Ground penetrating radar (GPR) survey is one of a number of methods used in archaeological geophysics. GPR can be used to detect and map subsurface archaeological artifacts, features, and patterning.

Overview

Ground penetrating radar survey of an archaeological site in Jordan.
GPR depth slices showing a crypt in an historic cemetery. These planview maps show subsurface structures at different depths. Sixty lines of data - individually representing vertical profiles - were collected and assembled as a 3-dimensional data array that can be horizontally "sliced" at different depths.)
GPR depth section (profile) showing a single line of data from the survey of the historic crypt shown above. The domed roof of the crypt can be seen betwee 1 and 2.5 meters below surface.
The concept of radar is familiar to most people. With ground penetrating radar, the radar signal – an electromagnetic pulse – is directed into the ground. Subsurface objects and stratigraphy (layering) will cause reflections that are picked up by a receiver. The travel time of the reflected signal indicates the depth. Data may be plotted as profiles, as planview maps isolating specific depths, or as three-dimensional models.

GPR can be a powerful tool in favorable conditions (uniform sandy soils are ideal). Like other geophyscal methods used in archaeology (and unlike excavation) it can locate artifacts and map features without any risk of damaging them. Among methods used in archaeological geophysics it is unique both in its ability to detect some spatially small objects at relatively great depths and in its ability to distinguish the depth of anomaly sources. The principal disadvantage of GPR is that it is severely limited by less-than-ideal environmental conditions. Fine-grained sediments (clays and silts) are often problematic because their high electrical conductivity causes loss of signal strength; rocky or heterogeneous sediments scatter the GPR signal, weakening the useful signal while increasing extraneous noise.

Individual lines of GPR data represent a sectional (profile) view of the subsurface. Multiple lines of data systematically collected over an area may be used to construct three-dimensional or tomographic images. Data may be presented as three-dimensional blocks, or as horizontal or vertical slices. Horizontal slices (known as "depth slices" or "time slices") are essentially planview maps isolating specific depths. Time-slicing has become standard practice in archaeological applications, because horizontal patterning is often the most important indicator of cultural activities.[1]

Further reading

  • Script error

A general overview of geophysical methods in archaeology can be found in the following works:

  • Script error
  • Script error

Notes and references

  1. Conyers, Lawrence B. And Dean Goodman 1997 Ground Penetrating Radar: An Introduction for Archaeologists. Walnut Creek, CA.: Altamira Press