Ground Penetrating Radar (C P R) is considered as an erivironmental tool. The basic concepts involved in GPR ure introduced briefly including the antennas, propagation. target scattering. and mapping. Target identification is important when usin GPR since the siutterer c m only he observed by evacuution. This is di.sc.ussed in terms of mapping and Comples Natural Resonances. GPR has been used and is being considered us U tooljor the detection of' U wide variety of subterranean jeutures. A very brief' description of the various upplir~ations of' GPR is presented. I n terms of environmental sensing, it has been upplied IO detect buried tanks. lundfill debris. Mnter levels, and contaminutedjluids. The detection OJ' iurious militury devices also represent a suious eni~ironmental coni~ern including land mines and une.xp1oded ordnance. There alp also possible applications inwlving the detection o_f' buried utilities highwsay voids. grave sites. It has been used for esumining urcheological sites. The above list is jar f i o m complete beuuse of the ever-expanding use if GPR.
Complexities associated with the theoretical solution of the near‐field interaction between the fields radiated from dipole antennas placed near a dielectric half‐space and electrical inhomogeneities within the dielectric can be overcome by using numerical techniques. The finite‐difference time‐domain (FDTD) technique implements finite‐difference approximations of Maxwell's equations in a discretized volume that permit accurate computation of the radiated field from a transmitting antenna, propagation through the air‐earth interface, scattering by subsurface targets and reception of the scattered fields by a receiving antenna. In this paper, we demonstrate the implementation of the FDTD technique for accurately modeling near‐field time‐domain ground‐penetrating radar (GPR). This is accomplished by incorporating many of the important GPR parameters directly into the FDTD model. These variables include: the shape of the GPR antenna, feed cables with a fixed characteristic impedance attached to the terminals of the antenna, the height of the antenna above the ground, the electrical properties of the ground, and the electrical properties and geometry of targets buried in the subsurface. FDTD data generated from a 3-D model are compared to experimental antenna impedance data, field pattern data, and measurements of scattering from buried pipes to verify the accuracy of the method.
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