CN112444823B - Ionospheric delay model system and modeling method - Google Patents
Ionospheric delay model system and modeling method Download PDFInfo
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- CN112444823B CN112444823B CN201910810024.6A CN201910810024A CN112444823B CN 112444823 B CN112444823 B CN 112444823B CN 201910810024 A CN201910810024 A CN 201910810024A CN 112444823 B CN112444823 B CN 112444823B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
- G01S19/07—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/40—Correcting position, velocity or attitude
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Abstract
The invention provides an ionospheric delay model system and a modeling method, the ionospheric delay model system comprises: the navigation server receives satellite observation data from a plurality of navigation terminal devices, calculates satellite navigation data of the navigation terminal devices based on the satellite observation data, and calculates ionospheric slant delay corresponding to the navigation terminal devices in the process of calculating the satellite navigation data of the navigation terminal devices; the satellite navigation reference station screening module screens out part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station, and the ionospheric delay model processing module models and updates the ionospheric delay model of the navigation satellite by utilizing the calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain a real-time ionospheric delay model of the navigation satellite. This allows a highly accurate ionospheric delay model to be obtained.
Description
Technical Field
The invention relates to the field of navigation, in particular to an ionosphere delay model system and a modeling method based on satellite navigation terminal equipment.
Background
Global satellite positioning systems (GNSS) generally cannot meet centimeter or decimeter level positioning accuracy requirements due to limited accuracy of atmospheric interference positioning by the propagated signals. There are generally two approaches to mitigating the effects of atmospheric delays (ionosphere and troposphere) on GNSS observations. Firstly, estimating through a precise atmospheric model; and secondly, performing differential calculation with GNSS reference stations nearby the user. These two strategies correspond to the precision single point location technique (PPP) and the network real-time differencing technique (NRTK), respectively. PPP and NRTK are theoretically completely equivalent. Compared with the traditional RTK technology, the NRTK can prolong the distance between reference stations to 50-100 km. Otherwise atmospheric error residuals need to be handled by additional parameters and modeling. Since the reference station spacing directly affects the accuracy of the atmospheric modeling, the positioning accuracy and convergence speed of the PPP technique are also limited by the reference station distance. However, since atmospheric regional modeling generally uses more complex models than NRTK, the reference inter-site distances for typical regional ionosphere modeling can be extended to 100-150 km. PPP can achieve centimeter-level accuracy in seconds after correction using the precise atmosphere model of the regional reference station network estimate. Ionospheric models are currently divided into global models and regional models. The global ionosphere model uses globally distributed GNSS reference stations to receive dual-frequency signals, and performs geometry-free (geometry-independent) combination estimation of bias ionosphere delay and DCB (pseudorange inter-frequency bias) on the dual-frequency observations. The ionospheric bias is projected into the vertical direction and the vertical ionospheric delay is described by parametric estimation using a Spherical Harmonics Analysis spherical harmonic analysis model. The vertical ionosphere delay precision estimated by the method can reach about 2 TECU (0.3 m). This accuracy cannot meet the rapid convergence of PPP (less than 5 minutes). The us Trimble company in 2016 proposed a regional ionosphere model based on Adjusted Spherical Harmonics Analysis improved spherical harmonic analysis model. After using the regional ionosphere model built by 100 reference stations in europe (distance between stations 150-200 km), PPP positioning errors using Trimble high-precision receivers can converge to within 4 cm in the horizontal direction within five minutes at 95%. Although positioning accuracy and convergence speed have met autopilot requirements, the overall system does not provide a reliable solution to ensure the reliability of the regional ionosphere model. In summary, the existing GNSS regional ionosphere modeling techniques mainly have the following technical drawbacks:
1) The method is focused on how to improve the precision research of the atmosphere model, and lacks the research of real-time precision evaluation and integrity detection methods of the atmosphere model.
2) The traditional GNSS reference station network component is very expensive, and the construction cost of each station is more than 10 ten thousand RMB (RMB) on average in consideration of power supply, network, site renting and hardware cost.
3) With the popularization of 4G/5G and cloud storage/computing technologies, the GNSS data of the user terminal are returned to a cloud server for centralized processing, so that a practical and efficient data processing mode is realized. The conventional ionosphere modeling method does not fully utilize GNSS original data transmitted by the users to improve the accuracy and reliability of ionosphere modeling.
