Ground penetrating radar survey is a non-invasive geophysical technology that allows archaeologists and other historical research teams to gather information about what’s below ground without disturbing the surface. The technique uses electromagnetic pulses that reflect off subsurface features in the ground and are picked up by a receiver antenna. By measuring the strength and time delay of these responses it’s possible to estimate their depth. By collecting this data across an entire area, it’s also possible to map below ground features and create a 3D image of the underground environment.
As the electromagnetic signals travel through the ground they hit interfaces with different electrical conductivities and dielectric constants. This results in a portion of the signal reflecting off each interface and passing through to the next interface. Each reflected signal changes the polarity of the radar waves and is recorded as a different color on the radar profile, representing different voltage peaks. The resulting information can then be displayed in various formats – such as radar profiles, plan view maps isolating specific depths or three-dimensional models.
Advantages of Utilizing GPR Surveys in Various Applications
The penetration depth of a GPR investigation is dependent upon the frequency of the antenna, soil conditions and moisture content. High frequencies provide greater resolution but do not penetrate as far as lower frequencies.
With proper training, geophysical technicians can interpret GPR data and identify buried pipe and other underground features. GPR can locate metallic and non-metallic objects, voids and construction layer interfaces. It can also estimate the dimensions of larger objects and their depth. This allows the technician to quickly scan a site for utilities, voids and other obstructions in a non-intrusive, non-destructive manner.
