This work shows the picture of human occupation and activity in the Vale of Pickering, pieced together from the oblique aerial photographic record, to be flawed, particularly as a result of the lack of continuous cover and the variable return provided by the oblique air photographs. The site-centred interpretation that the oblique record generates makes the overall assessment of the landscape both difficult and biased in favour of 'good-sites'. The low-level vertical photography and multi-spectral imagery acquired over the study area on a single date by the National Environment Research Council (NERC) proved to be a very effective method of enhancing the detail and the breadth of coverage of the conventional record collected over more than a decade. Donoghue and Shennan (1988a; 1988b) had already demonstrated the potential of multi-spectral data for the identification of archaeological features as soil marks; this research demonstrates the effectiveness of the combined use of colour APs and multi-spectral scanning for fields under crop on a wide range of agricultural land.
Simple visual scanning of the MSS data revels a wealth of information almost matching, and in many cases extending, that gathered over a ten year period of conventional air photography. The responsiveness of the thermal MSS band in particular provides crop-mark evidence in areas of grassland and pasture that cannot be seen using conventional techniques, although even in this case the response is poorer than in those areas under crop and producing conventional crop-mark evidence. The broad swathe width (1.5km), continuous coverage and speed of data collection provided by the MSS scanner make this an ideal tool for assessment of areas subject to pipeline and road schemes, as well as broader landscapes. For assessment terms full analysis is unnecessary, since visual scanning and simple filtering of the data will allow most features to be identified.
The Daedalus scanner used in the present experiment is now more than a decade old, in technological terms a period of intense development, and newer instruments with broader overall spectral resolution, more precise band-width control and greater ground recording resolution will give better results. Improved software and hardware have made on the fly rectification possible and the increasingly cheap availability of powerful computer work-stations has brought image-processing facilities within the range that is affordable by archaeological research and management organisations. The potential offered by the combination of a seamless mosaic of digital MSS imagery, draped onto a three-dimensional landscape model and superimposed with geophysical surveys, vector plots of plans, and databases linked to photographic images, field notes and spot find information in a Geographic Data Management System is tremendous; providing for the first time the facility for detailed landscape management and assessment on the desktop.
This project has demonstrated that an impressive picture of the archaeological landscape can be obtained without the use of invasive and expensive methods, by effective use of the array of remote sensing techniques now available to the archaeologist. The picture that emerges from the remote sensing is of course lacking in detail. Feature identification and dating is, as always, a matter of interpretation, relationships between features are generally unclear making the unravelling of the palimpsest of different features another matter of interpretation; only through excavation can these details be established. The picture established through remote sensing is moreover not complete; the very limited amount of detailed MSS work undertaken so far does not demonstrate that this method is a catch-all method. We need to undertake more experiments of this type at all times of the year, to test responsiveness under a broad range of climatic and ground conditions. Each type of non-invasive prospecting requires certain conditions to apply in order that features can be identified; even then small features such as post-holes and shallow pits, as well as features filled in with material similar to, or the same as, the surrounding subsoil, such as graves, are particularly difficult to detect. However, as a consequence of the increased level of archaeological knowledge of the areas surveyed, remote sensing provides a basis on which planning policy and excavation strategies can be established. Its usefulness in detecting sites invisible using conventional techniques is now proven beyond doubt, and as more of these surveys are carried out, our knowledge of how the landscape as a whole was utilised in the past can only increase.
©
Internet Archaeology
Last updated: Wed Apr 23 1997