Geophysical Surveying
At the beginning of September 2011, a professional geophysical surveyor, Ross Dean of Substrata, began a large-scale geophysical survey in the fields surrounding Poltimore House using a gradiometer.
Ross trained volunteers in this method of geophysical surveying, setting up grids and using GPS. At the end of each day, the results were downloaded so all the volunteers could not only see the results of their hard work but also learn how to process and interpret them.
.JPG)
.JPG)
Gemma Lissaman (volunteer and student) and Ross Dean conducting a gradiometer (Grad 601-2) survey in the 'deer park'
.JPG)
Volunteers discussing the first set of results from the gradiometer survey
We also started a programme of geophysical surveying in the gardens at Poltimore. The main area of focus for the survey was the lawn area located to the north-east of the house. We undertook a resistivity survey using a RM15 with a MPX15 multiplexer to explore the archaeology that may be lying just beneath the surface of the lawn.
This survey method feeds electric currents into the ground and measures the resistance to the flow of the electricity. When the currents meet buried wall foundations high resistance is measured and when the currents encounter silted-up ditches or pits a low resistance is recorded. During a survey areas of high and low resistance are mapped making it possible to identify the layout of buildings and/or enclosures.
RM15 resistivity meter, with a Multiplexer (MPX15) attached, and two probes
In addition, we carried out a gradiometer and resistivity survey with students and volunteers in a field next to the Church of St Mary, Poltimore, to see if we could find any subsurface features indicating the location of a medieval manor. Unfortunately, none were identified!
In the summer of 2012 further surveys were carried out using resistivity in order to sample particular areas that the earlier magnetometry survey had shown to be particularly interesting. Among the many areas surveyed was the flat area to the west of the house, between it and the Chinese garden. The results are very interesting and seem to show the remains of 'lost' gardens. Download the full report on this page to find out more.
