A high-precision calibration method and system based on dual-frequency multi-constellation GBAS

Abstract

The present invention provides a high-precision calibration method and system based on dual-frequency multi-constellation GBAS, comprising: receiving and processing dual-frequency multi-constellation satellite navigation signals, generating dual-frequency code and carrier phase observation information; removing satellites on paths that do not meet requirements according to dual-frequency integrated multipath errors; setting satellite elevation filter angle values, screening qualified GBAS ground station dual-frequency and multi-constellation observations; removing satellites that do not meet integrity monitoring requirements; constructing an objective function on GDOP values, selecting a satellite combination with the best geometric distribution and satellite quality; calculating the ionospheric gradient between any two stations in the GBAS, judging whether the monitored ionospheric gradient is normal, and performing different filtering processing operations according to whether the ionospheric gradient is normal; and outputting the calibration result according to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution.

Description

Technical Field

[0001] The present invention belongs to the field of satellite navigation enhancement technology application, and in particular relates to a high-precision calibration method and system based on dual-frequency multi-constellation GBAS. Background Art

[0002] The Ground-Based Augmentation System (GBAS) is a navigation system used for precision approach and landing guidance of airport aircraft. It mainly completes high-precision satellite navigation signal measurement, differential correction calculation, and integrity monitoring processing functions, and provides precision approach guidance services for airborne equipment. The GBAS system diagram is shown below: Figure 1 As a high-reliability navigation augmentation system, the accuracy and reliability of GBAS are crucial to aviation safety and other application areas.

[0003] The position calibration of special locations such as the reference receiver antenna of the GBAS ground station and the airport runway is an important prerequisite and key to GBAS providing accurate services. GBAS systems usually need to be deployed and operated under different geographical environments and climatic conditions. Equipped with calibration equipment that can adapt to environmental changes and technological development requirements in a timely manner, GBAS can maintain good service performance and functions.

[0004] High-precision calibration methods and equipment use dual-frequency and multi-constellation satellite signals to more effectively eliminate errors such as ionospheric delay, thereby significantly improving positioning accuracy and achieving decimeter-level or even centimeter-level positioning accuracy. At the same time, by integrating the signals of multiple satellite constellations, the dependence on a single constellation is reduced. When some satellites in a constellation fail or the signals are interfered with, the system can still maintain good performance, thereby improving the availability and reliability of the system. It can adapt to different geographical environments and complex signal conditions, and can provide stable and high-precision navigation services in various scenarios. It can support more application scenarios and can also be applied to other fields with high requirements for positioning accuracy and reliability, such as surveying and mapping, exploration, etc. Summary of the invention

[0005] In view of this, the present invention aims to propose a high-precision calibration method based on dual-frequency multi-constellation GBAS, comprising the following steps:

[0006] S1, receiving and processing dual-frequency multi-constellation satellite navigation signals, generating dual-frequency code and carrier phase observation information;

[0007] S2. Calculate the satellite dual-frequency integrated multipath error and remove the satellites on the path that do not meet the requirements;

[0008] S3. Set the satellite elevation filter angle value to screen the dual-frequency and multi-constellation observations of GBAS ground stations that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, and data quality of the GBAS station, and exclude satellites that do not meet the integrity monitoring requirements;

[0009] S4. Assign weight coefficients to different satellite measurements based on GBAS integrity monitoring results, construct an objective function for GDOP values, and select the satellite combination with the best geometric distribution and satellite quality;

[0010] S5, calculating the ionospheric gradient between any two stations in GBAS, and performing different filtering operations according to whether the ionospheric gradient is normal;

[0011] S6. If the ionospheric gradient monitoring is normal, the linear combination of the dual-frequency carrier phase observations is calculated, and the original code pseudorange is smoothed and filtered using the combined phase value; if the ionospheric gradient monitoring is abnormal, the received dual-frequency satellite signal pseudorange and carrier phase are combined to construct a new pseudorange and carrier phase value, forming a new carrier phase smoothed pseudorange value, and further high-precision position calibration is performed;

[0012] S7, calibration uses four positioning modes: RTK, code pseudorange difference, single point, and PPP. According to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution, the calibration results with positioning errors within 0.5 meters horizontally and 1 meter vertically in the comprehensive mode are output. Users can also independently select the positioning mode to output the calibration results.

[0013] Furthermore, the calculating of the satellite dual-frequency integrated multipath error and eliminating the satellites on the path that do not meet the requirements includes:

[0014] The multipath error MP0 is obtained by reconstructing the pseudorange using precise ephemeris, the multipath error MP1 of the dual-frequency point is calculated using the pseudorange of the first frequency and the dual-frequency carrier phase, the multipath error MP2 of the dual-frequency point is calculated using the pseudorange of the second frequency and the dual-frequency carrier phase, and the multipath error MP3 between multiple consecutive epochs is calculated, and the above four multipath errors are processed as follows:

[0015] Calculate the MP corresponding to each satellite i j The multipath error residual value is , j=1,2,3;

[0016] ;

[0017] Taking the ath satellite as an example, calculate The scaling factor ;

[0018] ;

[0019] They are , , , is the satellite i , is the satellite i , is the satellite i , is the satellite i , C is the set of observed satellites i, N is the total number of satellites; comprehensive multipath error , , The resulting judgment criteria are: Less than the preset threshold L is the decision criterion. If it is not satisfied, the satellite on the path will not be used when calibrating; j=1, 2, 3; is the MP corresponding to the ath satellite j The multipath error residual value; They are , , , is the ath satellite corresponding to , is the ath satellite corresponding to , is the ath satellite corresponding to ;

