jgg     2007 27 (5):  68-71    ISSN: 0412-1961  CN: 21-1139/TG CALCULATION OF IONOSPHERIC VTEC BY USING SINGLE EPOCHGPS DUAL FREQUENCY CARRIER-PHASE Lin Jian 1,2,3) ;Wu Yun 1,2) ;Zhou Yiyan 1,2) ;Shi Shunying 1,2) ; and Xing Lelin 1,2) 1)Institute of Seismology, CEA, Wuhan 4300712)Crustal Movement Laboratory , Wuhan 4300713)School of Geodesy and Geomatics,Wuhan University,Wuhan 430079 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null