This presentation is part of the 2017 3D Digital Documentation Summit.
Utilization of Bathymetric Surveys for the Location and Monitoring of Archaeological Shipwrecks
For many shipwrecks we have historic records of the location of sinking, but the precise current location is unconfirmed. Confirming these locations through diving or other onsite work is expensive and often hazardous. Bathymetric surveys provide a potential means to establish exact locations of wreck sites. Using this technique allows researchers to cover a large search area. This can be valuable in finding a specific wreck or in documenting a number of wrecks in a regional area. With repeated surveys it is possible to monitor the state of wreck sites even when it is not feasible to directly monitor a site via onsite work or reports from recreational divers. High-traffic maritime areas often have accessible bathymetry data available for navigation safety. The resolution of this data can sometimes be high enough to allow analysis at scales relevant to archaeological studies.
Here we present an example of such work, completed in September 2016, cataloging wrecks on the Goodwin Sands. This work utilized bathymetric surveys undertaken by the United Kingdom Hydrography Office between 2009 and 2015. The Goodwin Sands comprises a pair of large sandbanks off the southeast coast of England and has long been a major hazard due to its proximity to active shipping routes and tendency to shift dramatically. The overall bank has been calculated to have drifted around 1km shoreward between 1887 and 2000 (Bates et al., 2007), and localized features of the bank were determined by this work to have shifted as much as 400m in the span of 6 years. Swath bathymetry data from the UKHO (UKHO, 2013a; 2013b; 2013c) was combined with a comprehensive catalog of known wrecks in the area (SeaZone Solutions Limited, 2011a; 2011b) to investigate the presence or absence of known wrecks and to locate previously undocumented ones. Several of these wrecks use slope analysis to better illustrate the state of preservation of one of the wreck sites.
The repeated surveys allowed consideration of changes over time, both to the individual wrecks and the bank as a whole. Patterns of exposure and burial were investigated to assess where wrecks may become buried or exposed over time and to predict which wrecks may be at risk for damage due to the bank’s movement. The synthesis of historical information and modern spatial data allowed the identification of a number of formerly unidentified or misclassified wrecks, as well as the refinement of the location of several previously unlocated wrecks.
Swath bathymetric data is originally sampled as a 3D point cloud, but is often binned for ease of conventional analysis. Using the original high-resolution point cloud, we can construct a 3D model of the wreck and compare it to historic photographs and other documents. In addition to the obvious value in confirming a wreck’s identity, repeat swath surveys can be utilized to monitor a wreck for degradation.
Elizabeth Krueger is based in Boston, Massachusetts, where she volunteers with the Boston City Archaeology Program. She has also worked on projects with the Massachusetts Board of Underwater Archaeological Resources (BUAR). Elizabeth has an MSc in Maritime Archaeology from the University of Southampton and a BS in Archaeology and Materials from the Massachusetts Institute of Technology. Her interest is in using science and technology to facilitate cultural resource management. Specific interests include GIS, reflectance transformation imaging, and material conservation.