Introduction

Surface modelling is an important analytical tool and, particularly in the case of elevation modelling, is often the final stage of GIS project development. Constructing a digital elevation model (DEM) from secondary sources such as digitised contour lines and/or spot heights, or from primary data such as LiDAR or DGPS survey, is a frequent objective of surface modelling (Atkinson 2002). Surface models can also be derived from a wide range of point-based environmental and anthropomorphic data, such as artefact counts or soil chemistry (e.g. Robinson and Zubrow 1999; Lloyd and Atkinson 2004). The derivation of a continuous surface from a set of discrete observations involves a process called interpolation and the selection of an appropriate interpolation technique depends on the structure of the sample data plus the desired outcome and characteristics of the surface model. This chapter begins by reviewing some of the more common interpolation methods and is followed by a more detailed review of techniques for building DEMs from contour data.

Interpolation

Interpolation is a mathematical technique of ‘filling in the gaps’ between observations. More precisely, interpolation can be defined as predicting data using surrounding observations. It can be contrasted to extrapolation, which is the process of predicting values beyond the limits of a distribution of known points. To use a simple example, if n and m are unknown values within the set of numbers {2, 4, n, 8, 10, m}, then using a simple model of linear change n could be interpolated as being equal to 6.

Introduction

This chapter examines the different ways in which spatial datasets are acquired and structured to take advantage of the visualisation and analytical abilities of GIS. It is conventional to distinguish between primary and secondary data sources because acquisition methods, data formats and structuring processes differ considerably between the two. Primary data consist of measurements or information collected from field observations, survey, excavation and remote sensing. Secondary data refer to information that has already been processed and interpreted, available most often as paper or digital maps. Many users of GIS wish to integrate primary and secondary datasets (for example, to plot the location of primary survey data across an elevation model obtained from a data supplier). Both types of data have advantages and disadvantages, which this chapter examines in some detail. By the end of this chapter you will be familiar with the ways in which both primary and secondary data are obtained, and the issues and procedures for assessing the quality of combined datasets.

Primary geospatial data

Primary, or ‘raw’, geospatial data has not been significantly processed or transformed since the information was first captured. Archaeologists generate vast quantities of primary data during excavation and survey, such as the location of settlements, features and artefacts, geoarchaeological and palaeo-environmental data and the location of raw material sources within the landscape. Raw data may also be available from databases of information compiled by other agencies: the location of archaeological sites, for example, can be obtained from Sites and Monuments Records and published site ‘gazetteers’.

Introduction: thinking about regions

A GIS can be used to create, represent and analyse many kinds of region. Some regions have an objective reality, at least to the extent that they are widely recognised and have a readily detectable influence on aspects of human behaviour. The most obvious examples of this kind are sociopolitical regions such as the territories of modern nation states. Other regions have an objective reality in another sense: that they are defined by some natural process. A good example of a natural region is the watershed; that is, the area within which all rainfall drains to some specified point in a drainage network. A third kind of region is essentially just analytical in the sense that it is created for a specific short-lived purpose and may never be recognised by anyone other than the analyst. For example, an archaeologist might determine the region containing all land within 100 m of a proposed high-speed railway line in order to identify at-risk archaeological sites, but it is the list of sites and their locations, not the region, that is fed back into the planning process.

Regions are readily represented as polygons in a vector map, or less efficiently as cells coded in such a way as to distinguish between inside and outside a region in a raster map. Where the extent of regions are known in advance of GIS-based analysis, as is often the case with sociopolitical regions, their generation and manipulation within a GIS is mostly an issue of data capture and map query.

Introduction: point and spatial operations

In this chapter we introduce a number of point and spatial operations that can be performed on continuous field data. We begin with the use of map algebra, before moving on to the calculation of derivatives (e.g. slope and aspect) and spatial filtering (e.g. smoothing and edge detection), all of which are widely used by archaeologists. In the final section we introduce more specialised techniques that have archaeological potential.

Map algebra is a point operation, whereas the other techniques discussed in this chapter are spatial operations. Point operations compute the new attribute value of a location with coordinates (x, y) from the attribute values in other maps at the same location (x, y), (Fig. 9.1b). In contrast, spatial operations compute the new attribute value of a location from the attribute values in the same map, but at other locations – those in the neighbourhood (Fig. 9.1a). The neighbourhood used in a spatial operation may or may not be spatially contiguous. For example, slope is usually calculated using the elevation values in a neighbourhood comprising the four or eight map cells immediately adjacent to the location in question (see below), but we saw in Chapter 6 how inverse distance weighting interpolates elevation values from some number of nearest spot heights, irrespective of how far away those spot heights actually are.

