Ground Penetrating Radar is a subsurface exploration system that uses electromagnetic (EM) waves. It is very similar in principle to reflection seismic. The system sends EM pulses into the ground by a transmitting antenna and picks up reflections with a receiving antenna. These signals are amplified and processed to provide a ground profile record.
Recently this technique is most famous to detect karstic voids, caves, fractures, substructure systems, infrastructure lines (pipe/wire duct), historical structures, and tunnels etc. It is possible to monitor different depth levels of ground by using different frequency receiver antennas; therefore it is possible to make an evaluation in 2D and 3D.