jgg     2010 30 (第3期):  1-4    ISSN: 0412-1961  CN: 21-1139/TG ON PROGRESS IN TECHNOLOGY AND MODERNIZATION OF GPS Chen Junyong 1, 2) 1)State Bureau of Surveying and Mapping，Beijing 1008302)Wuhan University, Wuhan 430079 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null