Three-dimensional imaging of multicomponent ground-penetrating radar data

Scalar imaging algorithms originally developed for the processing of remote sensing measurements (e.g., the synthetic-aperture radar method) or seismic reflection data (e.g., the Gazdag phase-shift method) are commonly used for the processing of ground-penetrating radar (GPR) data. Unfortunately; these algorithms do not account for the radiation characteristics of GPR source and receiver antennas or the vectorial nature of radar waves. We present a new multicomponent imaging algorithm designed specifically for vector electromagnetic-wave propagation. It accounts for all propagation effects, including the vectorial characteristics of the source and receiver antennas and the polarization of the electromagnetic wavefield. A constant-offset source-receiver antenna pair is assumed to overlie a dielectric medium. To assess the performance of the scalar and multicomponent imaging algorithms, we compute their spatial resolution function, which is defined as the image of a point scatterer at a fixed depth using a single frequency. Application of the new multicomponent imaging algorithm results in a circularly symmetric resolution function, demonstrating that the radiation characteristics of the source and receiver antennas do not influence the derived image. In contrast, the two tested scalar imaging algorithms return distinctly asymmetric resolution functions with incorrect phase characteristics, which could result in erroneous images of the subsurface when these algorithms are applied to GPR data. The multicomponent and two scalar imaging algorithms are tested on data acquired across numerous buried objects with various dielectric properties and different strike directions. Phase differences between the different images are similar to those observed in the synthetic examples. Of the tested algorithms, we conclude that the multicomponent approach produces the most reliable results.