A method for high-precision and rapid positioning of GLONASS receivers

Abstract

The present invention discloses a method for high-precision and rapid positioning of a GLONASS receiver, comprising: calculating which satellites are currently available for positioning and judging whether hot start conditions are met according to the ephemeris information stored before the last shutdown and the current startup time; quickly completing the capture and tracking of the subcode synchronization to measure the code phase and enter the subframe synchronization state according to the corresponding stored Doppler and code phase information; constructing the satellite signal transmission time equation according to the code phase obtained by subcode synchronization and the stored navigation message; constructing the signal transmission time equation according to the satellite orbit height; solving the satellite signal transmission time through the satellite signal transmission time equation and the signal transmission time equation; according to the calculated satellite signal transmission time and the stored ephemeris information, using the satellite orbit long-term dynamic model, using the fourth-order Runge-Kutta method to obtain the position and speed of the satellite corresponding to the current transmission time, and then performing hot start positioning solution. This method can quickly improve positioning accuracy.

Description

Technical Field

[0001] The invention belongs to the field of navigation technology, and in particular relates to a method for high-precision and rapid positioning of a GLONASS receiver. Background Art

[0002] The working principle of the GLONASS receiver is to obtain basic distance measurement information such as satellite code phase and Doppler by capturing and tracking, and then obtain the satellite's ephemeris information by parsing the navigation bit, and then calculate the specific position of the receiver. Traditionally, the TTFF time for the first positioning of the GLONASS hot start is about 9 seconds to 32 seconds, and the main time is spent on satellite signal capture and tracking and message parsing. In order to reduce the hot start TTFF time, the current solution is to use the position of the receiver before shutdown, save the ephemeris and local real-time clock before shutdown, and calculate the satellite launch time. The ephemeris saved before shutdown is used to calculate the satellite position and velocity information at the launch time based on the traditional fourth-order Runge-Kutta method, and then the position and velocity information of the receiver is obtained. The above method has great limitations for GLONASS receivers. It requires that the time from the last power outage is within 2 hours, and based on the traditional satellite orbit differential equation, the fourth-order Runge-Kutta method is used to calculate the satellite orbit information. The effective accuracy is 0.77 meters within 15 minutes before and after the ephemeris reference time. As time goes by, the satellite position and velocity errors will increase further. Generally, hot start is defined as within 2 hours. If this method is used, the positioning accuracy is outside 100 meters, and the algorithm failure rate is high. Summary of the invention

[0003] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a method for high-precision and rapid positioning of a GLONASS receiver.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for hot-starting and fast positioning of a Beidou receiver comprises the following steps:

[0006] Step 1: The GLONASS receiver calculates the current power-on time, and based on the ephemeris information stored before the last shutdown and the current power-on time, calculates which satellites are currently available for positioning and determines whether the hot start conditions are met;

[0007] Step 2: The receiver calculates the reduced three-dimensional contraction range of signal capture based on the satellite Doppler and code phase information stored before the last power failure, quickly completes the capture, tracks the subcode synchronization, measures the code phase information, and enters the subframe synchronization state;

[0008] Step 3: The receiver constructs the satellite signal transmission time equation based on the code phase information obtained by subcode synchronization and the stored navigation message;

[0009] Step 4: According to the GLONASS satellite orbit height, construct the signal transmission time equation; solve the satellite signal transmission time through the satellite signal transmission time equation and the signal transmission time equation;

[0010] Step 5: Based on the calculated satellite signal transmission time and the stored ephemeris information, the long-term dynamic model of the satellite orbit is used, and the fourth-order Runge-Kutta method is used to obtain the position and velocity of the satellite corresponding to the current transmission time, and then a hot start positioning solution is performed to obtain a high-precision hot start positioning result.

[0011] The specific method of step 1 is:

[0012] The GLONASS receiver calculates the GLONASS time information corresponding to the current power-on time based on the clock information read at the power-on time and the clock information saved before the last power-off. u , and judge t u The reference time t of the saved satellite ephemeris b Whether it is within 4 hours, and count whether the number of satellites that meet the conditions is greater than or equal to 4. If so, execute step 2, otherwise the hot start process fails.

