Academic journal article Southeastern Archaeology

Reflectance Transformation Imaging (Rti) of a Little Known Southeastern Copper Plate

Academic journal article Southeastern Archaeology

Reflectance Transformation Imaging (Rti) of a Little Known Southeastern Copper Plate

Article excerpt

Artifact imaging techniques such as 3D technologies, visualizations, photogrammetry, and computational photography are among the most current methods used in the creation of "digital surrogates" (Mudge et al. 2007:1, 2010:1). These technologies are increasingly more common and user-friendly, opening the door for new and innovative research in the preservation and conservation of artifacts. For example, many institutions now incorporate the inexpensive NextEngine Desktop 3 D scanner to create virtual artifact collections for research and education (e.g., Means et al. 2013).

One visualization technique common within the museum community, but less so to U.S. archaeologists, is reflectance transformation imaging (RTI), a nondestructive advanced imaging tool that captures the shape, texture, and color of an object through numerous digital photographs from a fixed camera location, each of which has a light source from a different direction. The sequence of photographs produced shows the same subject, but with varying highlights and shadows. The applications of RTI are diverse and easily applied to look at hard-to-see characteristics of many different types of objects, such as deciphering faint inscriptions on papyrus, observing brushstrokes on paintings, detecting tool marks on stone, or examining the delicate surface features and designs. The Smithsonian Institution, the University of Oxford, the University of Southampton, the Oriental Institute at the University of Chicago, and the University of South Florida's Alliance for Integrated Spatial Technology (AIST) among others, all use RTI (Earl et al. 2010:2049; Mudge et al. 2010:5; Piquette 2011:17).

Despite its extensive use in museum settings, the application of RTI within the U.S. archaeological community continues to be limited (Earl et al. 2010:2041; Mudge et al. 2010:9). This is not to say that RTI is not used in archaeology since there have been several interesting studies in the past few years (Brognara et al. 2013, Diaz-Guardamino and Wheatley 2013; Duffy 2010; Earl et al. 2010, 2011; Gabov and Bevan 2011; García Fernández 2013; Goskar and Earl 2010; Kleinitz 2012; Miles et al. 2014; Piquette 2011; Purdy et al. 2011). However, when looking broadly in U.S. archaeological journals, they generally do not have publications featuring RTI research. This is unfortunate since the technique is inexpensive, flexible enough to use on large and small artifacts, and is especially effective in bringing out difficult-to-see surface features and textures. Not only are there vast archaeological implications for the use of RTI, but its versatility crosscuts the various specialties within archaeology and cultural heritage studies (Dellepiane et al. 2006; Earl et al. 2010; Mudge et al. 2005, 2006; Palma et al. 2010:1; Rabinowitz et al. 2009; Schroer 2012:41; Tamayo et al. 2013). Perhaps RTI has been more widespread in other areas of the world because the nature of the archaeological record outside of the U.S. lends itself to such approaches (e.g., imaging faint inscriptions and ancient writing). While the U.S. lacks formal ancient writing systems, there are many instances that would benefit from the use of RTI and its infrequent use could simply be due to a lack of knowledge about the technology. As this case study points out, RTI has great value in enhancing artifacts with engraved and embossed iconographic designs, such as those found on Mississippian period (A.D. 900-1600) ceremonial objects. The object in our study, a Mississippian copper plate from the Chauga site (38OC47), is an example of this tradition. RTI, however, is very versatile and easily applied to other objects with hard-to-see features. This approach can bring out inscriptions on grave markers, determine designs on petroglyphs, identify decoration on ceramics, or even see faint characters on coins. These are but a few examples of the many archaeological applications for RTI.

In this paper, we demonstrate the merits of RTI using the Chauga plate as an example. …

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