[0020] The calculation methods of MP0, MP1 and MP2 include:

[0021] ,

[0022] When x=0, A, B, and C are the pseudoranges calculated using precise ephemeris and the carrier phases of the two frequencies, respectively. At this time:

[0023] , ;

[0024] When x=1, A, B, and C are the pseudorange of the first frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0025] , ;

[0026] When x=2, A, B, and C are the pseudorange of the second frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0027] , ;

[0028] Among them, f r and f s is the center frequency of the two frequency points;

[0029] The calculation methods include:

[0030] ;

[0031] Where d is a certain epoch time, m is the number of epochs, c is the speed of light, P1(d) is the correlation peak of the satellite signal at epoch d, P2(d) is the correlation peak of the multipath signal at epoch d, the delay corresponding to P1 is T1, and the delay corresponding to P2 is T2.

[0032] Further, the objective function of the GDOP value is constructed, and the satellite combination with the best geometric distribution and satellite quality is selected, including:

[0033] Based on the geometric dilution of precision GDOP value, according to the GBAS ground station for different satellites i (S i , M i , D i , B i ) construct the objective function OBJ under different satellite combinations, where S i is the signal quality monitoring mean value of satellite i, M i is the mean value of the measurement quality monitoring of satellite i, D i is the mean value of data quality monitoring of satellite i, B i is the monitoring result of the B value of satellite i. The smaller the OBJ, the better the spatial distribution and satellite quality. The satellite combination with the smallest OBJ is used for calibration.

[0034] ;

[0035] in is the elevation angle of satellite i, ~ They are (S i , M i , D i , B i ) is the allocation weight coefficient.

[0036] Furthermore, according to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution factors, the calibration positioning results in the comprehensive mode are output, including four positioning modes: RTK, code pseudorange difference, single point, and PPP. The calibration results in the comprehensive mode are output by default to ensure that the positioning error of the comprehensive mode is within 0.5 meters horizontally and 1 meter vertically;

[0037] In the comprehensive mode, the positioning results of RTK, code pseudorange difference, single point, and PPP are P RTK , P PD , P SPP , P PPP , and the corresponding weight coefficients are ω RTK ,ω PD ,ω SPP ,ω PPP , and satisfies ω RTK +ω PD +ω SPP +ω PPP =1, comprehensive positioning result P 综合 It is expressed as:

[0038] P 综合 =ω RTK ×P RTK +ω PD ×P PD +ω SPP ×P SPP +ω PPP ×P PPP ;

[0039] ;

[0040] Among them, the proportional factor ω k According to the GBAS calibration time T k , Positioning precision factor A k , Deployment environment factor E k , calibration point position distribution factor D k , Positioning mode reliability factor R k , for evaluation and setting, k is a certain positioning mode.

[0041] Further, the calculating of the ionospheric gradient between any two stations in the GBAS comprises, according to whether the monitored ionospheric gradient is normal:

[0042] With the dual-frequency satellite data of the best satellite combination in terms of geometric distribution and satellite quality, the ionospheric gradient between any two stations in GBAS is calculated. The ionospheric gradient G of a satellite observed by a successfully paired monitoring station is the ionospheric differential delay of the two stations divided by the distance between the two stations. The total If the ionospheric gradients under all the two-station combinations are greater than or equal to the threshold Q, it is considered that the ionospheric gradient is abnormal.

[0043] .

[0044] Further, constructing different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal includes:

[0045] Depending on whether the monitored ionospheric gradient is normal, two different smoothing filtering processing methods are used: if the ionospheric gradient is normal, the linear combination of the dual-frequency carrier phase observations is calculated, and the combined phase value is used to smooth the original code pseudorange; if the ionospheric gradient monitoring is abnormal, the received dual-frequency satellite signal pseudorange and carrier phase are combined to construct new pseudorange and carrier phase values ​​to form a new carrier phase smoothed pseudorange value, and further high-precision position calibration is performed.

[0046] Furthermore, when the space ionospheric gradient monitoring is normal, that is: , using the first smoothing filter processing method, including:

[0047] Calculate the linear combination of the dual-frequency carrier phase observations and use the phase value at time t after the combination Original code pseudorange Perform smoothing filtering to obtain the filter value at time t :

[0048] ;

[0049] ;

[0050] Among them, f r and f s is the center frequency of the two frequency points, , is the dual-frequency carrier phase measurement value at time t, is the smoothing filter time, is the data sampling interval;

[0051] When the space ionospheric gradient monitoring is abnormal, that is: , using the second smoothing filter processing method, including the use of the ionospheric-free combination of code pseudorange and carrier phase at time t and , as the input of the smoothing filter to eliminate the ionospheric error and obtain the filtered value at time t , the specific method is as follows:

[0052] ;

[0053] ;

[0054] ;

[0055] Among them, f r and f s is the center frequency of the two frequency points, is the dual-frequency carrier phase measurement value at time t, and is the dual-frequency code pseudorange measurement value at time t, is the smoothing filter time, is the data sampling interval.

