基于归一化互相关成像条件的GPR逆时偏移成像

Reverse time migration of ground penetrating radar based on normalized cross correlation imaging condition

针对基于零时刻成像条件的探地雷达(GPR)逆时偏移精度低、难以对复杂结构进行高精度成像的缺点,将归一化互相关成像条件应用于GPR叠前逆时偏移成像。从二维GPR电磁波方程出发,采用基于完全匹配层(PML)边界条件的时域有限单元法(FETD)模拟电磁波正向和逆向传播,采用归一化互相关成像条件获取叠前逆时偏移的偏移结果,将空间高通滤波用于压制互相关过程中产生的低频噪声,然后编制相应的GPR叠前逆时偏移程序。在此基础上,建立2个复杂的GPR模型,利用基于归一化互相关成像条件的GPR逆时偏移程序进行计算,并与基于零时刻成像条件的GPR逆时偏移剖面进行对比。研究结果表明:与基于零时刻成像条件的GPR逆时偏移剖面相比,基于归一化互相关成像条件的GPR叠前逆时偏移剖面能更清晰地反映异常体空间形态和内部结构信息,其分辨率和成像精度更高。

On account of the low imaging precision of ground penetrating radar（GPR） reverse time migration（RTM） based on the zero time imaging condition and it is difficult to imaging complex structure with high resolution, normalized cross-correlation imaging conditions was applied in GPR pre-stack RTM imaging. Based on the two-dimensional GPR wave equation, the time domain finite element method based on perfectly matched layer（PML） boundary condition（FETD） was used to simulate the forward and reverse electromagnetic waves, normalized cross-correlation imaging condition was used to obtain the pre-stack RTM results, the spatial high-pass filtering was applied to suppress cross-correlation process of low frequency noise and the corresponding program of GPR pre-stack RTM based on normalized cross-correlation imaging condition was designed and implemented. After that, the two complex GPR models were established and calculated by GPR RTM program based on the normalized cross-correlation imaging condition and zero time imaging condition,respectively.The results show that,compared with imaging results with zero time imaging condition,the imaging results with those in the normalized cross-correlation imaging condition have higher image quality and can more clearly display the detailed spatial form and internal structure information of the abnormal body space.