Archaeologists are increasingly looking at remote sensing methods as techniques to explore sites with minimum disruption to the surroundings.
This work is delivering new means of mapping prehistoric and historic sites in three dimensions rather than traditional two-dimensional methods.
Magnetics is a primary remote sensing technique that offers both ease-of-use and cost efficiency.
Main benefits lie in the ability to resolve details non-invasively, the wide range of artifacts and cultural objects that are detectable, and the low-cost of magnetics in comparison to other methods.
Resource: Magnetic Surveying in Archeology
Tatyana N. Smekalova, Olfert Voss, and Sergey L. Smekalov have collected information about magnetic prospecting of archaeological sites using GEM’s GSM-19WG. They have concentrated on practical aspects of magnetic surveying for the investigation of archaeological sites situated in different geographical and geological conditions.
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Magnetometry and gradiometry resolve many structures, including buildings, cooking sites, furnaces used for smelting, burial grounds and other types of buried subsurface objects. To find out more about these applications, download GEM’s brochure on Magnetics for Archaeology.
Data is typically acquired using a gradiometer – a two-sensor configuration that serves to reduce natural noise from sunspot activity (diurnal effects) as well as focusing the depth of investigation to the near surface. Depths of penetration vary up to 10m depending on the type of target being investigated (i.e. highly ferrous as opposed to weakly ferrous).
A number of case histories are available from GEM. Note that these case histories have been digitized and appear with less resolution as compared with the originals. However, they still provide numerous examples on the application of magnetics to archaeological investigations. To access these case histories, click the links below:
Several different types of instruments are available for measuring a) total magnetic field (i.e. systems from GEM) and b) three components of the magnetic field (i.e. fluxgate systems). Total field systems offer a number of benefits over fluxgate systems, including high rates of acquisition and no requirement to calibrate systems during surveys for greater survey efficiency.
Processing of data is straight-forward, requiring a) downloading of magnetic and gradiometric data from the instrument to a personal computer and b) minor filtering for noise suppression related to geologic or other effects not of interest to the archaeologists. Simple software packages are available for these purposes from GEM.
Advanced users may also be interested in applying routines, such as Analytic Signal processing to convert dipolar total field anomalies to single peak anomalies that can be easier to visualize. Other advanced routines, such as modeling to determine depth to magnetic sources, can also be applied.
Note: For archaeologists considering applying magnetic methods, there are a range of programs that offer funding for instrumentation purposes. Users in the United States, for instance, may wish to consult the National Science Foundation for more information. Alternately, archaeologists from other countries can consult similar local funding agencies.
Archaeologists work in some of the most diverse terrains possible. From the world’s largest historic site at Angkor Wat to the Indigenous burial grounds in North America to the ancient Roman fortifications that cover Europe, archaeologists are “breaking new scientific ground” every day. GEM has aligned its product offerings to meet these demanding requirements with instruments that are non-intrusive to the sites under study.
Its very high sensitivity optically pumped Potassium system is capable of resolving the most subtle contrasts in materials (such as those of clay bricks in soil).
The unique Overhauser system has a wide range of “detectability” for low contrast and high contrast (ferrous) structures while matching specifications of optically pumped Cesium instruments at much lower cost.
And where economy is required, GEM also offers the world’s most feature-rich Proton Precession instrument – a tool with classic value that complements any archaeologist’s toolkit.BACK