North American Database of Archaeological Geophysics
North American Database of Archaeological Geophysics
Abstract/Summary:
Project Name: St. Paul's Cemetery, NB. Geophysical Survey
Reference:
On October 12, 2003 a magnetometer survey was conducted at St. Pauls Cemetery in New Brunswick, Canada. A Bartington 601 Grad fluxgate magnetic gradiometer was used with a vertical sensor seperatation of 1 meter (depth of scan is up to 3 meters). Two sized grids were surveyed (10x10m, 20x20m), each at 1m traverses with readings every 12.5cm. To avoid interference from the metal fence, a base line was established 5m from the west edge of the cemetery and 5m from the northern edge. Four 20m x 20m grids were laid out along the western side of the cemetery and three 10m x 20m grids were laid out in a north/south line adjacent to the northern 20m x 20m grid.The data logger was set with a sensitivity of .1nT (nanoTesla). Since the graves are oriented in an east/west direction, traverses were oriented perpendicular to the graves starting in the southwest corner of each grid (heading north) and walked in a parallel formation.
Data was processed using Golden Software's Surfer 7 and presented using Surfer's image map format with interpretation through Adobe Photoshop 7. Due to the extreme high (3000 nT) and low (-3000 nT) readings of the modern headstones and the cast iron headstone, data was clipped at a minimum of -100nT and a maximum of 100nT. This procedure effectively reduced the 'glare' from the modern headstones and detritus to illuminate the combination of the grave shafts and coffins. Many of the linear anomalies that showed up after processing were identified as graves by mapping that coincided with the geophysical survey.