§ Mr. DalyellTo ask the Secretary of State for Scotland what preliminary conclusions he has reached about the usefulness of radar surveys in establishing archaeological data about what went on in the outer precincts of great abbeys; and for establishing archaeological precautions on disburbance of ground levels.
§ Lord James Douglas-Hamilton[holding answer 18 June 1990]: Ground-probing radar has been primarily developed for use on building sites where it has been used to detect voids in standing buildings. It works by bouncing electromagnetic waves off boundaries between deposits of different electrical properties. Thus in suitable conditions it can detect stone walls, volumes of disturbed ground such as pits or wells, and some archaeological layers. Simple large features can be identified and interpreted easily. It will not, however, detect features in completely waterlogged soils, and it shares the limitation with other geophysical techniques that strong surface features can mask underlying ones. An advantage over magnetometry particularly relevant in Scotland is that it is not so vulnerable to igneous and metamorphic rocks with strong magnetic fields. Its advantage over other geophysical techniques is that it gives a three-dimesional picture.
Ground-probing radar has not yet been extensively tested and does have limitations. Thus failure to identify physical evidence of underlying structures does not necessarily mean that such evidence has not survived: it may be merely obscured. It is in the nature of archaeological deposits that intrusive methods of archaeological investigation, that is, excavation, remain the only satisfactory method of determining what lies beneath ground level.
It is clear that many of the great abbeys of Scotland had substantial precincts beyond the main nucleus of church and conventual buildings. In Scotland these are almost entirely unexplored. In managing properties in care, the aim of Historic Buildings and Monuments, Scotland (HBM) is the preservation of archaeological deposits in situ. Where this is not possible, HBM will continue to take advantage of modern technology including techniques such as ground-probing radar. This has been used in Scotland at Wardend of Durris and at Whithorn. Increased experience of comparisons between radar traces and features revealed by excavation should allow sampling strategies to replace full excavation, better planning of full excavation, and reduction in exploratory trenching with greatly increased efficiency and reduced costs.