We present MATLAB codes for finite-difference time-domain (FDTD) modeling
of ground-penetrating radar (GPR) in two dimensions. Surface-based
reflection GPR is modeled using a transverse magnetic (TM-) mode
formulation. Crosshole and vertical radar profiling (VRP) geometries
are modeled using a transverse electric (TE-) mode formulation. Matrix
notation is used in the codes wherever possible to optimize them
for speed in the MATLAB environment. To absorb waves at the edges
of the modeling grid, we implement perfectly matched layer (PML)
absorbing boundaries. Although our codes are two-dimensional and
do not incorporate features such as dispersion in electrical properties,
they capture many of the important elements of GPR surveying and
run at a fraction of the computational cost of more elaborate algorithms.
In addition, the codes are well commented, relatively easy to understand,
and can be easily modified for the user's specific purpose.