RAPID, HIGH-RESOLUTION TOPOGRAPHIC DATA COLLECTION FOR NEOTECTONIC STUDIES FROM PHOTO-BASED 3D RECONSTRUCTION TECHNIQUES

Neotectonic study areas that are remote or otherwise logistically difficult to access still require high-resolution topographic data but present unique challenges for common methods of survey data collection. For example, our recent active faulting investigations in remote federally-designated wilderness areas of Denali National Park and Preserve had to operate with limitations on the number of helicopter landings allowed, and thus limiting the equipment we could bring with us and the portability of this equipment once in the field. Therefore, along with the typical limitations of time and money, the variety of equipment transport limitations prevented us from utilizing terrestrial laser scanning or total station equipment for developing high-resolution topographic models of fault scarps and related neotectonic landforms. New approaches of photo-based 3D reconstruction accommodate the collection of high-resolution 3D topographic data with simply a handheld digital camera and means for providing scale or georeferencing within the photographed field-of-view. Resolution of photo-based topographic models depends upon the imaging quality of the camera and resolution of input photographs, distance to the target, amount of photograph overlap, angular change between photographs, and computer processing power. Most of these variables will contribute to a topographic model with a variable resolution and accuracy across the target area, but with an optimized data collection scheme can produce models with resolution comparable to airborne lidar and approaching that of terrestrial lidar. We provide examples of different possible data collection and scaling routines for photo-based 3D reconstructions and illustrate how these photo-based models compare with IfSAR and lidar-derived digital elevation models of the same localities.