Researches On Multi-GNSS ISB Modeling And Prediction Method

Beidou satellite navigation basic system was established on December 27,2018.It officially provided the basic navigation services to“the Belt and Road Initiatives”countries and regions,and it will be in the coexistence of BDS-2/BDS-3 for a time.BDS-3 satellite broadcasts new satellite signals B1C and B2a,and it also apply a number of new technologies,whose performance improvement needs to be further explored.With the continuous development of iGMAS,there are 22 stations can receive BDS-3 satellite signals,and it is also necessary to comprehensively evaluate the performance of each receiver.Combining with BDS-3 satellite,Multi-GNSS Precision Point Positioning?MGPPP?can improve positioning accuracy,reliability and availability.However,due to the improvement of BDS-3 satellite,whether there will be inter-system bias?ISB?between BDS-3 and BDS-2 satellite or not.For the above problems,the main research contents of this paper are as follows:?1?In this paper,five kinds of data quality analysis indexes and methods of data integrity,SNR,multipath effect,ionospheric delay and cycle slip are studied,and a multi-GNSS data quality analysis software is developed.The performance level of B1C and B2a signals of BDS-3 satellite are tested,and the observation data quality of BDS-3 satellite is comparable to that of GPS and Galileo satellites.?2?The receiver types and distribution of 22 iGMAS tracking stations are introduced,and the receiving ability of each station to BDS-3 satellite B1C and B2a signals is analyzed.The results show that the GNSS_GGR receiver's code observation values have a large gross error.The UB4B0-13478 receivers are seriously affected by the ionosphere.The cycle slip of CETC-54-GMR-4011 receivers are serious,while CETC-54-GMR-4016 receivers show good performance in all aspects.?3?The processing method of multi-GNSS ISB is studied,and a solution model of GPS/BDS-2/BDS-3 combined PPP estimation ISB is proposed.The ISB parameters of BDS-2 and BDS-3 relative to GPS for four types iGMAS stations are estimated,and the short-term stability of ISB(ISB_B2,B3)between BDS-2 and BDS-3are analyzed.The results show that ISB_B2,B32,B3 are related to receiver type and the diurnal variation are stable.For BDS-2?B1I,B3I?/BDS-3?B1I,B3I?observation combination,the magnitude of ISB_B2,B32,B3 is several nanoseconds,and the average daily STDs are about 3 ns.For the BDS-2?B1I,B3I?/BDS-3?B1C,B2a?observation combination,the magnitude of ISB_B2,B32,B3 is about 400 ns,and the average daily STDs are about 10 ns.?4?According to the characteristics of ISB_{B2?B1I,B3I?B3?B1C,B2a?},an ISB short-term prediction model with a combination of octave polynomial?OP?and autoregressive moving average model?ARIMA?is proposed,and the model accuracy and prediction accuracy are verified.The results show that the mean absolute error?MAE?of fitting and forecasting residuals are between 0.124 ns-0.226 ns and 1.322-5.470 ns,respectively.The root meam square?RMS?are between 0.345 ns-0.666 ns and1.623-6.025 ns,respectively.There is no significant difference among the stations,indicating that the proposed short-term ISB model has high fitting accuracy and good consistency.?5?A GPS/BDS-2/BDS-3 combined PPP model with additional ISB constraints is proposed,and the effect of ISB on MGPPP is verified.The results show that the convergence time of N,E and U components in open sky environment and blocked sky environment are shortened by 1.13%,1.97%,0.95%and 1.58%,1.63%,0.34%,respectively.The positioning accuracy are improved by 4.12%,6.31%,4.50%and15.79%,8.90%,8.28%,respectively.