Introduction

Cartographers have long recognised the influence that maps have on the shaping of spatial consciousness (Monmonier 1991; Wood 1992; Lewis and Wigen 1997). The purpose of this chapter is to explore the way maps, whether paper or digital, may be used to present spatial information and to highlight some design principles to maximise their effectiveness at this task. In doing so we describe a range of mapping techniques appropriate for the different sorts of data routinely handled by archaeologists. We also consider some major cartographic principles and design conventions that help make maps effective communication devices, and discuss the growing importance of the Internet and interactive mapping for the publication of spatial data.

Designing an effective map

As defined in Chapter 2, maps are traditionally divided into two categories: topographic and thematic. The former term describes maps that contain general information about features of the Earth's surface, whereas thematic maps are limited to single subjects, such as soils, geology, historic places, or some other single class of phenomena. Both types of map must contain some basic pieces of information so that the reader is able to comprehend and contextualise the data that is being presented. The most basic of these, without which a map is difficult if not impossible to understand, are: (i) a title; (ii) a scale; (iii) a legend and (iv) an orientation device, such as a north arrow (Table 12.1).

Introduction

This chapter describes the way that spatial and attribute data are structured and stored for use within a GIS. It provides the necessary information about data models and database design to enable archaeologists unfamiliar with computer databases to make appropriate decisions about how best to construct a system that will work well and efficiently.

A database is a collection of information that is structured and recorded in a consistent manner. A card catalogue that records information about archaeological sites, such as their location and date, is as much a database as a full-fledged web-searchable digital sites and monuments record. Digital databases differ from their paper counterparts mainly in that they are dependent on database software for searching and retrieving records. The complexity of the data structure will also be increased as digital databases are often broken into several different related files. This reduces the amount of duplicated information in a database, improves access speed and also enables the retrieval of small subsets of data rather than complete records. Software that is used to store, manage and manipulate data is referred to as a Database Management System (DBMS). The objectives of a DBMS are to store and retrieve data records in the most efficient way possible, from both the perspective of the overall size of the database and also the speed at which that data can be accessed.

The technology of DBMS is a major research focus in computer science.

Introduction

Spatial analysis lies at the core of GIS and builds on a long history of quantitative methods in archaeology. Many of the foundations of spatial analysis were established by quantitative geographers in the 1950s and 1960s, and adopted and modified by archaeologists in the 1970s and 1980s. For a variety of reasons, spatial analysis fell out of fashion both in archaeology and in the other social sciences. In part this was because of the perceived overgeneralisation of certain types of mathematical models, but also because of a shift towards more contextually orientated and relativist studies of human behaviour. Recently, however, there has been a renewed interest in the techniques of spatial analysis for understanding the spatial organisation of human behaviour that takes on board these criticisms. In the last decade there have been several advances within the social sciences, particularly geography and economics, in their ability to reveal and interpret complex patterns of human behaviour at a variety of scales, from the local to the general, using spatial statistics. Archaeology has participated somewhat less in these recent developments, although there is a growing literature that demonstrates a renewed interest in the application of these techniques to the study of past human behaviour. In this chapter we review some historically important methods (e.g. linear regression, spatial autocorrelation, cluster analysis) and also highlight more recent advances in the application of spatial analysis to archaeology (e.g. Ripley's K, kernel density estimates, linear logistic regression).

Introduction

The most valuable (non-human) resource that any organisation possesses is its data. Hardware and software are easily replaceable but the loss of data can be catastrophic for an organisation. Information loss, whether full or partial, is easily avoided through the routine taking of backups and the storage of data off-site. As there is plenty of readily available information on how best to implement a backup and data-recovery procedure, we do not consider it in any detail in this book. What is less obvious, particularly to those new to GIS and digital data, is the similarly important task of data maintenance. Consider, for example, the following three scenarios:

• An employee in a cultural resource management (CRM) unit is assigned the task of updating site locations from newly acquired GPS data. How should the fact that a few site locations have been updated be documented and where and how should the old data be stored?

• An aerial photograph of a portion of landscape has been rectified and georeferenced, and is ready to be used to delineate features of archaeological significance. How and where should information about the degree of error in the georeferencing be documented? Where and how should the errors for the newly digitised archaeological features be documented?

• A research student is collecting data on soil types for Eastern Europe from several different national agencies that each have different scales and recording systems. How is this student able to search and compare and ultimately integrate datasets in a manner that ensures the data will be appropriate for his/her needs?

