Measuring layer thicknesses with GPR - Theory to practice

Ground penetrating radar (GPR) technology has been used to assess pavement performance and structure for the past 30 years in a variety of ways. Yet after all this time, the main issue remains: How well does GPR work and under what conditions? Results show that GPR works well for some situations but not as well for others. It is not currently used on a routine basis by the Departments of Transportation in the US mainly because of difficulties encountered while interpreting GPR data. These difficulties are generally attributed to the fact that the GPR reflected signals that are collected depend largely on the a priori unknown dielectric properties of the structural materials. Additional difficulties arise from the fact that physically GPR cannot detect layers unless they have sufficiently dissimilar dielectric constants. In practice, GPR has been used primarily for pavement layer thickness estimation and moisture accumulation localization within the pavement layers. To improve GPR prediction capabilities, different data processing techniques have been developed that use the GPR reflected signal to estimate the dielectric properties of surveyed structures, thus determining their thicknesses. Other signal processing techniques have also been used successfully to enhance the quality of the GPR signal in order to increase the accuracy of the data interpretation results.