Cite this as: Allison, P. 2008 Dealing with Legacy Data - an introduction, Internet Archaeology 24. https://doi.org/10.11141/ia.24.8
Keywords: legacy data, GIS, non geo-referenced data, intra-site analyses
In the Mediterranean region particularly, but by no means exclusively, there exist large datasets from previous excavations, published and unpublished, whose digitisation, spatial mapping and re-analysis can greatly facilitate investigations of social behaviour and changing environmental conditions. Added to this there are also archives of historical maps and excavation plans, whose digitisation and combination with these other archaeological data for digital analyses give us greater understandings of the past.
This volume presents a number of projects that demonstrate the usefulness of digital environments for analysing such non-digital data. These projects use these 'legacy data' within true GIS, pseudo-GIS, or other digital environments to answer specific questions concerning social behaviour and particularly the social use of space. The articles discuss approaches taken to retrieve, format, and synthesise these data; to incorporate them with other recently collected and digitised data; and to analyse these large datasets. They also discuss the significance of spatial mapping to the specific aims of these projects. They include discussions on the various computer techniques used to collate and analyse these data, and on how digital environments facilitate the re-analysis of such data.
The majority of the articles in this volume are concerned with using GIS techniques to analyse these legacy data. I would, therefore, like briefly to situate these articles' use of GIS technology within the short history of GIS in archaeology. GIS is most widely used in archaeology, particularly in landscape archaeology, to map data from current excavations onto existing geo-referenced maps of the natural environment. However, this volume demonstrates that GIS is also a useful tool for revisiting old excavations and historical sources with new questions. The main areas in which it presents innovative approaches are its digitisation of non geo-referenced data (both archaeological data and geographical source data) and its use of GIS for small-scale intra-site analyses. While neither approach is totally new, the combination of these approaches, the types of data, and the questions being asked, are. The articles also cover a region that is, to date, poorly represented in the literature on GIS and archaeology. They deal with projects concerning sites and surveys in Greece and Italy.
In 1995 Gary Lock and Zoran Stančič (1995) sought to present a European perspective to complement what they saw as a North American bias in previous publications on GIS and archaeology that emphasised technology and large-scale data integration and management, related to the nature of the archaeological resource (e.g. Allen et al. 1990). Because of a 'fundamentally different set of archaeological problems' stemming from a seemingly more complex dataset, Lock and Stančič saw a predominantly 'European attempt to assimilate social theory within GIS technology' (1995, preface).
The articles in this volume are concerned with developing a more social approach to the use of GIS in archaeological research. The projects involve practitioners of Anglo-American backgrounds but with a noted prominence of practitioners with Australian connections, a country that has been involved in the development of GIS mapping techniques in archaeological research, and particularly in the archaeology of the Mediterranean region (e.g. Knapp and Johnson 1992; Johnson 1994, section 2). Because of its long history of investigation, the archaeology of the Mediterranean region, as well as of the Roman world more broadly, has a wealth of well-documented and well-archived archaeological material that is eminently suitable for the types of re-analysis with which this volume is concerned.
GIS is also traditionally linked to the theory and practices of landscape archaeology (Lock and Stančič 1995, preface xiii). Its primary significance is its use for exploring 'the larger relationship of archaeological and natural space', being 'predominantly used for mapping site distribution within landscapes, and for plotting the exploitation of natural resources' (Gaffney et al. 1995, 213).
In 2001 Dora Constantinidis, from Athens University, wrote that GIS in archaeology, within the landscape approach, is subdivided into two broad categories, 'managerial' and 'analytical', and further divided into data management, distribution analysis, predictive modelling and viewshed analysis (2001, 166-7). A quick perusal of the proceedings of recent Computer Applications and Quantitative Methods in Archaeology (CAA) conferences indicates that GIS is predominantly used for storing, retrieving, and visualising spatial data, or for modelling environmental and climactic conditions to analyse their relationships with occupation and settlement patterns (e.g. whole sections in CAA98 (Barceló et al. 1999, 213-94), and CAA2001 (Stančič and Veljanovski 2001, 185-239) and much of the GIS section in CAA2003 (Fischer Ausserer et al. 2004, 236-337).
