Boulders, outcrops, caves: Documenting cultural use of landscape features in the San Diego region of California

Cultural features such as mortars, basins, and slicks on rock outcrops, boulders, and cave floors have been identified in many parts of the world. They clearly evidence the long history of human use of landscape features; at the same time, they are under-investigated and not well incorporated into archaeological interpretation. Indeed, even accurate documentation of such features is rare, if presented at all. Advances in digital techniques offer archaeologists new tools to address the situation. We recently piloted a new methodological protocol for the efficient and precise documentation of cultural landscape features at two sites in San Diego County, California. In this paper, we describe techniques for the creation of a high-resolution model of each site, of specific rock outcrops or boulders within each site, and of individual cultural features by using Structure from Motion photogrammetry. We present examples of various analyses that are possible once the 3D models are constructed, on intra- and inter-site levels. Our use-wear studies of 159 features and of a curated handstone collection provide new insights into past use of shallow and deep features.