6. Discussion

6.1 Summary of results

The following conclusions were reached with regard to the geophysical survey objectives. A number of further elements of the fortress plan were identified. The gradiometer survey identified probable traces of internal structure in the south-western section of the rampart. The area of the south gate was marked by strong magnetic disturbances, related to modern disturbances or soil-improving materials, though some anomalies hint at the possibility of preserved structures of a gateway in this area. While no anomalies in the interior of the fortress can be confidently identified with fortress-features, some magnetic responses are found in locations that may indicate a relationship: at a road corner, in the middle of a courtyard, or in the gable room of a house. While the anomalies in question appear similar to many others, their location is conspicuous. Two strong linear anomalies aligned with the southern part of the north–south axial street appear to represent ditches relating to the fortress. Less prominent anomalies, though not specifically interpreted, probably relate to wall posts or principal posts, hearths or other features.

In general, the large buildings from the fortress seen in the excavations could not be confidently identified in the surveys. It is likely that the limited length of occupation of the fortress resulted in features that are not particularly magnetically prominent, and are obscured by the background of strong geological trends and pre-fortress activity. Moreover, the spacing of the traverses implies that it is unlikely such features could be traced consistently. The extent of areas with deep, anthropogenic soils, cultural layers or levelling layers could not be clearly identified.

The survey was very successful at locating activity interpreted as belonging to the pre-fortress phase. Concentrations of large, positive magnetic anomalies of a size and shape consistent with SFBs can be identified in the gradiometer survey adjacent to the areas where they are noted in excavations. A previously unknown concentration of possible SFBs in the south-east quadrant of the fortress area, together with linear features in the same area, suggests that structures associated with the pre-fortress settlement are also present in this area, either in the form of buildings relating to one or several additional farms, or an activity area connected with a landing place. The interpretation of these anomalies as representing more of the shallow, round cuttings with a diameter of 2-4m and cut to a depth of less than 50cm into the natural is substantiated by the radar survey, in particular GPR Grid 5. The radar survey also corroborates the absence of SFBs in areas where they are not indicated in the gradiometry survey, in particular GPR Grids 2 and 3.

The anomalies identified as potential SFBs occur only in some areas, and thus a clearer picture of the settlement structure is achieved. With few exceptions these features cluster in three areas: in the eastern half of the fortress area and east of the fortress; in the survey west of the fortress area; and in the south-east quadrant of the fortress and the adjacent area outside the fortress. The character of the magnetic responses over some of these features is such that they are interpreted as having burnt down, which ties in with the interpretation of excavated evidence from pre-fortress buildings. A row of SFBs to the west of the fortress can be observed to align exactly with the fortress gates, presumably following a path that emerged after the construction of the fortress. Finds from two excavated buildings in this row are dated to the 11th century, thus the survey confirms a hitherto ill-defined post-fortress phase of activity. Based on the integrated survey it may be proposed that as many as 200 SFBs exist within the surveyed area, in addition to those previously excavated. It is, however, worth noting that while the excavations have driven the assumption that other SFBs in the vicinity are of pre-fortress date, those identified by geophysical survey have no definitive dates associated with them. The degree of contemporaneity between these features is difficult to establish through magnetic data alone, although GPR Grid 5, for instance, suggests some overlapping of features.