[0013] The GLONASS satellite signal transmission time equation in step 3 is:

[0014] t (s) =TOW*2+t ca Where: t (s) is the time of satellite signal transmission, TOW is the starting edge of the next frame of the navigation message corresponding to each subframe in seconds;

[0015] t ca It represents the position of the code phase information in the current subframe navigation message, and its corresponding equation is: Wherein, b is the number of navigation message subcodes in the current subframe; c is the number of C / A code cycles in the corresponding subframe, and the period of the C / A code is 1 millisecond; CP is the measured value of the code phase.

[0016] The satellite signal transmission time equation in step 4 is:

[0017] t tran =t u -t (s) ;

[0018] Where, h represents the GLONASS satellite orbit altitude, and the corresponding value is 19100km; c vel Represents the speed of light.

[0019] The calculation method for the average satellite transmission time is:

[0020]

[0021] According to the transmission time equation, the transmission time t corresponding to the current moment is estimated (s)′ , using the satellite orbit long-term dynamic model, the fourth-order Runge-Kutta method is used to calculate the corresponding satellite position [x (n) ′,y (n)′ , z (n)′ ];

[0022] Then, according to the local receiver position stored at the time of power failure [x u ,y u , z u ], the estimated distance from the satellite to the receiver at the current moment is as follows:

[0023]

[0024] Then calculate the corresponding weekday time

[0025] Solve the GLONASS satellite signal transmission time equation and the signal average transmission time equation in parallel to obtain the satellite signal transmission time:

[0026] INT means rounding.

[0027] The long-term dynamic model of the GLONASS satellite orbit in step 5 is:

[0028]

[0029] a x =a x 0+a x1 (tt b )+a x2 (tt b ) 2 +a x3 (tt b ) 3 +a x4 (tt b ) 4

[0030] a y =a y0 +a y1 (tt b )+a y2 (tt b ) 2 +a y3 (tt b ) 3 +a y4 (tt b) 4

[0031] a z =a z0 +a z1 (tt b )+a z2 (tt b ) 2 +a z3 (tt b ) 3 +a z4 (tt b ) 4

[0032] Where r represents the geometric distance between the satellite and the center of the earth;

[0033] a e Indicates the major radius of the PZ-90 reference ellipsoid;

[0034] The second-order band harmonic coefficient representing the Earth's oblateness;

[0035] ω E represents the angular velocity of the Earth's rotation;

[0036] GM represents the product of the Earth's gravity and the Earth's mass;

[0037] (x, y, z) represents the satellite position;

[0038] (V x , V y , V z ) represents the satellite speed;

[0039] (x″, y″, z″) represents the acceleration value caused by the gravity of the sun and the moon;

[0040] t b represents the reference time of the ephemeris data; t represents the transmission time of the satellite signal (s) ;

[0041] (a x , a y , a z ) represents the additional acceleration for calculating the satellite position, where (a xi , a yi , a zi ) represents the coefficients of a quartic polynomial.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] Compared with the prior art, the high-precision rapid positioning method proposed in the present invention can reduce the receiver's solution time to the greatest extent, while more accurately obtaining the satellite's orbit information, and can maximize the extension of the hot start cycle duration on the basis of saving CPU computing resources. The present invention can enable the receiver to quickly and accurately complete the capture by calculating the time information of the power-on time and the stored satellite navigation message and original observation information, and track and obtain the code ranging information of the corresponding satellite, effectively reducing the time for capturing and tracking satellite signal loss. Further, according to the stored navigation message and original observation information, the accurate satellite launch time is calculated, and there is no need to wait for the subframe synchronization to complete before obtaining the launch time. The satellite signal launch time can be obtained only through the satellite signal launch time equation and the signal transmission time equation, which is simple and easy to implement; at the same time, according to the GLONASS satellite orbit long-term dynamic model, the effective duration of the hot start is extended from 2 hours to 4 hours, and the satellite position accuracy is improved to within 0.25-1 meters. Compared with traditional technologies, the TTFF time of the hot start is greatly reduced, and the satellite position accuracy is improved. There is no need to use the position of the receiver before it is turned off. Compared with the existing method that requires the actual position of the receiver to be within 15 km of the position before it is turned off, this method has stronger adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0048] See also Figure 1 The present invention provides a method for high-precision and rapid positioning of a GLONASS receiver, comprising the following steps:

[0049] Step 1: GLONASS receiver calculates the current power-on time t u , and based on the ephemeris and other information stored before the last shutdown and the current startup time, calculate which satellites are currently available for positioning and determine whether the hot start conditions are met;

[0050] Step 2: The receiver calculates the reduced three-dimensional contraction range of signal capture based on the satellite Doppler and code phase information stored before the last power failure, quickly completes the capture and tracking of the subcode synchronization to measure the code phase information and enter the subframe synchronization state.