[0056] On the other hand, the present invention provides a high-precision calibration system based on dual-frequency multi-constellation GBAS, including: a dual-frequency multi-constellation satellite navigation receiver and antenna, a multipath error monitoring module, a star selection preprocessing module, a geometric distribution selection module, an ionospheric gradient monitoring module, a dual-frequency filtering processing module and a calibration processing module, wherein:

[0057] The dual-frequency multi-constellation satellite navigation receiver and antenna are used to receive and process dual-frequency multi-constellation satellite navigation signals to generate observation information;

[0058] The multipath error monitoring module is used to monitor and process the multipath error in the system, and remove satellites on the path that do not meet the requirements according to the size of the dual-frequency integrated multipath error;

[0059] The satellite selection preprocessing module is used to set the satellite elevation filter angle value and screen the dual-frequency and multi-constellation observations of the GBAS ground station that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, and data quality of the GBAS station, and satellites that do not meet the integrity monitoring requirements are excluded;

[0060] The geometric distribution selection module is used to assign weight coefficients to different satellite measurement values ​​according to the GBAS integrity monitoring results, construct an objective function about the GDOP value, and select a satellite combination with the best geometric distribution and satellite quality;

[0061] The ionospheric gradient monitoring module is used to calculate the ionospheric gradient between any two stations in the GBAS by means of dual-frequency satellite data of the satellite combination with the best geometric distribution and satellite quality, and perform different processing operations in the dual-frequency filtering processing module according to whether the monitored ionospheric gradient is normal;

[0062] The dual-frequency filtering processing module is used to construct different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal, and then perform low-pass smoothing filtering respectively to form a new carrier phase smoothing pseudorange value for each satellite, and use this value to perform high-precision position calibration;

[0063] The calibration processing module is used to perform four-mode positioning using the new carrier phase smoothed pseudorange value, and can output the calibration positioning result in the comprehensive mode according to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution. The user can also independently select the positioning mode. On the other hand, the present invention provides a high-precision calibration system based on dual-frequency multi-constellation GBAS, including: a dual-frequency multi-constellation satellite navigation receiver and antenna, a multipath error monitoring module, a star selection preprocessing module, a geometric distribution selection module, an ionospheric gradient monitoring module, a dual-frequency filtering processing module, and a calibration processing module, wherein,

[0064] The dual-frequency multi-constellation satellite navigation receiver and antenna are used to receive and process dual-frequency multi-constellation satellite navigation signals to generate observation information;

[0065] The multipath error monitoring module is used to monitor and process the multipath error in the system, and remove satellites on the path that do not meet the requirements according to the size of the dual-frequency integrated multipath error;

[0066] The satellite selection preprocessing module is used to set the satellite elevation filter angle value and screen the dual-frequency and multi-constellation observations of the GBAS ground station that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, data quality, etc. of the GBAS station, and the satellites that do not meet the integrity monitoring requirements are excluded;

[0067] The geometric distribution selection module is used to assign weight coefficients to different satellite measurement values ​​according to the GBAS integrity monitoring results, construct an objective function about the GDOP value, and select a satellite combination with the best geometric distribution and satellite quality;

[0068] The ionospheric gradient monitoring module is used to calculate the ionospheric gradient between any two stations in the GBAS by means of the preferred dual-frequency satellite data, and perform different processing operations in the dual-frequency filtering processing module according to whether the monitored ionospheric gradient is normal;

[0069] The dual-frequency filtering processing module is used to construct different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal, and then perform low-pass smoothing filtering respectively to form a new carrier phase smoothing pseudorange value for each satellite, and use this value to perform high-precision position calibration;

[0070] The calibration processing module is used to perform four-mode positioning using the new carrier phase smoothed pseudorange value. It can output the calibration positioning results in the comprehensive mode according to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution. Users can also select the positioning mode independently.

[0071] The high-precision calibration method and system based on dual-frequency multi-constellation GBAS disclosed in this application have at least the following advantages over the prior art:

[0072] (1) The dual-frequency multi-constellation GBAS high-precision calibration method and device of the present invention, relying on the dual-frequency multi-constellation GBAS system architecture, can complete the position calibration of GBAS ground stations and special locations of airports without adding additional equipment, effectively reducing equipment investment costs and real-time costs.

[0073] (2) Satellite signals composed of dual frequencies and multiple constellations must undergo GBAS integrity monitoring and multipath error monitoring to select measurements that meet the established conditions in terms of signal quality, data quality, and measurement quality. This comprehensive result is used as the input for optimizing the constellation geometry, which can effectively improve the accuracy and reliability of positioning.

[0074] (3) The use of multiple constellations can improve the system's robustness to constellation failures. At the same time, an ionospheric spatial gradient monitoring model is constructed, and an appropriate smoothing filter processing method is selected according to the ionospheric monitoring results to effectively eliminate the influence of the ionosphere and further improve the calibration accuracy.

[0075] (4) The calibration method successfully implemented four positioning processing modes, greatly improving the flexibility of user use. The device can output the position calibration results in the comprehensive mode, and can also independently select the calibration mode according to the GBAS user's usage requirements to meet different applications and scenarios, thereby improving the applicability and versatility of the system. The robustness of the entire system to unexpected interference is also significantly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0077] Figure 1 This is a schematic diagram of the GBAS system;

[0078] Figure 2 A diagram showing the relationship between the internal modules of the system according to an embodiment of the present invention;

[0079] Figure 3 A flow chart of a high-precision calibration method based on dual-frequency multi-constellation GBAS provided by an embodiment of the present invention;

[0080] Figure 4 This is a working flow chart of the ionospheric gradient monitoring module of the device described in an embodiment of the present invention. DETAILED DESCRIPTION

[0081] The present invention is further described in detail below through the accompanying drawings and specific embodiments.

