

Ground penetrating radar (GPR) is a non-invasive geophysical technique which is capable of providing continuous high-resolution imaging of the subsurface. GPR is widely used in geotechnical engineering and most of the interpretations are visual based and qualitative. The objective of this study is to produce an effective algorithm to interpret a GPR wave form, so that it can be used to quantify the changes occurring in the subsurface more precisely. In this study, a GPR survey has been carried out at 10 selected locations in Coimbatore, India using low frequency (25MHz) ground coupled rough terrain antenna. Subsurface information was interpreted through a visual method by looking at the wave pattern changes. Time domain wave forms were converted as frequency domain; Fast Fourier Transform (FFT) spectrum were developed. The peak frequency (25MHz) ground coupled rough terrain antenna. Subsurface information was interpreted through a visual method by looking at the wave pattern changes. Time domain wave forms were converted as frequency domain; Fast Fourier Transform (FFT) spectrum were developed. The peak frequency (fp) from FFT has nearly the same range of values for all the traces within that layer. In the absence of borehole data, soil layer interfaces are estimated by measuring fp value at some fixed interval of depth (say every 1m) and by plotting it versus depth, where fp value changes abruptly at interfaces.