[0026] In practical applications, it can be known that for different application scenarios, the first positioning time may include hot start time, warm start time, and cold start time.
[0027] For hot start, that is, when the GNSS receiver restarts in a short time, the ephemeris, almanac, precise time, and receiver position obtained by the GNSS receiver are all valid, so that the carrier Doppler shift and PN can be calculated Code phase, realizing fast reacquisition and tracking of satellites. At the same time, the satellite position can be calculated based on the resolved ephemeris parameters to achieve rapid positioning. Normally, the hot start time of a GNSS receiver is a few seconds.
[0028] For a warm start, the ephemeris parameters received by the GNSS receiver are no longer valid, but the parameters such as the almanac and the approximate position of the receiver are still valid. At this time, the approximate position of the satellite and the approximate position of the receiver are calculated through the almanac, which can effectively reduce the PN code phase and the carrier Doppler frequency shift search range, and achieve fast acquisition and tracking of the satellite. Due to the need to re-analyze the navigation message, the warm start time of the GNSS receiver requires tens of seconds.
[0029] For cold start, the cold start time refers to the first positioning time when the receiver has not been turned on for a long time and no valid parameters are available. Since it is necessary to search for satellites in all directions to achieve satellite tracking and capture, it usually takes several minutes to realize the positioning function, which takes a long time.
[0030] In order to reduce the cold start time of the GNSS receiver, the existing A-GPS technology combines wireless communication technology to obtain auxiliary positioning data provided by the server to reduce the cold start time. However, in some remote areas, such as the sea or mountainous areas, GNSS receivers cannot connect to the mobile network, and thus cannot obtain the auxiliary positioning data provided by the server, so the cold start time cannot be reduced. In addition, in order to support wireless communication technology, the GNSS receiver is also equipped with corresponding hardware equipment, which results in a higher cost of the GNSS receiver.
[0031] In the embodiment of the present invention, when obtaining the predicted orbit of the satellite, it is determined according to the current time, stored historical broadcast ephemeris, and a priori visible satellite table. Therefore, there is no need to obtain auxiliary positioning data provided by the server, so there is no need to add The cost of the GNSS receiver. Since the forecasted orbit of the satellite is obtained, the cold start time of the GNSS receiver can be reduced.
[0032] In order to make the above objectives, features, and beneficial effects of the present invention more obvious and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0033] The embodiment of the present invention provides a satellite positioning method, refer to figure 1 , The following is a detailed description through specific steps.
[0034] Step S101, according to the pre-stored historical broadcast ephemeris and a priori visible satellite table, obtain the predicted orbits of all satellites in the a priori visible satellite table at the current moment.
[0035] In a specific implementation, the stored historical broadcast ephemeris can be first used to calculate all satellite position sequences corresponding to the historical broadcast ephemeris, and all satellite position sequences are converted from the geocentric-earth fixed system to the geocentric inertial system.
[0036] In the embodiment of the present invention, the historical broadcast ephemeris may be the most recently stored broadcast ephemeris, that is, the latest stored broadcast ephemeris. The historical broadcast ephemeris can also be other previously stored broadcast ephemeris, which can be selected according to actual needs.
[0037] In a specific implementation, after converting all satellite position sequences from a geocentric-earth fixed system to a geocentric inertial system, the state vectors corresponding to all satellites in the a priori visible satellite table can be initialized. The state vector corresponding to the satellite may include satellite position, satellite speed, and perturbation force model parameters.
[0038] After the perturbation force model is established, the close orbit corresponding to each satellite in the prior visual satellite table and the partial derivatives of its dynamic parameters can be calculated, and the equations of motion and variational equations can be established. According to the perturbation force model and the position sequence of all satellites in the prior visual satellite table, the initial orbits corresponding to all the satellites in the prior visual satellite table are fitted. Perform dynamic prediction according to the current time and the respective initial orbits of all satellites in the prior visual satellite table to obtain the predicted orbits of all satellites in the prior visual satellite table at the current time.
[0039] That is to say, in the embodiment of the present invention, the obtained orbit forecast is for all satellites in the prior visual satellite table. For the satellites in the non-a priori visible satellite list, orbit prediction is not required, which can reduce the calculation amount of orbit prediction.