[0051] Step 3: The receiver constructs the satellite signal transmission time equation based on the code phase information measured by bit synchronization and the stored navigation message;

[0052] Step 4: According to the GLONASS satellite orbit height, construct the signal transmission time equation; solve the satellite signal transmission time through the satellite signal transmission time equation and the signal transmission time equation;

[0053] Step 5: Based on the calculated satellite signal transmission time and the stored ephemeris information, the long-term dynamic model of the satellite orbit is used, and the fourth-order Runge-Kutta method is used to obtain the position and velocity of the satellite corresponding to the current transmission time, and then a hot start positioning solution is performed to obtain a high-precision hot start positioning result.

[0054] The present invention further improves the positioning time and accuracy by:

[0055] The specific method of step 1 is:

[0056] The receiver calculates the GLONASS time information corresponding to the current power-on time based on the clock information read at the power-on time and the clock information saved before the last power-off. u , and judge t u The reference time t of the saved satellite ephemeris b Whether it is within 4 hours, and count whether the number of satellites that meet the conditions is greater than or equal to 4. If so, execute step 2, otherwise the hot start process fails.

[0057] In step 2, the receiver uses the code phase and Doppler information stored in the satellite that can be used for hot start obtained in step 1 to quickly complete signal search and bit synchronization, and obtain the corresponding code phase information.

[0058] The GLONASS satellite signal transmission time equation in step 3 is:

[0059] t (s) =TOW*2+t ca

[0060] Where: t (s) is the time of satellite signal transmission, TOW is the starting edge of the next frame of the navigation message corresponding to each subframe in seconds;

[0061] t ca It represents the position of the code phase information in the current subframe navigation message, and its corresponding equation is: Wherein, b is the number of navigation message subcodes in the current subframe; c is the number of C / A code cycles in the corresponding subframe, and the period of the C / A code is 1 millisecond; CP is the measured value of the code phase.

[0062] The GLONASS satellite signal transmission time equation in step 4 is:

[0063] t tran =t u -t (s)

[0064] Where, h represents the GLONASS satellite orbit altitude, and the corresponding value is 19100km; c vel Represents the speed of light.

[0065] The calculation method for the average satellite transmission time is:

[0066]

[0067] According to the transmission time equation, the transmission time t corresponding to the current moment is estimated (s)′ , and bring it into step 5 to calculate the corresponding satellite position [x (n)′ ,y (n)′ , z (n)′ ].

[0068] Then, according to the local receiver position stored at the time of power failure [x u ,y u , z u ], the estimated distance from the satellite to the receiver at the current moment is as follows:

[0069]

[0070] Then calculate the corresponding weekday time

[0071] Solve the GLONASS satellite signal transmission time equation and the signal average transmission time equation in parallel to obtain the satellite signal transmission time:

[0072] INT means rounding.

[0073] The long-term dynamic model of the GLONASS satellite orbit in step 5 is:

[0074]

[0075] a x =a x0 +a x1 (tt b )+a x2 (tt b ) 2 +a x3 (tt b ) 3 +a x4 (tt b ) 4

[0076] a y =a y0 +a y1 (tt b )+a y2 (tt b ) 2 +a y3 (tt b ) 3 +a y4 (tt b ) 4

[0077] a z =a z0 +a z1 (tt b )+a z2 (tt b ) 2 -a z3 (tt b ) 3 +a z4 (tt b ) 4

[0078] Where r represents the geometric distance between the satellite and the center of the earth;

[0079] a e Indicates the major radius of the PZ-90 reference ellipsoid;

[0080] The second-order band harmonic coefficient representing the Earth's oblateness;

[0081] ω Erepresents the angular velocity of the Earth's rotation;

[0082] GM represents the product of the Earth's gravity and the Earth's mass;

[0083] (x, y, z) represents the satellite position;

[0084] (V x , V y , V z ) represents the satellite speed;

[0085] (x″, y″, z″) represents the acceleration value caused by the gravity of the sun and the moon;

[0086] t b represents the reference time of the ephemeris data; t represents the transmission time of the satellite signal (s) ;

[0087] (a x , a y , a z ) represents the additional acceleration for calculating the satellite position, where (a xi , a yi , a zi ) represents the coefficients of a quartic polynomial.

