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Field-walking Strategies

Field-walking Strategies


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The primary method of current survey archaeology has is the field-walking or pedestrian survey. Basically, a team of archaeologists hikes through the open fields of their study area recording all superficial archaeological evidence encountered. However, there are a few important variables in this method. The first one relates to the detail with which the surface record is documented; the more intensive the documentation, the less land is covered. Although these scales are rather fluid, there is a clear differentiation between intensive and extensive field-walking strategies. This is mainly a matter of resolution; hence an intensive survey studies a relatively small area in a very detailed way, whereas an extensive survey covers an enormous area, using far less meticulous methods.

Starting in post-war Italy in the 1950s (e.g. the early years of the South Etruria Survey; Ward-Perkins 1964) the main objective of survey archaeology was the large-scale regional mapping of antiquities in the landscape. To achieve this, archaeologists did not walk the entire landscape systematically, but chose their survey locations mainly on existing knowledge (i.e. known archaeological find spots) among the local population and/or expectations based on the topographical or geo-morphological characteristics of the landscape. These methods are now known as unsystematic reconnaissance or judgmental survey and in essence are always extensive. Taking into account their subjective character (a great part of the reliability of the data is based on the connoisseurship of the archaeologist and his local guides), chances are that the results from these projects will be highly biased.

Under the influence of the New Archaeology movement in the United States, from the 1960s survey archaeology ‘lost its innocence’ (after Clarke 1973). Not only did the discipline became more aware of the biases and limitations of an archaeological survey, the used methods and techniques were changed and extended into the realm of the natural and social sciences (e.g. The Minnesota University Messenia Expedition?; Plog?). Even though field-walking strategies remained extensive rather than intensive in these early years, survey areas and transects were often plotted systematically (or deliberately at random) to create a statistically legible sample of the archaeological landscape. At this point, survey archaeology was no longer just a way to discover and map archaeological sites for future excavation, it emerged as a discipline on its own, with appropriate research questions on a broad regional level.

However, three decades of extensive surveying created enormous site-databases, which were not satisfactorily explanatory for the archaeological reality encountered in the field. At the end of the 1970s and at the beginning of the 1980s, a growing critique on these large-scale extensive surveys, criticising their quality to generate 'complete' datasets, resulted in survey projects using systematic field-walking strategies on a more intensive scale and furthermore finds were collected according to a predetermined sampling method. In practice, this led to survey teams systematically walking the landscape which was divided into survey units/tracts or traverses, using a predetermined spacing between walkers in order to collect a fixed percentage of the archaeological data. All archaeological materials encountered were either collected or counted and these quantities were plotted on survey maps within their respective survey units.

For example, a commonly used coverage percentage, 20% often results in a field-walking strategy with five walkers, each covering a swath of two metres from which they will count and/or collect all archaeological materials, with a spacing between walkers of approximately ten metres. This way, each walker will cover for instance a 100 m.2 of a 50 x 50 m. survey unit, resulting in a total of 500 out of 2500 m.2. Hence, intensive survey strove to create a statistically valid dataset on an artefact-level, which was less dependent on the subjective, arbitrary decisions of the survey team, and which offered a whole new qualitative perspective on an archaeological landscape not consisting exclusively of sites. Of course, the downside of this intensification was an enormous increase of labour. Whether because of the field-walking itself or the processing of the vast amounts of collected potsherds, archaeological survey had become an increasingly time-consuming process.

This was aggravated even more by the recognition that the archaeological landscape is far from static. Experiments in the 1970s, in which a survey area was repeatedly visited at various moments under different conditions resulted in alarmingly big inconsistencies in the resulting archaeological data (e.g. Ammerman & Feldman 1978, Ammerman 1981). This, of course urged the necessity of revisiting the same survey area during various campaigns to come to a reliable result.

The past two decades intensive, artefact-based survey remained the most commonly used survey method in the Mediterranean, even though it has been heavily criticized. Two of the main problems encountered in intensive survey archaeology are the comparability of survey data derived from these projects and, even more importantly, the perpetual problem of the decreasing sample size caused by increasing survey intensity. To start with the latter, critical articles such as ‘What are we counting for?’ (Fentress 2000) and ‘Sample size matters!’ (Terrenato 2004) have pointed out the statistical and interpretative risks of using data from a small-scale intensive survey to explain large-scale, (mid-) long-term processes. Although the augmentation of the intensity and the collection and mapping of all (site and off-site) artefacts without a doubt has given us a richer and more varied dataset to study human-landscape relationships, according to these critics it has not improved the statistical reliability and consequently the scientific relevance of the research, because it does not produce a dataset containing a very large number of sites and it has not yet been proven that bias-correction doesn't introduce more biases than it solves.

Field documentation forms an integral part of the methodological research design of a project. A survey team usually records not just archaeological finds, but a wide array of relevant data, such as visibility conditions, topographical and geomorphological characteristics, present land-use, and so forth. Furthermore, the team adds a spatial reference to position the recorded data cartographically. Until the late 90's, this required a large amount of paperwork in the field, which all had to be digitized afterwards. Fortunately, the development of digital fieldbooks and PDAs has made it possible to record all data as well as the relevant spatial references digitally in the field, using mobile GIS-based applications. This has not only smoothed the process of field documentation, it has also opened a whole new area of possibilities for fieldwork techniques, making GPS-logging, aerial photographs, a virtually infinite amount of cartographical layers (e.g. survey data from previous visits), etc. directly available for the survey team in the field.

Bibliography and further reading

Ammerman, A. & M. Feldman, 1978, ‘Replicated collection of site surfaces’, in: AmerAnt 29, pp. 734-740.

Ammerman, A., 1981, ‘Surveys and Archaeological Research’, in: Annual Review of Anthropology, Vol. 10, pp. 63-88.

Cherry, J., 1983, ‘Frogs around the pond: perspectives in current archaeological survey projects’, in: Keller, D. & D. Rupp (eds.), Archaeological Survey in the Mediterranean Area (BAR International Series 155), Oxford, pp. 375-416

Cherry, J. 2003, ‘Archaeology beyond the site: regional survey and its future’, in: Leventhal, R. & J. Papadopoulos (eds.), Theory and Practice in Mediterranean Archaeology: Old World and New World Perspectives, Los Angeles, pp. 137-60.

Fentress, E., 2000, ‘What are we counting for?’, in: Francovich, R., Patterson, H. & G. Barker (eds.), The Archaeology of Mediterranean Landscapes 5: Extracting Meaning from Ploughsoil Assemblages, Oxford, pp. 44-52.

Mattingly, D., 2000, ‘Methods of collection, recording and quantification’, in: Francovich, R., Patterson, H. & G. Barker (eds.), The Archaeology of Mediterranean Landscapes 5: Extracting Meaning from Ploughsoil Assemblages, Oxford, pp. 5-15.

Terrenato, N., 2003, ‘Sample Size Matters! The paradox of global trends and local surveys’, in: Alcock, S. & J. Cherry, Side by Side Survey: Comparative Regional Studies in the Mediterranean World, Oxford, pp. 13-21.

Van Leusen, M., 2002, Pattern to Process, methodological investigations into the formation and interpretation of large-scale patterns in archaeological landscapes, PhD-thesis, Groningen.

Ward-Perkins, J., 1964, Landscape and History in Central Italy, Oxford.

Research topics: Survey Methodology