The 3D Gravity Vectors Method in China Land and Ocean Quasi-geoid Determination

The horizontal component of earth gravity field-vertical deflection is very sensitive to the information of terrain. Firstly, using 3D gravity vectors-grid vertical deflections which are calculated by gravity and terrain data by solving physical geodetic boundary value problems (GBVP), grid gravity anomaly and grid terrain data to calculate the differences of height anomaly, then, with the control of GPS/leveling points to form rigorous geometric conditions, after that, the grid height anomaly is calculated by L-S adjustment method. Finally, a quasi-geoid model with a high precision and resolution is achieved. Based on the method presented, a national quasi-geoid model is built which includes land and ocean by using more than 6600 GPS/leveling points data, 1'×1' grid vertical deflections, grid gravity anomaly and grid terrain data. Compared with the GPS/leveling points, the absolute precision of our national quasi-geoid is about 4 cm, while the relative precision is better than 7 cm