[0082] like Figure 3As shown, the present invention provides a high-precision calibration method based on dual-frequency multi-constellation GBAS, comprising:

[0083] S1. Receive and process dual-frequency multi-constellation satellite navigation signals to generate dual-frequency code and carrier phase observation information.

[0084] S2. Calculate the satellite dual-frequency integrated multipath error and eliminate satellites on paths that do not meet the requirements.

[0085] Specifically, the multipath error is calculated, and according to the size of the dual-frequency integrated multipath error, satellites on the path that do not meet the requirements are eliminated, including:

[0086] The multipath error MP0 is obtained by reconstructing the pseudorange using precise ephemeris, the multipath error MP1 of the dual-frequency point is calculated using the pseudorange of the first frequency and the dual-frequency carrier phase, the multipath error MP2 of the dual-frequency point is calculated using the pseudorange of the second frequency and the dual-frequency carrier phase, and the multipath error MP3 between multiple consecutive epochs is calculated, and the above four multipath errors are processed as follows:

[0087] Calculate the MP corresponding to each satellite i j The multipath error residual value is , j=1,2,3;

[0088] ;

[0089] Taking the ath satellite as an example, calculate The scaling factor ;

[0090] ;

[0091] They are , , , is the satellite i , is the satellite i , is the satellite i , is the satellite i , C is the set of observed satellites i, N is the total number of satellites; comprehensive multipath error , , The resulting judgment criteria are: Less than the preset threshold L is the decision criterion. If it is not satisfied, the satellite on the path will not be used when calibrating; j=1, 2, 3; is the MP corresponding to the ath satellite jThe multipath error residual value; They are , , , is the ath satellite corresponding to , is the ath satellite corresponding to , is the ath satellite corresponding to ;

[0092] The calculation methods of MP0, MP1 and MP2 include:

[0093] ,

[0094] When x=0, A, B, and C are the pseudoranges calculated using precise ephemeris and the carrier phases of the two frequencies, respectively. At this time:

[0095] , ;

[0096] When x=1, A, B, and C are the pseudorange of the first frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0097] , ;

[0098] When x=2, A, B, and C are the pseudorange of the second frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0099] , ;

[0100] Among them, f r and f s is the center frequency of the two frequency points;

[0101] The calculation methods include:

[0102] ;

[0103] Where d is a certain epoch time, m is the number of epochs, c is the speed of light, P1(d) is the correlation peak of the satellite signal at epoch d, P2(d) is the correlation peak of the multipath signal at epoch d, the delay corresponding to P1 is T1, and the delay corresponding to P2 is T2.

[0104] S3. Set the satellite elevation filter angle value to screen the dual-frequency and multi-constellation observations of GBAS ground stations that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, data quality, etc. of the GBAS station, and satellites that do not meet the integrity monitoring requirements will be excluded.

[0105] S4. Assign weight coefficients to different satellite measurement values ​​according to the GBAS integrity monitoring results, construct an objective function about the GDOP value, and select the satellite combination with the best geometric distribution and satellite quality.

[0106] Specifically, according to the GBAS integrity monitoring results, weight coefficients are assigned to different satellite measurement values, an objective function for the GDOP value is constructed, and the satellite combination with the best geometric distribution and satellite quality is selected, including:

[0107] Based on the geometric dilution of precision GDOP value, according to the GBAS ground station for different satellites i (S i , M i , D i , B i ) construct the objective function OBJ under different satellite combinations, where S i is the signal quality monitoring mean value of satellite i, M i is the mean value of the measurement quality monitoring of satellite i, D i is the mean value of data quality monitoring of satellite i, B i is the monitoring result of the B value of satellite i. The smaller the OBJ, the better the spatial distribution and satellite quality. The satellite combination with the smallest OBJ is used for calibration.

[0108] ;

[0109] in is the elevation angle of satellite i, ~ They are (S i , M i , D i , B i ) is the allocation weight coefficient.

[0110] S5. Calculate the ionospheric gradient between any two stations in the GBAS, and perform different filtering operations based on whether the monitored ionospheric gradient is normal.

[0111] Specifically, the ionospheric gradient between any two stations in the GBAS is calculated, and whether the monitored ionospheric gradient is normal includes:

[0112] With the help of the preferred dual-frequency satellite data, the ionospheric gradient between any two stations in GBAS is calculated. The ionospheric gradient G of a satellite observed by a successfully paired monitoring station is the ionospheric differential delay of the two stations divided by the distance between the two stations. If the ionospheric gradients under all the two-station combinations are greater than or equal to the threshold Q, it is considered that the ionospheric gradient is abnormal.

[0113] .

[0114] S6: If the ionospheric gradient monitoring is normal, calculate the linear combination of the dual-frequency carrier phase observations, and use the combined phase value to smooth the original code pseudorange; if the ionospheric gradient monitoring is abnormal, combine the received dual-frequency satellite signal pseudorange and carrier phase to construct a new pseudorange and carrier phase value, forming a new carrier phase smoothed pseudorange value, and further perform high-precision position calibration.

