IGS?????ν?????????GPS?????????????????????????

????2008???????87??95????????ν?????????IGS????????????????GPS??????????????????????????????IGS?????????????????????????????y???????40??IGS????????????GPS??????????????????????????侫???????4.9??3.6??3.4 cm????IGS?????????????GPS??????????????????????????????????????????????????????????????????IGS??????????IGS?????ν????????????????????

INFLUENCE OF GEOMETRY AND NUMBER OF IGS STATION ON PRECISE ORBIT DETERMINATION OF GPS NAVIGATION CONSTELLATION

One-day,three-day and seven-day orbit solutions of GPS navigation constellation based on the observations of IGS stations in different numbers and geometries from 87-day to 95-day in 2008 were determined.The final solutions were compared with IGS precise ephemeris.The result shows that the accuracy of one-day,three-day and seven-day orbit solutions could reach up to 4.9 cm,3.6 cm and 3.4 cm when optimal geometry of the 40 IGS stations are selected.With the increase of IGS stations,the orbit accuracy could not be remarkably improved when the IGS stations have reached a certain limit,but computing time become longer.Thus it is evident that the geometry is the key factor which affects the accuracy of the final solution when the number of IGS stations is fixed.