Rock Art Exhibit for Public Archaeology Week

Welcome Shumla blog readers. A special welcome to those joining us for the SAA online Public Archaeology Week!  

If this is your first time to learn about Shumla, we are a non-profit archaeological center conducting rigorous rock art documentation along the United States-Mexico border in southwest Texas. Our mission is to preserve the rock art of the Lower Pecos through documentation, research, and education in order to promote stewardship of this incredible window into our human past. (Click to learn more About Us and our History and Mission). We have developed cutting-edge systemic techniques to achieve our preservation goal. In 2016, Shumla resolved to conduct baseline documentation at nearly 300 known rock art sites in Val Verde County, Texas. This four-year intensive field work venture which began in 2017 is known as the Alexandria Project.

The Lower Pecos Canyonlands of southwest Texas and northern Coahuila, Mexico house some of the world’s most complex prehistoric art. Many of these rock art sites are murals, multicolored and highly complex compositions, painted to communicate indigenous peoples’ understanding of the natural and supernatural world, and their place within it.

In this post readers will have the opportunity to virtually visit one of these incredible sites and explore the rock art with the same tools we use as archaeologists for the Alexandria Project.

Rattlesnake Shelter

The site you will digitally explore today is Rattlesnake Shelter, also known as 41VV180 to archaeologists. The site is a large rockshelter near the Rio Grande. Pecos River style rock art at other sites has been dated between 2,250 BC and AD 660, indicating that the rock art at Rattlesnake Shelter likely has a similar age range. The rockshelter wall contains a long panel of Pecos River style rock art, dense with well-preserved imagery.

Pecos River style rock art is the most common style in the Lower Pecos and perhaps the most recognizable. A core set of motifs are found within the style repeatedly painted across the region, with depictions that remained consistent over the span of thousands of years. The complex compositions depict a wide range of often large, multicolored anthropomorphic, zoomorphic, and enigmatic imagery.

Rattlesnake is considered a “type site” for Pecos River style rock art and has received extensive archaeological attention.

Check out this fly-though video of the 2014 Rattlesnake Canyon 3D model to get a first look. This model was developed by Mark Willis. The video was developed by Jerod Roberts.

Rattlesnake Structure from Motion

Below is a Structure from Motion (SfM) 3D model we generated to record the rock art at Rattlesnake. SfM is a tool that can piece together 3D structures from a collection of two-dimensional photos. In the field we take a series of overlapping photographs with a handheld camera, moving along the rock art panel and making sure our photos capture every inch. In the case of Rattlesnake, the 3D model was constructed from 1165 individual photos covering the 33 meter (108 feet) long rock art panel.

In the lab we use software to stitch all the photos together into an accurate, scaled 3D model which allows us to continue studying the rock art in our offices. By referencing our SfM model to points of known location and scale in the real world, we can take accurate measurements from the computer model in the lab. This allows us to continue collecting data about the rock art long after we visit a site to explore new research questions without having to return to the field.

To navigate the model, use the left mouse button (or one finger drag on a touchscreen) to rotate the model in three dimensions. The right mouse button (or two finger drag) moves the view. To zoom, use the mouse scroll wheel (or pinch in and out with two fingers).

To get acquainted with the rock art at Rattlesnake there are hotspots which appear as numbers on the panel that provide additional information on specific figures. Click on the hotspot number to get more information or use the arrows found at the center bottom of the display to scroll through these hotspots.

But don’t let yourself be limited to these highlights. Feel free to explore Rattlesnake on your own! There’s an incredible number of figures and fine details to view.

Above we gave examples of the anthropomorph, zoomorph, and enigmatic figures we look for in the 3D model. At Rattlesnake our team has identified 98 anthropomorphs, 17 zoomorphs, and 143 enigmatic figures. Can you find a few examples of each in the 3D model?

Rattlesnake Gigapan

Another way we document rock art sites is with gigapixel panoramas or “Gigapans”. Gigapans combine hundreds of overlapping individual photos into a single gigapixel (one billion pixel) image. A robotic system automatically moves the camera in small steps, taking photo after photo. All photos are stitched together in the lab with software to create a single large panoramic photo. The resulting image has high-resolution, depth, and clarity.

Sometimes a rock art panel is so big we have to collect the Gigapans in smaller sections rather than all at once. Rattlesnake is such an example. It took us two days and five Gigapans to capture the whole panel. A tool that helps us identify figures that have faded over time and are difficult to see with the naked eye is “DStretch”. Below is the Gigapan of Rattlesnake Section 1, shown in real color and with DStretch LDS enhancement.

Click the images below to access the Gigapans and move around the panorama. Use the left mouse button to drag the view and the mouse wheel to zoom in and out.

DStretch is software that uses the decorrelation stretch method to manipulate colors, allowing subtle differences between the many colors of paint to be enhanced. Applying DStretch enhancements allows us to reveal paint of specific colors, for example highlighting red or black. In the example below, can you find any details with DStretch that you can’t see in the normal color photograph on the left?

We’ve shared one section of the rock art panel above, but there are four more sections with incredible imagery. The remaining Rattlesnake Gigapans can be explored at gigapan.com:

Section 2: http://www.gigapan.com/gigapans/220411

Section 3: http://www.gigapan.com/gigapans/220367

Section 4: http://www.gigapan.com/gigapans/220365

Section 5: http://www.gigapan.com/gigapans/220362

Shumla has created over 300 Gigapans and over 200 3D models in our quest to record Lower Pecos rock art sites over the course of the Alexandria Project. Many of these are available for public viewing online. See the links below to explore more sites. Thank you for exploring Rattlesnake with us today!

Links

Society for American Archaeology https://www.saa.org

Shumla Alexandria Gigapan Gallery http://gigapan.com/profiles/ShumlaArchaeologicalResearchCenter

Shumla Alexandria 3D Model Gallery https://sketchfab.com/shumlaarchaeologicalcenter

DStretch https://www.dstretch.com

More details on the tools used by Shumla can be found in our previous blog post “High-Resolution Rock Art Documentation and Digital Preservation”. https://shumla.org/high-res-rock-art-documentation-digital-preservation

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