This presentation is part of the 2017 3D Digital Documentation Summit.
A Bird’s Eye View: Photogrammetric Documentation using Drones
Technology is rapidly changing the way historic preservation specialists document and assess historical and cultural resources. Efficient methods for data collection are at the forefront of many preservation conferences and workshops. Much focus has been placed on 3D imaging technologies like laser scanning and photogrammetry as they are becoming more widely used for recording heritage sites. Developed in the late nineteenth century, photogrammetry is the science of acquiring measurements from photographs. Like many technologies of the period, photogrammetry developed rapidly during World War II and played a significant role in post-war restoration. The wider-scale acceptance and utilization of point cloud producing technologies, like photogrammetry, has led many preservationists to seek innovative solutions for streamlining the data collection process. This paper presents the workflow process and outcomes of a pilot study that utilized an unmanned aerial vehicle (UAV), commonly referred to as a drone , to conduct photogrammetry of a mid-century modern church. The tall, pointed roofline and character-defining copper spires of the building posed a challenge for access, making it a good candidate for the use of photogrammetry via drone. Among the benefits, drone-based photogrammetry provides preservationists with opportunities to acquire geo-located data of inaccessible areas of heritage resources, more cost effectively than aerial photography and, more safely than traditional harness and rope rappelling methods.
However, there are limitations due to recent Federal Aviation Administration licensing requirements, the operation of drones does require specialized training and a Remote Pilot Airman Certificate. There are often many uncontrolled site conditions that need to be addressed. One limitation of the drone used for this study is the rolling shutter mechanism of the built-in camera. A rolling shutter is a capture method which exposes the camera sensor line by line from top to bottom instead of exposing, like the traditional DSLR camera, the entire sensor simultaneously. Rolling shutter cameras sometimes produce artifacts on the image and extra care is needed in the acquisition process. This paper explores these and other outcomes in more detail and offers a set of considerations when recording heritage resources with drone-based photogrammetry. Demand for drone technology has increased the quality of drone cameras and flight software while decreasing price points. The rolling shutter limitation of the Phantom 4 has already been mitigated with the release of the next generation of this drone. Future improvements in drone technology promise increased flight control and automation which will lead to increased maneuverability and quicker data acquisition. These improvements and lower prices will increase the value of drones for historic preservation.
Marla Holden is a second-year PhD student at the University of Florida at the Center for Advanced Construction Information Modeling, where her research interests include the application of technologies to cultural heritage resources such as historic building information modeling (HBIM) and unmanned aerial vehicle (UAV) photogrammetry. Marla returned to graduate school after working in the construction industry for 20 years as a Preconstruction Executive specializing in High-End Resort Hotel Development. In addition to her studies and research, Marla has begun applying her industry knowledge and experience as a Graduate Teaching Assistant in the classroom. Upon completion of her degree, Marla’s goal is to obtain a posting as a lecturer professor and help educate the constructors and preservationists of the future.
Morris (Marty) Hylton III is Director of the Historic Preservation Program and Preservation Institute Nantucket at the University of Florida’s College of Design, Construction and Planning. His research addresses multifaceted strategies for documenting and advocating the preservation of endangered heritage sites, particularly cultural resources associated with modernism and the Recent Past and historic places and communities endangered by sea level rise and other threats. Marty also created and manages the Envision Heritage initiative to explore how new and emerging technologies like laser scanning can be used to document historic sites and cultural resources.