jgg     2012 32 (2):  139-142    ISSN: 0412-1961  CN: 21-1139/TG GPS ELEVATION FITTING BASED ON EM ALGORITHM FOR LACK OF DATA Lin Dongfang; Song Yingchun; Du Kun ;and Xiao Qinqin School of Geosciences and Info-Physics, Central South University, Changsha 410083 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null