Radar Tomography Conducted on Roanoke Island to Identify Potential Dig Sites

On July 21-22, a team from Craig A. Smith and Associates, an engineering firm holding a license to employ the RT (Radar Tomography) device developed by Witten Technologies, undertook a remote sensing survey at Fort Raleigh National historic site. The CAS members were Jim Driscoll, manager of radar tomography and Alan Lopez, field assistant for this project. The FCF archaeologist coordinating the project was Eric Klingelhofer, Jason Powell recorded it for the National Park Service, and Rob Bolling explained the project to on-site visitor tours.

The previous RT work at fort Raleigh in 2008 had been to test the procedures and to verify their accuracy. RT’s near pinpoint accuracy was proven, and this time the area scanned needed to be integrated into the NPS electronic GPS archaeological map of the park. Inconsistencies with previous measuring points had stopped the final compilation of the map, but fortunately Guy Prentice of the NPS Southeastern Archaeological Center came to Fort Raleigh and resolved the problem just a few days before the RT project began. Integration of the July survey into the map will be one of the goals this fall in preparation for continued manual survey and excavation.
Approximately three acres were scanned over two days, although the four acres of open woodland surrounding the restored “Fort Raleigh” earthwork had been the original goal. While open woodland did permit use of the SAS RT-mounted four-wheel tractor, what trees there were made it difficult to obtain clear line-of site surface measuring for the necessary GPI instrumentation. The slowed progress of the first day led to the decision not to scan the area northwest of the earthworks, which had already been heavily excavated and where activities by the State Park were known to have seriously disturbed original strata. The removal of this sector from the survey area, however, permitted the inclusion of a new area, which had previously been suggested by Doug Stover, the NPS liaison with FCF. Starting from the theater drive and extending onto the crest of the sand dunes east of the theater’s ancillary buildings, strip of ground was recently cleared for use in pre-performance activities. The area had never received serious archaeological attention, and it was the only site in which RT could be undertaken through a sand dune into the buried soils.
John Buford of the Lost Colony theater staff very kindly filmed the RT team in operation and recorded an interview by of Jim Driscoll by Eric Klingelhofer. These he combined into an informative video, which he placed on the internet with links to his organization and to FCF, NPS, and others.

Because the tomography of calibrating and refining numerical readings into visual images takes place in the lab over days and weeks (one sample of the readings was forwarded from CAS by mid-August), there was little to report from the field. It could not be readily determined, for instance, when the machine was recording radar scans of the deep “charcoal pit” found first in 1950 and re- excavated in 1991 and 1992. On the other hand, Driscoll’s team did note that in the area scanned north of the earthwork, two strong anomalies were recognizable. Learning whether these and other RT anomalies date to the 1580s or to the 1930s, like most of the features in the former park area, is the task that FCF now will undertake over the next excavation seasons.

Photos courtesy of Jason Powell


Phil Evans
First Colony Foundation