Detection and Identification of Archaeological Sites and Features Using Synthetic Aperture Radar (SAR) Data Collected from Airborne Platforms

Protocols for archaeological inventory of large areas using synthetic aperture radar (SAR) are presented here. They were developed during a 2002–2005 research project sponsored by a Department of Defense Strategic Environmental Research and Development Program Research Project (SERDP CS-1260) on San Clemente Island, California. Archaeological evidence has established that San Clemente Island has been occupied for almost 10,000 years. Some protocols can also be used with other aerial and satellite datasets, such as those acquired by multispectral sensors. Protocols rely upon algorithms to merge data from multiple flight lines, collection of spatially precise ground data with which to develop signatures, knowledge of site morphology, and elegant statistical treatments of sensing-device return values to automate the development of site signatures (in contrast to using the “trained eye” of remote sensing experts). The Introduction of the article presents the study rationale, SAR basics essential to this research, study-site description, and an overview of fieldwork done. The Results section details eight SAR protocols that were developed: data collection, including look angles, flight lines, and choice of band and polarization; data processing and image production, including orthorectification and the merging of data from multiple flight lines; image post-processing, including statistical techniques and iteration of images; corroborative use of multispectral datasets; spatial modeling; procedures for incorporation into and analysis with GIS; establishment of statistically based site signatures; and procedures for ground verification. In the Discussion, the authors extend some of their findings to archaeological research at San Clemente Island and beyond. The article concludes by highlighting some important management implications for the use of SAR as an archaeological evaluation tool for sizeable land areas. In environments not too dissimilar to those on San Clemente Island, these protocols can produce planning level inventories much more rapidly and inexpensively than field methods commonly used at present can.