jgg     2014 34 (1):  84-87    ISSN: 0412-1961  CN: 21-1139/TG PRECISE ORBIT DETERMINATION OF GPS NAVIGATION  CONSTELLATION BASED ON CLUSTERS METHOD USING  GLOBAL IGS STATION OBSERVATIONS 1）State Key Laboratory of Geodesy and Earth’s Dynamics，Institute  of Geodesy and Geophysics，CAS，Wuhan 430077 2）University of Chinese Academy of Sciences，Beijing 100049 Received: 2013-03-05  Revised: null  Online: 2014-01-23 Supporting info