The integrity requirement should be satisfied when GNSS is used in aviation.There are now two ways for integrity monitoring,that is,receiver autonomous integrity monitoring(RAIM) and GNSS integrity channel(GIC) based on augmentation system.The rapid development of the Beidou satellite navigation system(COMPASS) will significantly improve the satellite geometry.Besides,the effects of first order ionosphere delay will be mitigated by the combination of GNSS multi-frequency signals.The availability of RAIM will be enhanced,which makes it possible to provide a worldwide seamless integrity service for aviation by using RAIM.The contribution of COMPASS to the availability of RAIM is analyzed by simulation;and the integrity requirement of which aviation approaching phrase can be satisfied when using COMPASS single system and its combination with other satellite navigation system is analyzed.Moreover,the influence of user range accuracy(URA) of COMPASS on integrity performance is discussed.
BeiDou regional navigation satellite system(BDS)also called BeiDou-2 has been in full operation since December 27,2012.It consists of 14 satellites,including 5 satellites in Geostationary Orbit(GEO),5 satellites in Inclined Geosynchronous Orbit(IGSO),and 4 satellites in Medium Earth Orbit(MEO).In this paper,its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing,including satellite visibility,Position Dilution of Precision(PDOP)value,the precision of code and carrier phase measurements,the accuracy of single point positioning and differential positioning and ambiguity resolution(AR)performance,which are also compared with those of GPS.It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm,respectively,which are comparable to those of GPS,and the accuracy of BDS single point positioning has satisfied the design requirement.The real-time kinematic positioning is also feasible by BDS alone in the opening condition,since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS.The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km,which is on the same level with that of GPS.For the combined BDS and GPS,the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly.The accuracy of BDS/GPS carrier phase differential positioning is about 35 and 20%better than that of GPS for two short baseline tests in this study.The accuracy of BDS code differential positioning is better than 2.5 m.However it is worse than that of GPS,which may result from large code multipath errors of BDS GEO satellite measurements.
YANG YuanXiLI JinLongWANG AiBingXU JunYiHE HaiBoGUO HaiRongSHEN JunFeiDAI Xian
