Airborne GPR surveys via tomographic imaging: An analysis of the reconstruction capabilities

GPR systems installed on helicopters or spotter planes represent effective monitoring tools to cover surface and underground characterization of wide areas. In this respect, the paper discusses the on field reconstruction capabilities resulting from the joint exploitation of a novel sounder system and an advanced data processing approach. The sounder system was built by CORISTA in collaboration with the Italian Space Agency, which promoted and founded the project. It is a pulsed radar working at 163 MHz and transmits a 10 MHz linearly frequency modulated signal (chirp) by using DDS (Direct Digital Synthesizer) technique. The transmitted peak power is about 200W over a 3musec pulse length. The system exploits a log periodic antenna with four elements, GPS and an INS are used for storing position and attitude information. The data processing is faced by means of a microwave tomographic reconstruction approach, which is based on a simplified scattering model. In particular the Born approximation is adopted to formulate the imaging as a linear inverse scattering problem. The effectiveness of the system is shown by means of the tomographic images corresponding to the first trial surveys made with the sounder installed on a helicopter of the Italian Air Force.