The Côa Valley is home to a treasure trove of images from humanity's past.	Hard at work on location, documenting ancient petroglyphs at the UNESCO Prehistoric Rock-Art Sites in the Côa Valley, World Heritage Site in Portugal.

Rescuing Remarkable Rock Art A remote valley in Portugal contains a treasure trove of images from humanity’s distant past — Paleolithic petroglyphs in many shapes, sizes, and styles. The rugged, rocky terrain shelters at least 600 stone panels inscribed with thousands of drawings of animals, people, and mysterious symbols. These complex drawings were chipped and scratched into the rocks by humans living or traveling through the area as early as 22,000 years ago. Many of the drawings date from 14,000 to 12,000 years ago and some are as recent as the 20th century.

		Rare rock art features. The Côa Valley is home to world-class rock art not found anywhere else on the planet. The Foz Côa site in one area of the valley is a refuge for the only known examples of “portable” rock art — small stones incised with animals. Some of the carved stones are only a few inches in size. Another interesting feature is the presence of “animated” rock art showing animals with two or three heads looking in different directions.
Pictured above is an example of a "portable sketch pad" from the past. Little is known about what these rocks and images signify.

Working in the lab, capturing portable rock art.		CHI uses the highlight on a black ball to digitally document a portable petroglyph,

“CHI archives a process history of all the steps taken to document artifacts and gives every research group, no matter how small or little known, the ability to generate reputable data. The techniques we adopt and foster bring democracy to the cultural heritage field.” — Mark Mudge, President, Cultural Heritage Imaging

Boosting Traditional Techniques With New Technology
Computer science researchers from the Universidade do Minho, Dr. Alberto Proenca and Dr. Luis Paolo Santos, invited CHI co-founders Mark Mudge and Carla Schroer to visit the site and try their new tools. Prior to CHI’s arrival, Côa site researchers used painstaking traditional techniques to record the rock art designs with standard photographic methods and detailed drawings. The researchers look forward to adopting CHI's new techniques more widely.

Documentation challenges. While researchers can work with “portable” rock art in better conditions in the lab, the big rock panels cannot be moved. The scientists had to perform the time-consuming drawing and photography tasks at night and illuminate the rock art with floodlights. Parque Arqueologico do Vale do Côa (PAVC) and Centro Nacional de Arte Rupestre (CNART) staff often spend weeks on a single field drawing, dodging insects and other creatures that swarm to the lights at night, and they still may not capture all the rock art details. Because the site has such a long history, there are drawings scratched on top of older engravings, resulting in layers of important information that are difficult to record with standard photographs or illustrations.

Developing tools the CHI way. Mark Mudge, Carla Schroer, and CHI Imaging Director Marlin Lum collaborated with staff from the PAVC site and the CNART group, and scholars at the Universidade de Minho. Together, they collected digital image data to create 3-dimensional reflection transformation images (RTIs) of two types of rock art. They processed a “portable” petroglyph showing multiple animals, including an elegant deer drawing, in the lab to guide the Portuguese researchers in learning the CHI techniques. In the field, they collected data from an example of the “animated” rock art style — a two-headed goat looking forward and backward.

In the field, CHI personnel captured 60 images taken from different lighting directions in about a half an hour. The entire session took less than two hours to set up and take down gear and test the image files. The new techniques created images where layers of rock art from different eras are clearly defined. For the lab test, CHI staff showed their collaborators how to use the new methods with their existing gear in about half a day. The CHI “students” captured 60 images in about 20 minutes. They repeated the process to collect two more sets of data.

Locations like this one give researchers the ability to make new discoveries with the RTI technique.		Archaeologists and the CHI capture team use a measuring device to ensure proper light distance. View this rock art.

PTMs are shared online with archaeologists, researches, scientists, and scholars around the globe. Read about CHI's 'The Big Picture'.