A sampling investigation of GPR wave propagation velocity data to improve migration processing of concrete rebars

In this study, a demonstration of the potential of ground-penetrating radar (GPR) for improving location of rebars is given. To this purpose, a high-frequency GPR system with a 2000 MHz dual-polarised antenna (HH/VV polarisations) has been used to collect data on a reinforced concrete floor of dimensions 1m×0.80m (longitudinal and transversal acquisitions). The high-dense grid mesh of rebars and the use of the hyperbola fitting method allowed for the acquisition of a dataset of wave propagation velocity values. Hence, an analysis of the statistic distribution of propagation velocity values was carried out to assess the data dispersion throughout the area. A data sampling approach was then proposed and velocity values were sampled at different percentages and in an evenly-distributed manner throughout the inspected area. Corresponding values of velocity were therefore used for data migration purposes and C-scan maps were produced as a combination of longitudinal/transversal acquisitions and HH/VV polarisations. The optimum sampling rate of wave propagation velocity was then assessed by way of comparison of the migrated maps.