An Evaluation of Geophysical Survey Instruments for Detecting Unmarked Graves at the Mission Cemetery, Spalding, Idaho

In December 2000, a team working for the Midwest Archeological Center and Nez Perce National Historical Park evaluated the suitability of geophysical survey instruments for mapping the location of unmarked graves in the Mission Cemetery at Spalding, Idaho. A small grid was examined with a fluxgate magnetometer, a soil resistance meter, a conductivity meter, and a ground-penetrating radar unit. All but the conductivity meter detected positive anomalies in association with marked historic graves in the test grid. A more extensive use of the conductivity meter might also have yielded positive results. The ground-penetrating radar and magnetometer produced the best results, and additional work was accomplished with the ground-penetrating radar. Several graves that were not marked with stone monuments were confirmed, and the locations of these burial sites were recorded by personnel from Nez Perce National Historical Park. Selected areas outside the cemetery enclosure were examined to ensure that efforts to control pedestrian traffic would not impact graves.