The term geophysical instruments covers a wide range of tools and techniques which are used to analyze what is underground. It is used in a wide range of industries, from mining and engineering, to environmental spheres such as such as geosciences and energy exploration.
One environmental use for this kind of technology is in archaeology, where the preservation of both natural and man-made environments, and balancing the requirements of those two kinds of infrastructure, is crucial. The preservation aspects to the work in this area mean that intrusive methods of assessing areas of ground can often be problematic and destructive; using a range of scientific instruments can help ease the whole process, mapping the underground environment before more conventional work takes place.
The geophysical methods that are used in archaeology are therefore developed from those used in other areas of study and exploration, for example mining. However, while other techniques in other spheres often require the detection of large subterranean structures, archaeological environments are often defined by trying to discover features which are often within the top meter of earth.
Such features can often be extremely ephemeral, such as staining from wooden buildings which have subsequently decayed, and instruments need to be adjusted so that they can discover such features, as well as distinguishing them from naturally occurring materials, such as rocks or roots.
Geophysical techniques have been in use since the 1930s, and have been extensively used in archaeology since the 1940s and 1950s, when their use was pioneered in the United Kingdom. The process back then was very labor-intensive. Data had to be logged and plotted manually, and, without computer technology, analysis was difficult.
The tools of the trade have developed since then, with instruments equipped with greater sensitivity and depth of ground penetration. However, the most important developments have been in the field of data capture and analysis. Computers can now store and handle large amounts of data, while it is also possible to map vast areas quickly.
Prime considerations for the use of geophysics in archaeological environments include resistance to difficult weather or other impairing conditions and a capability to generate high sample densities, as well as the subtlety to reveal often ephemeral features. Some of the devices deployed by archaeological geophysicists include electrical resistance meters, electromagnetic (EM) conductivity meters, magnetometers and ground-penetrating radar (GPR).
This has meant that it is now possible to attain the necessary high density samples of areas which make it much easier to differentiate between naturally occurring features and archaeological targets. Advances in the kind of software used for imaging and processing mean that subterranean patterning is now much more easily discovered, allowing for vast improvements in data quality and a massive speeding up of analytical processes.
Survey systems for archaeology now include more advanced modeling features, allowing for the conversion of numerical data into maps. One technique becoming increasingly important is inverse modeling, which constructs image or contour maps in false relief. This means that archaeologists can spot patterns and visualize features in ways that would have been incomprehensible to their pre World War Two counterparts.
Geophysical instruments continue to occupy a crucial role in archaeological environments. With preservation of intact historical and natural environments so key, non-disruptive and non-invasive techniques help to manage the often competing interests which shape the direction of archaeological work.
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