The primary tasks of the archaeological team at the Warren Lasch Conservation Center (WLCC) is the excavation and study of the American Civil War submarine the H.L. Hunley, the forensic investigations of its crew , and the documentation and analysis of a large assembly of artifacts associated with the hull. Because of the challenging nature of the Hunley excavation, over the years a variety of techniques and technologies have been employed to collect the three-dimensional provenience and research data that is crucial to addressing the goals and objectives of the project. As a result of this work, archaeologists at the WLCC have developed a strong foundation and significant technical expertise particularly in the areas of 3D documentation, digital modeling, and visualization.
The primary 3D technology employed by the archaeological team at the WLCC for surface documentation is the Breuckmann OptoTOP-HE structured-light scanning system. Using fast light projection and a high resolution camera, the structured-light scanner can capture surface topography with a very high degree of accuracy and point resolution. The Breuckmann scanner also collects color photographic information in addition to three-dimensional point cloud data, providing complete 3D documentation of the target object.
To record discrete coordinate points, archaeologists employ the Vulcan Measurement System. This is a portable, hand-held device that allows for real-time point recording up to a range of 30 meters. Because the system works using an offset and adjustable measuring tip, it is an essential tool for mapping in situations where line of sight to the target is obscured.
Photogrammetry (in development)
The team is currently developing proficiencies in 3D documentation and coordinate measurement through the use of close range photogrammetry. The photography-based technique creates spatial measurements by triangulating known points through the comparison of two or more photographs. The technique can track known points on an object’s surface. The points recorded are identified in the photographic data and used to generate a 3D reconstruction. For large scale reconstruction the technique can create photorealistic 3D models with speed and efficiency.
Digital Modeling and Inspection
In addition to data collection and documentation, archaeologists have also developed expertise in modeling and comparative analysis or inspection of 3D data. Using industry-standard software packages, 3D point-cloud data can be aligned and merged to produce composite polygonal models in a variety of formats. These models can then be subjected to a number of procedures including inspection, deformation analysis, texture mapping, and reverse engineering. This is particularly useful for detailed surface studies, documenting changes over time of an artifact undergoing conservation treatment, or the rapid prototyping/digital printing of objects.
3D Visualization and Interpretation
3D data collected over the course of the Hunley Project has been studied primarily through the use of a 3D site plan. CAD-based software allows the integration of polygonal models into a single platform that incorporates the many layers of the archaeological information. The digital site plan is a critical tool that enables archaeologists and other researchers to virtually view, manipulate, and analyze the submarine and the entire artifact assembly. Based on this work, the team is also developing methodologies for integration non-spacial and spacial data, such as pointcloud and x-ray computed tomography, into a uniform 3D digital platform.