However, more recently Patrick Evans and Thomas Daly have emphasised that GIS techniques allow us to explore 'multiple scales simultaneously' (Evans and Daly 2005, 7). Throughout the CAA proceedings there are a few papers which include small-scale, intra-site analyses of the distribution of structures and artefacts. For example, Vullo et al. (1999) demonstrated intra-site analyses of lithics' distribution at individual Mesolithic sites in the Italian Alps. And Constantinidis discussed the potential of GIS for analysing the structural and decorative remains of houses at the Aegean Bronze Age site of Akrotiri on Santorini, noting that the two fundamental levels at which GIS can be utilised in archaeology are those of landscape and intra-site (2001, 165). Constantinidis termed the latter the 'sitescape' and argued that artefacts are 'sites' within a 'landscape' of buildings. Carol Palmer and Patrick Daly (2005) have also mapped artefact disposal at modern Bedouin sites in the Wadi Faynan in southern Jordan.
The majority of archaeological studies using GIS are dependent on geo-referenced data. Such data usually comprise available geographical source data and digital data from excavations carried out since the 1980s, although there are exceptions, particularly to the latter. For example, Neel Smith has demonstrated (1995, fig. 17.1), from Pausanias' 2nd-century AD written description, that this author's travels around Piraeus, the harbour of ancient Athens, can be plotted onto a digital map produced by the Perseus project. And the universities of Tübingen and Cincinnati are integrating over a century of records generated from the excavations at Troy, digital and non-digital, with high-resolution geo-referenced satellite images (Jablonka 2004). It is perhaps noteworthy that these projects, which are using GIS technology in innovative ways, are focused on the Mediterranean and Classical worlds.
These records just discussed - Pausanias's 2nd-century written description of Greece and the non-digital records from the 19th- and early 20th-century excavations at Troy - can be referred to as 'legacy data'. The technical definition of 'legacy data' is data from obsolete information systems. I suspect that most of us would not necessarily perceive of books, maps, ancient descriptions, excavation reports and notebooks as 'obsolete'. This term essentially means that these data are not already digitised and geo-referenced, but must be prepared, and often manipulated, before they can be used in a digital environment. These types of non-digital data are abundant in archaeology and particularly in Old World Archaeology - as historical material like Pausanias' description, as excavation data as at Troy, and as early surveys that did not use GIS. The use of legacy data is one of the areas in which archaeological uses of GIS can excel (see Stine and Decker 1990, esp. 135-6). To date, though, very few such projects are also dependent on non-geo-referenced geographical data.
One area in which this volume is particularly innovative is that some of its articles include, among their legacy data, non-digital geographical source data that is not, and cannot be, precisely tied into the global reference system. Examples of such geographical source data are maps and plans of archaeological sites which, when drawn or published, were not linked to the global coordinate system. Map and plans of this nature are abundant from archaeological excavations, particularly those carried out before the late 1980s. Many such maps can indeed be tied into the global coordinate system. An example is the AutoCAD map of Pompeii, produced by the SAP and used here by Steven Ellis (Introduction). However, this process can often be complex, time-consuming and imprecise. Also, it is not always necessary for less celebrated sites where intra-site, or small-scale inter-site, analyses are carried out but where the true geographical relationships between the different sites, or indeed between different components of a site, is not relevant to these analyses.
In such cases it is possible to set up a coordinate system for each site that is not tied to the global coordinate system but which can be used to produce digital maps of the spatial relationships of the relevant data - both the site plans and other aspects of excavation or archaeological survey. For example, a numeric grid of a site plan can be produced which has a set of pseudo-latitudinal and longitudinal readings, from which a set of pseudo-XY coordinates can be generated. However, it is important that the coordinate system for that site is internally consistent. Such a coordinate system produces a 'pseudo-GIS' or 'GIS-type' environment which can be analysed like any other GIS environment.