[0115] Specifically, two different smoothing filtering processing methods are adopted according to whether the monitored ionospheric gradient is normal: if the ionospheric gradient is normal, the linear combination of the dual-frequency carrier phase observations is calculated, and the original code pseudorange is smoothed using the combined phase value; if the ionospheric gradient monitoring is abnormal, the received dual-frequency satellite signal pseudorange and carrier phase are combined to construct new pseudorange and carrier phase values ​​to form new carrier phase smoothed pseudorange values, and further high-precision position calibration is performed.

[0116] Specifically include: When the space ionospheric gradient monitoring is normal, that is: , using the first smoothing filter processing method, including:

[0117] Calculate the linear combination of the dual-frequency carrier phase observations and use the phase value at time t after the combination Original code pseudorange Perform smoothing filtering to obtain the filter value at time t :

[0118] ;

[0119] ;

[0120] Among them, f r and f s is the center frequency of the two frequency points, , is the dual-frequency carrier phase measurement value at time t, is the smoothing filter time, is the data sampling interval;

[0121] When the space ionospheric gradient monitoring is abnormal, that is: , using the second smoothing filter processing method, including the use of the ionospheric-free combination of code pseudorange and carrier phase at time t and , as the input of the smoothing filter to eliminate the ionospheric error and obtain the filtered value at time t , the specific method is as follows:

[0122] ;

[0123] ;

[0124] ;

[0125] Among them, f r and f s is the center frequency of the two frequency points, is the dual-frequency carrier phase measurement value at time t, and is the dual-frequency code pseudorange measurement value at time t, is the smoothing filter time, is the data sampling interval.

[0126] S7, calibration uses four positioning modes: RTK, code pseudorange difference, single point, and PPP. According to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution, the calibration results with positioning errors within 0.5 meters horizontally and 1 meter vertically in the comprehensive mode are output. Users can also independently select the positioning mode to output the calibration results.

[0127] Specifically, they include:

[0128] In the comprehensive mode, the positioning results of RTK, code pseudorange difference, single point, and PPP are P RTK , P PD , P SPP , P PPP , and the corresponding weight coefficients are ω RTK ,ω PD ,ω SPP ,ω PPP , and satisfies ω RTK +ω PD +ω SPP +ω PPP =1, comprehensive positioning result P 综合 It is expressed as:

[0129] P 综合 =ω RTK ×P RTK +ω PD ×P PD +ω SPP ×P SPP +ω PPP ×PPPP ;

[0130] ;

[0131] Among them, the proportional factor ω k According to the GBAS calibration time T k , Positioning precision factor A k , Deployment environment factor E k , calibration point position distribution factor D k , Positioning mode reliability factor R k , for evaluation and setting, k is a certain positioning mode.

[0132] like Figure 1 and Figure 2 As shown, on the other hand, an embodiment of the present invention provides a high-precision calibration system based on a dual-frequency multi-constellation GBAS, including a dual-frequency multi-constellation satellite navigation receiver and antenna, a multipath error monitoring module, a star selection preprocessing module, a geometric distribution selection module, an ionospheric gradient monitoring module, a dual-frequency filtering processing module and a calibration processing module, wherein the dual-frequency multi-constellation satellite navigation receiver and antenna are used to receive and process dual-frequency multi-constellation satellite navigation signals to generate observation information.

[0133] The multipath error monitoring module is used to monitor the multipath error in the system and remove satellites on paths that do not meet the requirements; the multipath error MP0 is obtained by reconstructing the pseudorange using precise ephemeris, the multipath errors MP1 and MP2 of the dual-frequency points and the multipath error MP3 between multiple consecutive epochs are calculated using the original dual-frequency pseudorange and carrier phase, and the above four multipath errors are processed as follows:

[0134] Calculate the MP corresponding to each satellite i j The multipath error residual value is , j=1,2,3;

[0135] ;

[0136] Taking satellite a as an example, calculate The scaling factor ;

[0137] ;

[0138] is the satellite i , , , is the satellite i , C is the set of observed satellites i, N is the total number of satellites; comprehensive multipath error , , The resulting judgment criteria are: Less than the preset threshold L is the decision criterion. If it is not satisfied, the satellite on the path will not be used when calibrating; j=1, 2, 3; is the MP corresponding to the ath satellite j The multipath error residual value; is the ath satellite corresponding to , , ;

[0139] The calculation methods of MP0, MP1 and MP2 include:

[0140] ,

[0141] When x=0, A, B, and C are the pseudoranges calculated using precise ephemeris and the carrier phases of the two frequencies, respectively. At this time:

[0142] , ;

[0143] When x=1, A, B, and C are the pseudorange of the first frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0144] , ;

[0145] When x=2, A, B, and C are the pseudorange of the second frequency and the two carrier phases of the dual frequency, respectively. At this time:

[0146] , ;

[0147] Among them, f r and f s is the center frequency of the two frequency points;

[0148] The calculation methods include:

[0149] ;

[0150] Where d is a certain epoch time, m is the number of epochs, c is the speed of light, P1(d) is the correlation peak of the satellite signal at epoch d, P2(d) is the correlation peak of the multipath signal at epoch d, the delay corresponding to P1 is T1, and the delay corresponding to P2 is T2.

[0151] The satellite selection preprocessing module selects qualified dual-frequency and multi-constellation observations of GBAS ground stations by setting the satellite elevation filter angle value; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, data quality, etc. of the GBAS station, and satellites that do not meet the integrity monitoring requirements will be excluded.

