jgg     2015 35 (4):  662-665    ISSN: 0412-1961  CN: 21-1139/TG Beidou Navigation Constellation Orbit Determination Based on MGEX Data 1 Geomatics College, Shandong University of Science and Technology, 579 Qianwangang Road, Qingdao 266510,China 2 Chinese Academy of Surveying and Mapping, 28 West-Lianhuachi Road, Beijing 100830,China Received: 2014-06-30  Revised: null  Online: 2015-07-29 Supporting info