Low-orbit navigation enhanced transmitting terminal time difference calibration method, device, equipment and medium

Abstract

The embodiment of the invention discloses a low-orbit navigation enhanced transmitting terminal time difference calibration method, device and equipment and a medium, and relates to the technical field of satellite navigation, and the method comprises the steps: obtaining a low-orbit satellite satellite-borne receiver clock error, ground observation station coordinates, an observation station receiver clock error and other parameters through calculation of observation data of a GNSS satellite; the ground observation station calculates an inter-system deviation between a low earth orbit satellite system corresponding to each low earth orbit satellite and a GNSS system according to the downlink navigation data of each low earth orbit satellite; and selecting one low-orbit satellite as a reference satellite, obtaining the deviation between reference systems, calculating the time deviation of the navigation enhancement transmitting end of the deviation between other systems and the deviation between the reference systems, and compensating the clock error of the corresponding low-orbit satellite based on the parameter. The method can be used for calibrating the relative time difference of each low-orbit satellite navigation signal transmitting end, realizes low-orbit navigation signal time synchronization, is beneficial to improving the positioning, navigation and time service capabilities of a low-orbit satellite system, and provides more accurate services for users.

Description

Technical Field

[0001] The present application relates to the field of satellite navigation technology, and in particular to a method, device, equipment and medium for calibrating time difference of a low-orbit navigation enhancement transmitter. Background Art

[0002] Since the GNSS satellites of the Global Navigation Satellite System (GNSS) are in medium and high earth orbits, they have disadvantages such as slow convergence of carrier phase positioning, weak signal strength, and susceptibility to interference. Relatively speaking, low-orbit satellites have low orbit altitudes, fast platform movement, small signal loss, and much higher signal landing power than GNSS satellites. Therefore, incorporating the low-orbit navigation augmentation system of low-orbit satellites into the comprehensive PNT system can improve the positioning effect.

[0003] During the positioning process, inter-satellite time synchronization is a key prerequisite for satellite navigation systems. GNSS satellites can achieve high-precision clock error prediction through high-precision and high-stability atomic clocks. However, for low-orbit satellites, due to the limitations of satellite platform cost, size, weight and power consumption, low-orbit satellites use low-cost ultra-stable oscillators (USOs) instead of atomic clocks.

[0004] At present, in order to synchronize the onboard time of low-orbit satellites with the GNSS time scale and avoid the clock error of low-cost ultra-stable oscillators, the onboard GNSS receivers of low-orbit satellites and the onboard navigation direct-transmitted payloads of low-orbit satellites are generally traced to the same onboard time and frequency and driven by onboard GNSS technology. In this scheme, low-orbit satellites receive signals from GNSS multi-system navigation satellites in medium and high orbits, and calculate their own positions and receiver clock errors in real time to achieve low-orbit inter-satellite time synchronization; at the same time, the time and frequency of the onboard GNSS receivers are also used to synchronously drive the navigation direct-transmitted payloads, so that the navigation direct-transmitted signals can be processed directly based on the onboard GNSS receiver clock errors; the low-orbit clock error is predicted by fitting the real-time onboard GNSS receiver clock errors, so as to provide PNT services and enhanced services for ground users.

[0005] However, this method still has some defects. Since there is a hardware link delay between the onboard navigation signal transmitter and the onboard receiver of each low-orbit satellite, and the hardware link delay of each low-orbit satellite may be different, when using the low-orbit downlink signal for navigation and positioning, the systematic ranging error between the observation values ​​of each low-orbit satellite cannot be ruled out, thereby affecting the user's positioning and timing accuracy.

[0006] Therefore, there is currently a lack of a method that can not only improve the positioning effect of the PNT system by utilizing the low-orbit navigation augmentation system but also eliminate the above-mentioned systematic ranging errors. Summary of the invention

[0007] The present application provides a method, device, equipment and medium for calibrating the time difference of a low-orbit navigation enhancement transmitter, which is used to solve the defects in the above-mentioned related technologies. The technical solution is as follows:

[0008] In a first aspect, an embodiment of the present application provides a low-orbit navigation enhancement transmitter time difference calibration method, comprising:

[0009] Acquire first observation data of the GNSS satellite through an onboard receiver of the low-orbit satellite, and calculate the onboard receiver clock error and the low-orbit precise orbit of the low-orbit satellite based on the first observation data;

[0010] Acquire second observation data of the GNSS satellite through a station receiver of a ground station, and obtain station receiver coordinates, station receiver clock errors, and tropospheric parameters through ground precise point positioning based on the second observation data;

[0011] The downlink navigation data sent by each low-orbit satellite is obtained through the ground station, and the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite is calculated by combining the onboard receiver clock error, the low-orbit precise orbit, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data;

[0012] Select any low-orbit satellite as a reference star, obtain the reference system deviation of the reference star, calculate the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference star and the reference system deviation, and output the difference as the navigation enhancement transmitting end time deviation of the corresponding low-orbit satellite;

[0013] Based on the time offset of the navigation enhancement transmitter of each low-orbit satellite, the onboard receiver clock error of the corresponding low-orbit satellite is compensated, and the transmitter clock error of the low-orbit satellite navigation signal with a unified time reference is output.

[0014] In an optional solution of the first aspect, the satellite-borne receiver clock error is calculated based on the following steps, including:

[0015] Establishing an observation equation based on the first observation data to obtain a pseudorange observation equation and a carrier phase observation equation;

[0016] Based on the pseudorange observation equation and the carrier phase observation equation, the characteristics of ionospheric delay and frequency are utilized to construct a combined observation value without ionospheric delay, eliminate the first-order term of ionospheric delay, and construct a pseudorange observation equation without ionospheric delay and a carrier phase observation equation without ionospheric delay;

[0017] The pseudorange observation equation without ionospheric delay and the carrier phase observation equation without ionospheric delay are solved, and the satellite-borne receiver clock error is output.