Disclosure of Invention
The invention aims to provide an ionosphere delay model system and a modeling method based on satellite navigation terminal equipment, which can be used for modeling based on data of a plurality of satellite navigation terminals and can improve the accuracy and reliability of an ionosphere delay model.
To achieve the object, according to one aspect of the present invention, there is provided an ionospheric delay model system comprising: the navigation server receives satellite observation data from a plurality of navigation terminal devices, calculates satellite navigation data of the navigation terminal devices based on the satellite observation data, transmits the satellite navigation data back to the navigation terminal devices through a wireless network, wherein the satellite navigation data comprises satellite navigation positions and satellite navigation speeds, and calculates ionospheric slant delays corresponding to the navigation terminal devices in the process of calculating the satellite navigation data of the navigation terminal devices; the navigation server comprises a satellite navigation reference station screening module and an ionospheric delay model processing module, wherein the satellite navigation reference station screening module screens part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station, and the ionospheric delay model processing module models and updates an ionospheric delay model of a navigation satellite by utilizing calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain a real-time ionospheric delay model of the navigation satellite.
According to another aspect of the present invention, there is provided an ionospheric delay model modeling method comprising: the method comprises the steps that a navigation server receives satellite observation data from a plurality of navigation terminal devices, satellite navigation data of the navigation terminal devices are obtained through calculation based on the satellite observation data, the satellite navigation data are transmitted back to the navigation terminal devices through a wireless network, the satellite navigation data comprise satellite navigation positions and satellite navigation speeds, and ionosphere oblique delays corresponding to the navigation terminal devices are obtained through calculation in the process of calculating the satellite navigation data of the navigation terminal devices; screening part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station; and modeling and updating the ionospheric delay model of the navigation satellite by using the calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain the real-time ionospheric delay model of the navigation satellite.
Compared with the prior art, the method and the device can screen part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as satellite navigation reference stations, model and update the ionospheric delay model of the navigation satellite by utilizing the calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference stations, obtain the real-time ionospheric delay model of the navigation satellite, and improve the accuracy and reliability of the ionospheric delay model.
Drawings
FIG. 1 is a schematic diagram of the structure of a high-precision navigation system of the present invention in one embodiment;
FIG. 2 is a schematic diagram of a navigation terminal device in one embodiment of the present invention;
FIG. 3 is a schematic diagram of a navigation server according to an embodiment of the present invention.
Detailed Description
In order to further describe the technical means and effects adopted for achieving the preset aim of the invention, the following detailed description is given below of the specific implementation, structure, characteristics and effects according to the invention with reference to the attached drawings and the preferred embodiments.
In a first embodiment, the present invention provides a high-precision navigation system combining precision point positioning and inertial navigation systems, and the high-precision navigation system based on the architecture can run on a navigation terminal device with low cost (such as $ 50), so as to provide reliable high-precision navigation services, such as positioning precision to be within 10 cm, and further support automatic driving navigation.
FIG. 1 is a schematic diagram of a high-precision navigation system 100 according to an embodiment of the present invention. The high-precision navigation system 100 includes a navigation terminal device 102 and a navigation server 106.
The navigation terminal device 102 may be a plurality of devices. The navigation terminal device 102 may be mounted on a motor vehicle to perform high-precision navigation for driving navigation of the motor vehicle, particularly for unmanned driving. The navigation terminal device 102 may communicate with the navigation server 106 via a wireless network 104. The wireless network 104 may be a 2G, 3G, 4G or 5G network, or may be a combination of multiple networks, such as bluetooth+4g, wifi+4g, wifi+internet+5g, etc., and the present invention is not required to support a stable communication for a specific type of the wireless network 104.
Fig. 2 is a schematic structural diagram of the navigation terminal device 102 in one embodiment of the present invention. The navigation terminal device 102 comprises an inertial sensing unit 210, a satellite positioning receiver 220, a processing module 230 and a wireless transmission module 240. The inertial sensing unit 210 obtains inertial observation data. The inertial sensing unit 210 includes an acceleration sensor 211 and a gyroscope 212, and the inertial observation data includes acceleration sensing data obtained by the acceleration sensor 211 and angular velocity sensing data obtained by the gyroscope 212. The processing module 230 calculates the acceleration sensing data and the angular velocity sensing data to obtain an inertial position change δp r And an inertial velocity variation δv r Based on the previous inertial position and the inertial position variation δp r Obtaining the current inertial position based on the previous inertial velocity and the change δv of the inertial velocity r The current inertial velocity is obtained. The satellite positioning receiver 220 obtains satellite observations, including pseudorange observations, phase observations, and doppler observations.
