Ground-penetrating Radar for Archaeological Mapping

Abstract

Ground-penetrating Radar (GPR) is considered one of the more complicated of near-surface geophysical techniques, but also one of the more precise, because of its ability to map buried archaeological features in three-dimensions. Data from many two-dimensional reflections profiles within a tightly spaced grid, can be processed to remove noise, migrate reflections to their correct subsurface location, and then enhance important reflections from subsurface interfaces of interest. Three-dimensional images can then be constructed that produce realistic isosurfaces and amplitude slice-maps of buried features. When GPR reflections are incorporated with information derived from standard archaeological methods, and corrected to depth in the ground using velocity analysis, GPR maps can be used to display a large amount of information from limited excavations to produce a great deal of knowledge from a very large area. At the Albany, New York, town sites, historical maps of the city were compared to GPR images to determine neighborhood changes over time and the changing cultural landscape of one city block from early settlement through the early 20th century. At two sites in California and Colorado no reflections recognizable as cultural or geological were identified in reflection profiles, but amplitude slice-maps delineated spatial patterns that were found to be highly significant. Complex stratigraphy associated with buried cultural features can also be mapped, as illustrated in reflection profiles from aeolian dunes in coastal Oregon.