[0018] In an optional solution of the first aspect, the low-orbit precise orbit is calculated based on the following steps, including:

[0019] Establishing a motion equation of the low-orbit satellite based on the first observation data;

[0020] The state transfer matrix and the orbital state information of the low-orbit satellite at each moment are calculated based on the numerical integration method;

[0021] Based on the parameter estimation method, the orbital parameters of the low-orbit satellite are calculated in combination with the state transfer matrix and the orbital state information of the low-orbit satellite at each moment, and the low-orbit precise orbit is output.

[0022] In an optional solution of the first aspect, obtaining the station receiver coordinates, the station receiver clock error, and the tropospheric parameters by ground precise point positioning based on the second observation data includes:

[0023] An observation equation is established based on the second observation data to obtain a pseudorange observation equation of a ground station and a carrier phase observation equation of a ground station;

[0024] Based on the pseudorange observation equation of the ground station and the carrier phase observation equation of the ground station, a combined observation value without ionospheric delay is constructed by utilizing the characteristics of ionospheric delay being related to frequency, and the first-order term of ionospheric delay is eliminated to construct a pseudorange observation equation without ionospheric delay and a carrier phase observation equation without ionospheric delay;

[0025] The pseudo-range observation equation without ionospheric delay and the carrier phase observation equation without ionospheric delay corresponding to the ground station are solved by ground precise single-point positioning, and the station receiver coordinates, the station receiver clock error and the tropospheric parameters are output.

[0026] In an optional solution of the first aspect, the calculating the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters, and the downlink navigation data includes:

[0027] Constructing a ground station low-orbit observation equation that takes into account the hardware delay of the low-orbit satellite, including:

[0028]

[0029] The low-orbit satellite includes an onboard receiver for receiving GNSS signals and a navigation signal transmitter for sending downlink navigation data. The hardware delay is the clock difference between the onboard receiver clock error and the navigation signal transmitter clock error:

[0030]

[0031] Each time, the downlink navigation data of a low-orbit satellite is selected and substituted into the low-orbit observation equation of the ground station. Other bias terms and hardware delays are estimated as a whole to estimate the inter-system bias. The formula is applied:

[0032]

[0033] Among them, i is the low-orbit satellite number, G is the GNSS system, corresponds to the low-orbit satellite L i The satellite receiver clock error is corresponds to the low-orbit satellite L i The navigation signal transmitter clock error, ISB LEO,r is the other deviation term, corresponds to the low-orbit satellite L i The hardware delay, represents the geometric distance from the ground station r to the low-orbit satellite i, is the station receiver clock error, T r is the tropospheric parameter, is the fuzziness parameter, corresponds to the low-orbit satellite L i The inter-system deviation, ε P,IF is the measurement noise term of the pseudorange observation, ε l,IF is the measurement noise term of the carrier phase observation.

[0034] In an optional solution of the first aspect, the satellite receiver clock error is the error term of the relativistic effect and other clock error terms δt L The sum of:

[0035]

[0036] The navigation signal transmitting end clock error is the error term of the relativistic effect and other clock errors The sum of:

[0037]

[0038] The low-orbit satellite includes an onboard receiver for receiving GNSS signals and a navigation signal transmitter for sending downlink navigation data. The hardware delay is the clock error of the onboard receiver. Clock difference with the navigation signal transmitter The clock difference Application formula:

[0039]

[0040]

[0041] Eliminate the error term of low-orbit satellites affected by relativistic effects Application formula:

[0042] Δt L,ST =δt L -δt L .

[0043] In an optional solution of the first aspect, the compensating the clock error of the corresponding low-orbit satellite based on the navigation enhancement transmitting end time offset of each low-orbit satellite includes:

[0044] Obtain the navigation enhancement transmitter time offset of each low-orbit satellite respectively, and compensate the navigation enhancement transmitter time offset to the onboard receiver clock error of the corresponding low-orbit satellite using the formula:

[0045]

[0046] Output the compensated low-orbit navigation signal clock error sequence of each low-orbit satellite

[0047] Among them, i is the low-orbit satellite number, corresponds to the low-orbit satellite L i The navigation signal transmitter clock error is corresponds to the low-orbit satellite L i The satellite receiver clock error before compensation.

[0048] In a second aspect, an embodiment of the present application further provides a low-orbit navigation enhancement transmitter time difference calibration device, comprising:

[0049] A low-orbit satellite-borne data acquisition unit, configured to acquire first observation data of a GNSS satellite through an onboard receiver of the low-orbit satellite, and calculate a satellite-borne receiver clock error and a low-orbit precise orbit of the low-orbit satellite based on the first observation data;

[0050] A ground station data acquisition unit is configured to acquire second observation data of the GNSS satellite through a station receiver of the ground station, and obtain station receiver coordinates, station receiver clock errors, and tropospheric parameters through ground precise point positioning based on the second observation data;

[0051] a data processing unit, configured to obtain the downlink navigation data sent by each low-orbit satellite through the ground station data acquisition unit, and calculate the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data;

[0052] The data processing unit is further used to select any low-orbit satellite as a reference satellite, obtain the reference system deviation of the reference satellite, respectively calculate the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference satellite and the reference system deviation, and output the difference as the navigation enhancement transmitting end time deviation corresponding to the low-orbit satellite;

[0053] The data processing unit is also used to compensate the clock error of the corresponding low-orbit satellite based on the navigation enhancement transmitting end time offset of each low-orbit satellite.

[0054] In a third aspect, an embodiment of the present application further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method provided in the first aspect of the embodiment of the present application or any one of the implementation methods of the first aspect is implemented.

[0055] In a fourth aspect, the present application also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method provided by the first aspect of the embodiment of the present application or any one of the implementations of the first aspect.

