航空重力向上延拓的外部精度评估

Evaluation of the External Accord Accuracy of Airborne Gravity Data with Upward Continuation

分别采用基于梯度、基于泊松积分和基于快速傅里叶变换(FFT)的地面重力向上延拓方案,并提出交叉检验方法估计地面重力数据误差及其空中误差传播,对毛乌素测区GT-2A航空重力测量系统采集的空中测线数据进行外符合精度评价。对比结果表明:地面重力格网插值误差和代表性误差对空中点的影响达到0.66~0.92mGal(1Gal=1×10^(-2)m/s^2),航空重力数据误差估计必须扣除这一影响;基于泊松积分和基于FFT的地面重力向上延拓方法能够客观评价航空重力观测值的外符合精度,二者表现相当;扣除地面重力误差影响后,在包含残余边界效应的情况下,毛乌素测区GT-2A航空重力空中测线重力扰动的外符合精度优于1.42mGal。

Three methods for evaluating the external accord accuracy of airborne gravity survey line data,namely the gradient based,the Poisson integral based and the fast Fourier transform（FFT）based upward continuation（UPC）of terrestrial gravity,are introduced.A cross validation method is proposed for the estimation of terrestrial gravity errors and their propagation at flight altitude.The external accord accuracy of airborne gravity survey line data over Mu Us in Inner Mongolia is evaluated based on the three UPC methods and the proposed cross validation method.Numerical results show that the gridding interpolation error and representative error of terrestrial gravity range from 0.66 to 0.92 mGal,which demonstrates the necessity of removing these errors for error estimation of airborne gravity data.The Poisson integral and the FFT based UPC method are capable of evaluating the external accord accuracy of airborne gravity data,both have comparative performance.Applying the methods for the data acquired by GT-2 Aairborne gravimetry system over Mu Us in Inner Mongolia,it turns out the external accord accuracy of the airborne gravity disturbances is better than 1.42 mGal（1 Gal=1×10^-2 m/s^2） after the removal of terrestrial gravity error contribution,while some remaining integral edge effects still exist.