Aerial photography has for some time been of value to archaeologists. Although, as White points out, the features that can be detected using aerial photographs are principally sub-surface stonework (12), they can still contribute to the interpretation of features. When they are digitally enhanced and 'warped' to fit the contours of an Ordinance Survey grid, they offer a much clearer picture of the terrain under study.

The Wroxeter Hinterland Project used an image such as the one in Fig.4 and geo-referenced it onto a British Ordinance Survey grid to produce a raster image. Using this image with the data collected from the sub-surface geo-physical surveys, they were able to produce an accurate plan of the archaeology at the site.

At this stage the only advantage that the computer has over a printed image is that it can be accessed by anyone with a computer that has the correct software. But given that the computer has editing facilities, the image can be manipulated, enhanced and copied.

Therefore the computer can be used to view areas in order to work out project designs, such that notable features can be investigated before the logistical elements of a study are compiled. Furthermore, by using the techniques that were used by the Hinterland Project, the image can be manipulated to include the features of the terrain on the ground.

Image taken from BUFAU's web page. Click here for reference. Cambridge University Collection of Aerial Photographs RC8BC04. This is a vertical aerial photograph of the centre of Wroxeter, with an inset showing Roman roads leading up to a villa, and other features.

After enhancing the aerial photograph the Hinterland Project then geo-referenced it to an Ordinance Survey map of the same area, which means that it was mathematically plotted, as accurately as possible, to the corresponding area of the map. In Fig.4 the photograph was plotted onto a 1:25,000 scale map. Although the scale of the photograph might not be known, it is adapted to the scale of the map, thereby applying scale to the photograph.

Now that the aerial photograph has been given a scale other information can be superimposed onto it. The Hinterland project overlaid the Roman street plan onto the photograph, which showed the Insulae, as in Fig.5. Click here for reference.

Finally, the image was converted into a 3D representation of the site showing the actual elevation of the ground. This can be seen in Fig.6. Although it is shown here as a flat 2D image on paper [worded the same as that which was submitted], if it was viewed on a computer screen that had the necessary software, an operator could 'zoom in' to whatever feature they wanted. However, there are limitations. Depending on the pixel capability of the monitor, the resolution of the image would diminish and the image would lose clarity.

Thus far, what can be concluded about the impact of computers on the investigation of archaeological areas? All that has been shown is that the computer can store, enhance, and manipulate images to produce an accurate site plan. It could be argued that this can be achieved without a computer - and indeed has been by Wilson (13).

The computer does, however, allow a clearer visualisation of the area, and it allows for records to be stored and accessed remotely. The storage of the archaeological record in one medium is an important point. Already, widespread computerisation has had a major impact on the integration of Sites and Monuments Records and Cultural Resource Management (14). This systematic collection of the archaeological record allows the environment and landscape to be analysed before any developments are begun at any site. However, there are at least two very different areas where GIS is having an impact on the archaeological record.

One is the storage of the data for the purposes of keeping a record. The other is in the area of archaeological research and spatial analysis. The Wroxeter Hinterland Project is one of many such studies where the computer is used, firstly as a means by which data can be stored and retrieved using one medium, and secondly the databases provide a flexibility that allows hypothetical modelling and testing to take place. It is therefore having an impact on archaeological methodologies, and has sparked a debate on the relationship between theory and methodology. Before touching briefly on the theoretical side of using computers to investigate archaeological areas, the Wroxeter Hinterland Project offers other examples of how GIS can be used.

12. White, R., Current Archaeology 157 (1998): 14.
13. Wilson,DR., Antiquity LVIII 1984: 117-120.
14. Wilson,DR., Antiquity LVIII 1984: 117-120.