With increasing emphasis on shallow, high‐resolution geophysical techniques for environmental and engineering applications, it has become important to implement and evaluate tools for quantitative interpretation of ground‐penetrating radar (GPR) data. Both ray and Fourier algorithms are viable for numerical simulation of 2-D monostatic GPR data, but they have different characteristics. The ray algorithm uses geometrically complicated layers, where within each the dielectric permittivity and attenuation are constant. The algorithm produces accurate amplitudes for reflection but does not include wave effects such as diffractions from layer truncations. The Fourier algorithm uses a gridded parameterization in which reflections are constructed by superposition of diffractions in a background of constant dielectric permittivity and constant attenuation. This technique includes all wave effects, but it does not contain the antenna directivities. Both algorithms are able to simulate the main features in two representative, but very different, field data sets: one from a Quaternary fluvial/aeolian environment and one from a Cretaceous marine carbonate environment.