f Pulse distortion due to reflection in ground penetrating radar surveying

Conventional ground penetrating radar (GPR) surveys detect subsurface inhomogeneities by the reflection of radio-waves. A short pulse of radio-frequency energy (several nanoseconds in duration) is transmitted into the ground and variations of the electromagnetic field are recorded. The GPR interpreter then attempts to identify echoes in this record which will provide an indication of the subsurface structure. It is commonly believed that the shape of the echo will be either an exact or inverted replica of the transmitted pulse. This will be true when the radio-waves are normally incident on plane, perfect (non-conducting) dielectric boundaries. However, geological materials are usually considerably conductive and when the transmit and receive antennas are separated, normally incident reflections are not recorded. Therefore, to interpret GPR data and to design optimum survey configurations, it is important to realise that the radar pulse shape can change on reflection and to understand how it changes .