Introduction

Ground-probing radar (GPR), also variously known as ground-penetrating radar, ground radar or georadar, is a high-resolution technique of imaging shallow soil and ground structures using electromagnetic (EM) waves in the frequency band of 10–1000 MHz. The advantage of using EM waves is that signals of relatively short wavelength can be generated and radiated into the ground to detect anomalous variations in the dielectric properties of the geological material. In many respects, GPR methodology is similar to that of shallow seismic reflection surveying. Both methods use reflection of energy from underground features but they differ largely in their site-specific applicability. Radar will not penetrate into materials of high electrical conductivity, such as damp clays, which are excellent targets for the seismic reflection technique. On the other hand, radar penetrates dry sand and gravel that will not easily transmit high-frequency seismic waves. An important distinguishing feature of GPR is that the method is easy to use and is neither destructive nor invasive; this makes it suitable for use also in urban settings and archaeological environments.

A ‘young’ geophysical exploration method, GPR is only about 25 years old but has proven to be useful for a wide variety of environmental and engineering problems where the target depths are relatively shallow. The method is most effective when working with low-attenuation media (characterized by low electrical conductivity) such as ice, sand, crude oil, bedrock, fresh water, etc., and less effective or even ineffective when working with high-attenuation media such as wet clay/silt, salt water, etc.