A large number of archaeological sites are often discovered to be buried below soil and sediments only after construction activities, such as road building, pipeline burial, or other below-ground intrusion, have commenced. This leads to costly construction delays as compliance with regulations regarding cultural resources are met. Ground-penetrating radar (GPR) has recently proven to be efficient at producing three-dimensional images of buried cultural features when information about the nature of radar reflections can be determined. The success of GPR surveys is to a great extent dependent on soil and sediment mineralogy, clay content, ground moisture, depth of burial, surface topography, and vegetation. Although GPR is not a geophysical method that can be immediately applied to any geographic or archaeological setting, with thoughtful modifications in acquisition and data processing methodology, GPR can be adapted to many differing site conditions; however, the GPR signature for most archaeological features has not yet been estimated.
The objective of this project was to quantify and calibrate GPR for known archaeological features that are commonly found in many areas of the United States. A field and laboratory protocol that can be modified using specific site conditions and the extent of the target features (i.e., depth and aerial) was produced. A desired end result was to facilitate more accurate and efficient detection and mapping of buried cultural remains on Department of Defense installations and ranges and other managed lands, decreasing the reliance on traditional, arbitrary excavations that are both costly and destructive.
This project analyzed GPR data in detail at two test sites (one in Washington and one in Illinois) where subsurface conditions were known in advance and environmental variables such as soil moisture and composition were measured and then modeled. Many radar configurations, including different frequency surface antennas, transect spacing, depth of investigation, and filtering types, were used to collect the data. The stratigraphic framework, constructed from what was known about these test sites, enabled calibration of the GPR signal in a variety of common archaeological earth materials as never before. Field and laboratory data were modeled on the computer and reflection simulations compared and then adjusted in an iterative fashion to mimic and understand real-world conditions. Computer programs were developed and integrated for the efficient and accurate mapping of buried sites.
This project developed and refined the use of GPR technology in archaeology to the extent that the results will be central to the design and implementation of future GPR studies in cultural resource assessment. The results include a pre-data acquisition protocol for site analysis, which will enable researchers to predict conditions expected in the field and to adjust hardware and software configurations accordingly. Site analysis of this sort will promote an understanding of GPR energy radiation and reflection in the ground, which in turn will save money and time as conditions can be predicted and adjusted in advance. (Project Completed - 2006)