method and system for determining satellite clock corrections

专利摘要:
METHOD AND SYSTEM FOR DETERMINING SATELLITE CLOCK CORRECTIONS A satellite clock error is determined for each navigation satellite based on pseudo-range code measurements, carrier phase measurements, and diffusion satellite clock errors provided by a receiver network (S402). Differences are determined between the computed satellite clock errors and the diffusion clock errors for each satellite (S406). For each constellation, a clock reference satellite is selected from among the navigation satellites, where the clock reference satellite has a median value of difference in clock error for that satellite constellation (S408). A correction is determined for the diffusion clock error by applying a reference satellite clock error function to diffusion clock error for each satellite in one or more constellations (S410).
公开号:BR112013017960A2
申请号:R112013017960-0
申请日:2012-01-11
公开日:2020-06-30
发明作者:Liwen L. Dai；Michael A. Zeitzew；Yiqun Chen；Yujie Zhang
申请人:Deere & Company；
IPC主号:

专利说明:

“METHOD AND SYSTEM FOR DETERMINING SATELLITE CLOCK CORRECTIONS” This document claims priority based on US provisional application serial number 61 / 432.646, filed on January 14, 2011 and entitled METHOD AND SYSTEM FOR ' DETERMINING CLOCK CORRECTIONS, under 35 USC 119 (e). Field of the Invention This invention relates to a method and system for determining clock corrections for a satellite navigation system.
Background of the Invention A location determination receiver, such as a Global Navigation Satellite System (GNSS) receiver, can estimate the position and speed of an object or vehicle. The location determination receiver can derive inaccurate positions and speeds due to inaccurate clock data from one or more satellites. GNSS add-on systems that distribute corrections for GNSS errors provide user receivers with information that allows for more accurate navigation than would be possible. Such accretion systems typically include clock and orbit corrections for the transmitted clock and orbit information.
A GNSS addition system typically includes a network of receivers at known locations. These receivers transmit information to a Processing Center, where the information is combined and GNSS corrections are computed. Because each receiver in the network of the add-on system has its own local clock that is not synchronized with the other clocks in the network, it is necessary to have a single time source to which all the information of the receivers in the network can be referenced.
Under the prior art approach, at one or more receivers in the network, an accurate clock (typically a stern atomic clock to a network receiver) is used to provide timing signals to a network receiver. Such a receiver on the network thus has a very stable timing reference, and that receiver on the network can be used as the only time source to which information from other receivers on the network can be referenced. Because of the possible failure of the precise clock or the failure of 'communication links between this network receiver and the Processing Center, several precise clocks are usually deployed to improve the reliability of the system. The performance of these accurate watches is typically assessed and monitored in real time to facilitate switching - between accurate watches.
In practice, this prior art approach requires expensive atomic clocks to be located on several different sites with network receivers. Therefore, there is a need for an improved economic method and system for determining clock corrections for a satellite navigation system. In particular, there is a need for a method and system for determining clock corrections that do not require an accurate clock at any receiver on the network.
Summary of the Invention According to one embodiment, a method and system for - determining satellite clock corrections facilitates the determination of accurate position estimates by one or more mobile location determination receivers. The method and system comprise collecting pseudo-range code measurements, carrier phase measurements, and navigation message data (eg, diffusion clock error data or - diffusion clock deviation) from a network of stationary receivers of satellite signals transmitted by one or more constellations of navigation satellites. At each time interval (eg, a period of time), a clock error is computed for each navigation satellite based on pseudo-range code measurements, carrier phase measurements, and message data navigation data collected. Differences in clock error are formed between the computed satellite clock error and the diffusion clock error for each satellite. For each constellation, a clock reference satellite is selected from among the navigation satellites in that i 5 - constellation, which has the median value of difference in clock error for 'that satellite constellation. A correction for the diffusion clock error for each satellite in that constellation is then determined by adding a function of the clock error of the clock reference satellite to the diffusion clock error for each satellite in that constellation (eg, in a - satellite base by satellite within each constellation). The correction value for each time period or other time interval (eg, multiple time periods) is limited based on a control parameter limit (eg, where the control parameter limit is less than that or approximately equal to the clock error of the clock reference satellite, 15 "or where the control parameter limit comprises a fixed parameter, expressed in units of distance, as a Kalman filter solution converges in solution to the error of diffusion clock).
Brief Description of the Drawings FIG. | it is a block diagram of a first - modality of a system for determining clock corrections.
FIG. 2 is a block diagram of a second embodiment of a system for determining clock corrections.
FIG. 3 is a block diagram of a mobile location-determining receiver according to the system of FIG. | or FIG. 2.
FIG. 4 is a first example of a flowchart of a method for determining clock correction errors according to any modality of the system.
FIG. 5 is a second example of a flowchart of a method for determining clock correction errors according to any modality of the system.
FIG. 6 is a flow chart of a method for determining a position estimate or speed estimate on a receiver that receives clock correction errors.
l 5 Description of the Preferred Modality 'According to a system 11 modality for determining clock corrections for a satellite navigation system (eg, GNSS system), system 11 facilitates real-time determination of clock corrections accurate and regular satellite data for broadcast satellite clock error data to support increased reliability and accuracy of mobile location determination receivers 42 that can use real-time clock correction data 44. The method and system produce clock correction data 44 (eg, clock correction errors) that are well suited to provide increased precision and resolution in determining the position or speed of a mobile location determination receiver 42, or a associated object, in real time.
In one embodiment, the system 11 comprises a network of receivers 15 ie capable of communicating with a central electronic data processing system 16 via one or more communication links 13. The central electronic data processing system 16 is coupled to a earth-based satellite communications device 38 that facilitates the communication of clock correction data 44 or other correction data (eg, position correction data) to one or more mobile location determination receivers 42 via a communications device via 25 "remote satellite 40 (eg, satellite vehicle) in orbit above the Earth's surface. The mobile location determination receiver 42 is associated with a correction 41 communications device (eg, a satellite correction receiver) that is capable of receiving satellite signals (e.g., or clock correction data 44) processor from remote satellite communications device 40, although FIG. 1 i a land-based satellite communications device 38, a remote satellite communications device 40 and a correction communications device 41 for communicating or distributing correction data, the correction or correction data can be i 5 - distributed across any way with electronic communications, telecommunications, electromagnetic signals, or wireless communications.
In one embodiment, the receiver network 15 comprises a first reference station 10 to an Nth reference station 14, where N is equal to any positive or integer number greater than 2. As shown in FIG. 1, the receiver network 15 comprises a first reference station 10, a second reference station 12 and a third reference station where N is equal to three, for example. In one embodiment, the receiver network 15 may comprise reference stations (10, 12 and 14) that are distributed globally in different known locations (eg, coordinates of the geographical station), although regional or local distribution of the reference stations ( 10, 12 and 14) is possible. Each reference station (10, 12 and 14) comprises a reference receiver 51 in a respective known or fixed location, a central electronic data processing system 53, and a transmitter or transceiver 55. Each reference receiver 51 receives or detects one or more of the following: (1) pseudo-range code data or measurements, (2) carrier phase data or measurements, (3) broadcast satellite clock error data, (4) ephemeris data, and (5) other data - reference navigation. Reference receiver 51 can receive satellite signals, carrier signals and coded signals from one or more Global Positioning System (GPS) satellites, one or more Global Navigation Satellite System (GLONASS) satellites, or both . The data receiver processing system 53 can store, retrieve, and process reference navigation data associated with received satellite signals, carrier signals, and coded signals. In one embodiment, the transmitter or transceiver 55 of each reference station (10, 12 or 14) transmits one or more of the following i 5 data to a central 16 electronic data processing system or computer device via one or more links communication 13: (1) pseudo-range code data or measurements, (2) carrier phase data or measurements, (3) broadcast satellite clock error data, (4) ephemeris data, (5) reference navigation data, and (6) derivative data derived from analysis or processing of any of the preceding data items. For example, the data transmitted above may relate to a first constellation of navigation satellites (eg, Global Positioning System (GPS) satellites), a second satellite constellation (eg, GLONASS satellite), or both.
