Ground penetrating radar (GPR) is mainly used in pavement engineering to determine the thickness of pavement layers. The accuracy of layer thicknesses determined from GPR data depends largely on the accuracy of the dielectric properties of the construction materials used for interpretation. Different GPR data interpretation methods that use the GPR reflected signal to estimate the dielectric properties of construction materials have been developed. The most used methods are using data from the literature, known height method, common midpoint method, wide-angle reflection and refraction method and surface reflection method. Each of these methods has its own benefits and drawbacks.
The objective of this study was to evaluate the accuracy of asphalt layer thickness determined by the surface reflection method and the known height method. Data collection was performed using a survey vehicle equipped with a GPR system with 1 GHz air-coupled antenna. The GPR survey was carried out in seven measurement lines and a core was extracted from the pavement in each line. Thickness data from the core was used to determine the dielectric properties of the asphalt layer and to evaluate the reliability of interpretation methods.

ground penetrating radar; asphalt layer thickness; surface reflection method; known height method