In one embodiment, the wireless transmission module 230 transmits the satellite observations out over the wireless network 104. The navigation terminal device 102 may be one device packaged in a box, or may be two or more devices packaged in two or more separate boxes, which operate in combination to perform the function of the navigation terminal device 102. In implementation, the wireless transmission module 240 may be located in the same box as other modules, or may be located in a different box from other modules.
The navigation server 106 receives satellite observation data from the navigation terminal device 102, calculates satellite navigation data of the navigation terminal device 102 based on the satellite observation data, and transmits the satellite navigation data back to the navigation terminal device 102 through the wireless network 104, wherein the satellite navigation data includes a satellite navigation position and a satellite navigation speed.
The processing module 230 of the navigation terminal device 102 obtains a current integrated navigation position by taking the satellite navigation position as a reference and combining with a current inertial position, and obtains a current integrated navigation speed by taking the satellite navigation speed as a reference and combining with a current inertial navigation speed. The sample rate of the satellite observation data is lower than that of the inertial observation data, the sample rate of the satellite observation data refers to the number of the satellite observation data obtained per second, and the sample rate of the inertial observation data refers to the number of the inertial observation data obtained per second. Specifically, the sample rate of the satellite observation data is typically 1-10, i.e. 1-10 satellite observations, such as 1, are obtained per second, and the sample rate of the inertial observation data is 50-1000, i.e. 50-1000 inertial observations, such as 100, are obtained per second.
In a preferred embodiment, the wireless transmission module 240 further transmits the inertial measurement data to the navigation server 106 via a wireless network, and at this time, the navigation server 106 calculates satellite navigation data of the navigation terminal device 102 by combining the inertial measurement data and the satellite measurement data. In another alternative embodiment, the wireless transmission module 240 further transmits the inertial position variable amount and the inertial velocity variable amount to the navigation server 106 through a wireless network, and the navigation server 106 calculates satellite navigation data of the navigation terminal device 102 according to the inertial position variable amount, the inertial velocity variable amount and the satellite observation data. The navigation server 104 may also obtain gesture information according to the inertial observation data, or the inertial position variation and the inertial velocity variation, and the navigation server 104 may also transmit the gesture information back to the navigation terminal device 102 for navigation.
Because the PPP/INS combined positioning core algorithm is implemented on the navigation server 106, the navigation terminal device 102 only needs to transmit the observation data back to the navigation server 106 through a wireless network, and the final satellite navigation data is transmitted back to the navigation server 106 after the operation of the navigation server 106 is completed. In this way, the positioning-related computation and the subsequent data processing with a large computation amount are not involved in the navigation terminal 102, so that the computation power and the power consumption requirements of the navigation terminal can be greatly reduced, and the cost of the navigation terminal 102 can be reduced as much as possible.
The high-precision navigation system 100 of the present invention may be used for autopilot, as well as other applications for high-precision navigation.
The high-precision navigation system 100 may support four systems of GPS, GLONASS, GALILLEO and BEIDOU.
In one embodiment, the navigation server 106 calculates satellite navigation data of the navigation terminal device 102 based on the inertial position change amount, the inertial velocity change amount, and the satellite observation data as follows. Fig. 3 is a schematic diagram of the navigation server 106 in one embodiment of the present invention.
The PPP observations model is as follows
In equations (1), (2) and (3), P, L and D represent GNSS pseudo-ranges, phases and Doppler observations, respectively; subscripts j and s are frequency and satellite PRN number, respectively; p is the position; v is the speed; c is the speed of light; t is the clock difference; r is the receiver and d is the pseudorange bias; u is the phase deviation; t is tropospheric delay; i is ionospheric delay; n is the ambiguity. Δp and Δl are various error corrections for pseudoranges and phases. Epsilon is the observed value error.
For GPS, GLONASS, GALILLEO and BEIDOU four systems, the PPP model state parameters are:
the observation model of INS is:
in the formulas (5) - (7), S g And S is a Coefficient errors of the gyroscope and the accelerometer respectively; b (B) g And B a Zero offset for gyroscope and accelerometer, respectively.
And->
Respectively theoretical and actual angular velocity observations; />
And f b Respectively representing theoretical and actual acceleration observation values; />
Converting the INS coordinate system into a navigation coordinate system conversion matrix; />
Angular velocity of the inertial system relative to the ECEF coordinate system; />
The ECEF coordinate system is relative to the navigation coordinate system; g n Is the gravitational acceleration in the navigation coordinate system.
