Sedona Friends of the Forest volunteers generally find plenty to stay busy within the Red Rock District of the Coconino National Forest. Although most activities are currently suspended during the national health emergency, a typical busy season occupies scores of volunteers in trail maintenance, visitor information services, heritage site interpretation, trail patrol, graffiti removal and a wide array of special projects.
One group of specialized and passionate Friends volunteers finds itself in high demand beyond the boundaries of the Red Rock District. These volunteers have developed expertise in the field of 3D photogrammetry and are assisting other parts of the National Forest system, as well as National Parks, State Parks and Universities in a variety of studies and projects.
3D photogrammetry is the art and science of extracting three-dimensional information from photographs by taking overlapping photos of an object, structure, or space, and converting them into 3D digital models. When this technique was first explored by the Friends of the Forest team in 2016, former Red Rock District Archaeologist Travis Bone stated, “photogrammetry is the future of archaeology.”
As explained by FOF team leader Spence Gustav, “High-resolution 3D models of historical and pre-historic sites and objects provide archaeologists, historians, biologists and other scientists with a detailed and accessible database of information. It can be especially useful for comparative analysis to evaluate changes over time, or to reveal greater detail than two-dimensional documentation.”
Gustav and a core team of twelve colleagues have worked through a complex learning and experimentation process to fine-tune photography techniques and optimize the use of processing software in this relatively new field. Merely accessing remote sites by hiking with photographic and logistical equipment, while practicing “leave no trace” etiquette to protect the cultural sites, is a challenge of this work.
The next challenge is “photo acquisition”, the process of taking sometimes more than 1,000 photographs that comprise a single 3D model or the full photo documentation of a site. Acquisition can involve standing on a ladder, lying on lumpy rock, stooping in awkward positions for extended periods – or operating a drone where permitted. Through trial and error, the FOF team has developed methods for controlling variable light and stabilizing camera positions in often delicate and confined spaces to acquire high quality images.
An equally important aspect of this work is the processing of the photos into a high-resolution model. Software and computer capacity for image processing and storage have been donated by the volunteers and updated as the project and technologies progress.
To date, the team has completed detailed photo documentation of over 600 archaeological sites in the Coconino National Forest. This work includes over 100,000 photos of artifacts, stone habitation structures, petroglyphs, pictographs and archaeological features. 1,908 3D models have been produced and more than 14,000 volunteer hours logged.
The 3D photogrammetry work of Friends of the Forest has drawn the attention of individuals, institutions, and agencies well beyond the Red Rock District. Earning three awards in the past three years helped spread the word: USDA Forest Service Chief’s Honor Award, U.S. Department of Agriculture Under Secretary Award for Volunteer Innovation, and the Arizona Governor’s Archaeology Advisory Commission Award.
The FOF team has been approached to assist with documentation and photogrammetry for the National Park Service at multiple sites in Arizona. There has been recent collaboration with the Arizona State Park system at Red Rock and Slide Rock State Parks. A project with Arizona State University is in progress. These projects have taken the team into new subject matter and locations.
The ASU project involves assessment of the impact of lichen growth on rock art through comparative photogrammetry. The FOF team recently supported 3D modeling of an experimental archaeology project for the National Park Service. On the Kaibab National Forest and the Flagstaff District of the Coconino Forest, photographic documentation and 3D photogrammetry has recorded the detail of multiple historic wooden structures. This type of documentation assists in the planning and execution of preservation projects.
Neil Weintraub, district archaeologist with the Kaibab National Forest, said “These models are critical to preserving these fragile sites forever, especially with the threat that wildfires pose to our many historic wooden structures, such as the remote Kendrick Mountain Lookout Cabin. While prehistoric structures and rock art are a bit more resilient than wooden structures, they are certainly just as threatened by fire and vandalism, making the 3D models just as critical for those.”
When the FOF team returns to group activity, projects await on the Tonto and Prescott National Forests, and ongoing work here on the Red Rock District. FOF 3D models can be viewed at https://www.sketchfab.com/FOFSedona. To learn more about Friends of the Forest visit https://www.friendsoftheforestsedona.org
