GEOPHYSICAL SURVEYS
Since the site was discovered, geophysical surveys have been carried out on site. These surveys allow us to gain an understanding of archaeological features that lie below the surface of the ground, without causing any disturbance by digging. There are a number of different forms of geophysical survey, and each type of survey works in a different way to reveal the location and nature of the archaeological features.
COMBINING DIFFERENT TECHNIQUES TO OBTAIN THE CLEAREST PICTURE
The emphasis on collaboration has helped to reveal what lies beneath.
Geophysical survey works best when a variety of techniques are all combined, to give a cohesive picture. And that is exactly what has happened at Woodstown, where state of the art surveys have been conducted to give us an exciting glimpse of what lies beneath the surface.
WHAT LIES BENEATH
Geophysical Surveys are non-invasive, meaning that we can gain a good sense of the archaeology without impacting the features
Ground Penetrating Radar
In 2018 a detailed Ground Penetrating Radar Survey (GPR) was carried out by geophysicists from Vestfold Fylkeskommune in Norway, led by Dr. Petra Schneidhofer and Christer Tonning. This large scale survey of 10.7 hectares revealed the site in new resolution. Another phase of survey was carried out in 2024, and helped to complete the picture.
GPR works by transmitting an electromagnetic pulse into the ground at regular intervals. These pulses then reflect off features below the surface of the ground and are detected by a receiver antenna. By measuring the strength and time delay of the responses it is possible to estimate the depth and shape of the sub-surface features.
This survey technique is highly specialised, and it was possible at Woodstown thanks to the collaboration with Vestfold Fylkeskommune, and with support from National Monuments Service.
Resistivity and Magnetometry Surveys
In 2022, 2023 and 2024, further geophysical surveys were undertaken led by Dr Susan Curran of The Discovery Programme who carried out a large scale resistivity surveys and Ger Dowling who carried out magnetometry surveys.
Electrical resistivity survey is an effective geophysical technique, that helps to define archaeological features like the foundations of structures, or infilled ditches and pits. It works by sending an electrical pulse through the ground. The resistivity meter records localised variations in current flow and therefore resistance between metal probes inserted into the ground surface. If they meet high resistance, that may suggest a feature like a stone wall. Whereas low resistance might signify a ditch.
Magnetometry surveys record spatial variation in the Earth’s magnetic field. Different materials below the ground can cause local disturbances in the Earth’s magnetic field that are detectable with sensitive magnetometers. This might show up areas of burning, perhaps indicating a hearth or industrial activity. It can also detect infilled features like ditches and pits.
By combining these three datasets, along with the detailed topographical survey, we now have a much more detailed understanding of what lies below the surface of Woodstown. These surveys will help to guide future excavation at the site.
In 2021, there was a collaborative workshop with 18 participants, including some of the leading experts in Viking-Age archaeology from Ireland, the UK and Scandinavia. It helped to interpret and identify many of the features highlighted during the surveys, and underlined the international significance of Woodstown.
