When most people think of archeology, they usually think of excavations and lab work. But, there is another, lesser known facet of archeology that involves computers and above-ground, non-invasive technologies.
This past August, I attended a workshop offered by Brown University and the National Park Service on new technologies in the field of archeology. The workshop took place at Longfellow House – Washington’s Headquarters National Historic Site in Cambridge, MA. Attendees learned how using these new technologies can shed light on past occupants and changes to archeological and historic sites over time.
Technology in Archeology
In the training, we received an introduction to geophysical survey, 3D laser scanning, and data integration. In the geophysical survey portion of the workshop, we focused on ground penetrating radar, resistivity, magnetic susceptibility, and conductivity. All of these methods operate above ground and do not disturb the archeological deposits. These techniques are gaining popularity in archeology because they generate a great deal of information about the site in a relatively short amount of time.
Ground Penetrating Radar (GPR)
GPR resembles a baby carriage or lawn mower. The radar unit antenna sits in a carriage-like device that is pushed along the ground to collect data. Radar waves (like the ones Police use to check speed) are sent into the ground and then reflected back up to the antenna.
GPR can show underground anomalies such as cellar holes, foundations, large artifacts, and previous structures that may not have left much evidence otherwise. All without having to put a shovel into the ground.
With this technology, probes are inserted into the ground and the resistance of the soil is tested. A high resistivity means that electrical current cannot easily flow through the soil, while a low resistivity means that electricity can flow quite well. Resistivity can inform archeologists about the types of material underground since metal, water, and various types of rock and soils have different resistance levels.
This method works by measuring a materials ability to become magnetized in the presence of the earth’s magnetic field. Magnetic susceptibility works especially well when looking for evidence of fire, hearths, metal, and foundations, since they all have unique magnetic properties.
Also known as Electromagnetic survey, conductivity measures how well the soil, rocks, and other sub-surface features conduct an electrical current. Similar to Magnetic Susceptibility, knowing the level of conductivity can provide information to archeologists about the types of materials under the sub-surface.
While similar, Conductivity and Magnetic Susceptibility do not produce the same results; some things will show up on one, but not the other.
3D Laser Scanning
A 3D laser scanner uses a laser beam to scan a building, room, object, etc., and makes a 3D map of points that represent the scanned feature. This technology is valuable for creating a 3D image of a building that is falling down, or an object that is deteriorating. It is also useful to document buildings and rooms for the future. After the scanning is complete, it is refined and can create images like these from Boston College’s Gasson Hall.
At the end of the day, it is nice to see all of your hard work come together. In the case of geophysical survey and 3D laser scanning, this coming together is called data integration. All of the data points from the laser scanning are combined with the geophysical data to give the viewer a total view of the site. This can help in making interpretations about the site and is valuable for future scientists, archeologists, and historians who are studying the site.
Non-destructive and, where possible, non-invasive techniques should be considered first and foremost when conducting archeological work. These are only some of the examples of non-invasive techniques used by archeologists. Are there other techniques you use? Are there similar techniques/concerns in other fields?
Schmidt, A.2002. Geophysical Data in Archaeology: A Guide to Good Practice, 2nd ed. (Arts and Humanities Data Service Guides to Good Practice), Oxbow Books, Ltd.
http://www.crai-ky.com/education/reports/conductivity.pdf – Conductivity