For speed, position and rate of change of the coordinate transformation matrix. From equation (7), δp can be obtained r ，δv r Thereby obtaining the position speed at the current moment:
p r,INS ＝p r,k-1 +δp r,k (8)
v r,INS ＝v r,k-1 +δv r,k (9)
the tightly combined observations model is as follows:
the state parameters of the integrated navigation model are as follows:
in a preferred embodiment, the navigation server 106 performs interactive detection on high-precision satellite state space correction SSR correction data based on satellite observation data sent from a plurality of navigation terminal devices to correct the high-precision satellite state space correction. The navigation server performs interactive detection on satellite navigation data of one or more navigation terminal devices and satellite navigation data of another navigation terminal device. The specific application scenario is as follows: 1) Based on the ionosphere model, if the position of the terminal equipment in the area is converged, the ionosphere oblique direction delay corresponding to the equipment observation value can be calculated to detect and correct the ionosphere model; 2) If another terminal equipment data is found to be transmitted back to the server, the accurate point positioning mode can be directly switched to the RTK (Real time kinematic) model to accelerate the convergence of the position information.
In a preferred embodiment, the navigation server receives SSR correction data in RTCM format from other data sources, and the navigation server calculates satellite navigation data of the navigation terminal device based on the SSR correction data and satellite observation data in RTCM format from the navigation terminal device.
In one embodiment, to reduce the cost, the navigation terminal device 102 can only provide satellite observation data of a single frequency, and the navigation server 106 needs to estimate ionospheric delay in calculating satellite navigation data of the navigation terminal device 102 based on the satellite observation data. Preferably, the navigation server 106 uses a global ionospheric model as correction when estimating the ionospheric delay, so as to estimate and constrain the ionospheric delay and further estimate the ionospheric delay, thereby ensuring the positioning accuracy and convergence time of precise point positioning.
The global ionosphere model is adopted as correction, and the ionosphere oblique direction delay is estimated and constrained specifically as follows:
wherein vtec is the number of ionospheric electrons in the vertical direction; n and M are the number of spherical harmonic series and the order of the ionized layer respectively; c (C) nm And S is nm Spherical harmonic coefficients respectively; λs is the average longitude of the day point;
latitude of the ionosphere puncture point; kappa (kappa) j Is a frequency coefficient;
for ionospheric projection coefficients, P nm Is a full order Legend function.
The ionospheric delay constraint function is that,
in one embodiment, the navigation server 106 needs to perform ambiguity fixing in calculating satellite navigation data of the navigation terminal device 102 based on the satellite observation data. The navigation server 106 uses a integer ambiguity weighted average strategy when the ambiguities are fixed, uses an LAMBDA method to perform ambiguity decorrelation and integer ambiguity combination search after the floating ambiguity reaches a predetermined accuracy, calculates the weight of the ambiguity combination according to the sum of squares of residuals of the searched integer ambiguity and the corresponding floating ambiguity, obtains the optimal n groups of ambiguity combinations and weights thereof, calculates weighted average ambiguities, and directly fixes the weighted average ambiguities if the interpolation of the weighted average ambiguities and integers is smaller than a predetermined threshold, such as 0.001.
In one embodiment, the navigation terminal device 102 transmits satellite observations to the navigation server 106 in rtcm3 format at a frequency of 1 Hz. The navigation terminal device 102 calculates δp in equations (8) and (9) by equations (5) - (7) r ，δv r And sending the navigation information to the navigation server.
The navigation server receives, decodes satellite observation data, broadcasts ephemeris, SSR correction and GNSS various error correction required by PPP calculation.
Corresponding information can be obtained after decoding by RTCM3, and other corrections specifically corresponding to the information except for satellite orbit and clock bias can be found in formulas (1) - (3).
The RTCM3 track clock correction information is as follows:
Δ SSR (IODE,t 0 )＝(δO r ,δO a ,δO c ,δO′ r ,δO' a ,δO′ c ,C 0 ,C 1 ,C 2 ) (15)
δO in formulas (15) - (17) r ,δO a ,δO c ,δO′ r ,δO' a ,δO′ c ,C 0 ,C 1 ,C 2 Radial, tangential and normal orbit correction and correction rate of change, clock correction and correction rate and acceleration, respectively.
