Methodology

Operating under a grant from NOAA Office of Ocean Exploration, the Maritime Studies Program at East Carolina University has completed part one of a two-part program for the exploration and discovery of submerged cultural resources, primarily shipwrecks, between Cape Hatteras and Cape Lookout, North Carolina in the vicinity of Ocracoke Island. A systematic remote sensing survey will be conducted to assess the scope of existing archaeological resources. The first part of the survey is primarily focused on Ocracoke Inlet because historical sources reveal a high concentration of vessels lost in the area and Ocracoke Inlet's heavy use throughout the colonial period. The project incorporated four phases to accomplish its goals.

Phase I Historical Documentation

In order to create a valid research design it is necessary to compile a list of vessels lost in the proposed project area. The Maritime Studies Program at East Carolina University has created a database of shipwreck losses in the proposed project area using records compiled by the North Carolina Underwater Archaeology Branch. This agency is tasked to monitor underwater archaeological sites in the state and it maintains extensive files of vessel losses in North Carolina. Data in these files comes from primary and secondary sources and include vessel position when known. Approximately 25% of the files have position in latitude and longitude. The remaining files only have narrative descriptions that place a lost vessel on a general section of the coast.

Other sources included the National Archives and the Naval Historical Center in Washington, D.C., NOAA's AWOIS lists, and the Outer Banks Historical Center.  Material reviewed includes correspondence, newspapers, wreck reports, and logbooks kept by lighthouse keepers, the US Coast Guard and the US Life-Saving Service. Using this information a vessel list is created and used to plot site locations on a map. We have identified approximate locations for many vessels and clusters or concentrations of vessels. This data is used to create survey blocks based on the following criteria:

Reported location of individual vessel loss
High Risk Areas - shoals and other hazards to navigation
High Traffic Areas - inlets, channels, ports

Historical documentation is an ongoing process. Currently we have over 1600 vessels in a database for the overall project and over 1400 in the area between Cape Hatteras and Cape Lookout.

Phase II Survey

The Maritime Studies Program maintains an extensive inventory of instruments used in nautical archaeology. The survey will be conducted using the university's small boats and the 65-foot research vessel Perkins. Remote sensing survey instruments will include a Geometrics 886 Proton Precession magnetometer and a Marine Sonics 600 kHz side scan sonar. A Garmin 225D differential global positioning system will collect position information. Coastal Oceanographics Hypack Max hydrographic survey software is used to run the survey. In this multipurpose program the user can set up survey areas, navigate track lines, collect positioning and magnetometer data, and process data. Side scan sonar data is collected on a separate computer as geo-referenced TIF files.

Environmental conditions vary widely in the survey blocks. Turbulent, shallow water (in some places less than 3 meters) may be encountered in inlets and near-shore areas. Farther offshore currents, wind, and water depth (up to 100 meters) may effect the survey. These conditions dictate the survey strategy to employ. In shallow, near-shore waters, archaeological remains are expected to be buried under sediment. The magnetometer can detect buried ferrous materials and is the primary instrument used in these areas. Range and proximity is an important limiting factor of the magnetometer. The sensor must pass relatively close to ferrous materials to be detected. This limits its usefulness in deeper water. Side scan sonar is used as the primary instrument in water over 15 meters deep. Minimum line spacing is kept at 20 meters in the shallow water areas where the magnetometer is the primary survey instrument. In deeper water, where the side scan sonar is the primary survey instrument, line spacing will reach a maximum of 40 meters.

Phase III Data Analysis

Analysis and data interpretation will begin at the completion of each survey area. Magnetometer and side scan sonar data will undergo separate processing and is incorporated into a GIS for final analysis and interpretation. GIS incorporates and displays spatial data as layers. Analysis is accomplished by examining the interaction of data layers.

Analysis and interpretation of the magnetic record will involve several steps. Magnetometer and associated positioning data are collected in Hypack Max survey software. The programs editing and sorting functions are used to remove erroneous data. Data is then exported to Surfer to produce a graphical representation of the magnetic survey. This is then exported as a theme into Arc-View, a geographical information system.

Sonar data is collected on a separate computer operating Marine Sonics Sea Scan PC software. Sonar data is collected as images and saved as GeoTIF files. These files contain a file format description that specifies the content and structure for the management of geo-referenced imagery. This allows Sea Scan PC sonar images to be read and displayed by GIS applications. Each file is reviewed using a set of criteria to place targets into three possible categories: geology, unknown and possibly manmade. Targets identified as possibly manmade are considered for further investigation.
Results of the survey will provide a known cultural resource base with a temporal date, vessel type, and construction. Faculty in the Maritime Studies Program will use the baseline data to create research designs to investigate specific sites based on significance and the potential to recover archaeological information.

Phase IV Ground Truthing

The archaeologists will examine the magnetic and sonar targets to determine their identity. A target list of possible manmade objects developed during the analysis phase will be systematically examined. The archaeologists will examine targets using scuba when targets are within acceptable safe diving limits. They will determine if the target is manmade and then attempt to make a specific identification. This will include the type of cultural object, such as a shipwreck or vessel fragment, a date based on materials, construction style or diagnostic features, and historical significance using the Secretary of the Interior criteria for nomination to the National Register of Historic Places.