[0088] The differential equation of motion of the GLONASS satellite is derived from Newton's law of universal gravitation. The equation of motion of the GLONASS satellite can be expressed in the geocentric inertial (ECI) coordinate system as

[0089]

[0090] The acceleration vector a in the geocentric inertial coordinate system ECI for

[0091]

[0092] The acceleration value in the geocentric inertial coordinate system is expressed as a function of position, velocity and acceleration in the geocentric earth-fixed coordinate system. The right side of the equal sign replaces the acceleration value r" on the left side of the equal sign. ECI , and make some appropriate approximations and simplifications on the higher harmonics of the satellite's gravitational potential energy and other external perturbations acting on the satellite, and consider the derivative relationship between the velocity and position state variables with respect to time t to obtain this linearized differential form equation.

[0093] The long-term dynamic model of the GLONASS satellite orbit uses the fourth-order Runge-Kutta method to calculate the satellite position and velocity error within 4 hours, which is 0.25-1 meter.

[0094] This method can be applied to existing GLONASS receivers and can perform hot start fast positioning.

[0095] The FPGA hardware platform experiment shows that if the receiver is turned on again within 4 hours after being shut down, the first positioning time of the GLONASS receiver using the hot start method and the conventional hot start is shown in Table 1:

[0096] Table 1. Hot start first positioning time using this method and conventional hot start

[0097] Shutdown time (minutes) Time for first hot start positioning using this method (seconds) Conventional hot start first positioning time (seconds) 30 1.5 9.5 60 2 10.5 90 2 10 120 2 9.5 180 2 fail 240 2 fail

[0098] In a static scenario with a signal strength of -130 dBm on the FPGA hardware platform, the hot start first positioning accuracy of the GLONASS receiver using this method and conventional hot start is shown in Table 2:

[0099] Table 2 Hot start first positioning accuracy using this method and conventional hot start

[0100] Shutdown time (minutes) The first positioning accuracy of hot start using this method (meters) Conventional hot start first positioning accuracy (meters) 30 2.248 8.174 60 3.756 9.396 90 2.547 7.289 120 9.145 16.503 180 10.984 fail 240 10.073 fail

[0101] Through the above method, the receiver can first calculate the narrowed three-dimensional search range of signal capture based on the Doppler and code phase information stored before the last power failure, thereby accelerating the signal capture speed. In addition, the satellite signal transmission time equation is constructed by the navigation message, and the signal transmission time equation, that is, the satellite signal transmission time constraint equation, is given according to the GLONASS satellite orbit altitude and the current power-on time. The satellite signal transmission time can be obtained through the satellite signal transmission time equation and the satellite signal transmission time constraint equation. Through the satellite signal transmission time and the ephemeris information stored before shutdown, the GLONASS satellite orbit long-term dynamic model is solved by the fourth-order Runge-Kutta numerical integration method to obtain the satellite position and velocity information corresponding to the transmission time. Then perform hot start positioning solution to obtain the position and velocity information of the hot start receiver. Compared with the traditional method that needs to complete the capture and tracking through blind capture, and then wait for the completion of subframe synchronization to obtain the satellite signal transmission time, the time of the capture and subframe synchronization process is reduced; among them, the duration of GLONASS blind capture is 1.5s, and the subframe synchronization takes 8 seconds, thereby greatly reducing the time of hot start, and reducing the duration of the first positioning of hot start to 1-2s; at the same time, based on the long-term dynamic model of the GLONASS satellite orbit, the effective duration of the hot start is extended from 2 hours to 4 hours, and the satellite position accuracy is improved to within 0.25-1 meter. It is not necessary to use the position of the receiver before it is turned off. Compared with the existing method that requires the actual position of the receiver to be within 15km of the position error before it is turned off, this method has stronger adaptability. Using this method for hot start, the startup success rate is nearly 100%, which greatly improves the success rate of hot start.

