Evaluating the practical performance of absorbing boundary conditions (ABC) in higher-order, finite-difference, time-domain (FDTD) GPR modelling

Finite-difference, time-domain (FDTD) methods are now commonly used for the integrated forward modelling of practical GPR in a wide range of processing, inversion and analysis applications. The wide availability of high-performance computing resources has led to the development of sophisticated, higher-order, 3D models that are able to tackle real-world problems in practical time scales. However, these models are often truncated by computationally inefficient and/or poorly optimised outer absorbing boundary conditions (ABC). In this paper, we evaluate the practical performance of two of the most common techniques; (a) Perfectly Matched Layers (PML) and (b) wave matching boundaries (e.g., Higdon). We show that under certain 3D conditions, the computationally faster, wave matching boundaries can perform as well as the PML techniques and reduce the likelihood of unexpected internal reflections/errors occurring.