δt＝C 0 +C 1 (t-t 0 )+C 2 (t-t 0 ) 2 (18)
Δt s ＝Δt b -δt/c (19)
The user position, velocity, time, attitude information, GNSS related status information (atmospheric error, floating ambiguity, etc.), and INS related status information (accelerometer and gyroscope bias and scale factor, etc.) are then obtained by calculation of equations (1) - (14). After a reliable floating ambiguity is obtained, the ambiguity is updated using the integer ambiguity weighted average strategy described above. And obtaining a result after updating the ambiguity.
According to another aspect of the present invention, the present invention may be implemented as a high precision navigation method combining precision point positioning and inertial navigation systems. The high-precision navigation method comprises the following steps: the method comprises the steps that an inertial sensing unit of a navigation terminal device obtains inertial observation data, the inertial observation data comprise acceleration sensing data and angular velocity sensing data, a processing module of the navigation terminal device calculates the acceleration sensing data and the angular velocity sensing data to obtain an inertial position variable quantity and an inertial velocity variable quantity, obtains a current inertial position based on a previous inertial position and the inertial position variable quantity, and obtains a current inertial velocity based on a previous inertial velocity and the inertial velocity variable quantity; a satellite positioning receiver of the navigation terminal equipment obtains satellite observation data, wherein the satellite observation data comprises a pseudo-range observation value, a phase observation value and a Doppler observation value; the wireless transmission module of the navigation terminal equipment transmits the satellite observation data through a wireless network; the navigation server receives satellite observation data from the navigation terminal equipment, calculates the satellite navigation data of the navigation terminal equipment based on the satellite observation data, and transmits the satellite navigation data back to the navigation terminal equipment through a wireless network, wherein the satellite navigation data comprises satellite navigation positions and satellite navigation speeds, a processing module of the navigation terminal equipment takes the satellite navigation positions as references, obtains a current combined navigation position by combining the current inertial positions, obtains the current combined navigation speed by combining the current inertial navigation speeds as references, the sample rate of the satellite observation data is lower than the sample rate of the inertial observation data, the sample rate of the satellite observation data refers to the number of the satellite observation data obtained per second, and the sample rate of the inertial observation data refers to the number of the inertial observation data obtained per second.
For details regarding the implementation of the high-precision navigation method, reference is made to the high-precision navigation system above, which is not repeated here.
On the basis of the Wen Gao precision navigation system, in a second embodiment, the invention also provides an ionospheric delay model system, which comprises a navigation server 106, the navigation terminal device 102 and the navigation server 106. The related art of the navigation server 106 and the navigation terminal device 102 in the high-precision navigation system described above can be applied to an ionospheric delay model system, and will not be repeated here. Differences in the ionospheric delay model system relative to the high-precision navigation system are mainly described herein.
It should be noted that, in the process of calculating the satellite navigation data of the navigation terminal device 102, the navigation server 106 calculates the ionospheric bias delay corresponding to the navigation terminal device. As shown in fig. 3, the navigation server 106 further includes a satellite navigation reference station screening module 310 and an ionospheric delay model processing module 320. The satellite navigation reference station screening module 320 screens out a part of navigation terminal devices from the plurality of navigation terminal devices 102 as satellite navigation reference stations, and the ionospheric delay model processing module 320 uses the calculated ionospheric delay corresponding to the navigation terminal devices 102 as satellite navigation reference stations to model and update the ionospheric delay model of the navigation satellite, so as to obtain a real-time ionospheric delay model of the navigation satellite. In ionospheric delay model modeling, improved spherical harmonic analysis model modeling is preferred.
In this way, the present invention does not need to set a special satellite navigation reference station at a great cost, and in addition, along with the popularization of the high-precision navigation system, the navigation terminal device 102 can be tens of thousands, hundreds of thousands or millions, from which a plurality of satellite navigation reference stations can be selected, and the number and density of the satellite navigation reference stations can be greatly provided, so that the ionosphere delay model with high precision and high reliability can be obtained.
