Research On Intergrated Precise Point Positioning Method With BDS And GPS Observations

With the development of the four Global Navigation Satellite Systems(GNSS),the precise point positioning(PPP)with multi-GNSS observations has drawn a lot of attention and become a hot spot in the field of GNSS data processing.Focusing on the research of integrated PPP with BeiDou Navigation Satellite System(BDS)and Global Positioning System(GPS),this article covers the four main aspects as follows.(1)A new weighted method of observations based on positioning residual in BDS PPP is put forward in consideration of the different residual of three kinds of BDS satel-lites.The analysis of positioning residual finds that the residual of geostationary earth orbit(GEO)satellites is much greater than that of the other two types of satellites.Thus,the observations of various categories of satellites are weighted according to their post-fit residual when applied in BDS PPP.The results show that an positioning accuracy promo-tion of 16.9%,5.8%and 3.2%can be achieved in east,north and up direction respectively in BDS PPP when using the new strategy.(2)An accuracy analysis of BDS PPP and GPS PPP is done to compare the perfor-mance of two systems.For GPS PPP,the positioning accuracy is better than 0.7 cm and2.0 cm in horizontal and vertical direction respectively,showing no difference in different areas.For BDS PPP,the positioning accuracy of stations in area with latitudes 60~oS to60~oN and longitudes 40~oE to 180~oE is about 1.0 cm and 0.7 cm in east and north direc-tion,which is better than that of stations out of this region with 2.56 cm and 1.69 cm in the east and north.The positioning accuracy of all stations in up direction is better than 5.0cm.In conclusion,the positioning accuracy of BDS PPP is related to the area the station belonging to while the positioning accuracy of GPS PPP in different stations is consistent with each other.(3)The strategy dealing with combined observations of BDS and GPS is studied.The analysis of raw observations indicates that the hardware delay is the source of bias between observations from different system and an extra parameter is needed to absorb the system bias.In view of the hardware delay is relatively stable,the system bias is taken as a daily constant,which is proved reasonable according to the estimated result.(4)The principle to determine the system weight of BDS and GPS observations is studied in integrated PPP.The integrated PPP results with a sequence of system weights indicate that the positioning accuracy variation in east,north and up direction is not con-sistent with each other and the positioning accuracy of different stations change differ-ently when BDS system weight increases.Accordingly,the system weight of BDS is determined station by station with principle of best 1D RMS.Positioning results based on aforesaid strategy show that compared with GPS only PPP,integrated PPP is beneficial to the positioning accuracy improvement in east direction and can promote the positioning accuracy of stations,of which the positioning accuracy difference of BDS PPP and GPS PPP in up direction is not obvious.