The Use of Complementary GPR Surveys with Different Grid Spacing to Locate Unmarked Graves in a 19th Century Cemetery in Selinsgrove PA

Abstract:

Ground-penetrating radar (GPR) is a geophysical survey tool with many archaeological applications, including the search for graves. A 400 megahertz GPR was employed to locate unmarked graves and buried headstones in a neglected Pennsylvania cemetery dating from the 19th century. The site was initially scanned using a grid pattern with 50cm transect spacings. A smaller site within the cemetery was then selected and scanned at a higher ‘resolution,’ using smaller transect spacings, to determine whether this improved the accuracy of the findings. Supplementary perpendicular transects were also added. A number of potential sources of error were identified and their consequences were outlined. Short transects with small spacings were found to significantly improve the quality of the obtained data, as was the addition of perpendicular transects. The results are applicable to the search for graves and, more broadly, the use of GPR to identify and locate other subsurface features.