Geophysical methods are a way to explore the subsurface when archaeological targets may be present. Geophysical surveys can map and describe cultural remains economically in a non-invasive way. This approach enhances the possibility to study larger areas in a single project and allows an understanding of sites in a wider context. Geophysics can also help archaeologists to select excavation locations with previous geophysical information by optimizing resources and increasing the effectiveness of excavations.
Some of the more common methods include magnetometry, magnetic susceptibility mapping, resistivity and ground-penetrating radar (GPR). These are also known as remote-sensing or prospection techniques. They help archaeologists locate buried structures and deposits and are very useful for helping to target excavation areas.
The results of geophysical survey produce site plots of recognizable structures that reveal a picture of buried structures or objects before any excavation has taken place. Geophysics measure certain types of physical property in the soil, such as magnetism or electrical resistance.
Whatever the physical parameter being measured, the usual result of a geophysical survey is a matrix of data points, or transects of data, across a site. Following some data processing, patterns generated in these data can be interpreted in terms of buried archaeological features. The results are generally presented as either a two-dimensional site plan (e.g. in a conventional area earth resistance survey), or as a diagram showing the data from a transect as a section across the site (e.g. Ground Penetrating Radar (GPR) profiles). Multiple transect images can be compiled into a three-dimensional data set which can be visualized as two-dimensional images at increasing depths.
The benefits flowing from application of geophysics may be direct, as immediate cost reductions, or indirect in the form of an enhanced ore recovery, optimised blasting pattern, or early warning of a safety hazard.