[0152] The geometric distribution selection module, based on the geometric precision factor GDOP value, is based on the monitoring results of the signal quality monitoring mean, measurement quality monitoring mean, data quality monitoring mean, and B value of different satellites i by the GBAS ground station (S i , M i , D i , B i ), construct the objective function OBJ under different satellite combinations. The smaller the OBJ, the better the spatial distribution and satellite quality. The satellite combination with the smallest OBJ is used for calibration.

[0153] ;

[0154] in is the elevation angle of satellite i, ~ They are (S i , M i , D i , B i ) is the allocation weight coefficient.

[0155] like Figure 4 As shown in the figure, with the preferred dual-frequency satellite data, the ionospheric gradient between any two stations in GBAS is calculated. The ionospheric gradient G of a satellite observed by a successfully paired monitoring station is the ionospheric differential delay of the two stations divided by the distance between the two stations. The total If the ionospheric gradients under all the two-station combinations are greater than or equal to the threshold Q, it is considered that the ionospheric gradient is abnormal.

[0156] ;

[0157] The dual-frequency filtering processing module constructs different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal, and then performs low-pass smoothing filtering on each of them to form a new carrier phase smoothed pseudorange value for each satellite, which is used for high-precision position calibration.

[0158] When the monitored ionospheric gradient is normal, the first smoothing filter method is used. When the monitored ionospheric gradient is abnormal, the second smoothing filter method is used to better eliminate the influence of the ionosphere.

[0159] The two smoothing filtering methods in the dual-frequency filtering processing module are:

[0160] Smoothing filter processing method 1, calculate the linear combination of the dual-frequency carrier phase observations, and use the phase value at time t after the combination Original code pseudorange Perform smoothing filtering to obtain the filter value at time t :

[0161] ;

[0162] ;

[0163] Among them, f r and f s is the center frequency of the two frequency points, , is the dual-frequency carrier phase measurement value at time t, is the smoothing filter time, is the data sampling interval;

[0164] Smoothing filter processing mode 2, using the second smoothing filter processing mode, including using the ionosphere-free combination of code pseudorange and carrier phase at time t and , as the input of the smoothing filter to eliminate the ionospheric error and obtain the filtered value at time t , the specific method is as follows:

[0165] ;

[0166] ;

[0167] ;

[0168] Among them, f r and f s is the center frequency of the two frequency points, is the dual-frequency carrier phase measurement value at time t, and is the dual-frequency code pseudorange measurement value at time t, is the smoothing filter time, is the data sampling interval.

[0169] The calibration processing module includes four positioning modes: RTK, code pseudo-range differential, single point, and PPP positioning. The calibration results in the comprehensive mode are output by default to ensure that the positioning error in the comprehensive mode is within 0.5 meters horizontally and 1 meter vertically. Users can also choose the calibration mode independently. In the comprehensive mode, the positioning results of RTK, code pseudo-range differential, single point, and PPP are P respectively. RTK , P PD , P SPP , P PPP , and the corresponding weight coefficients are ωRTK ,ω PD ,ω SPP ,ω PPP , and satisfies ω RTK +ω PD +ω SPP +ω PPP =1, comprehensive positioning result P 综合 It is expressed as:

[0170] P 综合 =ω RTK ×P RTK +ω PD ×P PD +ω SPP ×P SPP +ω PPP ×P PPP ;

[0171] ;

[0172] Among them, the proportional factor ω k According to the calibration time factor T k , precision factor A k Environmental factors E k , calibration point position distribution factor D k , Positioning mode reliability factor R k , for evaluation and setting, k is a certain positioning mode.

[0173] The workflow of a high-precision calibration method based on dual-frequency multi-constellation GBAS in this scheme is as follows:

[0174] 1. The device is powered on to receive and generate dual-frequency multi-constellation satellite navigation signal measurements;

[0175] 2. Calculate the satellite dual-frequency integrated multipath error and eliminate satellite observations whose multipath error exceeds the threshold range;

[0176] 3. Set the satellite elevation filter value and use GBAS integrity monitoring to remove satellite observations that do not meet the requirements;

[0177] 4. Assign weight coefficients to different satellite measurements based on GBAS integrity monitoring results, construct an objective function for GDOP values, and select the satellite combination with the best geometric distribution and satellite quality;

[0178] 5. Use the dual-frequency data of GBAS stations to calculate the spatial ionospheric gradient between any two stations, and perform different smoothing and filtering operations according to the ionospheric gradient conditions under all dual-station combinations of GBAS ground stations;

[0179] 6. When the spatial ionosphere gradient monitoring is normal, the first smoothing filter processing method is used; when the spatial ionosphere gradient monitoring is abnormal, the second smoothing filter processing method is used. The two methods are as follows:

[0180] Calculate the linear combination of dual-frequency carrier phase observations as the input of low-pass filtering, and use the combined carrier phase value to smooth the code pseudorange;

[0181] The received dual-frequency satellite signal pseudorange and carrier phase are combined to construct new pseudorange values ​​and carrier phase values, which are used as input for low-pass filtering to form new carrier phase smoothed pseudorange values ​​for high-precision position calibration.

[0182] 7. The calibration modes include RTK, code pseudo-range differential, single point, and PPP. The calibration results in the comprehensive mode can be output. Users can also select the calibration mode to output the calibration results according to their needs.

