An Improved Borehole Radar Fusion-Imaging Method for Heterogeneous Subsurface Sensing

In this paper, a heterogeneous borehole radar fusion-before-imaging method (RFBI) is proposed and validated. Different from traditional fusion methods, RFBI firstly fuses radar sample sets from heterogeneous radar systems (such as monostatic, bistatic and multi-input multi-output) and then do imaging process once in high-dimensional space to obtain imaging result with high accuracy. Specifically, according to the relative positions of transceivers, the radar sample sets to be imaged are inserted into a high-dimensional sample space for fusion, and then the fused data is converted into virtual target space according to the conversion relationship between echo space and target space in frequency-wavenumber domain. Finally, the imaging result is extracted from the target space according to the imaging conditions. In the fused high-dimensional sample space of RFBI, the data diversity and redundancy are utilized, and the impact of clutters and other interference factors on imaging is effectively reduced, which brings the benefit of high imaging accuracy to RFBI. Meanwhile, all radar sampling sets are imaged once, which enable RFBI owns the advantage of high efficiency. The comparison results with conventional fusion-imaging methods indicates and validates that RFBI is more suitable for heterogeneous radar system imaging applications.