Ground penetrating radar signal processing improves mapping accuracy of underground voids and seawater table: an application in deteriorating coastal structure, Nanfangao Port, Taiwan

Efficient restoration of deteriorating coastal structures requires an accurate picture of both above ground and underground features. Although ground penetrating radar (GPR) can map underground features, it creates reflection artifacts. Here, a model for deconvolution calibration was developed in an outdoor small-scale experiment. GPR parameters were established, then applied at a deteriorating fishing port in northeast Taiwan. The deconvolution filter removed repetitive reflection patterns under the lowest part of the void creating a more accurate map. A 3D-map was created from interpolated sketched void boundaries. Due to its high lossy nature at radar frequencies and large contrasting relative dielectric permittivity (RDP) to the upper medium, the seawater table (SWT) is easily identified. The upper boundary of reflection-free area in the deconvoluted radargram, therefore, indicates the SWT. The methods developed here are easily modified to fit a wide range of situations.