Chapter 6: Toward True-amplitude Vector Migration of GPR Data Using Exact Radiation Patterns
J. van der Kruk, R. Streich, M. Grasmueck, 2010. "Toward True-amplitude Vector Migration of GPR Data Using Exact Radiation Patterns", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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The amplitudes and phases of raw ground-penetrating-radar (GPR) data depend on the antenna radiation patterns, the vector nature of electromagnetic (EM) wave propagation, and the EM properties of the subsurface. Migrated GPR data should accurately represent the subsurface EM property contrasts alone. To achieve this, migration algorithms must explicitly account for the radiation patterns and vector wave propagation. A specific vector-migration algorithm models and corrects for exact-field radiation patterns, which include far-, intermediate-, and near-field contributions and propagation effects. When applied to GPR data containing dipping planar reflections, the algorithm produces images largely invariant to the relative orientations of the antennae and reflectors, indicating that most radiation-pattern effects are corrected for. In contrast, strongly orientation-dependent amplitudes and phases in scalar Gazdag and far-field vector images show that these algorithms do not adequately account for radiation-pattern effects. For polarization-dependent features (e.g., most underground utilities), the exact-field vector-migration algorithm produces images with orientation-dependent amplitude variations in qualitative agreement with theoretical expectations, suggesting that the algorithm may serve as a starting point for reconstructing the scattering properties of the targets. In contrast, the scalar Gazdag and far-field algorithms yield distinctly false amplitude variations.