For the past week, Dr. Duncan McKinnon from the University of Central Arkansas has been teaching the students about near-earth remote sensing techniques. Archaeologists across the globe use these techniques in order to gain a better understanding of the landscape or site without the inherent destruction of classic excavation methods, and to carefully target excavation units to minimize their impact on archaeological record. The instruments used by archaeologists in the field quantify certain physical properties (e.g. magnetic susceptibility, electrical resistance, etc…) of the surface and subsurface. There are two main categories of instruments: passive and active. Passive geophysical instruments measure variations in the earth’s physical properties without any signal transmission from the instrument. Active methods, as the name suggests, actively produce an artificial signal that is broadcast into the earth’s surface. Based on the behavior of this signal in relation to the ground, archaeologists can glean information about variations in the earth’s physical properties. Magnetometry (passive), ground penetrating radar (active), and electromagnetic induction (active) are the three geophysical methods that our students have been working with over the past week.
So far, the most informative data have come from the magnetometry survey, which measures subtle variations in the local magnetic field. From this, we can detect subsurface features based on careful interpretation of the magnetic anomalies measured by the instrument. While the data collection itself is fairly quick and straightforward, the interpretation and data processing that occurs after collection is where the experience of a specialist such as Dr. McKinnon becomes crucial. We will continue to keep you posted as the students learn more about the data processing aspect of geophysical testing!