[0040] Generally speaking, within a period of time, the moving distance of the GNSS receiver will not be too far. Therefore, the a priori visible satellite corresponding to the GNSS receiver will not change much. Therefore, in specific implementation, the a priori visible satellite list can be determined according to the current time and the geographic location where the GNSS receiver was last positioned.
[0041] For example, if the current geographic location of the GNSS receiver is point A, and there is a difference of 2 hours between the current time and the last positioning time, you can set the prior visual satellite table corresponding to the GNSS receiver at the current time and the previous positioning time. The a priori visual satellite table is the same.
[0042] In a specific implementation, the GNSS receiver may first obtain the local clock provided by the built-in Real Time Clock (RTC) module, and obtain the current time according to the local clock combined with the forecast clock error.
[0043] Step S102: Perform a positioning operation according to the predicted orbits of all satellites in the a priori visible satellite table at the current moment.
[0044] In specific implementation, the GNSS receiver can perform positioning operations after obtaining the predicted orbits of all satellites in the a priori visible satellite table corresponding to the current moment.
[0045] It can be seen that, in the embodiment of the present invention, when obtaining the predicted orbit of a satellite, it is determined according to the current time, stored historical broadcast ephemeris and a priori visible satellite table, so there is no need to obtain auxiliary positioning data provided by the server. , So there is no need to increase the cost of the GNSS receiver. Since the forecasted orbit of the satellite is obtained, the cold start time of the GNSS receiver can be reduced.
[0046] The satellite positioning method provided in the foregoing embodiment of the present invention is mainly aimed at an application scenario of a GNSS cold start. In practical applications, before the GNSS receiver performs a cold start, it needs to make sure that the latest stored ephemeris and the stored almanac are invalid. In other words, when it is detected that the stored latest ephemeris and almanac are invalid, the steps S101 to S102 provided in the foregoing embodiment of the present invention are executed.
[0047] In specific implementation, when the GNSS receiver is turned on, it can first determine whether the latest stored ephemeris is valid. If it is determined that the stored latest ephemeris is valid, the GNSS receiver can perform a hot start operation, calculate the satellite position and perform positioning operations according to the resolved ephemeris parameters; if it is determined that the stored latest ephemeris is invalid, the GNSS receiver can determine to store Whether the calendar is valid. If it is determined that the stored ephemeris is valid, the GNSS receiver can perform a warm start operation.
[0048] When the GNSS receiver performs a warm start operation, it can first calculate the approximate position of the satellite and perform auxiliary acquisition and tracking. Then, according to the approximate position of the satellite and the approximate position of the GNSS receiver, the orbit prediction of the visible satellite corresponding to the approximate position of the current position is performed to realize the positioning function.
[0049] The following describes the specific work process after the GNSS receiver is turned on.
[0050] Reference figure 2 , Another satellite positioning method in the embodiment of the present invention is given, which is described in detail below through specific steps.
[0051] Step S201, obtain approximate local time.
[0052] In a specific implementation, the GNSS receiver can obtain the approximate local time by reading the built-in real-time clock unit.
[0053] In step S202, the approximate local time is corrected.
[0054] In specific implementation, the approximate local time can be corrected by quadratic polynomial fitting and the gray model method for clock error prediction, and the corrected local time can be obtained as the current time.
[0055] Step S203: Determine whether the stored latest ephemeris is valid.
[0056] In the embodiment of the present invention, when the stored latest ephemeris is valid, step S204 is executed; when the stored latest ephemeris is invalid, step S205 is executed.
[0057] Step S204, perform a hot start operation.
[0058] In a specific implementation, for the hot start operation, no ephemeris analysis is required, and the satellite position is calculated according to the resolved ephemeris parameters and the positioning operation is performed. In the subsequent navigation and positioning process, only the satellite clock error storage database and the satellite ephemeris storage database can be updated.
[0059] Step S205: It is judged whether the stored almanac is valid.
[0060] In a specific implementation, when it is determined that the stored latest ephemeris is invalid, the GNSS receiver cannot perform a hot start. At this point, it can be judged whether the stored almanac is valid. When the stored almanac is valid, step S206 can be performed; when the stored ephemeris is invalid, step S207 is performed.
[0061] Step S206, perform a warm start operation.
[0062] In a specific implementation, when the stored latest ephemeris is invalid and the stored almanac is valid, a warm start operation can be performed. When performing a warm start operation, you can first calculate the approximate position of the satellite for auxiliary acquisition and tracking. At the same time, the approximate position of the GNSS receiver and the approximate position of the satellite are judged to obtain the visible satellite corresponding to the approximate position of the current GNSS receiver, and the orbit prediction of the determined visible satellite is made.