The reference navigation data may comprise one or more of the following data items: (a) the respective location or geographical coordinates of the reference station of each corresponding reference station (10, 12 or 14), (b) the respective coordinates antenna geographic data for each reference receiver 51, (c) the respective reference station identifiers for each reference station (10, 12 or 14), and (d) the satellite identifiers for the respective satellites that provided the corresponding data diffusion clock error and corresponding ephemeris data.
2 Communication links 13 support real-time data transmission between the reference station (10, 12 or 14) and the central electronic data processing system 16. Communication links 13 can comprise one or more of the following: a packet data network, a data network, a virtual private network, an internet data communications path, telecommunications equipment, optical communications equipment, radio frequency communications equipment, microwave communications equipment , a fiber optic link, a microwave communication link dot to 5 dot, a dedicated wire line connection, a multi-conductor cable, a coaxial cable transmission line, an optical transmission line, a communication line, or other suitable communication links to communicate data in real time.
Pseudo-range code data or measurements can be —decoded by the reference receiver 51 from information that modulates or encodes the satellite signals that are received by each reference receiver 51.
The carrier phase measurement data can originate from a phase measurement device in the reference receiver 51 that —receives one or more carrier signals or data from a receiver front end, for example. In one embodiment, the phase measurement device can provide phase carrier measurements for GPS carrier signals, GLONASS carrier signals, or both.
Ephemeris data comprises orbital satellite information or data collection at satellite positions with reference from one or more reference positions on or near the Earth's surface according to a time schedule. Ephemeris data can be stored in a database or in one or more files. Satellites can transmit ephemeris data in a navigation message - which is capable of being received by the reference receiver 51.
In an alternative embodiment, the reference receiver 51 detects carrier phase data or carrier phase measurements associated with one or more carrier signals; the reference data processing system 53 at the reference station (10, 12 or 14) determines an initial carrier phase ambiguity solution or carrier phase ambiguity solution configured for multiple satellite signals received at the reference receiver 51 The reference data processing system 53 receives carrier phase data and the solution | The initial ambiguity corrects them, using the known or fixed location of the reference receiver 51, to determine a solution of increased ambiguity.
In one example, corrected carrier phase data comprises the estimated carrier phase and the enhanced ambiguity solution, or other data derived from them.
In turn, the corrected carrier phase data or other correction data is transmitted via a wireless signal or electromagnetic signal to the central data processing system 16. In one embodiment, the central electronic data processing system 16 comprises a central device of one or more computers.
The central electronic data processing system 16 comprises a data processor 18, a data storage device 22, and a communications interface 36 which are coupled to a data bus 20. Data processor 18 may comprise a microprocessor, a controller, a programmable logic matrix, an application-specific integrated circuit, an arithmetic logic unit, or another device that is suitable for processing data, performing mathematical operations on the data, or performing Boolean logic or arithmetic logic on the data.
The data storage device 22 may comprise electronic memory, an optical storage device, a magnetic storage device, or another device that is capable of storing and retrieving data.
As shown in FIG. 1, the data storage device 22 stores, supports or interfaces with one or more of the following modules: a data collection module 24, a parameter estimator 26, a main predictive filter 27, a clock difference module 28, a reference satellite selector 30, a clock correction module 32, and a communications module 34. Any of the above modules (24, 26, 27, 28, 30, 32 and 34) on the data storage device 22 can comprise a software module, an electronic module, | 5 software instructions, or a hardware or electronic module to 'carry out equivalent software instructions. If any of the modules above comprise software instructions or programs, those software instructions or software programs may be stored on the data storage device 22, on an optical storage medium, a magnetic storage medium or another storage medium which is non-transitory or substantially permanent. In one embodiment, the data collection module 24 provides software instructions for or being able to collect, organize, and manage the processing of, data or pseudo-range code measurements, carrier data or phase measurements, and data navigation message messages (e.g., including ephemeris and broadcast satellite clock error data) received by a network of receivers 15 that receive signals over multiple frequencies transmitted by one or more constellations of navigation satellites. The constellation of navigation satellites can refer to the constellation —doGPS, the GLONASS constellation, or other constellations, for example. In one embodiment, the data collection module 24 monitors the above information in a database, a map, a file, (eg, an inverted file) or another data structure that allows reference data to be identified , organized or classified by identifier - of reference station or geographical coordinates of the reference station (10, 12, 14).
Parameter estimator 26 provides software instructions for either being able to compute or determine computed satellite clock error data (eg, clock state data) on a time-by-time basis for each period satellite based on pseudo-range code data or measurements, carrier phase data or measurements, the respective known locations of the reference stations (or reference receivers) and the i 5 satellite clock error data - diffusion. In one configuration, parameter estimator 26 can compute 'or determine the computed satellite clock error based on navigation message data (eg, which includes broadcast satellite clock error data) in addition to pseudo-range code data or measurements, to carrier phase data or measurements, to the respective 10 known locations of reference stations (or reference receivers). In one embodiment, parameter estimator 26 may comprise, use or access one or more of the following: an orbit estimator, a clock estimator, a predictive filter, an error reduction filter, and a Kalman filter.
A time period can be defined by one or more of the following: a start date / time, an end date / time, a duration or interval, or a discrete time when a reference receiver 51 takes an incoming radio frequency snapshot or signal varying from microwave and generates a carrier / pseudo-range phase measurement. The current - time period refers to the most recent instant when the last measurement (eg GPS measurement) is generated.
The clock difference module 28 provides software instructions for or is capable of forming or determining the clock error differences between computed satellite clock error data pairs and the broadcast error clock data for each satellite in one or more constellations. In one embodiment, for each satellite received by reference receiver 51, the computed satellite clock error is determined or estimated based on carrier phase measurements, pseudo-range code measurements, at the respective fixed locations known to the stations (10, 12, and 14) in the diffusion satellite clock error. Clock difference module 28 can compute a first set of computed satellite clock error data with respect to the GPS constellation and a second set of computed error data from i 5 - satellite clock computed for the GLONASS constellation, or both.
In general, absolute clocks for each satellite and location determination receiver are not observable in each Global Satellite Navigation System (GNSS) (eg, GPS and GLONASS) for orbit and clock determination. At least one additional restriction, such as a pseudo-code measurement or a carrier phase measurement for each system of the global satellite navigation system (GNSS), is required to accurately determine the satellite clock error and the clock error of the receiver. In one embodiment, the broadcast satellite clock error data may represent a clock bias, a clock shift, or differential clock data with respect to the respective constellation system clock (eg, GPS system clock or GLONASS system clock). Clock difference module 28 or data processing system 16 determines differences in clock error or - error data between computed satellite clock error data and broadcast clock data for each satellite in each constellation in a satellite base to satellite, or as otherwise limited to particular subsets of satellites within each constellation. Differences in clock error or error data can be stored in one or more vectors or matrices in the data storage device 22, where each matrix corresponds to a particular constellation. Although each vector or matrix can cover all satellites in a constellation, it is possible that the matrix is confined to a subset of each constellation to improve data processing of input and output time or computational time
(eg from data processors 18) required to determine and group computed satellite clock error data or clock error differences in the central electronic data processing system 16 to achieve real-time responsiveness in provisioning i 5 - correction data (eg clock correction errors) for an end user 'of the mobile location determination receiver 42. For that purpose, certain core satellites, such as the AMC-1 satellite or other satellites that have historical accuracy of satellite clock data within 10 nanoseconds of precision with respect to the constellation system time (eg GPS system time) can be included in the subset of the satellite group in each constellation for which differences or error data are computed.