[0056] The beneficial effects brought about by the technical solutions provided by some embodiments of the present application include at least:

[0057] An embodiment of the present application provides a method for calibrating the time difference of a low-orbit navigation enhancement transmitter, which obtains the downlink navigation data of a low-orbit satellite through a ground station, thereby calculating the inter-system deviation between the low-orbit satellite system and the GNSS system at the station receiving end of the ground station. The obtained inter-system deviation can implicitly eliminate the influence of the relativistic effect received by the low-orbit satellite.

[0058] Furthermore, by selecting a reference star, the reference system deviation of the reference star is subtracted from the system deviation of other low-orbit satellites, and the time deviation of the navigation enhancement transmitter obtained by the difference is compensated to the clock error of the corresponding low-orbit satellite, thereby obtaining the clock error of the navigation signal transmitter of the accurately synchronized low-orbit satellite. The time synchronization calibration from the ground station receiver to the low-orbit satellite navigation signal transmitter can be completed using only the data from the ground station, avoiding the defects of different reception and transmission delays caused by hardware delays of different low-orbit satellites, and greatly simplifying the calculation model, which can improve the solution efficiency. Low-orbit satellites that compensate for hardware delays can provide users with higher-precision positioning, navigation and timing services. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 This is a schematic diagram of an application scenario of a low-orbit navigation enhancement transmitter time difference calibration method provided in an embodiment of the present application;

[0061] Figure 2 It is a flow chart of a method for calibrating a time difference at a low-orbit navigation enhancement transmitter provided in an embodiment of the present application;

[0062] Figure 3 It is a structural schematic diagram of a low-orbit navigation enhancement transmitting end time difference calibration device provided in an embodiment of the present application;

[0063] Figure 4 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0065] The terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device including a series of steps or modules is not limited to the listed steps or modules, but may optionally include steps or modules that are not listed, or may optionally include other steps or modules that are inherent to these processes, methods, products or devices.

[0066] It should be noted that the terms "first\second" involved in the present application are only used to distinguish similar objects, and do not represent a specific order for the objects. It is understandable that "first\second" can be interchanged with a specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described or illustrated herein.

[0067] Next, combine Figure 1 , introduces the application scenario of a low-orbit navigation enhanced transmitting end time difference calibration method provided in an embodiment of the present application.

[0068] In this application scenario, there are GNSS satellites 100, low-orbit satellites 110, and ground stations 120. Among them, the GNSS satellite 100 is used to send down GNSS navigation signals, and both the low-orbit satellite 110 and the ground station 120 can obtain the GNSS navigation signals, that is, the observation data of the low-orbit satellite 110 on the GNSS satellite and the observation data of the ground station 120 on the GNSS satellite; the low-orbit satellite 110 can play a role in navigation enhancement, and can receive the GNSS navigation signal sent down by the GNSS satellite 100 through the onboard receiver, and can also send the navigation enhancement signal to the ground station 120 through the onboard navigation signal transmitter; the ground station 120 can receive the GNSS navigation signal sent down by the GNSS satellite 100, and can also receive the navigation enhancement signal sent down by the navigation signal transmitter of the low-orbit satellite 110.

[0069] It should be noted that Figure 1 The GNSS satellites 100 shown may include a plurality of different GNSS satellites, including but not limited to Figure 1 GNSS satellite 101, GNSS satellite 102, GNSS satellite 103, GNSS satellite 104, and GNSS satellite 105 are shown. In actual applications, GNSS satellite 100 can be selected from one of the GNSS systems such as GPS, Beidou Navigation, and Galileo, or can be selected from a combination of multiple GNSS systems, which is not limited in the embodiments of the present application. Figure 1 The low-orbit satellite 110 shown may actually include a plurality of different low-orbit satellites, not limited to Figure 1 The low-orbit satellite 111 and the low-orbit satellite 112 are shown; similarly, Figure 1 Only one ground station 120 is shown. In actual application, multiple ground stations may be included. The ground stations may include base stations, GNSS receivers, and terminal devices with the function of receiving GNSS signals. The embodiments of the present application are not limited to this. In some application scenarios, the mobile terminal held by the user can also be regarded as a ground station.

[0070] The present application is described in detail below with reference to specific embodiments.

[0071] Next, combine Figure 2 , introduces a low-orbit navigation enhancement transmitter time difference calibration method provided by the embodiment of the present application. For details, please refer to Figure 2 , Figure 2 The figure shows a flow chart of a method for calibrating the time difference of a low-orbit navigation enhancement transmitter provided in an embodiment of the present application. Figure 2 As shown, the method comprises the following steps:

[0072] S201, acquiring first observation data of a GNSS satellite through an onboard receiver of a low-orbit satellite, and calculating a clock error of the onboard receiver and a low-orbit precise orbit of the low-orbit satellite based on the first observation data;

[0073] S202, acquiring second observation data of the GNSS satellite through a station receiver of a ground station, and obtaining station receiver coordinates, station receiver clock errors, and tropospheric parameters through ground precise point positioning based on the second observation data;

[0074] S203, obtaining the downlink navigation data sent by each low-orbit satellite through the ground station, and calculating the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data;

[0075] S204, selecting any low-orbit satellite as a reference satellite, obtaining the reference system deviation of the reference satellite, respectively calculating the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference satellite and the reference system deviation, and outputting the difference as the navigation enhancement transmitting end time deviation corresponding to the low-orbit satellite;

[0076] S205, based on the navigation enhancement transmitter time offset of each low-orbit satellite, the onboard receiver clock error of the corresponding low-orbit satellite is compensated, and the low-orbit satellite navigation signal transmitter clock error with a unified time reference is output.

