During the past decade tools for subsurface imaging of sites have been improved to the point where they are now playing a significant role in archaeology. These tools include ground penetrating radar, electrical resistance meters, soil conductivity meters, gradiometers, and magnetometers. The particular combination of technologies used depends upon the nature of the site and the soils surrounding the site. Devices that measure the relative resistance or conductivity of the soil to electrical currents can indicate areas of disturbed soil, such as ditches or stone structures. Those that measure electromagnetic radiation are better at detecting small areas of disturbance, such as pits, and at locating iron objects.
Ground penetrating radar operates by sending a signal into the ground.
When it encounters a buried object or a change of soil type, it bounces back and is registered in the radar unit. With all of these techniques, appropriate computer software facilitates analysis and interpretation of the readings. A technician tows the ground-penetrating radar across the ground surface, and the data is recorded in a laptop computer for later analysis.