The Study On Time-varing Characteristics Of Multi-GNSS Receivers' Differential Code Biases

Differential code bias(DCB,including satellite DCB and reciver DCB)is one of the most important errors,that must be consindered and deducted,when retrieving the pricise estimated value of TEC through the math model of TEC,is also one of important factors that decides the functions of receiver,and has a significant impact on standard point positioning.It is unable to meet the demand for the current GNSS applications that most researches on receiver DCB are limited to American GPS and Russian GLONASS,and that there are fewer types of DCB products released.With the modernization of American GPS and Russian GLONASS satellites,and the rapid development and improvent of Europea GALILEO,Chinese BDS,Indian NAVIC,Janpanses QZSS et al,the precise processing and timing-varying study of multi-GNSS receivers' DCB are more and more important to the position,navigation,time service of GNSS.Based on the above situations,this thesis systematically studies the solution of receiver DCBs,and timing-varing characteristics of receiver DCBs in oreder to meet the demand for the current GNSS applications:1.Study on short-term-varing characteristics of multi-GNSS receivers'intra-DCB(in one month)Based on the GNSS observation data from 15 stations of IGS tracking networks in January 2018,this thesis determines the intra DCB of multi-receivers by using the geometry-free technique and 'zero-reference',and analyzes the shor-term varition of intra DCB for one month.The short-term variation of DCB in the multimode receiver has excellent stability,and intra-frequency DCB(P1-C1)accuracy is significantly improved compared to P1-P2 type inter-frequency DCB.That different type receivers has different DCB values indicate that the receiver DCB is affected by its own hardware performance.The shor-term stability of the receiver DCB of SEPT POLARX5 is more optimal than other 4 types,and its STD is 0.01ns.2.Study on long-term-varing characteristics of multi-GNSS receivers,intra-DCB(in one year)Based on MGEX observation data of GPS and GLONASS(within 2018),the thesis estimates the intra-DCB of multi-GNSS receiver by introducing the 'Quasi-stable'threshold to optimize the zero reference(referred to 'Quasi-stable' in thesis),and analyzes the time-varying characteristics and relative effects of multi-GNSS receivers'DCB in one year.The results of experiment show that the variation of DCB(estimated by 'Quasi-stable' technique)in all types of frequency has a good stability within one year.The long-term(in one year)stability of the receiver DCB of SEPT POLARX5 is more optimal than other 4 types,and its STD(C2W-C2L)is 0.02ns.Based on the estimated value estimated by CODE and DLR,it analyzes the accuracy and reliability of receivers'intra-DCB estimated by introducing the "Quasi-stable" threshold,and the result of comparison shows that the "Quasi-stable" threshold to estimate receiver DCB has a good accuracy and reliability.3.Study on long-term-varing characteristics of multi-GNSS receivers' inter-DCB(in one year)Based on MGEX observation data of GPS and GLONASS(within 2018),the thesis estimates the intra-DCB of multi-GNSS receiver by using a generalized trigonometric series function model,geometry-free combination technique and a 'quasi-stable' zero reference,and analyzes the time-varying characteristics and relative effects of multi-GNSS receivers' inter-frequency DCB in one year.The results of experiment show that the variation of receivers' inter-DCB estimated by 'quasi-stable' zero reference within one year presents a law of fluctuations around a certain fixed value,has a relative stability,and the stability of receiver' DCB for GPS and GLONASS is better than that for GALILEO and BDS.The long-term(in one year)stability of the receiver DCB of SEPT POLARX5 is more optimal than other 4 types,and its STDs are seperately 0.30ns(GPS C1C-C2W),0.42ns(GPS ClC-C5Q),0.33ns(GLO C1C-C2P),0.50ns(GAL C1C-C5Q).The inter-frequency DCBs of 4 systems(GPS,GLONASS,GALILEO,BDS)estimated by 'quasi-stable' zero reference have higher accuracy and stability than DCB of DLR when the DCB of satellite has bad stability.