Davidson archeologists used what may be the world's longest selfie stick to extend the capability of their science into the third dimension last summer.
Professor of Anthropology Bill Ringle, a veteran of 35 years of exploring Mayan ruins in Mexico's Yucatan Peninsula, obtained a 22-foot-long selfie stick to help create extremely detailed screen images of 1,500-year-old civilization's material culture. Specialized software allowed him to create images of the objects and structures that can be rotated on any axis and viewed from various angles.
Ringle's team spent five weeks beginning making images at seven or eight sites in the Puuc Hills of Yucatan. The region was populated from 600 AD to 950 AD, and the large number of stone houses indicate that it was relatively prosperous. Ringle has been working in this area since 2000.
Before selfie sticks, Ringle said archeologists tried to get overhead views of structures by mounting a camera on a drone or balloon. But the hand-held selfie stick is more mobile and precisely controlled for making images showing structures from above, especially given the tree canopy covering most buildings.
The selfie stick and ground level images captured by the team's off-the-shelf Canon Rebel digital camera were then manipulated with PhotoScan Pro to create three-dimensional views of objects and structures. The software identifies common, overlapping points between frames of the picture and "stitches" together a final image that appears to be three-dimensional.
Ringle said the new technique, called "photogrammetry," yields a screen image that can be turned and twisted to show objects from various angles in extreme detail. But outputting a high quality image requires inputting a huge number of images.
"We would often take many hundreds of images of a structure," explained Charles Rappe '16, an anthropology major who worked on site with Ringle. "You take a picture, then move one step to the side so the next view overlaps slightly with the first. You take a picture there and move another step until you have images of the entire structure. It can be pretty tedious," Rappe confessed.
"Our computer files were enormous," Ringle added. "It took all night for the computer to process the images of a small palace 40 feet long or so."
There were other challenges as well. If image points were misaligned, the program registered blank spots in that area, and the image had to be re-photographed. Additionally, the weather determined the work schedule. Sunny days were bad for photography because of strong shadows. Overcast days with even light worked much better.
And sites often had to be cleared of brush before they were ready to photograph. Rappe said it was often hard work. The typical day began before 6 a.m. with a little breakfast, then a ride to the various sites, some of which were 90 minutes away.
"We were in the back woods a lot, and it seemed like every plant you touched had thorns," said Rappe. "There was also a lot of insect biodiversity-but all of them seemed large! We got scratched, bitten and dirty."
Ringle estimates they made 50,000 exposures in creating images of 60 to 70 buildings and objects this summer. Several examples of the images they created are online.
The selfie stick was also valuable in examining cisterns that the Maya dug to obtain water. Lowering the camera and a light into the cistern, they could take photos of the inside, process the images to produce an image of it, and accurately measure its volume. That was valuable information in estimating the number of people who may have lived nearby and used the cistern.
Just as their work documented the inside of cisterns, they also photographed the inside of structures. In looking at many images, the viewer can pass through doorways from an outside view to a view of the inside.
The work was part of a long-term project in the area directed by Ringle and co-directors Professor Tomas Gallareta Negron, a native Yucatecan who works for the Mexican National Institute of Anthropology and History, and Professor George Bey from Millsaps College.
Ringle has taken students on his summer explorations of Yucatan for 28 years. Rappe, a native of Fort Collins, Colo., who runs hurdles for the Wildcat track team, was thrilled to have been selected for the project this summer.
Rappe said he has become more and more interested in anthropology with each passing semester at Davidson. During the late fall of his junior year he told Ringle, his adviser, that he would like to pursue a doctorate in the field. With that in mind, he asked Ringle to recommend a fieldwork project he could pursue.
Rappe was pleasantly surprised with Ringle's response.
"He said he'd love for me to come to Yucatan with him," Rappe recalled. "I didn't know that he went there every year. Having him offer me the opportunity was great. It showed me he not only appreciated what I put into his courses, but that he wanted to share his interest and his research with me."
Pleased with his first experience in photogrammetry, Ringle expects it will become a standard part of his basic exploration "tool kit." He will also teach students the technique in his classes in Mesoamerican archeology, and present a paper about his recent work at a national meeting along with Rappe as coauthor.