EDUCATIONAL
LINKS
Survey Density and Spacing
The density of
geophysical measurements taken per unit area can profoundly affect the quality
of survey results. Dense measurements can result in the location of small
archaeological features (such as post holes, small hearths, etc.) that might
otherwise go undetected. Click the link below for an example of improved feature
resolution with intensive surveys.
http://ds.dial.pipex.com/town/terrace/ld36/close.htm
Modes of Data Presentation
The way in which
data is displayed can alter perceptions about the nature and magnitude of
anomalies. Archaeogeophysists use a number of digital image processing techniques
to extract feature information from the raw data. The results can be displayed
in a variety of ways. Click here for a couple of examples.
http://ds.dial.pipex.com/town/terrace/ld36/fentrace.htm
For another example
of a stacked trace plot, see the link below.
http://www.cast.uark.edu/%7Ekkvamme/geop/sluss_r2.gif
The use of shadowing
effects and digitizing archaeological features can enhance the presentation
of survey results. Click below to see an example from Navan Fort, Ireland.
http://www.cast.uark.edu/%7Ekkvamme/navan/navan.htm
The results of multiple
types of geophysical surveys can be combined by using a technique known as
color compositing. The Whistling Elk Subsurface Imaging Project contains
an example of this technique.
http://www.cast.uark.edu/%7Ekkvamme/Whistle/Composite.htm
Magnetic Surveys
Magnetic surveys
can be particularly informative about subsurface deposits because they respond
to changes in iron compounds in soils, burned areas and features, and the
presence of iron artifacts.
http://ds.dial.pipex.com/town/terrace/ld36/grad.htm
http://www.planetinternet.it/archaeosurvey/
Civil War battlefields
provide excellent opportunities to conduct magnetic surveys. The large
amounts of iron associated with these sites produce excellent results.
http://www.cast.uark.edu/%7Ekkvamme/geop/geop.htm#PRARIE_G
Magnetic survey produced
quality results at historic Pokagon Village where resistivity and conductivity
surveys were not effective due to very dry conditions.
Magnetic Susceptibility
Human occupation,
through practices of burning and admixing of burnt or imported materials,
tend to increase the magnetic susceptibility of soils at settlements. Click
on the links below to see different expressions of magnet susceptibility.
Ground Penetrating Radar
Ground penetrating
radar (GPR) has been used to document a number of archaeological sites that
have become buried over time. The link below shows how this technology can
be used to map house structures buried under volcanic lava flows and to locate
burials, both prehistoric and forensic.
http://www.geophysical.com/archlaw.htm
A general explanation
GPR in archaeology and great images of a Japanese burial mound and Anasazi
kiva in Utah.
http://www.sciam.com/exhibit/062298radar/kiva.html
Ground penetrating radar
was used at Navan Fort (Ireland) to explore subsurface archaeological features.
Geoelectric Survey Methods
Human activity results
in changes in the soil's ability to resist or conduct electrical current.
Both positive and negative changes in resistivity can be indicators of cultural
anomalies. Click on the link below to see some examples from archaeological
sites in Italy.
http://www.planetinternet.it/archaeosurvey/
Performing both resistivity
and conductivity surveys on the same site can produce a more complete picture
of the archaeological features that lie below the ground surface.
http://www.cast.uark.edu/%7Ekkvamme/Whistle/Cross.htm
Geophysics and Cultural
Resource Management
Geophysical techniques
are increasingly becoming an important part of cultural resource management.
Survey techniques can produce rapid results and do not involve the destruction
of archaeological features. Technical advances over the past two decades have
made geophysical surveys a viable option in the CRM realm. Click on the link
below to see several examples of CRM project results.
http://www.crai-ky.com/geophysical/
Metal Detectors
Metal detectors
can serve as valuable tools by complementing information collected by using
other geophysical techniques. Metal detectors can also be used alone
to produce interesting results. See the following link for a description
of metal detection methodology.
http://www.har-indy.com/Methods.html
Click on the link below
to see how metal detectors and GPS were used to further understand a poorly
documented battle in the southwestern United States.
http://www.gpsworld.com/feature/1097victorio/victorio.htm
Metal detection has
also been used to analyze the Battle of the Little Big Horn.
http://www.mwac.nps.gov/libi/
Multiple Technique Studies
The use of multiple geophysical techniques on a single archaeological
project can produce unique data. As a result, subsurface archaeological
features are more easily identified. See the links below for examples.
The Hinxton Quarry
Project used magnetometry, magnetic susceptibility, and electrical resistivity
to define archaeological features.
http://www.eng-h.gov.uk/reports/hinxton/
The Whistling Elk Project
included electrical resistivity, electromagnetic conductivity, magnetic gradiometry,
and ground penetrating radar to aid in the identification of archaeological
features.
http://www.cast.uark.edu/%7Ekkvamme/Whistle/Whistle.htm
References
Full text documents are available on-line regarding the use
of geophysical techniques in archaeology. Detailed survey procedures are also
available at the first link below.
http://www.ttser.demon.co.uk/geophys/Dox.htm
Geometrics offers
a series of geophysical papers that address archaeological and non-archaeological
issues. Some are available in PDF format and others are available in
print.
http://www.geometrics.com/sci.html
Geophysical
Data in Archaeology: A Guide to Good Practice
Published by Archaeology Data Service, United Kingdom. A guide to digital
preservation of geophysics data by Armin Schmidt with contributions from Tony
Austin, Andrew David, Kate Fernie, William Kilbride, Paul Linford, Julian
Richards, and Damian Robinson. Also provides a good history of archaeological
geophysics and guidelines for documenting a geophysical survey.