jgg     2008 28 (1):  123-126    ISSN: 0412-1961  CN: 21-1139/TG VERTICAL FREE-AIR CORRECTION IN MARINE MAGNETIC SURVEY Yu Bo 1) ;Zhai Guojun 2) ; Liu Yanchun 1) ; Bian Gang 1) ; and Bian Guanglang 1) 1)Dept. of hydrography and Mapping, Dalian Naval Academy, Dalian 1160182)Institute of Hydrographic Surveying and Charting , Tianjin 300061 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null