[0183] The high-precision calibration method and system based on dual-frequency multi-constellation GBAS provided by the present invention, relying on the dual-frequency multi-constellation GBAS system architecture, can complete the position calibration of GBAS ground stations and special airport locations without adding additional equipment, effectively reducing equipment investment costs and real-time costs. Satellite signals composed of dual-frequency and multiple constellations need to undergo processes such as GBAS integrity monitoring and multipath error monitoring to screen out measurement values ​​that meet established conditions in terms of signal quality, data quality, and measurement quality, and use this comprehensive result as the input content for optimizing the constellation geometry, which can effectively improve the accuracy and reliability of positioning; the use of multiple constellations can improve the robustness of the system to constellation failures; at the same time, an ionospheric spatial gradient monitoring model is constructed, and a suitable smoothing filter processing method is selected according to the ionospheric monitoring results to effectively eliminate the influence of the ionosphere and further improve the calibration accuracy. The calibration method successfully implemented four positioning processing modes, greatly improving the flexibility of user use. The equipment can output the position calibration results in the comprehensive mode, and can also independently select the calibration mode according to the GBAS user's needs to meet different applications and scenarios, thereby improving the applicability and versatility of the system. The robustness of the entire system to unexpected interference is also significantly enhanced.

[0184] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the invention, and the methods for obtaining the parameters in the above explained formulas are all technologies known to those skilled in the art.

Claims

1. A high-precision calibration method based on dual-frequency multi-constellation GBAS, characterized in that: The following steps are involved: S1, receiving and processing dual-frequency multi-constellation satellite navigation signals, generating dual-frequency code and carrier phase observation information; S2. Calculate the satellite dual-frequency integrated multipath error and remove the satellites on the path that do not meet the requirements; S3. Set the satellite elevation filter angle value to screen the dual-frequency and multi-constellation observations of GBAS ground stations that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, and data quality of the GBAS station, and exclude satellites that do not meet the integrity monitoring requirements; S4. Assign weight coefficients to different satellite measurements based on GBAS integrity monitoring results, construct an objective function for GDOP values, and select the satellite combination with the best geometric distribution and satellite quality; S5, calculating the ionospheric gradient between any two stations in GBAS, and performing different filtering operations according to whether the ionospheric gradient is normal; S6. If the ionospheric gradient monitoring is normal, the linear combination of the dual-frequency carrier phase observations is calculated, and the original code pseudorange is smoothed and filtered using the combined phase value; if the ionospheric gradient monitoring is abnormal, the received dual-frequency satellite signal pseudorange and carrier phase are combined to construct a new pseudorange and carrier phase value, forming a new carrier phase smoothed pseudorange value, and further high-precision position calibration is performed; S7, calibration uses four positioning modes: RTK, code pseudorange difference, single point, and PPP. According to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution, the calibration results with positioning errors within 0.5 meters horizontally and 1 meter vertically in the comprehensive mode are output. Users can also independently select the positioning mode to output the calibration results.

2. The method according to claim 1, characterized in that The calculation of satellite dual-frequency integrated multipath error and elimination of satellites on paths that do not meet the requirements include: The multipath error MP0 is obtained by reconstructing the pseudorange using precise ephemeris, the multipath error MP1 of the dual-frequency point is calculated using the pseudorange of the first frequency and the dual-frequency carrier phase, the multipath error MP2 of the dual-frequency point is calculated using the pseudorange of the second frequency and the dual-frequency carrier phase, and the multipath error MP3 between multiple consecutive epochs is calculated, and the above four multipath errors are processed as follows: Calculate the MP corresponding to each satellite i j The multipath error residual value is , j=1,2,3; ； Taking the ath satellite as an example, calculate The scaling factor ; ； They are , , , is the satellite i , is the satellite i , is the satellite i , is the satellite i , C is the set of observed satellites i, N is the total number of satellites; comprehensive multipath error , , The resulting judgment criteria are: Less than the preset threshold L is the decision criterion. If it is not satisfied, the satellite on the path will not be used when calibrating; j=1, 2, 3; is the MP corresponding to the ath satellite j The multipath error residual value; They are , , , is the ath satellite corresponding to , is the ath satellite corresponding to , is the ath satellite corresponding to ; The calculation methods of MP0, MP1 and MP2 include: ， When x=0, A, B, and C are the pseudoranges calculated using precise ephemeris and the carrier phases of the two frequencies, respectively. At this time: ， ； When x=1, A, B, and C are the pseudorange of the first frequency and the two carrier phases of the dual frequency, respectively. At this time: ， ； When x=2, A, B, and C are the pseudorange of the second frequency and the two carrier phases of the dual frequency, respectively. At this time: ， ； Among them, f r and f s is the center frequency of the two frequency points; The calculation methods include: ； Where d is a certain epoch time, m is the number of epochs, c is the speed of light, P1(d) is the correlation peak of the satellite signal at epoch d, P2(d) is the correlation peak of the multipath signal at epoch d, the delay corresponding to P1 is T1, and the delay corresponding to P2 is T2.

3. The method according to claim 1, characterized in that The objective function of the GDOP value is constructed, and the satellite combination with the best geometric distribution and satellite quality is selected, including: Based on the geometric dilution of precision GDOP value, according to the GBAS ground station for different satellites i (S i , M i , D i , B i ) construct the objective function OBJ under different satellite combinations, where S i is the signal quality monitoring mean value of satellite i, M i is the mean value of the measurement quality monitoring of satellite i, D i is the mean value of data quality monitoring of satellite i, B i is the monitoring result of the B value of satellite i. The smaller the OBJ, the better the spatial distribution and satellite quality. The satellite combination with the smallest OBJ is used for calibration. ； in is the elevation angle of satellite i, ~ They are (S i , M i , D i , B i ) is the allocation weight coefficient.

