NEW DEVELOPMENTS IN ROCK ART IMAGING:

Recovered image of a deer,

white lines reproduced on the

computer generated image,

Grottes d'Agneux II,

archaeology.org.

Back in the 1980s I was contacted by a small tech startup company that was developing what they presented as new technology for imaging. Essentially, their work involved taking a number of high definition photographs of a site and then performing magic in a computer that turned them into a three dimensional image that could be used among other things, for taking precise measurements. They were looking to develop new markets and wanted me to guide them to some archaeological sites. I countered by offering to take them to some rock art sites, and they accepted although not fully enthusiastically. I think they pictured themselves working at places like Mesa Verde, but, with me, they ended up in the Picketwire River Canyon south of La Junta, Colorado, recording two different petroglyph sites. I had it in mind that what they had been promoting to me might be useful for things like analyzing superimposition, and bringing out details that might be difficult to see from just one angle. I never found out because after our return to home I never heard from them again, and never even got a response to my inquiries. My guess is that they were less than successful. I bring this up as an introduction to the following subject.

Scientists have recently recovered the engraved images of a horse and a deer from one of two caves known as Grottes d'Agneux in eastern France. The images on the walls of Agneux II had been totally obscured with layers of names, initials, and graffiti left by visitors from the 16th to 19th centuries.

"Scientists with the university (of Tubingen) in Germany and researchers from Spain recently used scanning technology to peer through graffiti layers, reconstructing carved prehistoric images of a horse and a deer buried underneath. After scans revealed the figures, the scientists reconstructed the artwork with image-processing software." (Weisberger)

Although the articles I have seen so far do not mention the specific technology I suspect that the work was done with a laser scanner. I can imagine a process like Lidar should be quite effective.

Having recovered the images "then, they used charcoal found in the caves in order to determine the age of (the) drawings. Using carbon dating, researchers determined that both pieces are approximately 12,000 years old and belonged to the Upper Palaeolithic period." (Bashir)

Modern technological developments are allowing almost miraculous new techniques in analysis, imaging, and recording. This might truly be the golden age of rock art studies.

NOTE: The image in this posting was retrieved from the internet with a search for public domain photographs. If this image is not intended to be public domain, I apologize, and will happily provide the picture credits if the owner will contact me with them. For further information on these reports you should read the originals at the sites listed below.

REFERENCES:

Bashir, Hira

2018 Prehistoric Cave Art Found Hidden In Graffiti, November 16, 2918, https://www.i4u.com/2018/11/130135/prehistoric-cave-art-found-hidden-graffiti

https://www.archaeology.org/images/News/1811/France-cave-grafitti.jpg

Weisberger, Mindy

2018 Ice Age Cave Art Found Under Layers of Centuries-Old Graffiti, November 15, 2018, https://www.livescience.com/64099-cave-art-under-graffiti.html

AN EXCITING NEW TECHNIQUE – 3-D RECORDING OF PETROGLYPHS WITHOUT TOUCHING THE ROCK SURFACE:

Back about 30 years or so rock art recording was much less sophisticated and technical than it has become since. It was also less effective and often caused serious damage to the rock surface. Rubbings required pressure on the rock face and often bled chemicals through to the rock surface. Photographic recording was often done with materials applied to the petroglyph to enhance the contrast in the photo. The most egregious example of that I know of is in the canyon of the Purgatoire River in southeastern Colorado where a line of petroglyph characters was carefully painted in with aluminum paint to show up well in photos. One very popular technique was the creation of a silicon latex or rubber peel, or mold taken by painting the liquid latex on the surface. This was peeled off the rock after curing and then used as a mold to make casts of the petroglyph with plaster. One problem with this technique is that it all too often pulled portions of the rock surface away too, irreparably damaging the petroglyph. As somewhat of an aside, I have seen one site where some moron tried to make a plaster cast of a petroglyph, and didn’t even know enough to use a release agent on the rock surface. The plaster stuck, of course, and was then obviously chipped off by hand with results you can imagine.

Fig. 1 - Scan of shield figure petroglyph,

input on computer screen.

Photo: Tim Urbaniak.

I received some truly exciting information and pictures from Tim Urbaniak at Montana State University in Billings, Montana, about a new technique of three dimensional recording of petroglyphs that does not require any touching of the rock surface, let alone adding material to it. Tim is a doctoral student, and has spent the last decade exploring applications of technology to archaeology and historic studies as the director of the MSU Billings Archaeology Field Team.
The recording was done with a Polhemus FastSCAN Scorpion unit. Tim has found it to be accurate to about 1/3 millimeter. A handheld unit contains two cameras and a laser unit which sweeps the rock face when the trigger is pulled while the cameras record the resulting sweep from two different angles. The resulting signals are analyzed with software which provides a detailed record of the distance to any point on the rock surface. Figure 1 shows the resulting scan pattern on the computer monitor screen. The data can then be used to generate a three dimensional image of the surface in the computer as shown in Figure 2.

Fig. 2 - Scan data result processed, shown

on computer screen. Photo: Tim Urbaniak.

The best part comes with the final option offered by this digital technique. The computer can also use this data to recreate a three dimensional facsimile of the surface using rapid prototyping techniques. Figure 3 shows a resulting reproduction in ¼-scale in (I presume) Tim’s hand. This rapid prototyping might be done using a milling machine to carve the shape into a block of material, or with other techniques which build the shape up with layers of cut paper or by selective hardening of liquid plastic cast in thin layers. Many other methods can be imagined as well, the point being that once the original scan has been done and the digital recording is made, it can be used in many different ways and preserved digitally for future developments.

Fig. 3 - Shield figure petroglyph reproduced

with rapid prototyping. Photo: Tim Urbaniak.

Think of it, a virtually perfect, permanent, three dimensional record, made with no touching of the rock face, digitally preserved for future possibilities. Thank you Tim!