The reference satellite selector 30 provides software instructions for or being able to select (eg, on a dynamic time-to-time basis) a particular constellation satellite as the clock reference satellite for each constellation , where the clock reference satellite has a median value of the differences formed above for each satellite constellation (eg, GPS and GLONASS) for a particular respective period of time. For example, the median value can - be used more properly than the median value to exclude any erroneous influence or impact other than peripheral satellite clock data such as the resulting differences or error data. If the median value was used, the resulting error data could be inappropriately distorted by peripheral satellite clock data from an improperly functioning satellite clock.
The clock correction module 32 provides software instructions for either being able to compute or determine the correction (e.g., clock correction data 44 or satellite clock correction data) for the satellite clock error data broadcast by adding or adjusting the broadcast satellite clock data on a satellite satellite basis. For example, clock correction module 32 is adapted to determine clock correction errors by adding a function (eg, mathematical function, linear algebraic function, or matrix expression) from i 5 - clock difference or error data associated with reference satellite 1 selected for each diffusion satellite clock error of the other satellites in the constellation. In one embodiment, the clock correction module 32 comprises one or more of the following: a predictive filter, an error reduction filter and a Kalman filter. In another embodiment, the clock correction module 32 and the parameter estimator 26 can access, share usage or incorporate a main predictive filter
27. The main predictive filter 27 comprises a predictive filter, error reduction filter, or Kalman filter. The communications module 34 provides software instructions for or being able to support a distribution of computed clock correction data 44 to user receivers (eg via a satellite communication system as illustrated in FIG. | Or via the system) wireless communication).
In one embodiment, one or more accurate satellite clocks (eg, atomic clocks) on each orbiting satellite are used as a broadcast satellite clock, as a potential master satellite clock, or as the source of clock data of satellite. One or more satellite clocks can be selected as the source of clock data for correction data or the position solution of the mobile location determination receiver 42. For example, a GPS satellite clock, a GLONASS satellite clock, or a hybrid of the GPS satellite clock and the GLONASS satellite clock can be selected as the source of clock data. In a first example, satellite clock data that is used in clock correction data 44 comprises the median of the GPS satellite clock across the entire GPS constellation, or a portion of material (eg, majority or a size statistically significant sample) of the constellation that serves a wide area. In a second example, satellite clock data is used in the correction data for | 5 - clock 44 comprises the GLONASS 'satellite clock median across the entire GLONASS constellation, or a portion of material (eg, majority or a statistically significant sample size) of the constellation that serves a wide area. In a third example, the satellite clock data is used in the clock correction data comprised — the average of the GPS satellite clock across the entire GPS constellation and the median of the GLONASS satellite clock across the entire GLONASS constellation.
According to one embodiment, the system and method for the adaptive diffusion master clock is well suited for eliminating the input external precision clock frequency (eg atomic receiver clock, atomic reference oscillator on reference receiver 51) and reducing the complexity of daily operation and the cost of developing a wide-area or global differential correction system. As used here, the master clock must refer to the clock reference satellite clock for the GPS constellation for the GLONASS constellation which has the median value of the clock error differences for any period of time, such that the master clock can change from one time period to another. Because there is an extraordinary number of satellites as a possible clock data source under a method and system, the reliability of clock data can be further improved. Another advantage of the system and method is to facilitate clock corrections or clock correction data 44 which have zero mean statistical values (eg, or close to zero mean statistical values) and which can be delimited correction fluctuation rate according to pre-established or pre-defined restrictions.
The system 111 of FIG. 2 is similar to system 11 of FIG. 1, except that the system 111 of FIG. 2 replaces the earth-based satellite communications device 38 and the remote satellite communications device 40 with a wireless base station 138. The wireless base station 138 | 5 - can represent part of a wireless communications network, for example. In addition, the mobile location determination receiver 42 is associated with a correction communications device 141 that comprises a transceiver or wireless communications device (e.g., cellular, Global System for Mobile Terminal Communications (GSM) device , a code division multiple access device (CDMA) or other wireless communications device) to communicate with wireless base station 138. The same reference numbers in FIG. | and FIG. 2 indicate similar elements.
In FIG. 2, clock correction data 44 (e.g., clock correction errors) is transmitted and made available to one or more mobile location receivers 42 associated with respective correction communication devices 141 within the coverage area.
FIG. 3 illustrates an example of the mobile location determination receiver 42 that can be used in an embodiment of FIG. 1 or FIG. 2.0 The mobile location determination receiver 42 comprises a front-end receiver 302 coupled to an analog to digital converter input 306. The output (eg digital baseband) of the analog to digital converter 306 is coupled to the system electronic data processing of the receiver 308.
The receiver's electronic data processing system 308 comprises a receiver data processor 310, a receiver data storage device 312, a receiver data bus 324, a data port 322, a decoder 320, and a device phase measurement device 304. The data processor of the receiver 310, the data storage device of the receiver 312, the data port 322, the phase measurement device 304, and the decoder 320 are coupled to the data bus of the receiver 324 to support communications between the preceding components of the SS 308 receiver's electronic data processing system The receiver 310's data processor may comprise a microprocessor, a controller, a programmable logic matrix, an application-specific integrated circuit, an arithmetic logic unit , a logic device, an electronic data processing device, or another device for executing software, logic, arithmetic, or i program instructions.
The data storage device of the receiver 312 comprises electronic memory, an optical storage device, a magnetic storage device, or another storage device. The receiver's data storage device 312 comprises a real-time kinematic mechanism 314, a predictive filter 316 (e.g., Kalman filter), and a position estimator 318.
The location determination receiver 42 is associated with a correction communications device (41 or 141). A correction communication device (41 or 141) can be integrated into the location determination receiver 42 or can communicate with the location determination receiver via data port 322. A correction communication device (41 or 141 ) receives correction data (eg, clock error correction data (ie, 44) and / or reference carrier phase correction data) from the central electronic data processing system 16 via one or more devices intermediary communication channels via satellite or wireless (eg, 38, 40 in FIG. 1, or 138 in FIG. 2). The receiving end 302 may comprise any suitable circuit for receiving satellite signals transmitted by one or more satellites (e.g., navigation satellites). The front-end receiver 302 may be able to receive both satellite signals from GPS and GLONASS, for example. The receiver front-end 302 may comprise a spread-spectrum receiver or multiple-division-code (CDMA) receiver that is capable of receiving multiple carriers transmitted by one or more satellites within a constellation of satellites. For example, receiver front end 302 may comprise a preamplifier or amplifier to amplify satellite signals, a mixer and a reference oscillator, where the amplifier input is coupled to an antenna, the amplifier output is coupled to an input of the mixer, the reference oscillator is coupled to the other input of the mixer, and the output of the mixer is coupled to the 308 receiver data processing system.
In one embodiment, the analog to digital converter 306 provides an interface between the front end receiver 302 and the electronic data processing system of the receiver 308. The analog to digital converter 306 converts analog phase measurements into phase measurement data. digital carrier that can be processed or manipulated by the 308 receiver's electronic data processing system.
The decoder 320 determines pseudo-range code measurements and provides the pseudo-range code measurements for the receiver's electronic processing system 308. In one embodiment, a decoder 320 comprises a modulation-removing device or another device for removing modulation from the pseudo-random noise code (eg, gross acquisition code (C / A) or other more precise civil or military coding) that modulates one or more carriers. For example, the decoder 320 may comprise a group of 351 correlators (eg, a GPS channel correlator and a GLONASS channel correlator), where each correlator
351 is coupled to the pseudo-random noise code generator 390 to provide signal components in phase (1) and quadrature (Q) from which modulation has been removed (eg, amplitude and phase or vectors). For GPS, the L1 carrier signal is modulated with the coarse acquisition code | 5 (C / A) is the precise code to which P (Y) encryption has been applied, whereas' the L2 signal is modulated with the precise code to which P (Y) encryption has been applied. In one embodiment, the decoder may comprise a code generator coupled to an input delay module, where an output from the delay module is coupled to a correlation device to measure the correlation between a reference pseudo-random noise code, which is liable to be delayed by increments known to the delay module, and a pseudo-random noise code received from a receiver front end 302. The decoder 320 can also facilitate decoding the navigation information that modulates a carrier signal, - such as ephemeris data.