4. The method according to claim 1, characterized in that According to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution factors, the calibration positioning results in the comprehensive mode are output, including four positioning modes: RTK, code pseudorange difference, single point, and PPP. The calibration results in the comprehensive mode are output by default to ensure that the positioning error of the comprehensive mode is within 0.5 meters horizontally and 1 meter vertically; In the comprehensive mode, the positioning results of RTK, code pseudorange difference, single point, and PPP are P RTK , P PD , P SPP , P PPP , and the corresponding weight coefficients are ω RTK ,ω PD ,ω SPP ,ω PPP , and satisfies ω RTK +ω PD +ω SPP +ω PPP =1, comprehensive positioning result P 综合 It is expressed as: P 综合 =ω RTK ×P RTK +oh PD ×P PD +oh SPP ×P SPP +oh PPP ×P PPP ; ； Among them, the proportional factor ω k According to the GBAS calibration time T k , Positioning precision factor A k , Deployment environment factor E k , calibration point position distribution factor D k , Positioning mode reliability factor R k , for evaluation and setting, k is a certain positioning mode.

5. The method according to claim 1, characterized in that The calculating of the ionospheric gradient between any two stations in the GBAS, based on whether the monitored ionospheric gradient is normal, comprises: With the dual-frequency satellite data of the best satellite combination in terms of geometric distribution and satellite quality, the ionospheric gradient between any two stations in GBAS is calculated. The ionospheric gradient G of a satellite observed by a successfully paired monitoring station is the ionospheric differential delay of the two stations divided by the distance between the two stations. The total If the ionospheric gradients under all the two-station combinations are greater than or equal to the threshold Q, it is considered that the ionospheric gradient is abnormal. 。 6. The method according to claim 5, characterized in that The constructing of different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal includes: Depending on whether the monitored ionospheric gradient is normal, two different smoothing filtering processing methods are used: if the ionospheric gradient is normal, the linear combination of the dual-frequency carrier phase observations is calculated, and the combined phase value is used to smooth the original code pseudorange; if the ionospheric gradient monitoring is abnormal, the received dual-frequency satellite signal pseudorange and carrier phase are combined to construct new pseudorange and carrier phase values ​​to form a new carrier phase smoothed pseudorange value, and further high-precision position calibration is performed.

7. The method according to claim 6, characterized in that When the space ionospheric gradient monitoring is normal, that is: , using the first smoothing filter processing method, including: Calculate the linear combination of the dual-frequency carrier phase observations and use the phase value at time t after the combination Original code pseudorange Perform smoothing filtering to obtain the filter value at time t : ； ； Among them, f r and f s is the center frequency of the two frequency points, , is the dual-frequency carrier phase measurement value at time t, is the smoothing filter time, is the data sampling interval; When the space ionospheric gradient monitoring is abnormal, that is: , using the second smoothing filter processing method, including the use of the ionospheric-free combination of code pseudorange and carrier phase at time t and , as the input of the smoothing filter to eliminate the ionospheric error and obtain the filtered value at time t , the specific method is as follows: ； ； ； Among them, f r and f s is the center frequency of the two frequency points, is the dual-frequency carrier phase measurement value at time t, and is the dual-frequency code pseudo-range measurement value at time t, is the smoothing filter time, is the data sampling interval.

8. A high-precision calibration system based on dual-frequency multi-constellation GBAS, characterized in that: include: Dual-frequency multi-constellation satellite navigation receiver and antenna, multipath error monitoring module, satellite selection preprocessing module, geometric distribution selection module, ionospheric gradient monitoring module, dual-frequency filtering processing module and calibration processing module, among which, The dual-frequency multi-constellation satellite navigation receiver and antenna are used to receive and process dual-frequency multi-constellation satellite navigation signals to generate observation information; The multipath error monitoring module is used to monitor and process the multipath error in the system, and remove satellites on the path that do not meet the requirements according to the size of the dual-frequency integrated multipath error; The satellite selection preprocessing module is used to set the satellite elevation filter angle value and screen the dual-frequency and multi-constellation observations of the GBAS ground station that meet the conditions; the satellite signal observations also need to pass the integrity monitoring of the signal quality, measurement quality, and data quality of the GBAS station, and satellites that do not meet the integrity monitoring requirements are excluded; The geometric distribution selection module is used to assign weight coefficients to different satellite measurement values ​​according to the GBAS integrity monitoring results, construct an objective function about the GDOP value, and select a satellite combination with the best geometric distribution and satellite quality; The ionospheric gradient monitoring module is used to calculate the ionospheric gradient between any two stations in the GBAS by means of dual-frequency satellite data of the satellite combination with the best geometric distribution and satellite quality, and perform different processing operations in the dual-frequency filtering processing module according to whether the monitored ionospheric gradient is normal; The dual-frequency filtering processing module is used to construct different code pseudoranges and carrier phase pseudoranges according to whether the monitored ionospheric gradient is normal, and then perform low-pass smoothing filtering respectively to form a new carrier phase smoothing pseudorange value for each satellite, and use this value to perform high-precision position calibration; The calibration processing module is used to perform four-mode positioning using the new carrier phase smoothed pseudorange value. It can output the calibration positioning results in the comprehensive mode according to the GBAS calibration time, positioning accuracy, deployment environment, and location distribution. Users can also select the positioning mode independently.

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