In a preferred embodiment, the satellite navigation reference station screening module 310 may screen a part of the navigation terminal devices from the plurality of navigation terminal devices 102 as the satellite navigation reference station by: determining a navigation terminal device with positioning precision higher than a preset precision threshold and/or with the ambiguity fixing rate higher than a preset fixing threshold as a candidate satellite navigation reference station; and comparing the calculated ionospheric slant delay corresponding to the candidate satellite navigation reference station with the ionospheric slant delay of the candidate satellite navigation reference station calculated by using the current ionospheric delay model, and taking the candidate satellite navigation reference station as a satellite navigation reference station if the difference value of the ionospheric slant delay and the ionospheric slant delay is smaller than a preset difference value. It can be seen that a navigation terminal device with high positioning accuracy may be determined as a candidate satellite navigation reference station, whereas a navigation terminal device with low positioning accuracy may not be determined as a candidate satellite navigation reference station, and the positioning accuracy may be obtained from satellite navigation data of the navigation terminal device. A navigation terminal device with a high ambiguity fixing rate (i.e., a low ambiguity fluctuation and close to an integer) may be determined as a candidate satellite navigation reference station, whereas a navigation terminal device with a low ambiguity fixing rate (i.e., a high ambiguity fluctuation and not close to an integer) may not be determined as a candidate satellite navigation reference station. In addition, if the difference between the calculated ionospheric bias delay (the value of the ionospheric bias delay calculated by the navigation server) corresponding to the candidate satellite navigation reference station and the ionospheric bias delay calculated by the candidate satellite navigation reference station using the current ionospheric delay model is greater than a predetermined difference threshold, it is indicated that the calculated ionospheric bias delay corresponding to the candidate satellite navigation reference station is not suitable for modeling of the ionospheric delay model, and the candidate satellite navigation reference station is abandoned.
Preferably, when part of the navigation terminal devices are selected from the plurality of navigation terminal devices as the satellite navigation reference station, the satellite navigation reference station screening module 310 determines a precision factor of the satellite navigation reference station, the precision factor determining a degree of reliance on data of the satellite navigation reference station in the ionospheric delay model, the precision factor being related to an ionospheric bias delay, a receiver type and/or a dynamic condition of the satellite navigation reference station. For example, the smaller the difference between the ionospheric bias delay of the satellite navigation reference station and the ionospheric bias delay of the satellite navigation reference station calculated by using the current ionospheric delay model, the higher the precision factor, for example, the higher the precision factor of the satellite receiver belonging to a high-precision satellite receiver, for example, the precision factor of the stationary navigation terminal device may be higher than the precision factor of the navigation terminal device moving at a high speed.
In a preferred embodiment, the satellite navigation reference station screening module 310 selects a predetermined number of calculated ionospheric bias delays corresponding to the navigation terminal devices 102 that do not participate in modeling of the ionospheric delay model for evaluation of the ionospheric delay model, and evaluates the accuracy and integrity of the ionospheric delay model in real time by comparing the calculated ionospheric bias delays corresponding to the predetermined number of navigation terminal devices with the calculated ionospheric bias delays of the navigation terminal devices calculated using the current ionospheric delay model. And evaluating the ionospheric delay model by using navigation terminal equipment which does not participate in modeling of the ionospheric delay model, wherein an evaluation result is more reliable and reliable.
In a preferred embodiment, when the navigation server calculates satellite navigation data of the navigation terminal device based on the satellite observation data, an optimal satellite navigation reference station around the navigation terminal device is selected and an RTK (real time dynamic positioning) mode is started to accelerate to obtain the satellite navigation data of the navigation terminal device. Because the optimal satellite navigation reference stations around the navigation terminal equipment are selected, the RTK mode can be started when satellite navigation data of the navigation terminal equipment are calculated, so that the position convergence speed is accelerated, and the position positioning accuracy can be improved.
According to another aspect of the present invention, there is also provided an ionospheric delay model modeling method including: the method comprises the steps that a navigation server receives satellite observation data from a plurality of navigation terminal devices, satellite navigation data of the navigation terminal devices are obtained through calculation based on the satellite observation data, the satellite navigation data are transmitted back to the navigation terminal devices through a wireless network, the satellite navigation data comprise satellite navigation positions and satellite navigation speeds, and ionosphere oblique delays corresponding to the navigation terminal devices are obtained through calculation in the process of calculating the satellite navigation data of the navigation terminal devices; screening part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station; and modeling and updating the ionospheric delay model of the navigation satellite by using the calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain the real-time ionospheric delay model of the navigation satellite.