The 304 phase measurement device comprises any device, integrated circuit, electronic module, or data processor for measuring the phase of a carrier signal. In one configuration, the phase measurement device 304 comprises a signal generator, a phase delay module coupled to a first correlator and second correlator. The phase measurement device measures or estimates the observed phase of one or more carrier signals provided by the receiving front end 302. The measured phase can be expressed in whole wavelengths of the carrier signal, the carrier signal, lengths of - fractional wave of the carrier signal, and / or degrees of the carrier signal.
The phase measurement device 304 can determine one or more of the following: (1) a phase component measured from fractional wavelengths of the first carrier signal, the second carrier signal, or both, and (2) a second component of measured phase of complete wavelengths of the first carrier signal, the second carrier signal, or both. The last second measured phase component can be determined by a counter (eg, counter crossing zero) that counts transitions from a received, reconstructed or processed carrier signal that | 5 - intersects with an x-axis at a reference magnitude (eg, voltage) in the time domain, where x represents time and the y axis represents magnitude of the carrier signal. However, the phase measuring device 304 relies on further processing in the data processing system of the receiver 308 to determine or resolve a full-cycle ambiguity that can cause the second measured phase component to be in error or shifted from a complete number of wavelength cycles (eg, to estimate a distance or interval between a corresponding satellite and the location determination receiver). The phase measurement device 304 determines and provides carrier phase measurement data for the 308 receiver's electronic processing system.
The real-time kinematic mechanism 314, the predictive filter 316, and the position estimator 318 can communicate with each other. The real-time kinematic mechanism 314, the predictive filter 316, and the position estimator 318 can communicate with each other via logical data paths, physical data paths, or both. A logical data path means a virtual data path or data communication between a software module or between one or more software programs, for example. A physical data path means — a transmission line or one or more data buses of receiver 324 that support data communications, logic level signals, electrical signals, or electromagnetic signals, for example. In one embodiment, the real-time kinematic mechanism 314 comprises a search engine or other software instructions to search for, determine a set of solutions of entire ambiguity for the phase of one or more carrier signals received from the multiple satellites. The kinematic mechanism 314 can search the carrier phase data provided by the phase measurement device 304, for example. The whole ambiguity solution sets refer to the whole cycle phase ambiguities in the carrier phase received from the received carrier signals (eg, L1 signal at 1.57542 GHz, L2 signal, and, 1,22760 GHz for GPS or similar signals) transmitted by one or more satellites, for example. The kinematic engine 314 or its search engine can use Kalmam or least squares filtering techniques to reduce the search space or achieve one or more ambiguity set solutions for the full cycle phase ambiguities of carrier signals transmitted from satellites. In one configuration, the predictive filter 316 (eg, 15º Kalman filter) facilitates search by the search engine to more efficiently, quickly, or precisely achieve ambiguity set solutions for the entire cycle phase ambiguities of the signals. carrier transmitted from satellites. In an alternative embodiment, techniques based on non-alternative research (eg - wide carrier phase and data processing combinations) can be used to resolve entire carrier phase ambiguity solution sets.
Estimator 318 comprises a receiver 310 data processor or other data processing device to estimate a position, speed, altitude, or any of the preceding attributes of an object or vehicle associated with the location determination receiver 42. Estimator 318 is coupled to or communicates with the real-time kinematic mechanism 314 and receiver data processor 310. Once the set of whole ambiguity solutions is determined, the position estimator 318 or location determination receiver 42 can use carrier phase measurement data to provide an accurate estimate of the distance or interval between each satellite and the location determination receiver). In turn, the distances between | 5 three or more satellites and the location determination receiver can be 'used to estimate the receiver's position, speed or attitude 42.
The predictive filter 316 comprises an error reduction filter, a Kalman filter or a variant thereof to reduce or decrease errors, such as measurement error. A Kalman filter can - comprise a predictive filter device or circuit that uses signal sum, delay, and feedback to process data and compensate for the effects of noise and uncertainty on the measured data or otherwise. Reconfiguration or reset can refer to the same reset of the Kalman filter or error reduction states.
Is The position estimator 318 comprises an electronic module, a software module, or both to estimate a position of an object or vehicle associated with the location determination receiver. The position estimator can use one or more of the following sources of following data to determine an estimated position or altitude of a location-determining receiver antenna or an associated object or vehicle: the decoded pseudo-random noise code, carrier phase measurement, the precise code to which encryption has been applied (eg, P (Y)), the route acquisition code, navigation information, and full cycle phase ambiguity data, and phase data - the reference station carrier, where the phase data of the reference station carrier can be integrated into the full cycle phase ambiguity data.
The predictive filter 316 can comprise an error reduction filter that receives input data from the real-time kinematic mechanism 314, where the input data comprises ambiguity data (e.g., entire ambiguity set) for correspondents carrier phase measurement data. In one embodiment, the reference receiver 51 in FIG. | and FIG. 2 can comprise i 5 - substantially the same elements as the mobile location determination receiver 42 of FIG. 3, except that the reference receiver 51 is not coupled to a correction communications device (41 or 141).
FIG. 4 is a first example of a one-method flowchart for determining clock correction data 44. The method of FIG. 4 starts at step S400, At step S400, a data collection module 24 or central electronic data processing system 16 collects pseudo-range code measurements, carrier phase measurements, and broadcast clock errors received by a network of receivers 15 of reference stations (eg 10, 12 and 14). For example, a network of reference station receivers 15 comprises stationary reference receivers 51 located in respective known locations or in known geographic coordinates, where reference receivers 51 receive signals over multiple frequencies (e.g., multiple carrier frequencies) transmitted by one or more constellations from the navigation satellites. The one or more constellations can comprise a GPS constellation, a GLONASS constellation, or another navigation satellite constellation. For the GPS satellite constellation, multiple frequencies can comprise carrier frequency L1 and carrier frequency L2, for example. For the GLONASS satellite constellation, multiple carrier frequencies are assigned to different satellites.
In the reference receiver 51, a phase measurement device or data processing system of the receiver 53 measures carrier phases of the respective carrier signals received by the reference receiver 51. Carrier phase measurements may include phase measurement data carrier data and GLONASS carrier phase measurement data, for example. A decoder on the receiver | 5 - reference 51 can decode ephemeris data, broadcast satellite clock errors, and other navigation transmitted navigation data that is transmitted or that modulates at least one of the carrier signals of one or more satellite signals. In one configuration, carrier phase measurements, pseudo-range code measurements, and navigation message data are transmitted from the receiver network 15 to the central data processing system 16 via one or more links communication 13.
Each satellite typically broadcasts ephemeris data and satellite clock error data (eg, differential clock data with respect to GPS system time or GLONASS system time for a particular satellite). Diffusion clock data is a set of second order polynomial matching coefficients used by a receiver to correct the pseudo-range and carrier phase measurements of a location determination receiver (eg, reference receiver 51 ). Each navigation satellite transmits ephemeris data about its own orbit and satellite clock. The accuracy of broadcast satellite clock errors typically is within a 2-3 meter level relative to 2-3 GPS time, for example. In step S402, at each time interval (eg period - time), parameter estimator 26 or the central electronic data processing system 16 estimates computed satellite clock error data for each satellite based on one or more of the following data collected: the pseudo-range code measurements from the receiver network 15 for each satellite, the carrier phase measurements from the receiver network 15 for each satellite, the respective known locations of the reference stationary receivers 51 within a network of receivers 15, and the broadcast satellite clock errors. Step S402 can be performed according to several techniques i 5 - which can be applied alternatively or cumulatively. According to a first technique, at each time interval (eg, time period), parameter estimator 26 or central electronic data processing system 16 estimates satellite clock error data for each satellite, which is active or properly functioning in one or more - constellations (eg, GPS, GLONASS or both), based on pseudo-range code measurements, carrier phase measurements, the respective known locations of stationary receivers, and broadcast satellite clock errors or navigation message data (eg, which include broadcast satellite clock errors).
