HR: 08:45h
AN: NS31A-02    [Abstracts]
TI: Archaeological Applications of Rapid Multi-offset Ground Penetrating Radar Data
AU: * Berard, B
EM: bberard@ucalgary.ca
AF: University of Calgary Department of Geology and Geophysics, 2500 University Drive N.W., Calgary, AB T2N1N4 Canada
AU: Maillol, J
EM: maillol@ucalgary.ca
AF: University of Calgary Department of Geology and Geophysics, 2500 University Drive N.W., Calgary, AB T2N1N4 Canada
AB: The most widely used method of ground penetrating radar (GPR) data acquisition is common-offset (CO) surveying, whereby transmitter and receiver antennas are held a fixed distance apart. The CO method's merits lie in its speed and ease of acquisition and processing. Multi-offset (MO) surveying, also known as wide aperture or multifold surveying is becoming more prevalent. The distance between the transmitter and receiver is progressively increased, resulting in traces from multiple offsets which are then stacked. The benefits of MO data include direct determination of the velocity structure and an increased signal to noise ratio. These advantages are paramount for successful investigations of subsurface archaeological material, which is often structurally complex and has minimal dielectric contrast with surrounding sediments. The main limitation of MO surveys is the onerous task of data acquisition, as the single transmitter and receiver must be painstakingly placed along the profile multiple times to achieve satisfactory subsurface coverage. For faster data acquisition, MO surveys can be automated by mounting one of the antennas on a sled and leaving the other antenna stationary. The traces are recorded while the sled antenna is in motion, and then later interpolated to discrete positions along the profile. This method of rapid multi-offset (RMO) profiling is basic in design and can be easily performed with a bistatic radar unit. RMO data collection is 3-5 times faster than "stationary" multi-offset profiling, while still maintaining comparable subsurface coverage. Two case studies highlight the usefulness of RMO data. The Roman bath-house of Tourega, located near Evora, Portugal, consists of highly structural and complex ruins. 200 MHz RMO data revealed crucial lower levels of occupation at a higher resolution and less noise than 200 MHz CO data. RMO data has also been used in at Fish Creek Park, Alberta, Canada. This site, located on a river terrace, contains Native American artifacts to depths greater than 2m and sedimentary layers of geoarchaeogical interest. CO 250 MHz GPR data was used for site reconnaissance and localization of large anomalies. Rapid multi-offset data was acquired for more accurate imaging of specific anomalies and for delineating different strata by velocity analysis.
DE: 0900 EXPLORATION GEOPHYSICS
DE: 0910 Data processing
DE: 0933 Remote sensing
DE: 0999 General or miscellaneous
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly