The Influence of Viewshed on Prehistoric Archaeological Site Patterning at San Clemente Island as Suggested by Analysis of Synthetic Aperture Radar Images

The use of synthetic aperture radar (SAR) imagery collected by the NASA AirSAR platform to detect archaeological site location on San Clemente Island, one of the Southern Channel Islands, has been described in several publications. Here we provide a concise review of the use of SAR for that purpose, as well as a description of how a precise surface model also generated by SAR data was used to examine the spatial distribution of sites by means of viewshed modeling. Results of the direct detection model are evaluated using gain statistics that make use of a recently completed 100% survey of all accessible areas on San Clemente Island. Viewshed analyses generated by use of the surface model suggest a number of economic and ideological factors that might have influenced the distribution of archaeological sites on the island. Among these are intervisibility among locations on both San Clemente Island and nearby Santa Catalina Island that provided the means by which to coordinate crucial substance activities, such as hunting sea mammals, and reinforced the social relationships that were essential to such activities.