According to the second technique, if a satellite provides corrupted or unreliable satellite signals or corrupted or unreliable data for a certain period of time, parameter estimator 26 or central data processing system 16 can suspend data processing clock error from the satellite to the faulty or suspect satellite for a period of time, until the received satellite signal has sufficient signal quality or reliability level of the received data.
According to a third technique, parameter estimator 26 or the central electronic data processing system 16 uses a - single difference procedure or another procedure to determine the computed satellite clock error data for each corresponding satellite on a or more constellations (eg, GPS or GLONASS constellations). For example, in one embodiment each possible pair of different receivers, combinations or simple satellite exchanges that are available (eg, received with adequate signal strength or signal quality at any pair of reference receivers 51) are used for estimation. clock error or polarization (eg computed satellite clock error) for each satellite in a particular constellation according to application | 5 - repeated single difference between carrier phase measurements from reference receivers 51. The computed satellite clock error data can be expressed as time or differential polarization with reference to GPS system time or GLONASS system time .
According to a fourth technique, the clock difference module 28 or the central electronic data processing system 16 uses a double difference procedure or another procedure to determine the computed satellite clock error data.
For example, the double difference procedure refers to a difference between carrier phase measurements from two reference receivers 51 (eg, at fixed locations or known geographical coordinates) that are substantially, simultaneously, receiving carrier signals. from the same pair of two satellites to determine satellite clock error data computed with clock error or reduced polarization.
For example, in a modality each possible different combination or exchange of satellite pair - receiver pair that is available (eg, received with adequate signal strength or signal quality at any pair of reference receivers 51) is used to estimate error clock or polarization for each satellite in a particular constellation according to repeated application of a double difference between carrier-phase measurements from reference receivers 51. In practice, a double difference can be determined by taking a second difference from two determinations of unique difference.
The computed satellite clock error data can be expressed as time or differential bias with reference to GPS system time or GLONASS system time.
In step S406, the clock difference module 28 or the central electronic data processing system 16 forms or determines clock error differences (eg, differential data or differential clock error data) between corresponding data pairs of clock error | 5 - computed satellite and corresponding broadcast clock data for each satellite. For example, the computed satellite clock error data is the satellite clock data that is consistent with the known fixed location of the reference receiver 51 on the particular reference station (eg, 10, 12 or 14) and the carrier phase measurements from the particular reference station (eg 10, 12 or 14) for a given satellite.
The broadcast clock data is provided by or derived from accurate clocks (eg, Rubidium, Cesium or atomic clocks) on board each satellite. In one embodiment, the broadcast clock data comprises differential clock data or polarization clock data with reference to a constellation system clock. In another embodiment, the broadcast clock data represents the transmitted satellite clock data (and associated ephemeris data).
Step S406 can be performed according to various techniques that can be applied separately or cumulatively.
According to a first technique, the clock difference module 28, the central electronic data processing system 16, or the main predictive filter 27 (eg, Kkalman filter) in the data processing system 16 uses one or more than the following to resolve the clock error difference on a satellite to satellite basis for one or - more constellations and for each successive period of time: (1) the respective satellite clock error data computed for one or more satellites in a common constellation, (2) respective broadcast satellite clock error data for the one or more satellites in the common constellation, and (3) respective broadcast satellite clock error data for the common constellation, as adjusted or corrected based on data from attached ephemeris for a particular satellite. The common constellation refers to the same constellation of satellites, which can comprise a GPS constellation or a GLONASS constellation, for example.
i 5 According to a second technique, the clock difference module 28 or data processing system 16 determines the differences or error data between the computed satellite clock error data and the diffusion clock error data for each satellite in each constellation on a satellite to satellite basis, or as otherwise limited to a particular subset of satellites within each constellation. The differences or error data can be stored in one or more vectors or matrices in the data storage device 22, where each vector corresponds to a particular constellation. In step S408, a reference satellite selector 30 or the electronic data processing site 16 selects one of the satellites within each constellation as the clock reference satellite for that constellation, where the clock reference satellite has the median value of clock error differences (eg, from step S406) for that constellation. In a first example to perform step S408, a reference satellite selector 30 or the electronic data processing system 16 selects one of the satellites within the GPS constellation as the clock reference satellite for the GPS constellation, where the satellite Clock reference value has the median value of the differential data or clock error data for the GPS constellation. In a second example to perform step S408, a reference satellite selector 30 or the electronic data processing system 16 selects one of the satellites within the GLONASS constellation as the clock reference satellite for the GLONASS constellation, where the satellite Clock reference values have the median value of differential data or clock error data for the GLONASS constellation.
In step S410, the clock correction module 32 or the electronic data processing system 16 determines or computes a correction or correction data for the diffusion clock data by adjusting | 5 the diffusion clock error data for each satellite in one or more constellations. For example, the clock correction module 32 or the data processing system 16 adjusts the diffusion clock error data for each satellite by adding a clock error function of the clock reference satellite to the diffusion clock error. for each satellite in one or more constellations, where the value of the correction by time period or other time interval (eg, several adjacent time periods) is limited based on a control parameter limit.
Step S410 can be performed according to several procedures that can be applied separately or cumulatively.
Under a first procedure, the control parameter limit is proportional to the clock error of the clock reference satellite. Under a second procedure, the control parameter limit is less than or approximately equal to the clock error of the clock reference satellite. Under a third procedure, the control parameter limit - comprises a fixed parameter expressed in units of distance, after a main predictive filter 27 (eg, kalman filter) converges into a correction solution for the satellite clock error diffusion.
Under a fourth procedure, for each respective navigation satellite in a first constellation in one or more constellations, the computed correction is limited in each time period to a first clock error of the clock reference satellite of the first constellation; and, for each respective navigation satellite in a second constellation in one or more constellations, the computed correction is limited in each time period to a second clock error of the clock reference satellite of the second constellation, where the first clock error is independent of the second clock error. For example, the first constellation can comprise a global positioning system constellation and is characterized by the fact that the second constellation can comprise the i 5 - GLONASS constellation.
'Under a fifth procedure, after convergence of a solution for the correction for the diffusion clock error, the computed correction is limited in each period of time so as not to exceed a limit value. Under a sixth procedure, the limit value is approximately one millimeter in units of distance, or approximately 0.00333 nanoseconds in units of equivalent time, where the conversion factor between units of distance and units of time is the speed of light (eg ., 3 x 10 meters per second). Under a seventh procedure, the clock error of the clock reference satellite is applied as an additional constraint to a main predictive filter 27 (eg, kalman filter).
