两种测高重力异常反演海底地形方法比较

Comparison of two methods for retrieving sea bottom terrain bathymetry prediction from altimetry gravity anomalies

针对基于测高重力异常反演海底地形理论众多、选取标准无法确定的情况,利用中国南海海域内的测高重力异常和船测水深数据研究比较了重力地质法(GGM)和Smith&Sandwell(SAS)法两种精度高、计算速度相对较快的海底地形反演理论。其中,GGM方法的密度差异常数Δρ由向下延拓技术确定为2.15 g·cm^-3,SAS方法采用移去-恢复技术得到反演波段内重力异常和水深数据。结果表明:测线分布条件一定时,水深多在-1000 m左右或反演区域岛礁、海山等复杂海底地形较多时选取SAS方法,水深主要在-3000 m以深的区域或海底地形复杂程度不高时选取GGM方法则能获取更好的效果,其效果最优处与船测水深在检核点处的差值最优平均值能达-0.61 m,标准差可达14.67 m。

In view of the fact that the theory of bathymetry prediction based on altimetry gravity anomalies is quite numerous and the selection criteria cannot be determined,the gravity-geology method(GGM)and the Smith&Sandwell(SAS)method,which are both high quality and fast-calculating,were chosen to be compared with the altimetry gravity and ship data in the South China Sea.Among them,the density difference constantΔρof the GGM method was determined to be 2.15 g·cm-3 by the downward continuation technique and the gravity anomalies and depth data in the inversion band were obtained by removerestore technique in the SAS method.The results show that,under the premise of measurement line distribution conditions are certain,the SAS method should be adopted at the area with more complex seabed topography such as island reef and seamount,or the area that water depth is about-1000 m,when the water depth is about-3000 m,or the area with a lower complexity of bathymetry,chossing the GGM method can obtain better results,the difference between the interpolation depths of the most accurate GGM model and the ship-data of check points reached approximate mean value of-0.61m,standard deviations of 14.67 m.