This technical report defines the Department of Defense (DoD) World GeodeticSystem 1984 (WGS 84). This third edition reflects improvements which have been made to theWGS 84 since the second edition. The present WGS represents the National Imagery an

EGM2008是近来由NGA(US National Geospatial-IntelligenceAgency)释放的全球超高阶地球重力场模型,该模型的阶次完全至2 159 (另外球谐系数的阶扩展至2 190,次为2 159),相当于模型的空间分辨率约为5′(约9 km)。该模型采用了GRACE卫星跟踪数据( ITG-GRACE03S位系数信息以及相应的协方差信息)、卫星测高数据和地面重力数据等,该模型无论在精度还是在分辨率方面均取得了巨大进步,采用该模型以及GPS/水准数据有望获得更高精度