BLM sets trend in research of Puebloan ruins

3-D modeling photo technology tested at Canyons of Ancients

A photogrammetric 3-D model of an ancestral Puebloan mug was created at the Anasazi Heritage Center research labs.


The BLM is at the forefront of a new trend in archeological research that uses digital photography combined with a modern desktop computer.

Called close-range photogrammetry, the technology uses overlapping digital photos and advanced software to create the most accurate 3D computer models of artifacts and ruins ever recorded.

A new pilot program spearheaded by the BLM National Operations Center is using Canyons of the Ancients National Monument as a testing ground for photogrammetry, and the results are promising.

Vince MacMillan, CANM archaeologist, has been experimenting with the process on museum pieces at the Anasazi Heritage Center, and in the field to analyze the condition of at-risk ruins on the monument.

"We're able to build 3D photographic models with accuracy down to less than a millimeter, about the size of a grain of sand," he said during a demonstration of the technique. "The scale of the technology is amazing, and there are many uses for monument management and public education."

As an educational tool, there are many advantages.

The super-accurate 3-D images of ruins can be rotated to view from any perspective.

They can be e-mailed to Native American tribes for input during the consultation process. Sharing the images with universities, high-school classrooms, and researchers will be much easier as well. An 800-year-old vessel can be intensely studied on a screen, without fear of dropping it.

Museums can show hyper-accurate digital displays of remote, fragile structures on the monument, allowing public access without the risk of over-visitation.

"Another use is that we can create a archival 3-D model of our special exhibit room with all of the displays so it could be revisited," MacMillan said, noting that the process was successfully applied to the recent Stanton Englehart art exhibit.

Computer power

The applications of photogrammetry are poised to change the way the archaeology profession documents, archives and researches ruins and artifacts.

And it is all thanks to the powerful processing power of a typical desktop computer and basic digital cameras.

When a ruin undergoes photogrammetry documentation, a huge amount of data is collected from the camera. Millions of data points from hundreds, even thousands, of overlapping photographs are entered into specialized computer software to eventually create the precise 3-D digital image.

"There has been such an increase in processing power, you don't need a supercomputer to do this stuff now," MacMillan said. "Even so, it is a lot of data. For my computer to process a 3-D model it takes 3-4 days, running 24 hours per day at 100 percent CPU."

Ten years ago, the process would have required a bank of hard drives.

New information

At Moosehead Tower, the process revealed problems that archaeologists were previously unaware of, MacMillan said.

The fragile, Hovenweep-style tower has a 25-foot wall that looks unstable at the foundation because of missing mortar. But after a 3D model was created from 900 photographs, researchers realized the wall is actually dangerously leaning.

"The base corner looked like our priority, but it has self-stabilized. The west wall is leaning in a way we did not know until we saw it in the model," MacMillan said.

At the Lightning Tree ruin, photogrammetry revealed an oblong shape rather than the perfect circle previously thought. The 3-D process can also be used to more precisely document rock art panels.

The technique is getting attention because it is more convenient and efficient, and can document a structure at a particular moment in time allowing for comparison later.

Plus it saves time and money.

"Using levels and tape measures, laser surveys, doing the drawings, takes months. Photogrammetry presents opportunity for huge savings, and it is more accurate," MacMillan said. "As a management tool we can better prioritize where to spend out tax dollars."

The BLM is seeking additional funding to ramp up the pilot program.

"It provides us greater efficiency," said monument manager Marietta Eaton. "We can document status of sites with standing walls and rock art in a fraction of the time, and the information can be broadly transferred."

Monument officials want to focus on creating 3-D models of the 13 ruin sites the public is encouraged to visit.

"We could use this in public presentations and with visits with tribal elders who may not be able to make it to the field," Eaton said.

CU collaboration

The University of Colorado's architecture and preservation department in Denver has teamed up with the BLM and the monument on the project.

Students at the Denver campus have been getting training in modern photogrammetry at select ruins on the monument.

Monument officials hope to develop a masters level field school in photogrammetry with CU Denver. Students would spend weeks at time documenting ruins at the monument using the technology.

"Students love it because all they need to get started is a basic camera," MacMillan said.

Canyons of the Ancients has several thousand standing structures, and most have not been comprehensively documented.

"My dream would be to have additional archaeologists conducting photogrammetry on ruins in the monument," MacMillan said. "Just capturing the data with a camera would be a start. When the time comes and you want to look at a site, you can tell the computer to build the 3D model."

Photogrammetry does not replace traditional Light Detection and Range (LIDAR) laser technology used to document archeological structures. And there will always be a need for hands-on surveys and detailed drawings.

"There are limitations, for instance photogrammetry requires good lighting, difficult in kivas and inside rooms," McMillan said. "It's another tool."

Digital archives are not guaranteed either, he said.

"We don't have a good idea of the archivability of data. Will anyone be able to open this file in a hundred years? A drawing is something more permanent."

Vince MacMillan, an archaeologist with Canyons of the Ancients National Monument, explains photogrammetry technology, which creates 3-D images of ruins and artifacts. Enlargephoto

Jim Mimiaga/Dolores Star

Vince MacMillan, an archaeologist with Canyons of the Ancients National Monument, explains photogrammetry technology, which creates 3-D images of ruins and artifacts.

A photogrammetric 3D model of a Pueblo III masonry tower, AD 1250, located on the monument. Enlargephoto

Cortez Journal/Jim Mimiaga

A photogrammetric 3D model of a Pueblo III masonry tower, AD 1250, located on the monument.

A photogrammetric 3D model of a Pueblo III masonry tower, AD 1250, located on the monument. Enlargephoto

Cortez Journal/Jim Mimiaga

A photogrammetric 3D model of a Pueblo III masonry tower, AD 1250, located on the monument.

Vince MacMillan, an archaeologist with Canyons of the Ancients National Monument, explains measuring devices used in photogrammetry, a 3D technology being tested on local ruins. Enlargephoto

Cortez Journal/Jim Mimiaga

Vince MacMillan, an archaeologist with Canyons of the Ancients National Monument, explains measuring devices used in photogrammetry, a 3D technology being tested on local ruins.