Assessing Contactless Versus Contact GPR for Vertical Structure Inspection

Nondestructive inspection of penetrable vertical structures demands innovative investigation paradigms and ad hoc tools to support timely and efficient maintenance interventions. Although ground penetrating radar (GPR) is an established technology, the inspection of large vertical structures with classical ground-based systems remains challenging when there is limited accessibility, the equipment is difficult to maneuver, the operator’s safety is placed at risk, and the time to perform the survey becomes long. A promising solution to address these limitations suggests the use of mini drones equipped with GPR systems. However, this possibility introduces new challenges in both system design and data processing. A practical approach for drone-based GPR monitoring involves adapting a traditional contact GPR system, combined with appropriate data processing techniques, to perform contactless surveys. This study delves deeper into this approach by comparing the imaging performance achieved when the same ground-coupled GPR system paired with a microwave tomography (MWT)-based data processing is exploited for contact and contactless surveys. The experimental results related to the inspection of a reinforced concrete wall are presented and discussed.