Ground Penetrating radar

Abstract

Abstract Ground‐penetrating radar (GPR) is a geophysical method that can accurately map the spatial extent of near‐surface objects or changes in soil media and produce images of those features. Data are acquired by reflecting radar waves off subsurface features in a way that is similar to radar methods used to detect airplanes in the sky. Radar waves are propagated in distinct pulses from a surface antenna, reflected off buried objects, features or bedding contacts in the ground, and detected back at the source by a receiving antenna. As radar pulses are being transmitted through various materials on their way to the buried target feature, their velocity changes, depending on the physical and chemical properties of the material through which they are traveling. When the travel times of the energy pulses are measured and velocity through the ground is known, distance (or depth in the ground) can be accurately measured. A three‐dimensional data set is then produced. In the GPR method, radar antennas are moved along the ground in transects, and two‐dimensional profiles of a large number of periodic reflections are created. Thus produces a profile of subsurface stratigraphy and buried features along lines. When data are acquired in a series of transects within a grid and reflections are correlated and processed, an accurate three‐dimensional picture of buried features and associated stratigraphy can be constructed. Ground‐penetrating radar surveys allow for a wide aerial coverage in a short period of time, with excellent subsurface resolution of buried materials and geological stratigraphy. Some radar systems have been able to resolve stratigraphy and other features at depths in excess of 40 meters, when soil and sediment conditions are suitable. More typically, GPR is used to map buried materials of interest at depths from a few tens of centimeters to five meters in depth. Radar surveys cannot only identify buried objects for possible future excavation but also interpolate between excavations, projecting subsurface knowledge into areas that have not yet been, or may never be excavated. GPR surveys are most typically used by geologists, archaeologists, hydrologists, soil engineers, and other geoscientists.