频域航空电磁法地形影响及校正研究

为研究起伏地形对航空电磁响应的影响，利用二维频域交错网格有限差分方法( FDFD) 计算模型中电磁场分布情况，并且用不完全乔里斯基预处理的双共轭梯度法求解大型稀疏复线性代数方程组。设计山脊和山谷两种起伏地形，同时改变坡度大小，比较不同坡度对电磁响应的影响程度。在此基础之上，提出线性校正方法，该方法具有简单快速的优点，弥补了耗时巨大的带地形的反演方法的不足。任意地形下的地形校正后的结果表明，该方法可以准确指示地下异常的存在。

Topography effects on HEM response and the correction method in frequency domain

To study the effect of undulate topographies on helicopter-borne electromagnetic ( HEM) response， we use the staggered-grid finite difference method in frequency domain ( FDFD) ，simulate the electromagnetic distribution of two dimensional models，and use the in-complete Cholesky decomposition procedures and the Bi-conjugate gradient solver to calculate largely sparse linear matrix． Two topographies of hill and valley with various slope angles are used to compare the effects of electromagnet in different slopes． We offer a linear correction method， with simple and quick characters，which wakes up the deficiency of the inversion method with topographies to consume too much time． We check the terrain correction at random topographies，which proves the method effective to indicate the place with anomaly．