利用航空重力确定局部大地水准面的精度分析

探讨了空中重力扰动的滤波尺度和向下延拓方法对局部大地水准面确定精度的影响。实测数据分析表明,直接代表法不受测区形状及范围大小限制且无边界效应,成为最合适的向下延拓方法;100~250 s的滤波尺度均适用于大地水准面的确定,顾及滤波器边界效应的影响,宜采用小一些的滤波尺度如100 s。无论是空中比较还是地面比较,利用航空重力数据确定的局部大地水准面,其与参考大地水准面的比较精度可以达到±3 cm。

Detemining Accuracy of Local Geoid Determined from Airborne Gravity Data

The methods for processing airborne gravimetry data are summarized.The effects of the downward continuation approaches and the filtering amount on the precise local airborne geoid determination are discussed in detail.The results show that the accuracy of airborne geoid with 3 cm can be obtained by all three downward continuation approaches,namely by the direct representation method,Tikhonov regularization and point-mass model,but the direct representation method may be optimal since it is not limited by the observed area and has little edge effect.It is also shown that the filtering amounts of 100-250 s can be all suited for airborne geoid determination,but a smaller amount e.g.100 s will be desired due to the less edge effect.The geoid determined from airborne gravity arrives 3 cm compared with the reference geoid on a 5′×5′ grid.