Research On Comprehensive Quality Evaluation Method Of BDS Tri-band Observations

The BeiDou-2 satellite navigation System(BDS)is one of the important economic,strategic and livelihood projects in China and only the BDS on-orbit satellites could provide three frequency signal service.BDS is currently on the way from regional navigation systems to global one and it is expected to have the global service capability of 35 full-constellation satellites by 2020.The BDS satellite constellation also has a heterogeneous structure and contains three types of satellites named GEO,IGSO and MEO.Besides,as the indicators and stability of the domestic satellite equipment and ground receiver equipment are different from that of GPS,those reasons would lead to the differences and complexity of BDS quality assessment.Considering that the observations quality assessment is the foundation of the follow-up BDS PNT service,this paper aims at the comprehensive evaluation method and index of data quality based on the BDS triple frequency observations.In this paper,the differences of BDS multipath error are revealed from many aspects and the data quality index of BDS working satellites and new generation BDS satellites are evaluated.Finally,a set of comprehensive quality evaluation software for BDS/GNSS observation data is developed.The main contents and achievements of this paper include the following four parts:(1)Methods and indicators of observing data quality assessmentBased on the conventional data quality evaluation indexes including data integrity rate,multipath error,cycle ratio and signal to noise ratio.After a series of research and evaluation,a series of BDS data service performance quality indicators are proposed including accuracy of pseudorange measurement,accuracy of carrier phase measurement,accuracy of single point positioning of pseudorange,relative positioning accuracy of zero baseline,relative positioning accuracy of short baseline,relative positioning accuracy of long baseline,orbit determination accuracy of single system and orbit determination accuracy of multisystem.This paper also displays the calculation methods and test results of different indexes.(2)The Differences of Multipath Error of BDS Triple-frequency ObservationsMultipath error is an important index to evaluate the quality of observations.As the BDS contains three satellites with different orbital altitudes,the characteristics of multipath error in different types of satellites may be different.Based on above reasons,the diversity of BDS multipath error is analyzed from five aspects of elevation angle,signal frequency,receiver type,tracking station distribution and satellite constellation.At the same time,the multipath error of GPS observations are compared with that of the same stations observations.(3)Quality analysis of observation data of the new BDS satellitesChina launched a next generation of four new satellites: C31(IGSO)?C32(IGSO)?C33(MEO)and C34(MEO).This paper analysis the observations qualities of new BDS satellites from four aspects: data integrity rate,multipath error,SNR and cycle slip ratio.(4)BDS/GNSS comprehensive quality evaluation softwareA set of comprehensive quality evaluation software for BDS/GNSS observations is developed.It could assess the quality of BDS triple-frequency observations and is compatible with GPS,GLONASS,and Galileo system.