Under an eighth procedure, the clock correction module 32 or the electronic data processing system 16 determines or computes the correction data for the diffusion clock error data limiting the clock correction error to the diffusion clock error for a maximum clock quantity correction per time period or other time interval (eg, multiple adjacent time periods) this is less than or equal to one or more of the following: (a) a corresponding maximum limit ( eg, approximately equal to or less than | millimeter per time period or another time interval, or - approximately equal to or less than 0.00333 nanoseconds), (b) an average square root error (RMS ) in the interval estimate, or (c) a corresponding maximum limit expressed in units of distance or units of equivalent time, where the speed of light is the conversion factor. For example, the change per unit of time in the clock error correction data may be limited based on the navigation message data (eg, ephemeris data and diffusion clock error data) such that the clock error correction or time correction data from the location determination receiver 42 is shifted less than one | 5 - maximum displacement per unit of time unit of quantization than per. the other hand would cause unwanted discontinuities, discrepancies, or inaccuracies in the estimates of associated positions determined by the end user's mobile determination receiver 42. Under a ninth procedure, at regular or - periodic intervals (eg, time periods) the clock correction 32 or electronic data processing system 16 determines the next clock error correction data for the diffusion clock error data dynamically by adjusting in real time a change in clock error data per unit of time that is less than or equal to one - corresponding maximum limit (eg, less than approximately | millimeter per time period or another time interval, or less than approximately 0.00333 nanoseconds per time period or another time interval). Under a tenth procedure, step S410 can be performed - defining a control parameter limit on the change per unit time in the clock error correction data based on a median difference between computed satellite clock error data pairs and diffusion clock error data (or ephemeris clock data) within a particular constellation of navigation satellites.
For example, —the step4S410 can be performed by limiting the clock correction errors (or maximum correction deviation) determined by the central data processing system 16 or clock correction module 32 for transmission to the location determination receiver 42 as the follow: In Equation 1, the median GPS clock difference between the satellite clock error data computed from parameter estimator 26 and the ephemeris clock data or diffusion satellite clock error data received from of a network of receivers 15 can be determined as follows: Glikços = Madion (ciock 'Qui) ciock'Gph)): = 1:32 for GPS, (1) - 5 where 3E'tsrPs is the median clock difference of the GPS for the GPS constellation, ziask QE) are the clock error data computed for the i-th satellite, clock'GEshAd is the ephemeris clock data or diffusion clock error data for the i-th satellite, hey is the satellite identifier of each d the 32 GPS satellites.
In one embodiment, the computed satellite clock error data and the ephemeris clock data or broadcast satellite clock error data are normalized to equivalent units and for the same or substantially the same time period before computing the difference. median GPS clock above for the GPS constellation.
As later described in Equations 3 and 4, the above definition of the median GPS clock difference, “E * tsss can be used by the data processing system 16, or its predictive filter (eg, kalman filter), to determine limits on clock error correction data (eg clock correction errors), or the maximum change in clock error correction data per unit of time, or its application on the mobile location determination receiver 42.
In Equation 2, the GLONASS median clock difference between the satellite clock error data computed from parameter estimator 26 and ephemeris clock data or clock error data - broadcast satellite received from the transmission network. 15 receivers can be determined as follows: dliEaoxass = Madian (ciork! QD) = soci Gom)) 1 = 1: 24for GLONASS, (2) where FEtgsiovnass is the median clock difference from
GLONASS for the GLONASS constellation, clock! Qrub) are the satellite clock error data computed for the j-th satellite, siock 'rh) are the ephemeris clock data or satellite clock error data disseminated for the j-th satellite, and j is the identifier of each of the 24 GLONASS satellites.
'In one embodiment, the computed satellite clock error data and the ephemeris clock data or broadcast satellite clock error data are normalized to equivalent units and for the same or substantially the same time period before computation - the average GLONASS clock difference. As later described in Equations 3 and 4, the above definition of the GLONASS median clock difference can be used by the data processing system 16, or its main predictive filter 27 (eg, kalman filter), for determine limits on clock correction data (eg, clock correction errors), or the maximum change in clock correction data per unit of time, or its application in the mobile location determination receiver
42. In one embodiment, the data processing system 16, the clock correction module 32, or the predictive filter (eg, —Kkalman filter) maintains or determines that clock correction errors are regular or continuous ( eg, as possible or practicable) to avoid any possible discontinuity of correction or jump in clock correction errors; then, position dependent on speed estimates based on clock correction errors in the location determination receiver —mobile42.The maximum clock change per unit time (eg, time period or other time interval) of the constraint update (eg, update to a correction data or status update of predictive filter 27) in parameter estimator 26, correction module 32, or predictive filter 27 (eg, kalman filter) in central data processing system 16 must be limited according to Eq. 3: dX = - EL (dc) <= Limit G) H 'PH + R where dX is a state update for the estimate of clock correction; H is the design matrix containing the coefficients of. sensitivity; P is the matrix of variance - covariance; dCIk is the clock error of the clock reference satellite, Limit is the limit for the maximum offset change in displacement in units of distance (eg, 1 mm) or in units of equivalent time; R is the variance of the applied correction data.
Based on Equation 3, the R variance or adaptive variance — for the GPS and GLONASS satellite diffusion master clock can be reversedly computed from either the main predictive filter 27 (eg, kalman filter) or the parameter estimator 26, then the adaptive constraint (eg, adaptive correction data for the adaptive master clock or the reference satellite clock for the GPS constellation or the 15th GLONASS constellation) can be applied to the main predictive filter 27 or the estimator of parameter 26.
A limit level of variance, Tr, can be defined according to the following Equation 4: = E get) -H'PH 4) where Tg is the limit level of variance for R, and where the other - parameters are defined above .
In one example, if the computed variance R is greater than the threshold level of variance, Tr. clock correction module 32 or main predictive filter 27 uses computed variance R to limit or update correction status or clock correction data (eg, clock correction errors). In another example, if the computed variance R is less than the threshold variance level Tr, the clock correction module
32 or the predictive filter 27 uses the limit variance level, Tr, to limit or update correction data (eg clock correction errors). In an alternative modality, the limit level of variance, Tr, can comprise a level of variance level or constant parameter | 5 predefined that can be defined by the user, based on studies: empirical of the performance of the master clock, or based on the historical accuracy of position estimates of the mobile location determination receiver 42. For example, the level of Limit variance can be pre-configured or pre-defined as 0.01 nm.
The median (eg, GPS median or GLONASS median) of difference in clock error between parameter parameter estimator 26 (e.g., orbit / clock estimator) and diffusion clock error (e.g. , ephemeris clock) received by a network of receivers 15 improves reliability because some satellites may have abnormal satellite clocks 13, out of operation or aberration, at least occasionally.
If a constraint entered in the main predictive filter 27 (eg, kalman filter) or parameter estimator 26 is too tight or restricted, this can cause a significant jump of correction data in the resulting correction data.
If the constraint entered in the main predictive filter 27 (eg Kalman filter) or parameter estimator 26 is too loose, this can cause a slow shift in the resulting correction data and a large variance for clock estimation due to non-observance between the satellite clock and the receiver's clock (eg, reference receiver 51). In order to overcome the previous technical problems, according to one - modality an adaptive diffusion master clock is proposed in which the change in clock correction is limited within certain predetermined or predefined intervals.
In step S412, the communication modules 34, a communications interface 36 or the data processing system 16 distribute or transmit the computed clock correction data 44 (e.g., clock correction errors) to the determination receivers 42 mobile location signals (eg, user location determination receivers) via a satellite, or another wireless communications system. In an example consistent with the system of FIG. 1, the data processing system 16 'distributes or transmits the clock correction data 44 through the earth-based satellite communications device 38 which provides a satellite uphill communication link communications channel to the satellite remote satellite communications 40 on a satellite orbiting Earth. The remote satellite communications device 40 provides a downlink communication link channel in communication with a correction communications device 41 to receive the correction data for entry into the mobile location determination receiver 42. In another example consistent with the system of FIG. 2, the data processing system 16 transmits clock correction data 44 through wireless base station 138 to a correction communications device 141 or transceiver associated with the mobile location determination receiver 42.
According to the system and method, the estimated parameters - of all satellite clocks and location determining receiver clocks can be defined as relative to a constraint, called master clock data or clock reference satellite clock for the particular constellation. For a global real-time differential correction system or wide area correction system or any modality of the - system and method disclosed herein, the electronic data processing system is well suited to produce regular clock correction data (e.g. , without transient jumps) and a very limited range of clock correction data to conserve bandwidth of the communication links between portions of the differential correction system and to predict the clock corrections in real time with minimal processing delay.