[0102] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for high-precision and rapid positioning of a GLONASS receiver, characterized in that: The following steps are involved: Step 1: The GLONASS receiver calculates the current power-on time, and based on the ephemeris information stored before the last shutdown and the current power-on time, calculates which satellites are currently available for positioning and determines whether the hot start conditions are met; Step 2: The receiver calculates the reduced three-dimensional contraction range of signal capture based on the satellite Doppler and code phase information stored before the last power failure, quickly completes the capture, tracks the subcode synchronization, measures the code phase information, and enters the subframe synchronization state; Step 3: The receiver constructs the satellite signal transmission time equation based on the code phase information obtained by subcode synchronization and the stored navigation message; Step 4: According to the GLONASS satellite orbit height, construct the signal transmission time equation; solve the satellite signal transmission time through the satellite signal transmission time equation and the signal transmission time equation; the satellite signal transmission time equation is: t tran =t u -t (s) ; The calculation method for the average satellite transmission time is: Where, h represents the GLONASS satellite orbit altitude, and the corresponding value is 19100km; c vel represents the speed of light; According to the transmission time equation, the transmission time t corresponding to the current moment is estimated (s) ′, using the satellite orbit long-term dynamic model, the corresponding satellite position [x (n) ′,y (n) ′,z (n) ′]; Then, based on the local receiver position stored at the time of power failure [x u ,y u , z u ], the estimated distance from the satellite to the receiver at the current moment is as follows: Then calculate the corresponding weekday time Solve the GLONASS satellite signal transmission time equation and the signal average transmission time equation in parallel to obtain the satellite signal transmission time: INT means rounding, t ca Indicates the position of the code phase information in the current subframe navigation message; Step 5: Based on the calculated satellite signal transmission time and the stored ephemeris information, the long-term dynamic model of the satellite orbit is used, and the fourth-order Runge-Kutta method is used to obtain the position and velocity of the satellite corresponding to the current transmission time, and then a hot start positioning solution is performed to obtain a high-precision hot start positioning result.

2. The method for high-precision rapid positioning of a GLONASS receiver according to claim 1, characterized in that: The specific method of step 1 is: The GLONASS receiver calculates the GLONASS time information corresponding to the current power-on time based on the clock information read at the power-on time and the clock information saved before the last power-off. u , and judge t u The reference time t of the saved satellite ephemeris b Whether it is within 4 hours, and count whether the number of satellites that meet the conditions is greater than or equal to 4. If so, execute step 2, otherwise the hot start process fails.

3. The method for high-precision rapid positioning of a GLONASS receiver according to claim 1, characterized in that: The GLONASS satellite signal transmission time equation in step 3 is: t (s) =TOW*2+t ca Where: t (s) is the time of satellite signal transmission, TOW is the starting edge of the next frame of the navigation message corresponding to each subframe in seconds; t ca It represents the position of the code phase information in the current subframe navigation message, and its corresponding equation is: Wherein, b is the number of navigation message subcodes in the current subframe; c is the number of C / A code cycles in the corresponding subframe, and the period of the C / A code is 1 millisecond; CP is the measured value of the code phase.

4. The method for high-precision rapid positioning of a GLONASS receiver according to claim 1, characterized in that: The long-term dynamic model of the GLONASS satellite orbit in step 5 is: a x =a x0 +a x1 (t-t b )+a x2 (t-t b ) 2 +a x3 (t-t b ) 3 +a x4 (t-t b ) 4 a y =a y0 +a y1 (t-t b )+a y2 (t-t b ) 2 +a y3 (t-t b ) 3 +a y4 (t-t b ) 4 a z =a z0 +a z1 (t-t b )+a z2 (t-t b ) 2 +a z3 (t-t b ) 3 +a z4 (t-t b ) 4 Where r represents the geometric distance between the satellite and the center of the earth; a e Indicates the major radius of the PZ-90 reference ellipsoid; The second-order band harmonic coefficient representing the Earth's oblateness; ωE represents the angular velocity of the Earth's rotation; GM represents the product of the Earth's gravity and the Earth's mass; (x, y, z) represents the satellite position; (V x , V y , V z ) represents the satellite speed; (x″, y″, z″) represents the acceleration value caused by the gravity of the sun and the moon; t b represents the reference time of the ephemeris data; t represents the transmission time of the satellite signal (s) ; (a x , a y , a z ) represents the additional acceleration for calculating the satellite position, where (a xi , a yi , a zi ) represents the coefficients of a quartic polynomial.

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