Interference Removal for Autofocusing of GPR Data From RC Bridge Decks

Strong interferences can substantially deteriorate the performance of autofocusing techniques in ground penetrating radar (GPR) data analysis for reinforced concrete (RC) bridge deck evaluation. In this paper, we propose a new approach based on F-K dip filtering to remove interferences, including direct waves and cross rebar reflections. Different from previously related work, the surface roughness and uneven cross rebar reflections resulted from GPR signals propagating through rough surface and inhomogeneous medium are carefully modeled as reflectors with small dipping angles, and hence dip relaxations are introduced in the F-K dip filtering to remove strong interferences. The mechanism of the F-K filter without dip relaxation and the correctness of the rebar modeling are first illustrated using simulation data. Then its effectiveness with adequate dip relaxation is demonstrated by both experimental and field data. Additionally, the performance of the F-K dip filter with adequate dip relaxation is also compared with that of the background subtraction (BS) method that is commonly used for direct wave removal in GPR data processing for RC bridge deck evaluation.