In a preferred embodiment, a part of the navigation terminal devices are screened out of the plurality of navigation terminal devices as satellite navigation reference stations by: determining a navigation terminal device with positioning precision higher than a preset precision threshold and/or with the ambiguity fixing rate higher than a preset fixing threshold as a candidate satellite navigation reference station; and comparing the calculated ionospheric slant delay corresponding to the candidate satellite navigation reference station with the ionospheric slant delay of the candidate satellite navigation reference station calculated by using the current ionospheric delay model, and taking the candidate satellite navigation reference station as a satellite navigation reference station if the difference value of the ionospheric slant delay and the ionospheric slant delay is smaller than a preset difference value. Preferably, when part of the navigation terminal devices are selected from the plurality of navigation terminal devices as satellite navigation reference stations, a precision factor of the satellite navigation reference stations is also determined, wherein the precision factor determines the degree of reliance on data of the satellite navigation reference stations in an ionospheric delay model, and the precision factor is related to ionospheric oblique delay, receiver type and/or dynamic condition of the satellite navigation reference stations.
In this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a list of elements is included, and may include other elements not expressly listed.
In this document, terms such as front, rear, upper, lower, etc. are defined with respect to the positions of the components in the drawings and with respect to each other, for clarity and convenience in expressing the technical solution. It should be understood that the use of such orientation terms should not limit the scope of the protection sought herein.
The embodiments described above and features of the embodiments herein may be combined with each other without conflict.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (14)
1. An ionospheric delay model system, comprising:
the navigation server receives satellite observation data from a plurality of navigation terminal devices, calculates satellite navigation data of the navigation terminal devices based on the satellite observation data, transmits the satellite navigation data back to the navigation terminal devices through a wireless network, wherein the satellite navigation data comprises satellite navigation positions and satellite navigation speeds, and calculates ionospheric slant delays corresponding to the navigation terminal devices in the process of calculating the satellite navigation data of the navigation terminal devices;
the navigation server comprises a satellite navigation reference station screening module and an ionospheric delay model processing module, wherein the satellite navigation reference station screening module screens part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station, and the ionospheric delay model processing module models and updates an ionospheric delay model of a navigation satellite by utilizing calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain a real-time ionospheric delay model of the navigation satellite.
2. The ionospheric delay model system of claim 1,
the satellite navigation reference station screening module screens part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station by the following operation:
determining a navigation terminal device with positioning precision higher than a preset precision threshold and/or with the ambiguity fixing rate higher than a preset fixing threshold as a candidate satellite navigation reference station;
and comparing the calculated ionospheric slant delay corresponding to the candidate satellite navigation reference station with the ionospheric slant delay of the candidate satellite navigation reference station calculated by using the current ionospheric delay model, and taking the candidate satellite navigation reference station as a satellite navigation reference station if the difference value of the ionospheric slant delay and the ionospheric slant delay is smaller than a preset difference value.
3. The ionospheric delay model system of claim 2, wherein the satellite navigation reference station screening module further determines a precision factor of the satellite navigation reference station when the satellite navigation reference station screening module screens out a part of the plurality of navigation terminal devices as the satellite navigation reference station, the precision factor determining a degree of reliance on data of the satellite navigation reference station in the ionospheric delay model, the precision factor being related to an ionospheric bias delay, a receiver type, and/or a dynamic condition of the satellite navigation reference station.
4. The ionospheric delay model system of claim 1 wherein a satellite navigation reference station screening module selects calculated ionospheric bias delays corresponding to a predetermined number of navigation terminal devices that do not participate in modeling of the ionospheric delay model for use in evaluating the ionospheric delay model,
and evaluating the accuracy and the integrity of the ionospheric delay model in real time by comparing the calculated ionospheric delay corresponding to the preset number of navigation terminal devices with the ionospheric delay calculated by the current ionospheric delay model.
5. The ionospheric delay model system of claim 1, wherein the navigation server, when calculating satellite navigation data of the navigation terminal device based on the satellite observation data, selects an optimal satellite navigation reference station around the navigation terminal device and starts an RTK (real time kinematic) mode acceleration to obtain the satellite navigation data of the navigation terminal device.
6. The ionospheric delay model system of claim 1, wherein the modeling of the ionospheric delay model is performed and updated for the navigation satellite using the calculated ionospheric bias delay corresponding to the navigation terminal device as a satellite navigation reference station, using a spherical harmonic analysis model.
7. The ionospheric delay model system of claim 1, further comprising:
each navigation terminal device comprises a satellite positioning receiver, a processing module and a wireless transmission module, the satellite positioning receiver obtains satellite observation data, the satellite observation data comprises a pseudo-range observation value, a phase observation value and a Doppler observation value, and the wireless transmission module transmits the satellite observation data out through a wireless network.
