Quantifying GPR responses

Antenna height, shielding and subsurface properties all impact the observed GPR responses. While the basic concepts are generally understood, our long term goal is to develop parameterized models that will provide for quantitative interpretation of data acquired with real systems. Our first step was to develop modelling capacity and response presentation tools to help with development. We are using three-dimensional (3D) finite-difference time-domain (FDTD) modelling. Model results are then presented in a variety of forms. In this paper we compute emitted energy characteristics and display in radiation pattern format for infinitesimal dipoles, resistively loaded dipoles and shielded dipoles. Patterns are computed for free-space and over loss-less half-spaces with various properties as a function of height above the surface. The numerical simulations show the advantage of ground-coupling and the impact of shielding on GPR responses. Further, we demonstrate that total radiated energy is a very effective means of characterizing radiated signal directivity for GPR transient emissions.