Geophysical survey at Low Bewley: Project Information
About the project
The principal aim of the survey is to assess the nature and extent of any sub-surface features of potential archaeological significance, particularly any that might be associated with the ruins at Beaurepaire. To this end, we’ll use two complementary geophysical techniques across two fields close to the ruins: a magnetic technique, fluxgate gradiometry, and an electrical resistance technique. The magnetic technique uses hand-held magnetometers to detect and record anomalies in the vertical component of the Earth’s magnetic field caused by variations in soil magnetic susceptibility or permanent magnetisation; such anomalies can reflect archaeological features. The earth electrical resistance survey also uses hand-held instruments and can be particularly useful for mapping stone and brick features. When a small electrical current is injected through the earth it encounters resistance which can be measured. Since resistance is linked to moisture content and porosity, stone and brick features will give relatively high resistance values while soil-filled features, which retain more moisture, will provide relatively low resistance values. The techniques and instruments will be explained and demonstrated to community volunteers, who will then conduct geophysical surveys over parts of the site under professional supervision. However, before collecting any geophysical data we will set out a 20m grid across both fields using a global navigation satellite system with real-time kinematic corrections typically providing 10mm accuracy. All data will be downloaded on site into a laptop computer for initial processing and storage and subsequently transferred to a desktop computer for processing, interpretation and archiving. Participants will be able to see preliminary results of their work whilst still on site.
Practical Information
On a practical note, it is very important that volunteers are non-magnetic for conducting the magnetometer surveys. The instruments are extremely sensitive and their ability to detect sub-surface remains is severely hampered if the operator has any magnetic material about their person. Particular things to avoid include: Any metal in footwear and clothing/waterproofs, watches, wallets/coins, phones etc, Under-wired bras We can check each operator against the sensors to see if they are non-magnetic. If anyone cannot be non-magnetic then they can still go through the motions of collecting data, ie still get hands-on experience, but of course we wouldn’t include their data in the final plots. The resistance survey can be undertaken without these considerations, but be aware that this technique involves inserting steel probes into the ground as we walk along and so stout footwear is recommended (for both techniques).
Arrangements and Access
Please meet at the point indicated by the yellow star on the map below - there is ample parking. The working day is 9.30-4.30 (although it may end slightly earlier depending on the light).
The principal aim of the survey is to assess the nature and extent of any sub-surface features of potential archaeological significance, particularly any that might be associated with the ruins at Beaurepaire. To this end, we’ll use two complementary geophysical techniques across two fields close to the ruins: a magnetic technique, fluxgate gradiometry, and an electrical resistance technique. The magnetic technique uses hand-held magnetometers to detect and record anomalies in the vertical component of the Earth’s magnetic field caused by variations in soil magnetic susceptibility or permanent magnetisation; such anomalies can reflect archaeological features. The earth electrical resistance survey also uses hand-held instruments and can be particularly useful for mapping stone and brick features. When a small electrical current is injected through the earth it encounters resistance which can be measured. Since resistance is linked to moisture content and porosity, stone and brick features will give relatively high resistance values while soil-filled features, which retain more moisture, will provide relatively low resistance values. The techniques and instruments will be explained and demonstrated to community volunteers, who will then conduct geophysical surveys over parts of the site under professional supervision. However, before collecting any geophysical data we will set out a 20m grid across both fields using a global navigation satellite system with real-time kinematic corrections typically providing 10mm accuracy. All data will be downloaded on site into a laptop computer for initial processing and storage and subsequently transferred to a desktop computer for processing, interpretation and archiving. Participants will be able to see preliminary results of their work whilst still on site.
Practical Information
On a practical note, it is very important that volunteers are non-magnetic for conducting the magnetometer surveys. The instruments are extremely sensitive and their ability to detect sub-surface remains is severely hampered if the operator has any magnetic material about their person. Particular things to avoid include: Any metal in footwear and clothing/waterproofs, watches, wallets/coins, phones etc, Under-wired bras We can check each operator against the sensors to see if they are non-magnetic. If anyone cannot be non-magnetic then they can still go through the motions of collecting data, ie still get hands-on experience, but of course we wouldn’t include their data in the final plots. The resistance survey can be undertaken without these considerations, but be aware that this technique involves inserting steel probes into the ground as we walk along and so stout footwear is recommended (for both techniques).
Arrangements and Access
Please meet at the point indicated by the yellow star on the map below - there is ample parking. The working day is 9.30-4.30 (although it may end slightly earlier depending on the light).
