Ground Penetrating Radar (GPR) systems operate by transmitting polarised pulses of electromagnetic energy into the ground and then recording the energy that is reflected back to the surface. The method responds to variations in the electrical properties of subsurface materials (dielectric constant and conductivity) that are a function of material type, moisture content and pore fluid type. Where a contrast in dielectric properties exists between adjacent materials a proportion of the electromagnetic pulse will be reflected back. Subsurface structures are mapped by measuring the amplitude and travel time of this reflected energy.
The electromagnetic energy is transmitted via an antenna at a specified central frequency and can be recorded with either the same antenna or a separate antenna (monostatic mode or dis-static mode). Digital radar systems can also operate with multiple receiving antennae.
