Structure from Motion

Structure from Motion (SfM) is a photogrammetric technique that reconstructs three-dimensional models of archaeological subjects from sets of ordinary overlapping photographs. Borrowed from computer vision, it works by automatically finding the same physical points in many images, solving simultaneously for where each photograph was taken and where those points lie in space, and then building a dense point cloud, a meshed surface, and a photo-textured model. Because it needs only a camera and overlapping coverage, SfM has made high-resolution 3D recording of excavation surfaces, standing structures, artifacts, and whole landscapes (often from drones) fast and affordable. Scaled and georeferenced with control points, the resulting models integrate with GIS for measurement, analysis, and archiving, making SfM a core tool of digital field recording as reflected in Renfrew and Bahn and in the GIS workflows described by Conolly and Lake.