Introduction
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AERIAL ARCHAEOLOGY AND AIR PHOTO MAPPING IN BRITAIN Introduction The published papers of the fourth Ciclo di Lezioni at Siena in January 1991 already contain a general description – from the British viewpoint – of the basic principles and practice of oblique and vertical air photography for archaeological research and conservation (MUSSON, WHIMSTER 1992). Only a few points need further emphasis here, as an introduction to an up-dated de scription of procedures for the mapping and documentation of information from air-photographs in Wales (and, in passing, in other parts of Britain). The merits of vertical air photography for the discovery, recording, mapping and documentation of archaeological sites and landscapes, of all periods, have long been recognised, and this source of information has been extensively exploited in northern Europe, and to a certain extent at least in Italy. The particular value of overlapping, and therefore stereoscopic, images covering the whole of any landscape under study, needs no emphasis, com pared with the more partial record provided by targeted oblique photogra phy. But archaeologists often experience problems in gaining access to the vertical archives, and quickly come to recognise that vertical photography taken for military purposes, for survey or for monitoring has all too rarely been taken in conditions of lighting or crop-development that favour the rendering of archaeological detail. These shortcomings will always limit the power of vertical photography if applied in isolation. The papers given at Siena in the 1999 symposium, moreover, made it abundantly clear that high-resolution satellite imagery, at 1m or better dis crimination and with passes every few days over any part of the globe, will very soon supplement the information available from traditional vertical pho tography, and may in some respects (in time) replace it. In theory, at least, tomorrow’s archaeologist will be able to choose from repeated coverage of any desired target area, and will enjoy a greater chance of identifying im agery which shows cropmarks, soilmarks, earthworks or built remains to best advantage. Progress in this area will surely be rapid in the coming years, not least through the opportunity to experiment with a wide variety of dig ital data, readily capable of manipulation to enhance archaeological detail or context. ©2003 Edizioni all’Insegna del Giglio - vietata la riproduzione e qualsiasi utilizzo a scopo commerciale – 1 That said, experience from Britain and other parts of Europe suggests that relatively traditional oblique air-photography, undertaken preferably by archaeologists and in any case specifically for archaeological purposes, will continue to be a fruitful – indeed essential – component in the effective ex ploitation of the aerial viewpoint for the discovery, recording, interpreta tion, mapping and documentation of the historic environment (see MUSSON 1994). While digital cameras (soon but not quite yet) and increasingly so phisticated in-flight aids (like GPS and digital displays of the known archae ology of the flight area) may enhance the efficiency of the air-borne opera tion – and to some extent the time-consuming post-flight procedures – the advantages of such purpose-made air photography will remain the same. – The photography will from the outset benefit from clear archaeological ob- jectives, whether in primary reconnaissance (the first search over areas of sus pected but as-yet unrealised potential) or in problem-oriented research (such as the definition of road-lines or agricultural patterns round Roman or later settlements). – The objectives will be directly understood by the archaeologist-photographer, through years of archaeological and aerial experience, so that every part of the landscape will be examined, with understanding, for its archaeological potential. – Recording will be done at the time of year, time of day or state of crop development best capable of revealing archaeological information, and the angle of view will be chosen to provide the most striking, most informative or most ‘mappable’ presentation of the evidence available by the camera. – While the information in the photographs will best reach other archaeolo- gists, planners and conservators through mapped and documented transcrip tions, the photographs themselves will still have an intrinsic value. Powerful images – whether of ‘new’ sites or of known monuments, landscapes or townscapes – will (on British experience) figure prominently in the public pres entation of archaeology and hence in raising awareness of the historic environ ment and of the need to protect it from unnecessary damage or destruction. The more ‘remote’ forms of aerial recording (by vertical photography, satellite imagery and the like) will never replace these characteristics of ar- chaeologically-directed low-level air photography, taken by well-informed aerial archaeologists who know the current state of recording and research in their area, who appreciate the kind of information needed for research and conservation, and who have an eye for the striking image (along with the experience to capture it on film). Equally essential, however, will be the capacity to find practical ways of getting into the air (at reasonable cost, within the local context), and of over coming bureaucratic or other restrictions on the practice of aerial photography. While experience elsewhere may provide helpful examples, the lesson from re- ©2003 Edizioni all’Insegna del Giglio - vietata la riproduzione e qualsiasi utilizzo a scopo commerciale – 2 cent experience in central and eastern Europe is that local people must find local solutions, not only to bureaucratic impediments but also to the definition and exploitation of an aerial archaeology adapted to local needs and conditions. There is no single kind of aerial archaeology to which people elsewhere should aspire (such as the rich cropmark archaeology of lowland Britain or, in Italy, of the Tavoliere). Regions without significant cropmark evidence may offer much by way of soilmark recording or earthwork archaeology. The traces of urbanisation or industry will almost always be susceptible to fruitful recording from the air. And everywhere there will be the broader landscape of topography and land-use which provides both the modern and the ancient context for archaeological remains of all periods. The contribution of aerial archaeology will inevitably vary from country to country, and from region to region. But, wherever it is applied, it will only realise its full potential when it mobilises low-level oblique photography along side vertical photography, satellite imagery and other remote-sensing techniques in a mutually supportive co-operation. Further, it will be at its most effective only when it forms part of an integrated approach to the discovery, recording, interpretation, presentation and conservation of the historic environment. In this pursuit individual photographs (to be sure) will still have their uses, but the key element will be the conversion of information from myriads of photo graphs into a smaller number of mapped and documented records, intelligible and accessible to archaeologists and other end-users, whether in research, edu cation, presentation, conservation or rescue and salvage work. If we were asked to name a single main advance in British aerial archae ology in the last decade it would be the progress made in the application of aerial evidence, through structured and progressively-digital mapping and record-creation, and through the routine inclusion of aerial evidence in the daily processes of local and national archaeological services. For air-photog- raphers one of the greatest satisfactions is to see their results used in other people’s research, through mapped and text-based information rather than through the photographs themselves. For example, air-photographic infor mation, mapped and documented by experts in the art, is now regularly used in many parts of Britain to identify the archaeological context of potentially destructive development projects, and hence to support protective measures or to assist salvage work when it becomes unavoidable. In the light of this and other applications British aerial archaeologists can feel some satisfaction that their particular skills and perspective are now finding a proper place in the mainstream practice of archaeological exploration, interpretation, pres entation and conservation. On this note of (not yet fully justified) optimism, we now turn to prac tical examples of air-photo mapping and documentation in Wales and other parts of Britain. C.R.M. ©2003 Edizioni all’Insegna del Giglio - vietata la riproduzione e qualsiasi utilizzo a scopo commerciale – 3 Air photo mapping and applications in Britain SUMMARY In Wales, air photo mapping by the Royal Commission the Ancient and Historical Monuments of Wales is increasingly playing a part in the record ing of a number of the country’s most important archaeological landscapes. This method of survey has been found to be extremely effective for creating a record both of plough-levelled lowland landscapes but also for preserved upland landscapes, as a preliminary to measured ground survey but also as a method of rapid survey in its own right (see http://rs6000.univie.ac.at/AARG/ worldwide/wales/wales.html). Air photo mapping is now increasingly being linked to the Uplands Initiative programme of field survey, funded by the Royal Commission. Since its inception