A New Chinese Geoid with High Resolution and High Accuracy

By using high resolution DTM,global gravity model and surface gravity data Chinese gravity geoid is determined at first,which then is merged into Chinese GPS leveling network to obtain a Chinese mainland geoid.The Chinese ocean geoid is calculated by using the deflection of the verticals,which are derived with the satellite altimeter (Sa) data.Finally the new Chinese geoid is obtained by the combination of mainland and ocean geoids with extending merge tech-nique.There are three steps for the combination.Firstly a local coastal district including coastal area and sallow sea is selected.A local gravity geoid of the district is computed with all the mean girded gravity values in the district.Secondly the land part of the local gravity geoid is fitted to Chinese mainland geoid with some fit-parameters,and the latter keeps in variation during the fitting.Thirdly the Chinese ocean geoid is merged into Chinese mainland geoid with the above fit-parameters.So a new Chinese quasi geoid (CQG2000) covering whole China land and sea territory is obtained with 15'×15' resolution and dm accuracy.CQG2000 has been examined by 80 GPS leveling points of the Chinese crustal movement monitoring network.The examining results demonstrate that the accuracy of the new quasi geoid is reliable,i.e.the absolute accuracy of the CQG2000 is higher than ±0.3 m in the east of longitude E102°,±0.4 m in the west of E102° and north of latitude N36°,±(0.4~0.6) m in the west of E102° and south of latitude N36°.