8. The ionospheric delay model system of claim 7, wherein the navigation terminal device further comprises an inertial navigation unit that obtains inertial observation data including acceleration sensing data and angular velocity sensing data, the processing module calculates the acceleration sensing data and the angular velocity sensing data to obtain an inertial position variation and an inertial velocity variation, obtains a current inertial position based on a previous inertial position and the inertial position variation, obtains a current inertial velocity based on a previous inertial velocity and the inertial velocity variation,
the processing module of the navigation terminal equipment takes the satellite navigation position as a reference, combines the current inertial position to obtain the current combined navigation position, takes the satellite navigation speed as a reference, combines the current inertial navigation speed to obtain the current combined navigation speed, the sample rate of satellite observation data is lower than the sample rate of inertial observation data, the sample rate of satellite observation data refers to the number of satellite observation data obtained per second, and the sample rate of inertial observation data refers to the number of inertial observation data obtained per second.
9. The ionospheric delay model system of claim 8, wherein said wireless transmission module further transmits said inertial observation data to said navigation server via a wireless network, said navigation server calculating satellite navigation data of said navigation terminal device in combination with said inertial observation data and said satellite observation data, or,
the wireless transmission module is used for transmitting the inertial position variable quantity and the inertial speed variable quantity to the navigation server through a wireless network, and the navigation server is used for calculating satellite navigation data of the navigation terminal equipment by combining the inertial position variable quantity, the inertial speed variable quantity and the satellite observation data.
10. An ionospheric delay model modeling method, comprising:
the method comprises the steps that a navigation server receives satellite observation data from a plurality of navigation terminal devices, satellite navigation data of the navigation terminal devices are obtained through calculation based on the satellite observation data, the satellite navigation data are transmitted back to the navigation terminal devices through a wireless network, the satellite navigation data comprise satellite navigation positions and satellite navigation speeds, and ionosphere oblique delays corresponding to the navigation terminal devices are obtained through calculation in the process of calculating the satellite navigation data of the navigation terminal devices;
screening part of navigation terminal equipment from a plurality of navigation terminal equipment to serve as a satellite navigation reference station;
and modeling and updating the ionospheric delay model of the navigation satellite by using the calculated ionospheric oblique delay corresponding to the navigation terminal equipment serving as the satellite navigation reference station to obtain the real-time ionospheric delay model of the navigation satellite.
11. The ionospheric delay model modeling method of claim 10,
selecting a part of navigation terminal devices from a plurality of navigation terminal devices as satellite navigation reference stations by the following operations:
determining a navigation terminal device with positioning precision higher than a preset precision threshold and/or with the ambiguity fixing rate higher than a preset fixing threshold as a candidate satellite navigation reference station;
and comparing the calculated ionospheric slant delay corresponding to the candidate satellite navigation reference station with the ionospheric slant delay of the candidate satellite navigation reference station calculated by using the current ionospheric delay model, and taking the candidate satellite navigation reference station as a satellite navigation reference station if the difference value of the ionospheric slant delay and the ionospheric slant delay is smaller than a preset difference value.
12. The ionospheric delay model modeling method of claim 11, characterized in that, when part of the navigation terminal devices are screened out from the plurality of navigation terminal devices as satellite navigation reference stations, a precision factor of the satellite navigation reference stations is also determined, which decides a degree of reliance on data of the satellite navigation reference stations in the ionospheric delay model, which precision factor is related to ionospheric diagonal delays, receiver types and/or dynamic conditions of the satellite navigation reference stations.
13. The ionospheric delay model modeling method of claim 10, further comprising:
and selecting calculated ionospheric bias delays corresponding to a predetermined number of navigation terminal devices as the evaluation of the ionospheric delay model, wherein the calculated ionospheric bias delays corresponding to the navigation terminal devices do not participate in the modeling of the ionospheric delay model, and evaluating the accuracy and the integrity of the ionospheric delay model in real time by comparing the calculated ionospheric bias delays corresponding to the predetermined number of navigation terminal devices with the ionospheric bias delays of the navigation terminal devices calculated by using the current ionospheric delay model.
14. The ionospheric delay model modeling method of claim 10, wherein the navigation server selects an optimal satellite navigation reference station around the navigation terminal device and starts RTK mode acceleration to obtain satellite navigation data of the navigation terminal device when calculating satellite navigation data of the navigation terminal device based on the satellite observation data.
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