One of the capabilities of GIS-assisted analyses, which I believe sets it apart from standard binary analyses, is the facility it provides to visualise the uncertainty or fuzziness of archaeological data. Tuija Kirkinen (1999, 255) discussed problems of handling data of uncertain quality. But many data from archaeological contexts, particularly when used to answer questions concerning socio-spatial behaviour, are of uncertain meaning or significance.
In 1995 Gaffney et al. wrote (1995, 227), that the 'future of innovative work in GIS will be in the development of more sophisticated mathematical modules explicitly for archaeological purposes', although, in the same volume, Lock and Stančič stressed that it is 'not the procedures themselves that are important but the underlying archaeological approaches and questions determining their use'. They felt that the challenge for GIS in archaeology was to 'escape its roots in scientism and work with theoretical models at a more humanistic level' (1995, preface xiv). Kathleen Allen, Stanton Green and Ezra Zubrow had already written that GIS in archaeology involved 'sampling space in order to understand human behaviour'(Green 1990, 3) and that the 'importance of GIS is that it provides ways of asking sophisticated questions' (Allen et al. 1990, 383). Neel Smith stressed that 'GIS does not provide definite answers but suggests new lines of research' (Smith 1995, 246).
As feminist geographers have stated, GIS' capacity for pluralist readings is important for 'critical/qualitative' analyses as well as for 'empirical/quantitative' analyses (Kwan 2002a). Kwan also explained (2002b, 648) that GIS can be used 'to understand the gendered experiences of individuals across multiple axes of difference', and that 'aspects of everyday life ... can be meaningfully depicted using GIS methods'. One of the aims of this volume is to show how digital and spatial analyses can be used to visualise material-cultural patterning that potentially has social significance but where this patterning, because of factors that have impacted on these legacy data (both before and after excavation), is less clearly articulated in standard quantitative methods. That is, the data used in the articles in this volume are often very variable in quality and sometimes also in their relative significance.
Non geo-referenced and non-digital data are abundant in archaeology. The main aims of all the articles in this volume are to demonstrate the value of digitising such data to facilitate analyses which seek to answer questions concerning social behaviour in its spatial and chronological contexts. More explicitly the volume aims to demonstrate:
The contributions to this volume cover a range of different types of social spaces and environments - rural, urban, military, funereal, and landscapes that combine all these. Most concern intra-site analyses but one takes a more landscape approach. Some use pseudo-GIS environments and all involve legacy data and processes by which these data can be used for research into social behaviour.
The first article is by Lisa Cougle and concerns dress and burial in Iron Age Italy. Cougle has re-analysed the excavations of the Iron Age cemetery of Osteria dell'Osa, near Rome, and studied the spatial distribution of grave good between graves to investigate relationships between dress and status.
Robert Witcher's article discusses the integration into a GIS environment of non-digital data from two surveys that were carried out between the late 1960s and 1980s in the Biferno valley, central Italy. He has developed a reflexive approach to these surveys which overlap, in part, but which use different scales and processes for data collection. He demonstrates how this integration into a GIS environment provides fresh perspectives on Iron Age to the Late Roman settlement patterns in this area.
The article by Steven Ellis, Timothy Gregory, Eric Poehler and Kevin Cole revisits excavations carried out in the early 1970s at Isthmia in Corinth, to the east of the Temple of Poseidon. By analysing both the stratigraphical relationships of on-site physical remains from these excavations and the excavation notebooks, and by incorporating these data into a database tied to a GIS system, they have been able to untangle the complicated phasing of the Roman period buildings in this part of this important Panhellenic Sanctuary.