FIG. 5 is a second example of a flowchart of a method for determining clock correction data 44. Same numbers as | 5 reference in FIG. 4 and FIG. 5 indicate similar procedures or methods. The method of FIG. 5 starts at step S401.
In step S401, a data collection module 24 or central electronic data processing system 16 collects pseudo-range code measurements, carrier phase measurements, and navigation message data (eg, ephemeris data and clock data) received by a network of receivers 15 from reference stations (e.g., 10, 12 and 14). For example, a network of reference station receivers 15 comprises stationary reference receivers 51 located in their respective known locations or in known geographic coordinates, where reference receivers 51 receive signals over multiple frequencies (e.g., multiple carrier frequencies) transmitted by one or more constellations from the navigation satellites. One or more constellations may comprise a GPS constellation, a GLONASS constellation, or another navigation satellite constellation. For a GPS satellite constellation, multiple frequencies can comprise carrier frequency L1 and carrier frequency L2, for example. For the GLONASS satellite constellation, multiple carrier frequencies are assigned to different satellites.
In the reference receiver 51, a phase-measuring device or data processing system of the receiver 53 measures carrier phases of the respective carrier signals received by the reference receiver 51. Carrier phase measurements may include measurement data from GPS carrier phase and GLONASS carrier phase measurement data, for example. A decoder at reference receiver 51 can decode transmitted ephemeris data, satellite clock data, and other navigation data that is transmitted or modulated by said one of the carrier signals of one or more satellite signals.
Carrier phase measurements, pseudo-range code measurements, and navigation message data are transmitted from a receiver network 15 to the central data processing system 16 via one or more data link communication 13. Each satellite typically broadcasts broadcast ephemeris data and broadcast satellite clock error data (eg, differential clock data with respect to GPS satellite time or GLONASS system time for a particular satellite). Diffusion ephemeris data is a set of second-order polynomial matching coefficients used by a receiver to predict the receiver's clock behavior of a location-determining receiver (eg, reference receiver 51). Each navigation satellite transmits ephemeris data about its own satellite orbit and clock.
The accuracy of diffusion ephemeris clocks is typically within 2 - 3 meters relative to GPS time, for example.
In step S403, for each time interval (eg, time period), parameter estimator 26 or central electronic data processing system 16 estimates computed satellite clock error data for each satellite based on a or more of the following data collected: the pseudo-range measurements of the receiver network 15 for each satellite, the carrier phase measurements of the receiver network 15 for each satellite, the respective known locations of the reference stationary receivers 51 within of a network of receivers 15, and the navigation message data (e.g., ephemeris data and broadcast satellite clock error data). Step S403 can be performed according to various techniques that can be applied alternatively or cumulatively. According to the first technique, in each time interval (eg time period), parameter estimator 26 or the central electronic data processing system 16 estimates satellite clock error data for each i 5 - satellite, which is active or properly functioning in one or more 'constellations (eg, GPS, GLONASS or both), based on pseudo-range code measurements, carrier phase measurements, on the respective known locations of the receivers stationary, and navigation message data.
According to the second technique, if a satellite provides corrupted or unreliable satellite signals or corrupted or unreliable data for a given period of time, parameter estimator 26 or central data processing system 16 can suspend data processing from satellite clock error for the faulty or suspect satellite for a period of time, until the received satellite signal has a sufficient signal quality or level of reliability of the received data level.
According to a third technique, parameter estimator 26 or the central electronic data processing system 16 uses a single difference procedure to determine the computed satellite clock error data for each corresponding satellite in one or more constellations ( eg GPS or GLONASS constellations c). For example, a single difference procedure if there is a difference between carrier phase measurements from two reference receivers 51 (eg, a fixed location or known geographical coordinates) that are substantially, simultaneously, receiving signals from carrier from the same satellites to determine satellite clock error data computed with clock error or reduced polarization. The computed satellite clock error data can be expressed as differential time or polarization with reference to GPS system time or GLONASS system time.
According to a fourth technique, the clock difference module 28 or the central electronic data processing system 16 uses a double difference procedure to determine the error data of the 'computed satellite clock.
For example, the double difference procedure refers to a difference between carrier phase measurements from two reference receivers (eg, at fixed locations or geographic coordinates) that are substantially, simultaneously, receiving carrier signals from the same pair of two satellites to determine satellite clock error data computed with clock error or reduced polarization.
In practice, a double difference can be determined by taking a second difference from two single difference determinations, where the single difference refers to a difference between carrier phase measurements from two reference receivers 51 (eg, at fixed locations or known geographic coordinates) that are substantially, simultaneously, receiving carrier signals from the same satellites to determine satellite clock error data computed with clock error or reduced polarization.
The computed satellite clock error data can be expressed as differential time or polarization with reference to the GPS system time or the GLONASS system time.
The other steps or procedures in FIG. 5, including steps S406, S408, S410 and S412, are identical to or substantially - similar to those established in the method of FIG. 4. FIG. 6 is a flow chart of a method for determining a position estimate or speed estimate on a receiver that receives clock correction errors.
The method of FIG. 6 starts at step S600, The method of FIG. 6 can use a location determining receiver embodiment illustrated in FIG. 3 or another configuration of a location determination receiver that is capable of receiving and using clock correction errors to provide more accurate position estimates than would be possible. In step S600, the decoder 320 or electronic data processing system of the receiver 308 decodes pseudo-range code measurements received by the location determination receiver 42 into corresponding carrier signals transmitted by one or more navigation satellites.
In step S602, a phase measurement device 304 or electronic data processing system of receiver 308 determines carrier phase measurements for the corresponding carrier signals.
In step S604, a decoder 320 or electronic data processing system of receiver 308 receives broadcast satellite clock errors in the carrier signals from one or more navigation satellites.
In step S606, a correction communications device (41 or 141) or data port 322 of the receiver's electronic data processing system 308 receives a correction for a diffusion clock error from each navigation satellite comprising one of the clock error of the clock reference satellite added to the diffusion clock error for each navigation satellite in one or more constellations, where a correction value per time period is limited based on a control parameter limit.
In step S608, a data processing system 308 or position estimator 318 determines a position estimation of the location determination receiver based on the decoded pseudo-range code measurements, the determined carrier phase measurements, broadcast satellite clock received and correction received. For example, the data processing system 308 or position estimator 318 can resolve phase ambiguities or whole phase ambiguities in the carrier phase measurements determined to arrive at a location estimate consistent with the correction received for the clock error. “5 diffusion: Step S608 can be performed according to various techniques, which can be applied separately or cumulatively. Under a first technique, the data processing system 308 or the position estimator 318 can determine a position estimate and a speed estimate from the location determination receiver based on decoded pseudo-range code measurements, measurements of carrier phase, received broadcast satellite clock errors and received clock error corrections. (e.g., on a time-to-time basis).
Under a second technique, the control parameter limit is proportional to the clock error of the clock reference satellite. Under a third technique, the control parameter limit is less than or approximately equal to the clock error of the clock reference satellite. Under a fourth technique, the change in a clock correction or correction by time period or other time interval (eg, multiple adjacent time periods) is limited by the following equation: dX = —EP (ge) <= H'PH + R threshold where dX is the state update for the clock correction estimate; H is the design matrix with sensitivity coefficients; P is the matrix of variance - covariance; R is the variance of the correction data - applied; dCIk is clock error of the clock reference satellite; and Threshold is the maximum correction change allowed for a period of time as defined in the claim. Under a fifth technique, if the computed variance R of the applied correction data is greater than the Tg value determined below, the computed variance R is used for the update correction status.
x Z = - ZE (acn) - H 'PH. Under a sixth technique, if the computed variance R is less than the value Tr, Tr is used in place of R to update the correction state according to the equations provided under the fourth and fifth techniques. Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the appended claims.

