Evaluation of pavement layer thicknesses using GPR: A comparison between full-wave inversion and the straight-ray method

The characterization of pavement properties is essential to manage transport infrastructures. In this paper, we aim at assessing the abilities of the ground-penetrating radar (GPR) full-wave inversion and straight-ray methods to achieve this task. The first approach consists in combining a full-wave- inversion procedure with a recently developed electromagnetic model. The latter takes advantage of a closed-form solution of Maxwell’s equations to describe the antenna-medium system. The second approach resorts to the surface reflection coefficient method. We showed through numerical experiments that the straight-ray method in general provides fast and good results, but full-wave inversion applies to a wider range of model configurations and is subject to less important errors. A laboratory experiment was also conducted to take into account the effects of measurement errors as well as inherent pavement heterogeneities. The results evidence that noisy data and a lack of information can sometimes lead to an inappropriate estimation of the parameters. Nonetheless, applying an adequate processing before invert- ing the data made both inversion methods able to provide an estimation of the pavement thickness along the acquisition profile.