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对重力自由空间异常值进行中间层引力改正和局部地形改正以求出布格异常值,这是沿用已久的计算方法.其中,中间层引力改正值按“无限延伸水平板状体”计算,局部地形改正通常仅计及测点周围几公里或十几公里范围内的地形影响.在我国,海洋重力测量一般不进行海底地形改正.区域重力测量中要在更广阔的范围内研究重力异常并且要求以参考椭球面(或大地水准面)为计算布格异常的基准面.这种情况下仍然使用无限平板公式是不妥当的,而且十几公里以外的地形影响和海底地形起伏的影响也都不容忽视.所谓“广义地形改正”就是针对这些问题提出来的.广义地形改正要求直接计算全球海洋和陆地对重力观测值的影响.相当于移去参考椭球面以上的陆地质量并且按地壳的平均密度充填海洋.由于这种改正是以参考椭球面为基准面,而且改正范围遍及全球海陆,因此它既把中间层引力改正和地形改正融为一体,又使改正更趋合理、完善.为区别起见,有的人把进行广义地形改正得到的布格异常称为“完全的布格异常”.
It is a well-established method to calculate the out-of-plane gravitation and local gravitation to correct the gravity anomaly of the gravity free space, where the gravitational correction value of the middle layer is calculated according to “infinitely extended horizontal plate” Local topographic correction usually only takes into account the topographic effects within a few kilometers or a few ten kilometers around the measuring point.In our country, the ocean gravity survey generally does not make the correction of the seafloor topography.It is necessary to study the gravity anomaly in the regional gravimetry and The reference ellipsoid (or geoid) is required to calculate the Bouguer anomalous datum, and in this case, it is not proper to use the infinite plate formula, and the influence of terrain more than ten kilometers and the undulation of the seafloor topography Can not be ignored.The so-called “generalized terrain correction” is put forward for these issues.General topographic correction requires a direct calculation of global ocean and land on gravity observations equivalent to remove the reference ellipsoid above the terrestrial mass and according to the average crust Density filling the ocean.Because this correction is based on the reference ellipsoid as the reference plane, but also to correct the scope of the global land and sea , So it not only integrates the gravity correction with the terrain correction but also makes the correction more reasonable and perfect.For the sake of difference, some people refer to the Bouguer anomaly obtained by generalized terrain correction as “complete Bouguer anomaly ”.