Rock Art of the Caribbean

14. A New Method for Recording Petroglyphs: The Research Potential of Digitized Images

14 A New Method for Recording Petroglyphs The Research Potential of Digitized Images GeorgeV. Landon and W. Brent Seales Introduction In this chapter we outline a method for recording, preserving, and visualizing rock art, in particular petroglyphs. The process creates accurate threedimensional (3-D) textured models of carved surfaces, making the intricate geometry clearly and readily available for study. Rock art researchers can overcome problems concerning limited access to the images and the lack of investigative tools for the images, as well as expand research opportunities through interactive computer techniques. The Instituto de Cultura Puertorriqueña graciously granted permission to use our technology (Seales and Landon 2005) in the summer of 2004 on the petroglyph-adorned boulders that line the central Plaza A of the Late Ceramic Period (a.d. 1300–1460) civic-ceremonial site of Caguana,Utuado Municipio (local political division),Puerto Rico (Oliver 2005).The rich detail of the carved images has invited various iconographic interpretations (see especially Oliver 1998,2005,summarized in Hayward,Roe,et al.,Chapter 9, this volume). In contrast, application of new technology to improve the recording and dissemination of the petroglyphs has been limited. Accepted standards for recording rock art have remained the same for many years. Two of the most prevalent techniques involve tracing and photography (Loendorf 2001). Both of these methods possess obvious limits. Tracing requires physical contact with each petroglyph and the quality of the image reproduction depends on the recorder’s perception and accuracy. Photography introduces a loss of information that is inherent when capturing a real-world object with a two-dimensional picture.While lighting certainly enhances image details,it can also limit them.For either method,all recording decisions,such as light position in photography,must be made while on site. In the Caribbean, as elsewhere, the destructive forces of natural elements , in addition to postexecution human alterations, can affect the figures Research Potential of Digitized Images / 189 on rock surfaces. Accurate recording techniques thus become critical in addressing the possibilities for information loss. Recently,state-of-the-art technology has provided researchers with more accurate renderings of different types of rock surfaces. Goskar et al. (2003) and Wessex Archaeology and Archaeoptics Ltd. (2006), for example, have employed laser-based acquisition techniques to scan the boulders at Stonehenge .These authors’ results provide an improved record of Stonehenge carvings underscored by their discovery from their high-resolution 3-D scans of previously undetected carvings of axelike shapes on Stone 53. The Digital Michelangelo Project has produced very precise recordings of Michelangelo’s David sculpture (Levoy et al.2000).The scans yielded enough detail to allow further study of even the chisels Michelangelo used when carving the statue. In this case, obvious parallels exist for investigators interested in the tools used to carve designs on rock surfaces. Cultural Heritage Imaging (Mudge et al. 2006) has developed Polynomial Texture Maps as a means of acquiring many possible lighting positions and generating one cohesive texture image of the rock art surface. Our solution to problems of recording and preservation begins with the development of a laser-based scanner in order to acquire high-resolution scans of carved surfaces. This scanner also has to be flexible enough to allow recording in remote areas while still producing images to the quality standards needed for digital preservation.We additionally discuss investigative possibilities for the digitized rock images resulting from our or others’ methods.Remote or off-site examination of these digitized images or virtual copies becomes feasible through networks,such as the Internet,using various display techniques,ranging from computer monitors to high-resolution tiled projector displays. In addition, structuring of the data is important and can play a facilitative role in further study. This becomes apparent when one wishes to save expert annotation and markup employed in subsequent studies using tools such as interactive lighting and false coloring. Preservation through Digitization The availability of new technologies further underscores the need for more robust recording techniques in rock art research. For example, both Wasklewicz et al. (2005) and Barnett et al. (2005) employed 3-D scanning for recording rock art; in particular, the former measured degradation of the rock images using recorded models.Barnett and colleagues relied on a commercial scanner from Konica Minolta Sensing Americas, Inc. (2006), while Wasklewicz and colleagues used one from Cyra (Leica Geosystems HDS, LLC 2007). Commercial offerings provide obvious benefits to researchers who 190 / Landon and Seales need “out of the box” scanning.The ease of use offered...