[0077] Specifically, S201 includes the following sub-steps:

[0078] S2011, receiving GNSS observation data, namely, first observation data, through a satellite-borne receiver of a low-orbit satellite, and establishing an observation equation based on the first observation data:

[0079] For example, pseudorange observations have the following pseudorange observation equation:

[0080]

[0081] Among them, the superscript G indicates that the GNSS satellite is used as the transmitting end, the subscript L indicates that the low earth orbit satellite (LEO) is used as the receiving end, that is, the low earth orbit satellite receives the GNSS signal transmitted by the GNSS satellite through the onboard receiver, the subscript j indicates the observation value frequency; P indicates the pseudorange observation value, the unit is meter; Represents the geometric distance between the low-orbit satellite and the GNSS satellite. If the coordinates of the low-orbit satellite are (x L ,y L , z L ), the coordinates of the GNSS satellite are marked as (x G ,y G , z G ), then:

[0082]

[0083] Among them, δt L is the receiver clock error of the onboard receiver of the low-orbit satellite; δt G is the clock error of the GNSS satellite. Both are defined at the gravity potential W0 at the mean sea level. The relativistic effect of the low-orbit satellite is The relativistic effect of GNSS satellites is represents the ionospheric error at frequency j; d L,j is the pseudo-range hardware delay of the onboard receiver of the low-orbit satellite representing the channel correlation, is the pseudorange hardware delay of the channel-related GNSS satellite; ε P,j Represents unmodeled errors such as pseudorange observation noise and multipath error.

[0084] For carrier observations, there are the following observation equations:

[0085]

[0086] Where, l represents the carrier phase observation value, in meters; b L,j is the channel-related phase delay of the onboard receiver of the low-orbit satellite, is the phase delay of the GNSS satellite associated with the channel; is the carrier phase integer ambiguity; λ j is the wavelength of frequency j; εl,j represents the carrier observation noise.

[0087] It should be noted that the orbital parameters and clock errors of GNSS satellites are known values, which are then used to estimate the orbital parameters and clock errors of low-orbit satellites.

[0088] S2012, using the characteristics of ionospheric delay and frequency correlation, constructs a combined observation value without ionospheric delay, eliminates the influence of the first-order term of ionospheric delay, reduces unknown parameters, and only estimates the low-orbit orbit, satellite clock error and ambiguity parameters. The specific combined model constructed is:

[0089]

[0090] in,

[0091]

[0092] λ IF =A·λ j1 +B·λ j2 ;

[0093]

[0094] Among them, M P is the error in the pseudorange observation that can be modeled, M L is the error in the carrier phase observation that can be modeled; IF means ionosphere-free.

[0095] Among them, the tropospheric error can be corrected by the Saastamoinen model and the GMF projection function model; the GNSS satellite antenna phase center deviation PCO and the antenna phase center variation PCV can be corrected by the antenna products released by IGS; the phase winding error δφ of the GNSS satellite end can be corrected by the following model:

[0096]

[0097] Where k is the unit vector from the GNSS satellite to the LEO satellite onboard receiver; D′ and D are the effective dipole vectors of the GNSS satellite and onboard receiver antennas, respectively, which are calculated from the unit vector (x′, y′, z′) in the satellite-fixed system and the unit vector (x, y, z) in the ground-fixed system.

[0098] It should be noted that for the GNSS system, the correction method for the relativistic effect can apply a unified protocol specification, and only correct its periodic variation term, using the formula:

[0099]

[0100] Among them, RG is the position vector of the GNSS satellite, V G is the velocity vector of the GNSS satellite, and c represents the speed of light.

[0101] It should be noted that in actual processing, as long as the relativistic effect correction model used by the server for processing GNSS data and the user end using GNSS data is consistent, the relativistic effect of GNSS satellites can be basically eliminated. The influence of the low-orbit satellite, and the low-orbit satellite is different from the GNSS satellite. The orbital altitude of the low-orbit satellite is lower, and the gravity potential changes faster. The relativistic effect is more significantly affected by the high-order gravity field and the tide than the GNSS satellite. The impact on the low-orbit satellite clock is more significant, and the correction method is more complicated. Therefore, the above method cannot eliminate the influence of the relativistic effect of the low-orbit satellite. The relativistic effect on the low-orbit satellite Requires special consideration.

[0102] Specifically, the onboard receiver clock error of the low-orbit satellite has absorbed the influence of the low-orbit relativistic effect. It can be understood that the actual onboard receiver clock error is The error term of the relativistic effect is included in It should be the error term of relativistic effect and other clock error terms δt L The combination can be expressed as:

[0103]

[0104] Based on the steps of S2011-S2012, the total clock error including the relativistic effect can be obtained. That is, the satellite receiver clock error finally obtained in S201

[0105] Further, the satellite orbit of the low-orbit satellite is determined by the following steps:

[0106] S2013, Establish the equations of motion for low-orbit satellites.

[0107] It should be noted that the satellite orbit of a low-orbit satellite is a series of state quantities characterized by initial orbital parameters and a dynamic model, which can be specifically expressed as:

[0108]

[0109] The differential equation is as follows:

[0110]

[0111] Among them, function F is an n-dimensional nonlinear functional, and x0 is the initial state.

[0112] Let X = xx * Then we have:

[0113]

[0114] in, Assume the solution of the above formula is:

[0115] X=ψ(t,t0)X0;

[0116] Then we have:

[0117]

[0118] Among them, I is the unit matrix, ψ(t, t0) is the state transfer matrix, which is specifically expressed as:

[0119]

[0120] Finally, the state transfer matrix and the orbital state information of the low-orbit satellite at each moment are calculated through numerical integration methods such as RKF and ADAMS, which can be used for the linearization of subsequent observation equations to solve the satellite orbit of the low-orbit satellite.

[0121] S2014, parameter estimation.

[0122] Optionally, the parameter estimation method includes least squares estimation, Kalman filtering, etc.

