbitrarily without conflict to obtain new method embodiments. The features disclosed in several method embodiments provided by the present invention can be combined arbitrarily without conflict to obtain new method embodiments.

[0084] As described above, only the embodiments of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A BDS / INS fusion navigation and positioning method assisted by a ground-based long-wave timing system, characterized in that: include: A mobile experimental platform equipped with BDS satellite receivers, inertial navigation devices and long-wave receivers was established in the time laboratory; Using the ground-based mobile equipment on the mobile experimental platform to simultaneously receive BDS satellite signals and ground-based long-wave timing signals; Monitor the quality of BDS satellite signals and the number of visible satellites, and select a target positioning mode based on the monitoring results to calculate the absolute position coordinates of the ground-based mobile device; The absolute position coordinates are used as initial observation data to perform fusion navigation positioning with the INS system, and the error state Kalman filter algorithm is used to perform fusion navigation positioning solution to obtain the final position information of the ground-based mobile device; Among them, the target positioning mode is selected based on the monitoring results to solve the absolute position coordinates of the ground-based mobile device, including: when the BDS satellite signal is normal and the number of visible satellites is greater than 4, selecting and using at least 4 BDS satellite original pseudo-range observation data to solve the absolute position coordinates of the ground-based mobile device; when the BDS satellite signal is abnormal and the number of visible satellites is less than 4, introducing ground-based long-wave timing signals and BDS satellite signals for fusion to solve the absolute position coordinates of the ground-based mobile device; when the BDS satellite signal is abnormal and there are no valid visible satellites, introducing 4 long-wave timing signals to replace the BDS system for independent positioning and solution; wherein the 4 long-wave timing signals have a unified time standard.

2. The method according to claim 1, characterized in that The BDS satellite original pseudo-range observation data is obtained through the following pseudo-range observation equation: ； in, are the coordinates of the BDS satellite; is the absolute position coordinate of the ground-based mobile equipment, is the parameter to be estimated; P is the BDS satellite pseudorange observation value; c is the speed of light; is the clock error of the BDS receiver, is the parameter to be estimated; is the clock error of the BDS satellite, obtained from the satellite ephemeris; , are the ionospheric delay and tropospheric delay, respectively, which are calculated by the empirical model; is the modelable error and observation noise.

3. The method according to claim 1, characterized in that When the number of visible satellites is less than 4, the ground-based long-wave timing signal is introduced to fuse with the BDS satellite signal to calculate the absolute position coordinates of the ground-based mobile device, including: When the number of visible satellites is less than 4, the pseudo-range observation value obtained by the ground-based long-wave timing signal is used as supplementary observation information, and the absolute position coordinates of the ground-based mobile device are solved by a filtering algorithm using a simultaneous equation group, wherein the equation group is as follows: ； In the formula, For the i Pseudorange observations of BDS satellites; For the The position coordinates of the BDS satellites, is the position coordinate of the long-wave transmitting station; is the absolute position coordinate of the ground-based mobile device, is the parameter to be estimated; c is the speed of light; is the BDS receiver clock error, is the parameter to be estimated; is the pseudorange observation value of the longwave receiver; is the time difference between the long-wave receiver and the long-wave transmitter, obtained through the previous calibration; and represent BDS observation noise and long-wave observation noise respectively.

4. The method according to claim 1, characterized in that: When the BDS satellite signal is abnormal and there is no valid visible satellite, four long-wave timing signals are introduced to replace the BDS system for independent positioning and solution, including: The long-wave receiver simultaneously receives the timing signals from four long-wave transmitters and uses the timing signals to calculate the position coordinates of the ground-based mobile equipment. The calculation formula is as follows: ， In the formula, S 1、 S 2、 S 3、 S 4 respectively represent the pseudo-range observations of the four long-wave transmitting stations; ( X 1 ,Y 1 ,Z 1) ( X 2 ,Y 2 ,Z 2) ( X 3 , Y 3 ,Z 3) ( X 4 ,Y 4 ,Z 4) are the position coordinates of the 1st, 2nd, 3rd and 4th long-wave transmitting stations respectively; c is the speed of light; They represent the clock differences between the four long-wave transmitters and the long-wave receivers, which are parameters to be estimated; They represent the observation noise of four long-wave transmitting stations respectively; Represents the position coordinates of the ground-based mobile equipment, which is the parameter to be estimated.

5. The method according to any one of claims 1 to 4, characterized in that: In the process of using the error state Kalman filter algorithm to perform fusion navigation and positioning solution, the discretized system state equation and observation equation are as follows: ； In the formula, , are the state error vectors at the current moment and the previous moment respectively, is the state transfer matrix, is the process noise at the previous moment, is the observation error vector at the current moment, representing the difference between the absolute position coordinates of the ground-based mobile device and the position coordinates estimated by the INS system, is the observation matrix at the current moment, is the observation noise at the current moment.

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