jgg     2015 35 (3):  499-502    ISSN: 0412-1961  CN: 21-1139/TG Local Ionospheric TEC Extraction Based on GPS Phase  Observations and Global Ionospheric Maps 1 School of Civil Engineering and Architecture, East China Jiaotong University, 808 East-Shuanggang Street,Nanchang 330013, China[JP] 2 Yunnan Branch of China Three Gorges New Energy Corp., Chuncheng Road, Kunming 650000, China Received: 2014-04-30  Revised: null  Online: 2015-06-02 Supporting info