[0123] Based on the state transfer matrix calculated by S2013 and the orbital state information of the low-orbit satellite at each moment, the following formula is applied:

[0124]

[0125] Where x * (t) is the reference orbital parameter obtained by integration under the initial conditions. * (t) is x * (t) is the observed value calculated. * (t) and y * (t) and taking the first term we get:

[0126]

[0127] in:

[0128]

[0129] Solving the differential equation yields:

[0130] X=ψ(t,t0)X0;

[0131] Among them, the transfer matrix ψ(t,t0) satisfies:

[0132]

[0133] The solution of the transfer matrix is ​​realized by orbital integration, and we can get:

[0134] Y i =H i ψ(t i ,t0)X0+V i ;

[0135] is the partial derivative of the observed quantity with respect to each parameter to be estimated, based on the above formula:

[0136] L = BX0 + V;

[0137] Subsequently, the satellite orbit parameters of the low-orbit satellite can be obtained by least squares estimation or filtering estimation methods.

[0138] Based on this, through the above steps S2011-S2012, the onboard receiver clock error of each low-orbit satellite can be determined. Through the above steps S2013-S2014, the orbital parameters of each low-orbit satellite can be determined, that is, the satellite orbit of the low-orbit satellite can be determined.

[0139] In some embodiments, in S202, each ground station receives a GNSS signal transmitted by a GNSS satellite through a station receiver, that is, obtains second observation data of the GNSS satellite through the station receiver, and obtains ground precise point positioning parameters through ground precise point positioning solution, which specifically includes the following steps:

[0140] S2021, establishing an observation equation based on the GNSS observation data obtained by the station receiver.

[0141] The pseudorange observation equation is as follows:

[0142]

[0143] Where r is the number of the ground station, G is the number of the GNSS satellite, and P represents the pseudorange observation value in meters; Represents the geometric distance from the ground station r to the GNSS satellite G. If the position coordinates of the ground station are (x r ,y r , z r ), the position coordinates of the GNSS satellite are (x G ,y G , z G ), then is the station receiver clock error of the ground station, specifically the clock error of the ground station relative to the GNSS reference system, δt G represents the clock error of GNSS satellite; T r is the tropospheric delay error; represents the ionospheric delay error at frequency j; is the hardware delay at the ground station’s receiver on frequency j, is the hardware delay of the GNSS satellite at frequency j; ε P,j represents the measurement noise term of the pseudorange observation.

[0144] For carrier observations, there are the following observation equations:

[0145]

[0146] Where l represents the carrier phase observation value in meters. is the wavelength of the signal with frequency number j transmitted by the GNSS system satellite. For a given system and signal frequency, this value is a constant. is the carrier phase hardware delay corresponding to the signal with frequency j at the receiver end of the ground station, is the carrier phase hardware delay corresponding to the signal with frequency j at the GNSS satellite end, in units of weeks; is the integer ambiguity of the carrier phase observation, in weeks; ε l,j Then represents the measurement noise term of the carrier phase observation.

[0147] The hardware delay of pseudorange and carrier phase is often absorbed into the clock error parameter, so the observation equation can be further written as follows:

[0148]

[0149] in, is the station receiver clock error of the ground station, δt G It is the clock difference including hardware delay of GNSS satellite.

[0150] S2022, construct ionospheric-free delay combined observations.

[0151] By using the frequency-dependent characteristics of ionospheric delay, a combined observation value without ionospheric delay is constructed to eliminate the influence of the first-order term of ionospheric delay and reduce unknown parameters. The specific combined model is:

[0152]

[0153] S2023, perform parameter estimation.

[0154] Optionally, parameter estimation may be performed by least square estimation, Kalman filtering, etc. During the calculation process, filtering may be performed by a suitable stochastic model.

[0155] Specifically, the ionospheric-free delay combination model of S2022 is a linear combination of the original observations, and the initial variance can be calculated according to the error propagation law.

[0156] Specifically, weighting can be performed using the satellite elevation angle, wherein the receiver of the ground station can be considered to be stationary, and strong constraints can be placed on the position coordinates of the station receiver during filtering, and the station receiver can be considered to be static.

[0157] Specifically, after parameter estimation, the ground precise point positioning parameters are output. The ground precise point positioning parameters calculated based on S2021-S2023 include the coordinates of the station receiver, the station receiver clock error, and the tropospheric parameter T r .

[0158] It should be noted that the embodiment of the present application does not limit the execution order of S201 and the corresponding sub-steps S2011-S2014 and S202 and the corresponding sub-steps S2021-S2023. S201 and the corresponding sub-steps S2011-S2014 may be executed first, and then S202 and the corresponding sub-steps S2021-S2023 may be executed; or S202 and the corresponding sub-steps S2021-S2023 may be executed first, and then S201 and the corresponding sub-steps S2011-S2014 may be executed; the two may also be executed simultaneously.

[0159] Further, S201 calculates the satellite orbit of the low-orbit satellite and the onboard receiver clock error of the low-orbit satellite based on the observation data of the GNSS satellite by the receiver of the low-orbit satellite, and S202 calculates the ground precise single-point positioning parameters including: station receiver coordinates, station receiver clock error and tropospheric parameters after performing ground precise single-point positioning based on the observation data of the GNSS satellite by the ground station, and then executes step S203.

[0160] Specifically, in S203, the ground station can obtain the downlink navigation data sent by each low-orbit satellite, and calculate the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite based on the downlink navigation data of each low-orbit satellite.

[0161] Satellite receiver clock error calculated based on S201 S202 Calculated station receiver clock error and the tropospheric parameter T r, construct the ground station low-orbit observation equation taking into account the time difference of the low-orbit navigation enhancement transmitter, specifically:

[0162]

[0163] Among them, i is the low-orbit satellite number, G is the GNSS system, corresponds to the low-orbit satellite L i The onboard receiver clock error, ISB LEO,r represents other deviation terms, corresponds to the low-orbit satellite L i The hardware latency of low-orbit satellites; Represents the geometric distance from the ground station r to the low-orbit satellite i. If the position coordinates of the ground station are (x r ,y r , z r ), low-orbit satellite L i The position coordinates are Then there are:

[0164]

[0165] Specifically, the above equation can be solved by least squares or Kalman filtering.

