The GPR system consists of a transmitter, antenna, and radargram. The transmitter emits pulses of electromagnetic radiation into the surface to be surveyed. The difference in permittivity is an indication of change in sub-surface features. Some of the electromagnetic energy reflects when any change is encountered. The antenna receives these reflected waves, and the corresponding variations are recorded. The information is interpreted and displayed on the radargram. The time taken by the reflected signals to travel back is measured, which is an indication of the depth and location of interruption.