Use of 2D FDTD simulation and the determination of the GPR travel path angle for oblique B-scans of 2D geometries

Scattering from a subsurface point object, such as a reinforcing steel bar embedded concrete or a tunnel buried in sand, results in a B-scan contour that is essentially hyperbolic as the Ground Penetrating Radar (GPR) passes over the object. The shape of the hyperbola can be used to determine the angle at which the GPR traveled over the point object. This information is very useful in determining the orientation and size of an object such as reinforcing steel, buried utilities, and subsurface tunnels. A 2D Finite Difference Time-Domain (FDTD) method can be used to simulate the GPR B-scan when the geometry is invariant in the third dimension and the sensors are appropriately located. The shape of the hyperbola extracted from 3D simulation, analogous to field-collected data, can be compared to a library of hyperbolas extracted from 2D simulations and used to determine the angle of the GPR travel path from the cross-sectional plane.