[0166] Among the known parameters, the station receiver clock error and the tropospheric parameter T r It has been determined in step S202 that the low-orbit satellite L i The satellite receiver clock error In step S201, it is determined that;

[0167] Thus, the unknown parameters include other bias terms ISB LEO,r , low-orbit satellite hardware delay

[0168] It should be noted that since only one LEO satellite data is used each time, it is impossible to distinguish other bias terms and LEO satellite hardware delays. LEO,r , low-orbit satellite hardware delay That is, the inter-system deviation calculated by the ground station low-orbit observation equation based on the downlink navigation data of each low-orbit satellite in S203 is actually the sum of other deviation terms and the low-orbit satellite hardware delay, thereby calculating each low-orbit satellite L i The corresponding inter-system deviation between the low-orbit satellite system and the GNSS system is denoted as As shown in the following formula:

[0169]

[0170] It should be noted that low-orbit satellites not only have onboard receivers for receiving GNSS data, but also have navigation signal transmitters for sending downlink navigation data. Ground stations can obtain downlink navigation data sent by low-orbit satellites, that is, ground stations' observation data of low-orbit satellites. They can also obtain GNSS navigation data sent by GNSS satellites, that is, ground stations' observation data of GNSS satellites. It is understandable that there is a hardware delay between each low-orbit satellite's onboard receiver for receiving GNSS signals and the navigation signal transmitter for sending downlink navigation data, and different low-orbit satellites have different hardware delays. The above formula That is, each low-orbit satellite L i The corresponding hardware delay, that is, the clock difference between the onboard receiver and the navigation signal transmitter, is as follows:

[0171]

[0172] in, is the clock error of the navigation signal transmitter, is the satellite receiver clock error.

[0173] It should be noted that the station coordinates, station receiver clock errors, and troposphere parameters calculated based on the GNSS system can be regarded as fixed values, and only the observation data of the low-orbit satellite tracked by the ground station at a certain moment are selected for calculation, and the deviation value due to the ground station directly receiving the GNSS satellite signal and receiving the downlink navigation data sent by the low-orbit satellite (that is, the other deviation term ISB in the above formula) is LEO,r Considered as a constant.

[0174] Understandably, the other bias terms ISB for each LEO satellite LEO,r is a satellite-independent term, so different low-orbit satellites can be considered to have the same other bias terms ISB LEO,r .

[0175] Furthermore, in S204, any low-orbit satellite can be selected as a reference satellite to obtain the reference system deviation of the reference satellite, which is recorded as Calculate other low-orbit satellites L i The inter-system deviation Deviation from the reference system The difference is the low-orbit satellite L i The navigation enhancement transmitter time deviation.

[0176] Specifically, the formula is applied:

[0177]

[0178] From the above formula, we can see that other deviation terms ISB LEO,rIt is a satellite-independent term and is eliminated in the process of calculating the difference, leaving only the low-orbit satellite L i Hardware latency Hardware delay with low-orbit satellite L0 The relative difference of the low-orbit satellite L i The navigation enhancement transmitter time deviation

[0179] Further, in S205, the low-orbit satellite L calculated in S204 can be i The navigation enhancement transmitter time deviation Compensation to low-orbit satellite L i The formula is applied to the satellite receiver clock error:

[0180]

[0181] This ensures that the clock errors of the satellite navigation signal transmitters have the same time reference after compensation.

[0182] It should be noted that when navigation positioning enhancement is performed based on the compensated navigation signal transmitter clock error, the influence of hardware delay between the onboard receiving end and the navigation signal transmitter of the low-orbit satellite can be avoided, which is beneficial to improving the positioning accuracy of low-orbit navigation enhancement performed through low-orbit satellites.

[0183] In some embodiments, each low-orbit satellite L i The navigation enhancement transmitter time deviation Compensation is performed to obtain the low-orbit navigation signal clock error sequence with time delay correction between the satellite receiver and the navigation signal transmitter.

[0184] In this way, the impact of hardware delays of multiple low-orbit satellites can be eliminated, allowing users to combine multiple low-orbit satellites to enhance navigation and positioning, solving the problem of relative time deviation between navigation enhancement signals broadcast by different low-orbit satellites.

[0185] In some embodiments, taking into account the influence of relativistic effects, the actual satellite receiver clock error It should be the error term of relativistic effect and other clock error terms δt L In the process of S203 making a difference to obtain the navigation enhancement transmitter time deviation, the error term of the relativistic effect will also be eliminated, as shown below:

[0186]

[0187] Eliminate the error term of low-orbit satellites affected by relativistic effects Application formula:

[0188] ΔtL,ST =δt L -δt L .

[0189] Therefore, when calculating the inter-system deviation between the low-orbit satellite system corresponding to each low-orbit satellite and the GNSS system in step S203, the relativistic effect be eliminated.

[0190] In this way, the method provided in the embodiment of the present application can implicitly correct the low-orbit relativistic effects, is highly efficient and simple to calculate, and can provide a fast, simple and efficient relativistic effect correction method, which is beneficial to improving the efficiency of low-orbit satellites in providing navigation enhancement services.

[0191] The following are device embodiments of the present application, which can be used to execute the method embodiments of the present application. For details not disclosed in the device embodiments of the present application, please refer to the method embodiments of the present application.

