Greta Bridge

Project Profile

Project Title :

Greta Bridge Community Archaeology Project

Client :


Type of Work :

Community Archaeology, Geophysical Survey

Project Gallery 

let survey commence   resistivity survey underway  
 general view across the fort   the magnetometer cart  
magnetometer cart in action - giddy up   review of the magnetometer result  


Greta Bridge Community Archaeology Project

Revealing the Roman Fort at Greta - Greta Bridge Roman Fort Community Archaeology Project

We have just finished a short programme of geophysical survey at Greta Bridge Roman Fort, commissioned by the Architectural and Archaeological Society of Durham and Northumberland (AASDN). This was a community archaeology project undertaken as part of the HLF funded 'Heart of Teesdale' Landscape Partnership Project.

NAA conducted the survey in accordance with a project brief prepared for the society by Dr David Mason and Niall Hammond. The aim of work was two-fold; both to expand our current understanding of this nationally important Roman site and to provide training in non-intrusive archaeological field survey techniques to local volunteers.

The project started on a chilly Monday in early December with a team of enthusiastic volunteers who were all relative new-comers to geophysical survey. By the end of the week, with expert tuition in resistivity from NAA's Paul Johnson and magnetometry from GSB's Jimmy Adcock, the group went away with a good general understanding of the principles and practices involved in archaeological prospection.

The research aim was to determine the potential survival of any structural remains within the fort interior, and to then examine the areas beyond the ramparts in search of a vicus - a civilian settlement attached to a fort.

NAA first conducted a resistivity survey. This involves the injection of an electrical current through the earth using a twin-Probe electrode system which measures the subtle sub-surface variations in ground resistance. This technique is particularly suited to detecting buried buildings and structural remains but can be adversely affected by localised variations in geological conditions. This appears to have been the case at Greta where the initial results of the survey were vague.

GSB, who many people may recognise from Channel 4's Time Team, then came along to conduct a magnetometry survey of the same area. A magnetometer (sometimes called a gradiometer) records small fluctuations in the earth's magnetic field. This technique is particularly suited to the detection of sub-surface archaeological features such as ditches, large pits, kilns, ovens and other areas of human occupation. The preliminary results of this were a revelation! An area of activity could be clearly identified to the south of the fort, along with a clear plan of the internal fort layout including buildings and a grid of roads.

In addition to the two ground surveys we were also able to build up a 3D digital terrain model of the site using data gathered from the GPS mounted on the magnetometer cart. This model was further enhanced by using high resolution digital photographs taken from a kite-mounted camera. NAA's head of survey, Damien Ronan was then able to enhance the 3D model using a range of techniques we have developed in-house.

Overall, a fantastic amount of new information was gathered across the week. Preliminary results were presented to the volunteers at our offices in Barnard Castle. This was followed by a discussion on what this new information may mean in terms of our understanding of the site. Hopefully the success of this element will lead to further community participation in archaeological fieldwork at Greta Bridge in the future.

Finally, the success of the project was due in no small part to our fantastic and dedicated group of volunteers - Rory Abraham, Eilean Connelly, Stephen Murray and Heather Roberts - who braved the December weather to join us.