Comparison of scanning strategies in UAV-mounted multichannel GPR-SAR systems using antenna arrays

Ground Penetrating Radar (GPR) systems on board Unmanned Aerial Vehicles (UAVs) have been successfully used for subsurface imaging applications. Their capability to detect buried targets avoiding the contact with the soil turn these systems into a great solution to detect buried threats, such as landmines and Improvised Explosive Devices (IEDs). Significant advances have been also conducted to enhance the detection capabilities of these systems, complementing the Synthetic Aperture Radar (SAR) processing methods with several clutter mitigation techniques. However, the improvement in the scanning throughput (i.e., increasing the inspected area in a given time) remains a significant challenge. In this regard, this article compares several scanning strategies for UAV-mounted multichannel GPR-SAR systems using antenna arrays. In particular, two different scanning strategies have been compared: a uniform scheme and a non-uniform strategy called 3X. In addition, different across-track spacing values to generate dense and sparse sampling distributions were considered for each scanning scheme. After conducting a theoretical analysis of these strategies, they have been experimentally validated with measurements gathered with a portable scanner and during flights in realistic scenarios. Results show that the dense configurations of both scanning strategies yield good quality images of buried targets while improving the scanning throughput (compared to a single-channel architecture). In particular, the dense uniform scheme (with a 20 cm across-track spacing) achieves a greater reduction in the inspection time, compared to the dense 3X strategy, at the expense of a slightly smaller signal to clutter ratio.