[0192] See next Figure 3 , is a schematic diagram of the structure of a low-orbit navigation enhancement transmitter time difference calibration device provided by an exemplary embodiment of the present application. The device can be implemented as all or part of the terminal through software, hardware or a combination of both, and can also be integrated on the server as an independent module. A low-orbit navigation enhancement transmitter time difference calibration device in an embodiment of the present application can be applied to a terminal or a cloud. The device 30 includes a low-orbit satellite data acquisition unit 301, a ground station data acquisition unit 302 and a data processing unit 303, wherein:

[0193] The low-orbit satellite-borne data acquisition unit 301 is used to acquire first observation data of the GNSS satellite through the satellite-borne receiver of the low-orbit satellite, and calculate the satellite-borne receiver clock error and the low-orbit precise orbit of the low-orbit satellite based on the first observation data;

[0194] The ground station data acquisition unit 302 acquires second observation data of the GNSS satellite through a station receiver of the ground station, and obtains station receiver coordinates, station receiver clock errors and tropospheric parameters through ground precise point positioning based on the second observation data;

[0195] The data processing unit 303 is used to obtain the downlink navigation data sent by each low-orbit satellite through the ground station data acquisition unit 302, and calculate the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data;

[0196] The data processing unit 303 is further used to select any low-orbit satellite as a reference satellite, obtain the reference system deviation of the reference satellite, respectively calculate the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference satellite and the reference system deviation, and output the difference as the navigation enhancement transmitting end time deviation of the corresponding low-orbit satellite;

[0197] The data processing unit is also used to compensate the onboard receiver clock error of the corresponding low-orbit satellite based on the navigation enhancement transmitter time offset of each low-orbit satellite, and output the low-orbit satellite navigation signal transmitter clock error with a unified time reference.

[0198] It should be noted that when the device 30 provided in the above embodiment executes a method for calibrating the time difference of a low-orbit navigation enhancement transmitter, only the division of the above functional modules is used as an example. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the device provided in the above embodiment and the embodiment of the method for calibrating the time difference of a low-orbit navigation enhancement transmitter belong to the same concept. The implementation process is detailed in the method embodiment and will not be repeated here.

[0199] An embodiment of the present application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of any of the above-mentioned method embodiments when executing the program.

[0200] See also Figure 4 , which is a structural block diagram of an electronic device provided in an embodiment of the present application.

[0201] like Figure 4 As shown, the electronic device 400 includes: a processor 401 and a memory 402 .

[0202] In the embodiment of the present application, the processor 401 is the control center of the computer system, which can be a processor of a physical machine or a processor of a virtual machine. The processor 401 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 401 may be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), and PLA (Programmable Logic Array).

[0203] The processor 401 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the awake state, also called a CPU (Central Processing Unit); the coprocessor is a low-power processor for processing data in the standby state.

[0204] The memory 402 may include one or more computer-readable storage media, which may be non-transitory. The memory 402 may also include a high-speed random access memory, and a non-volatile memory, such as one or more disk storage devices, flash memory storage devices. In some embodiments of the present application, the non-transitory computer-readable storage medium in the memory 402 is used to store at least one instruction, which is used to be executed by the processor 401 to implement the method in the embodiment of the present application.

[0205] In some embodiments, the electronic device 400 further includes: a peripheral device interface 403 and at least one peripheral device 404. The processor 401, the memory 402 and the peripheral device interface 403 can be connected via a bus or a signal line. Each peripheral device 404 can be connected to the peripheral device interface 403 via a bus, a signal line or a circuit board. Specifically, the peripheral device 404 includes: a display screen, a camera and an audio circuit. The peripheral device interface 403 can be used to connect at least one peripheral device related to I / O (Input / Output) to the processor 401 and the memory 402.

[0206] In some embodiments of the present application, the processor 401, the memory 402, and the peripheral device interface 403 are integrated on the same chip or circuit board; in some other embodiments of the present application, any one or two of the processor 401, the memory 402, and the peripheral device interface 403 can be implemented on a separate chip or circuit board. This embodiment of the present application does not specifically limit this.

[0207] The electronic device structure block diagram shown in the embodiment of the present application does not constitute a limitation on the electronic device 400. The electronic device 400 may include more or fewer components than shown in the figure, or combine certain components, or adopt a different component arrangement.

[0208] The embodiment of the present application also provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the steps of the method of any of the above embodiments are implemented. The computer-readable storage medium may include, but is not limited to, any type of disk, including a floppy disk, an optical disk, a DVD, a CD-ROM, a micro drive, and a magneto-optical disk, a ROM, a RAM, an EPROM, an EEPROM, a DRAM, a VRAM, a flash memory device, a magnetic card or an optical card, a nanosystem (including a molecular memory IC), or any type of medium or device suitable for storing instructions and / or data.

[0209] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution can be essentially or in other words, the part that contributes to the relevant technology can be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiment.

[0210] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for calibrating the time difference of a low-orbit navigation enhancement transmitter, characterized in that: include: Acquire first observation data of the GNSS satellite through an onboard receiver of the low-orbit satellite, and calculate the onboard receiver clock error and the low-orbit precise orbit of the low-orbit satellite based on the first observation data; Acquire second observation data of the GNSS satellite through a station receiver of a ground station, and obtain station receiver coordinates, station receiver clock errors, and tropospheric parameters through ground precise point positioning based on the second observation data; The downlink navigation data sent by each low-orbit satellite is obtained through the ground station, and the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite is calculated by combining the onboard receiver clock error, the low-orbit precise orbit, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data; Select any low-orbit satellite as a reference star, obtain the reference system deviation of the reference star, calculate the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference star and the reference system deviation, and output the difference as the navigation enhancement transmitting end time deviation of the corresponding low-orbit satellite; Based on the time offset of the navigation enhancement transmitter of each low-orbit satellite, the onboard receiver clock error of the corresponding low-orbit satellite is compensated, and the low-orbit satellite navigation signal transmitter clock error with a unified time reference is output.

2. According to claim 1, a low-orbit navigation enhanced transmitter time difference calibration method is characterized in that: The satellite receiver clock error is calculated based on the following steps, including: Establishing an observation equation based on the first observation data to obtain a pseudorange observation equation and a carrier phase observation equation; Based on the pseudorange observation equation and the carrier phase observation equation, the characteristics of ionospheric delay and frequency are utilized to construct a combined observation value without ionospheric delay, eliminate the first-order term of ionospheric delay, and construct a pseudorange observation equation without ionospheric delay and a carrier phase observation equation without ionospheric delay; The pseudorange observation equation without ionospheric delay and the carrier phase observation equation without ionospheric delay are solved, and the satellite-borne receiver clock error is output.