Steven Ellis' own article, on identifying various types of food and drink outlets from past excavations in the Roman town of Pompeii, warns of the dangers of incorporating, uncritically into one's analyses, text-based interpretations of the uses and functions of such excavated spaces. Such interpretations have crept into the modern literature on Pompeii's commercial life, and are often treated as if they are part of the actual primary data, or legacy data. Ellis shows how a more comprehensive analysis and systematisation of the physical remains of these establishments, combined with information from the original excavation notebooks, can, through digitisation and a basic form of GIS, lead to a better understanding of how these outlets functioned in Pompeii's urban landscape.
Penelope Allison's article provides an outline of the approaches used in a project which assessed artefact distribution patterns for investigating the presence of women and children in Roman military bases. Data from published printed excavation reports of five early imperial military sites in Germany were digitised and integrated into GIS-type environments. This article discusses how the artefacts catalogued in these reports were ascribed interpretative categories, concerning gender and activities, and shows some of the results when these categories were plotted in GIS. It also discusses the usefulness of GIS for this type of qualitative analysis with uncertain, interpretative, categories.
And finally, the article by Penelope Allison, Patrick Faulkner, Andrew Fairbairn and Steven Ellis discusses in more detail the processes used in the above project to digitise data from these non-digital excavation reports and to incorporate them into GIS environments so that they could be used for analysing both inter- and intra-site artefact distribution patterns at these Roman military bases. With the exception of Steven Ellis, participants in this project were not essentially GIS users. This chapter, thus, demonstrates how only basic skills in GIS are necessary to carry out such analyses.
These contributions approach the objectives of this volume in different but complementary ways. However, there are some common features with which many of them are concerned.
Legacy data can take a number of forms. In the first instance, re-analysing previous excavations can involve both the re-analysis of the documentation of those excavations and of the extant physical remains themselves - often the structural remains of buildings. The preservation of such physical remains is a frequent situation in the archaeology of the Mediterranean, and particularly, of the classical world, where past excavations have not been backfilled but have been left exposed, often for tourist and cultural heritage uses. Both the articles by Ellis et al. on Isthmia in Greece and by Ellis on Pompeii, involve re-analysis of the physical remains that have previously been excavated but which have been left extant above ground.
In addition, as with the other contributions to this volume, these two projects involve collecting and analysing information from the reports and plans of those previous investigations. In the case of Pompeii this involves analysing physical remains and reports from some 250 years of excavation.
As discussed by Witcher it is also sometimes necessary to use data from more than one excavation or survey. Witcher discusses processes for developing data from two different surveys, which were carried out at different scales. Likewise, the project covered in the articles by Allison and Allison et al. required the standardisation of digital data from a number of different excavations but not, in this case, the standardisation of the geo-referencing system.
Less positively, Ellis's article on Pompeian bars draws our attention to another type of information that can be found in previous investigations and which is sometimes considered the actual data and used as legacy data but instead is rather interpretative information. While it is widely acknowledged there is no such thing as a totally objective observation in the recording of that archaeological data (e.g. Hodder 1992, 148-53), many archaeological data, particularly from the classical world, have been over-interpreted by the often inappropriate application of terminology, or analogical inference, from textual sources. That is, archaeological phenomena have been interpreted through the application of labels from textual sources (see Allison 1999). As Ellis points out, this is particularly relevant for many recent interpretations and mappings of archaeological data from Pompeii.
All these articles demonstrate that using legacy data is often complicated, in that 'manipulation' of these data may be needed and discrepancies accounted for before they can be analysed digitally.
A problem faced by many scholars using legacy data is that they are attempting to analyse data for which they had no role in either collecting or recording. This means that these investigations rely on the previous recorders' assessments and classifications of these data, and also on their selective collation of them. A key concern for many of the articles in this volume is the extent to which data collected for one purpose can be used in analyses that seek to answer different research questions.
There are also minor technical problems involved in integrating these legacy data with digital processes. For example, Allison et al. (section 2.2.3) note that question marks and other qualifiers in the original data need to be replaced with qualifier symbols that are SQL-consistent and, where necessary, quantifiable.
