Utilizing Historic Cartography in 3D for Archaeological Prospection on Alcatraz

Archaeologists have used non-destructive investigations to assess the potential and predict the presence of archaeological resources; aerial and geophysical surveys being the predominant methods to accomplish this task. Some historic sites have the benefit of many years of cartographic documentation offering up another non-destructive method of investigation. By georeferencing high resolution scans of 19th century maps of Alcatraz procured from the National Archives and digitizing contour lines and structures within the maps, a three-dimensional (3D) model can be created within a Geographic Information System (GIS). Each map surface can then be superimposed over subsequent map surfaces to visualize changes through time. The potential for buried features can then be deduced by analyzing these changes. This paper presents the results of recent cartographic work demonstrating this method of archaeological prospection and subsequent archaeological work that has validated the cartographic analysis.