3. The method for calibrating the time difference of a low-orbit navigation enhancement transmitter according to claim 1, characterized in that: The low-orbit precise orbit is calculated based on the following steps, including: Establishing a motion equation of the low-orbit satellite based on the first observation data; The state transfer matrix and the orbital state information of the low-orbit satellite at each moment are calculated based on the numerical integration method; Based on the parameter estimation method, the orbital parameters of the low-orbit satellite are calculated in combination with the state transfer matrix and the orbital state information of the low-orbit satellite at each moment, and the low-orbit precise orbit is output.

4. The method for calibrating the time difference of a low-orbit navigation enhancement transmitter according to claim 1, characterized in that: The obtaining of the station receiver coordinates, the station receiver clock error and the tropospheric parameters by ground precise point positioning based on the second observation data includes: An observation equation is established based on the second observation data to obtain a pseudorange observation equation of a ground station and a carrier phase observation equation of a ground station; Based on the pseudorange observation equation of the ground station and the carrier phase observation equation of the ground station, a combined observation value without ionospheric delay is constructed by utilizing the characteristics of ionospheric delay being related to frequency, and the first-order term of ionospheric delay is eliminated to construct a pseudorange observation equation without ionospheric delay and a carrier phase observation equation without ionospheric delay; The pseudo-range observation equation without ionospheric delay and the carrier phase observation equation without ionospheric delay corresponding to the ground station are solved by ground precise single-point positioning, and the station receiver coordinates, the station receiver clock error and the tropospheric parameters are output.

5. The method for calibrating the time difference of a low-orbit navigation enhancement transmitter according to claim 1, characterized in that: The calculating the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data includes: Constructing a ground station low-orbit observation equation that takes into account the hardware delay of the low-orbit satellite, including: The low-orbit satellite includes an onboard receiver for receiving GNSS signals and a navigation signal transmitter for sending downlink navigation data. The hardware delay is the clock difference between the onboard receiver clock error and the navigation signal transmitter clock error: Each time, the downlink navigation data of a low-orbit satellite is selected and substituted into the low-orbit observation equation of the ground station. Other bias terms and hardware delays are estimated as a whole to estimate the inter-system bias. The formula is applied: Among them, i is the low-orbit satellite number, G is the GNSS system, corresponds to the low-orbit satellite L i The satellite receiver clock error is corresponds to the low-orbit satellite L i The navigation signal transmitter clock error, ISB LEO,r is the other deviation term, corresponds to the low-orbit satellite L i The hardware delay, represents the geometric distance from the ground station r to the low-orbit satellite i, is the station receiver clock error, T r is the tropospheric parameter, is the wavelength corresponding to the ionosphere-free combination, is the fuzziness parameter, corresponds to the low-orbit satellite L i The inter-system deviation, ε P,IF is the measurement noise term of the pseudorange observation, ε l,IF is the measurement noise term of the carrier phase observation.

6. The method for calibrating the time difference of a low-orbit navigation enhancement transmitter according to claim 5, characterized in that: The satellite receiver clock error is the error term of the relativistic effect The low-orbit satellite includes an onboard receiver for receiving GNSS signals and a navigation signal transmitter for sending downlink navigation data. The hardware delay is the clock error of the onboard receiver. Clock difference with the navigation signal transmitter The clock difference Application formula: Eliminate the error term of low-orbit satellites affected by relativistic effects Application formula: Δt L,ST =δt L -δt L 。 7. A method for calibrating the time difference of a low-orbit navigation enhancement transmitter according to any one of claims 1 to 6, characterized in that: The method of compensating the clock error of the corresponding low-orbit satellite based on the navigation enhancement transmitting end time offset of each low-orbit satellite includes: Obtain the navigation enhancement transmitter time offset of each low-orbit satellite respectively, and compensate the navigation enhancement transmitter time offset to the onboard receiver clock error of the corresponding low-orbit satellite using the formula: Output the compensated low-orbit navigation signal clock error sequence of each low-orbit satellite Among them, i is the low-orbit satellite number, corresponds to the low-orbit satellite L i The navigation signal transmitter clock error is corresponds to the low-orbit satellite L i The satellite receiver clock error before compensation.

8. A low-orbit navigation enhancement transmitter time difference calibration device, characterized in that: include: A low-orbit satellite-borne data acquisition unit, configured to acquire first observation data of a GNSS satellite through an onboard receiver of the low-orbit satellite, and calculate a satellite-borne receiver clock error and a low-orbit precise orbit of the low-orbit satellite based on the first observation data; A ground station data acquisition unit is configured to acquire second observation data of the GNSS satellite through a station receiver of the ground station, and obtain station receiver coordinates, station receiver clock errors, and tropospheric parameters through ground precise point positioning based on the second observation data; a data processing unit, configured to obtain the downlink navigation data sent by each low-orbit satellite through the ground station data acquisition unit, and calculate the inter-system deviation between the low-orbit satellite system and the GNSS system corresponding to each low-orbit satellite by combining the onboard receiver clock error, the low-orbit precise orbit of the low-orbit satellite, the station receiver coordinates, the station receiver clock error, the tropospheric parameters and the downlink navigation data; The data processing unit is further used to select any low-orbit satellite as a reference satellite, obtain the reference system deviation of the reference satellite, respectively calculate the difference between the inter-system deviation corresponding to each low-orbit satellite except the reference satellite and the reference system deviation, and output the difference as the navigation enhancement transmitting end time deviation corresponding to the low-orbit satellite; The data processing unit is also used to compensate the onboard receiver clock error of the corresponding low-orbit satellite based on the navigation enhancement transmitter time offset of each low-orbit satellite, and output the low-orbit satellite navigation signal transmitter clock error with a unified time reference.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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