Another problem that needs to be resolved is the matter of differences in scales of analysis. As Witcher (section 2.3) notes, a key feature of recent surveys is the increase in the intensity of coverage and the dramatic decline in size of regions covered. The digitisation of legacy data from different sources does not automatically make these data comparable. Often metadata (i.e. not the results of surveys but data about the results) need to be analysed to understand the significance of individual survey results and to allow meaningful comparison with other surveys.
However, there are good reasons why using legacy data can produce interesting information on past human behaviour where more recent excavation or survey may not be able to.
In the past, excavation, particularly of settlement sites, has been much more extensive than is often possible, both financially and ethically, today. While past data-collection procedures may not have been as comprehensive as they are today, many old excavations, and particularly those in the Mediterranean region, have involved large open-area excavation and the collection of large assemblages from those excavations. It is often the very size of the datasets that make them suitable for digital analyses.
Also, with regard to using old survey data or resurveying, as Witcher (section 2.1) points out, information that may have been available on the surface 50 years ago often no longer exists. Intensification of land use, both urban and rural, in the last half-century has had a dramatic impact on the long-term survival of the surface record. One can no longer collect such information, even if it were financially and ethically viable.
All the contributions to this volume emphasise that the investment of time and effort necessary in order to digitise legacy data should not be underestimated.
Legacy data are not objective archives of facts and figures. Investigators need to take a critical perspective of these data and their characterisation. Witcher (section 2.4) stresses the general need for more emphasis on what has been termed 'source criticism'. The process of data collation, data preparation and data entry is an integral part of data characterisation. As is evident from Allison's article, to investigate social behaviour using large and complex datasets interpretative characterisation may be useful for simplifying their complexity so that such behaviour can be digitally and spatially analysed. The decisions involved in establishing interpretative categories is a valuable part of the analysis but it is important that the subjectivity of such processes is acknowledged.
The application of GIS is an interactive process which focuses on enriching our knowledge of data structures, helping us to interpret socio-spatial behaviour at varying scales of analyses.
Gaffney et al. commented that in the 'alluring visual products of GIS - aesthetics may dominate interpretations' (Gaffney et al. 1995, 211). They also warned that 'GIS can manipulate space according to variable imposed values'. We can assign values to space which can then be interactively analysed with other forms of mapped data' (Gaffney et al. 1995, 213). The articles in this volume all demonstrate processes for ascribing 'value to space', while conscious that the results can often be more exploratory than descriptive. But, more importantly, they use data whose 'value' has not been fully realised by the original investigators. Nevertheless, these investigators have 'manipulated' these data such that they are appropriate for re-investigation using new approaches to spatial analyses. In many cases the visualisation capabilities of GIS provide a key for this re-investigation.
Neel Smith wrote that there is an 'Urgent need for geo-referenced, familiar, well-published archaeological features at high resolution' (1995, 246). But many of these articles demonstrate that GIS techniques can also be used with material that was not initially geo-referenced but which, through such processes, can still produce new perspectives on past social behaviour.
In all these articles digitisation has greatly enhanced our abilities to use 'legacy data' for answering, and indeed posing, new questions, demonstrating that such data are far from 'obsolete' but continue to be valuable for archaeological inquiries.
This volume had its embryonic beginnings in two events at the Australian National University where I held an Australian Research Council QEII Fellowship (2001-2006). The first event was a workshop, 'Databases and GIS in Archaeology', held in November 2004. The second was a conference session and workshop, 'GIS and "Legacy Data"', at the Australasian Archaeometry Conference held in December 2005. Some of the contributions to this volume result from papers that were presented at these events. I am grateful to the Australian National University for hosting them and to the ARC for the funding my research and these workshops. I am also grateful to the organisers of the Australasian Archaeometry Conference, and particularly Andrew Fairbairn who convinced me of the 'archaeometric' nature of my research interests in GIS. And finally I thank the University of Leicester for appointing me to a 'New Blood' lectureship in 2006 to provide time to prepare this volume for publication.
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