Contactless Ground Penetrating Radar Imaging: State of the Art, Challenges, and Microwave Tomography-Based Data Processing

This article provides a comprehensive overview of the current state of the art in contactless ground-penetrating radar (GPR) systems. These devices offer many largescale subsurface sensing possibilities based on different observation platforms and measurement configurations. On the other hand, new challenges must be faced because the radar system is not coupled directly to the ground; hence, data processing plays a crucial role to achieve reliable imaging results. In this respect, microwave tomography (MWT) turns out to be a very flexible tool to address the aforementioned challenges. This methodology allows modeling, in a relatively simple way, of the radar signal propagation in an inhomogeneous medium as well as the handling of arbitrary measurement modalities and radar configurations. Experimental examples regarding different types of contactless GPR are presented to validate the effectiveness of MWT when combined with ad hoc signal filtering procedures.