[0063] Step S207, perform a cold start operation.
[0064] In a specific implementation, when the latest stored ephemeris is invalid and the stored almanac is also invalid, it can be determined that the GNSS receiver is currently performing a cold start operation. For the specific process of the cold start operation performed by the GNSS receiver, reference may be made to step S101 to step S102 provided in the foregoing embodiment of the present invention, which will not be repeated here.
[0065] In a specific implementation, the satellite positioning method provided in the foregoing embodiment of the present invention can be executed by the orbit prediction module in the GNSS receiver. The orbit prediction module can be implemented by hardware or software.
[0066] When the orbit prediction module is implemented by hardware, after the GNSS receiver completes the demodulation of the ephemeris parameters of the navigation satellite, the orbit prediction module can be controlled to turn off to reduce the power consumption of the GNSS receiver. When the orbit prediction module is implemented by software, after the GNSS receiver completes the demodulation of the ephemeris parameters of the navigation satellite, the orbit prediction function can be turned off to reduce the power consumption of the GNSS receiver.
[0067] In practical applications, it can be known that the positioning of the GNSS receiver can be achieved by using 4 navigation satellites. Therefore, after completing the demodulation of the ephemeris parameters of the 4 navigation satellites, the orbit prediction module can be controlled to close.
[0068] Reference image 3 , A satellite positioning device 30 in an embodiment of the present invention is provided, including: an acquiring unit 301 and a positioning unit 302, wherein:
[0069] The obtaining unit 301 is configured to obtain the predicted orbits of all satellites in the a priori visible satellite table at the current moment according to the pre-stored historical broadcast ephemeris and the a priori visible satellite table;
[0070] The positioning unit 302 is configured to perform positioning operations according to the predicted orbits of all satellites in the a priori visible satellite table at the current moment.
[0071] In a specific implementation, the acquiring unit 301 may be used to calculate the position sequence of all satellites at the corresponding time according to the historical broadcast ephemeris, and convert the position sequence of all satellites from the geocentric to the geocentric Inertial system; initialize the state vector corresponding to all satellites in the prior visual satellite table, establish the corresponding perturbation force model; fit the initial orbit according to the perturbation force model and the position sequence of all the satellites; Dynamic prediction is performed at the current time and the initial orbit, and the predicted orbits of all satellites in the prior visible satellite table at the current time are obtained.
[0072] In a specific implementation, the a priori visible satellite list may be determined in the following manner: the a priori visible satellite list is determined according to the current time and the geographic location where the last positioning is located.
[0073] In a specific implementation, the satellite positioning device 30 may further include: a determining unit 303, configured to determine the latest stored orbit before the acquiring unit 301 acquires the predicted orbits of all satellites in the prior visible satellite table at the current moment The ephemeris is invalid and the stored almanac is invalid.
[0074] In a specific implementation, the satellite positioning device 30 may further include: a hot start unit 304, configured to perform a hot start operation when the stored latest ephemeris is valid; the positioning unit is also configured to perform a hot start operation according to the analyzed Ephemeris parameters calculate the satellite position and perform positioning operations.
[0075] In a specific implementation, the satellite positioning device 30 may further include a warm start unit 305, configured to perform a warm start operation when the stored latest ephemeris is invalid and the stored almanac is valid, and the warm start operation includes: computing a satellite The approximate position and auxiliary acquisition and tracking are performed; according to the approximate position of the satellite and the approximate position of the current location, the orbit prediction of the visible satellite corresponding to the approximate location of the current location is performed.
[0076] The embodiment of the present invention also provides a computer-readable storage medium on which computer instructions are stored. When the computer instructions are executed, the steps of the satellite positioning method provided in any of the foregoing embodiments of the present invention are executed, which will not be repeated here. .
[0077] An embodiment of the present invention also provides another satellite positioning device, including a memory and a processor. The memory stores computer instructions. When the computer instructions run, the satellite positioning method provided in any of the foregoing embodiments of the present invention is executed. The steps are not repeated here.
[0078] Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable storage medium, and the storage medium can include: ROM, RAM, magnetic disk or CD, etc.
[0079] Although the present invention is disclosed as above, the present invention is not limited to this. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.