权利要求:
Claims (25)
[1]
1. Method for determining satellite clock corrections to allow at least one location determination receiver to provide at least one of a position estimate or a speed estimate or a time estimate, characterized by the fact of 'understanding: collecting pseudo-range code measurements, carrier phase measurements, and broadcast satellite clock errors from a network of stationary satellite signal receivers transmitted by one or more - navigation satellite constellations; in each time period, compute a computed satellite clock error for each navigation satellite based on pseudo-range code measurements, carrier phase measurements, and diffusion satellite clock errors; form clock error differences between corresponding pairs of the computed satellite clock error and a diffusion satellite clock error for each navigation satellite; for each constellation, select a clock reference satellite from among the navigation satellites in that constellation, which has a - median value of the clock error differences for that satellite constellation; and compute a correction for the diffusion clock error of each navigation satellite by adding a function of the clock error of the clock reference satellite to the diffusion clock error for each - navigation satellite in one or more constellations, where a correction value by time period or other time interval is limited based on a control parameter limit.
[2]
2. Method according to claim 1, characterized by the fact that the control parameter limit is proportional to the clock error of the clock reference satellite.
[3]
3. Method according to claim 1, characterized by the fact that the control parameter limit is less than or approximately equal to the clock error of the clock reference satellite.
[4]
4. Method according to claim 1, characterized by the 'fact that the control parameter limit comprises a fixed parameter, expressed in units of distance or units of time, after a predictive filter converges into a solution for the correction for the diffusion satellite clock error.
[5]
5. Method according to claim 1, characterized by the fact that, for each respective navigation satellite in a first constellation in one or more constellations, the computed correction is limited in each time period for a first satellite clock error clock reference number of the first constellation; and, that for each respective navigation satellite in a second constellation in one or more constellations, the computed correction is limited in each time period to a second clock error of the second reference clock's reference satellite, the first clock error being independent of the second clock error.
[6]
6. Method according to claim 5, characterized by the fact that the first constellation comprises a global constellation positioning system and that the second constellation comprises a GLONASS constellation.
[7]
7. Method according to claim 1, characterized by the fact that after converging a solution for a correction for the diffusion clock error, the computed correction is limited in each period of time so as not to exceed a limit value.
[8]
8. Method according to claim 7, characterized by the fact that the limit value is approximately one millimeter or equivalent time limit.
[9]
9. Method according to claim 1, characterized by the fact that applying the clock error of the clock reference satellite as the control parameter limit is implemented as a constraint - in addition to a predictive filter.
[10]
'10. Method according to claim 1, characterized by the fact that the change in a clock correction or correction by time period is limited by the following equation: dx = ana (dCIk) <= H'PH + R limit where dX is the status update for the clock correction estimate; There is the project matrix with sensitivity coefficients; P is a matrix of variance - covariance; R is the variance of the applied correction data; dCIk is clock error of the clock reference satellite; and limit is a change of maximum correction by time period or the control parameter limit.
[11]
11. Method according to claim 1, characterized by the fact that if a computed variance of the correction data, R, of the applied correction data is greater than a threshold variance level, Tr the computed variance, R, is used for updating the correction status, consistent with the following equation: H'P; g Te = (dC) H 'PH where H is the design matrix with sensitivity coefficients; P is a matrix of variance - covariance; dClk is the clock error of the clock reference satellite; and limit is a change of maximum correction by time period or the control parameter limit.
[12]
12. Method according to claim 1, characterized - by the fact that if the computed variance R is less than a limit variance level, Tr, Tr is used in place of R to update the correction state, consistent with the following equation: H'P: T Ta = Fis "(dCIk) - H 'PH where H is the design matrix with coefficients of' sensitivity; P is a variance matrix - covariance; dClk is the. clock reference satellite, and limit is a change of - maximum correction per time period or the control parameter limit.
[13]
13. System for determining satellite clock corrections to allow at least one location determination receiver to provide at least one of, a position estimate or a speed estimate or a time estimate, characterized by the fact that it - comprises: a module data collection to collect pseudo-range code measurements, carrier phase measurements, and broadcast clock errors from a network of stationary satellite signal receivers transmitted by one or more navigation satellite constellations; a parameter estimator for computing a computed satellite clock error for each navigation satellite based on pseudo-range code measurements, carrier phase measurements, and diffusion clock errors; a clock difference module to form clock error differences between corresponding pairs of computed satellite clock error data and a corresponding broadcast clock data for each navigation satellite; a reference satellite selector to select a clock reference satellite among the navigation satellites that have a median value of clock error differences for that satellite constellation; and a clock correction module to compute a correction for the diffusion clock error by adding a function of the clock error of the clock reference satellite to the diffusion clock error for each navigation satellite in one or more constellations, where a correction value by time period or other time interval is limited based on a control parameter limit. 5
[14]
14. System according to claim 13, characterized by the fact that the control parameter limit is proportional to the clock error of the clock reference satellite.
[15]
15. System according to claim 13, characterized in that the control parameter limit is less than or - approximately equal to the clock error of the clock reference satellite.
[16]
16. System according to claim 13 characterized by the fact that the control parameter limit comprises a fixed parameter, expressed in units of distance or units of time, after a predictive filter converges in a solution for a correction for the error of broadcast satellite clock.
[17]
17. System according to claim 13 characterized by the fact that, for each respective navigation satellite in a first constellation in one or more constellations, the computed correction is limited in each time period to a first clock error of the satellite. clock reference of the first constellation; and, that for each respective navigation satellite in a second constellation in one or more constellations, the computed correction is limited in each time period to a second clock error of the second reference clock's reference satellite, the first clock error. being independent of the second error - clock.
[18]
18. System according to claim 17 characterized by the fact that the first constellation comprises a global constellation positioning system and that the second constellation comprises a GLONASS constellation.
[19]
19. System according to claim 13, characterized by the fact that after converging a solution for the correction for the diffusion clock error, the computed correction is limited in each period of time so as not to exceed a limit value.
[20]
i 5 20. System according to claim 19 characterized by the fact that the limit value is approximately one millimeter or equivalent time limit.
[21]
21. System according to claim 13 characterized by the fact that a correction module comprises a predictive filter - adapted to receive the clock error from the clock reference satellite as an additional restriction.
[22]
22. System according to Claim 13 characterized by the fact that the change in a clock correction or correction by time period is limited by the following equation: di = EP (em) <= H'PH + R limit where dX is the state update for the clock correction estimate; H is the design matrix with sensitivity coefficients; R is the variance of the applied correction data; dCIk is a clock error of the clock reference satellite; and limit is a change of maximum correction by time period or the control parameter limit.
[23]
23. System according to claim 13, characterized by the fact that, in a main predictive filter of the clock correction module, if a computed variance of the correction data, R, of the applied correction data is greater than a level limit variance, Tg; the computed variance, R, is used to update the correction state, consistent with the following equation: H'P ã T Tr = 5 (dCIk) - H 'PA where H is a design matrix with sensitivity coefficients; P is a matrix of variance - covariance; dCIk is clock error of the clock reference satellite; and limit is a change of maximum correction by time period or the control parameter limit.
[24]
24. System according to claim 13, characterized '5 - by the fact that, in a main predictive filter of the clock correction module, if the computed variance R is less than a limit variance level, Tr, Tr is used in place of R for updating the correction status, consistent with the following equation:
T Tam Ai (CH) -H'PH where H is a design matrix with sensitivity coefficients; P is the matrix of variance - covariance; dClk is a clock error of the clock reference satellite; and limit is the maximum correction change per time period or the control parameter limit.
[25]
25. System according to claim 13, characterized by the fact that the correction module comprises a predictive filter, in which after initialization of the predictive filter the correction data for the broadcast clock data, the computed correction data are limited to a maximum value per time interval that does not exceed a clock error of the clock reference satellite.

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同族专利:

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公开号 | 公开日

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CN103370635A|2013-10-23|

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AU2012205602A1|2013-07-25|

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CA2823697A1|2012-07-19|

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US20120182181A1|2012-07-19|

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JP2014510260A|2014-04-24|

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RU2013136046A|2015-02-20|

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US8456353B2|2013-06-04|

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WO2012097022A1|2012-07-19|

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EP2673658B1|2017-12-13|

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CA2823697C|2018-11-13|

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EP2673658A1|2013-12-18|

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CN103370635B|2015-02-25|

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AU2012205602B2|2016-01-28|

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