jgg     2013 33 (6):  24-27    ISSN: 0412-1961  CN: 21-1139/TG GOCE GRAVITY FIELD MODELING BY USING AVERAGE  ACCELERATION APPROACH School of Geoscience and Environment Engineering, Southwest Jiaotong University, Chengdu 610031 Received: 2013-05-05  Revised: null  Online: 2013-12-13 Supporting info