This chapter reviews four typical applications of GIS in archaeology: management of archaeological resources, excavation, landscape archaeology and the spatial modelling of past human behaviour. For each application we discuss some general issues concerning the use of GIS in that particular context, followed by a presentation of a case study that illustrates the contribution that GIS has made. Although these examples are in no way exhaustive, they do provide a good overview of the capabilities and potential contributions that GIS can make to archaeological management and research.

Management of archaeological resources

It is not our intention to discuss the objectives of cultural resource management (CRM), nor the appropriate structure of a spatial database for managing the archaeological record, as these decisions are most appropriately made by government bodies and the archaeologists charged with the tasks of recording and managing the archaeological resource. However, we note that archaeological and historic databases have increasingly been subject to government scrutiny. In the UK, this most recently occurred in a parliamentary review of archaeology that took place in 2003 (APPAG 2003; Gilman 2004). In particular, the UK archaeological databases termed ‘Sites and Monuments Records’ (SMRs) are under review in light of recent developments in information technology, especially GIS and the Internet (e.g. Newman 2002). This report makes it clear that SMRs should evolve into broader Historic Environment Records (HERs) that include information such as historic buildings, parks and gardens, historic aircraft crash sites, etc.

Introduction

The analysis of territory as a changing focus for political power has moved beyond the exclusive confines of the geographic discipline during the past decade. The study of territory and borders now constitutes a multidisciplinary research focus, drawing in political scientists, sociologists, anthropologists, and legal experts, as they seek to understand the role of territory in the contemporary globalized world (Coakley 1993; Diehl 1999b; Dijkink and Knippenberg 2001). The globalist position argues that we are moving into a deterritorialized and borderless world. At the same time, the existence of ethnoterritorial conflicts reminds us that many groups continue to lay claim to specific pieces of territory in what could be described as a primordial, pre-modern, fashion. This raises questions concerning the functions and role of territory as part of the changing world political map. This chapter seeks to examine this resilience of territory as a factor of major political and functional significance, focusing on such contemporary cases as Israel–Palestine and the Balkans.

The territorial discourse within political geography has experienced a renaissance during the past two decades (Agnew 2000; Paasi 2002). An important framework for understanding the role of territory as a key factor in the political organization of space, and as a basis for the re-emergence of political geography as a bona fide discipline after three decades of shunning due to its “guilt by association” with the German school of Geopolitik (Newman 2002a),was provided by Edward Soja in what proved to be a seminal paper published by the Association of American Geographers in 1971 (Soja 1971).

The world of the early twenty-first century displays both persistent attachments to territory and violent conflict over those territorial stakes. Even as interstate conflict has declined, many costly internal conflicts have taken on a territorial dimension. The persistence of territoriality and the conflict that it inspires run counter to one popular view of the consequences of growing globalization: capital, goods, and populations display increased mobility, and their detachment from territory should reduce the importance of conventional territorial boundaries. Globalization has produced changes in territoriality and the functions of borders, but it has eliminated neither. We do not live in a “borderless world” or one that has seen the “end of geography” (Ohmae 1990; O'Brien 1992). Conflict over territory continues in an increasingly integrated world.

Spanning the social sciences, the authors in this volume present converging investigations into the complex causal relations among territoriality, conflict, and globalization. The study of globalization and the persistence of ethnic conflict have stimulated an interest in borders of all kinds, questioning their permanence and defining the consequences when social and cultural identities do not coincide with political boundaries and territorial claims. The contributors display skepticism toward both an unreconstructed view of the sovereign territorial state and the competing claim that globalization has completely transformed the existing territorial regime. The modern territorial state is seen as one historically bounded exemplar of territoriality, rather than the defining expression of territorial rule.

More than three decades ago, Richard Cooper stated that “the trend toward economic interdependence between countries will require substantial changes in their approach to foreign policy in the next decade or so” (1972, 159). A wide range of studies has since been premised on the proposition that interdependence has significantly raised the costs to governments and the economies they govern of taking unilateral action. One solution to problems of coordination and collaboration among states has been to develop international institutions that reduce transactions costs and uncertainty, allowing states to enjoy greater mutual gains than would have been possible in the absence of such institutions.

The institutional paradigm has informed a broad range of studies in international political economy (Simmons and Martin 2002). The same cannot be said of international conflict studies. Scholars looking at interstate disputes have typically bypassed institutional theory, focusing instead on the basic constellations of state power. The irony is that war and peace often revolve around the most ubiquitous international institution of the modern age: sovereign authority over delimited territorial space.

This chapter argues for a reconceptualization of international borders as they have come to be understood in the international relations literature. One branch of that literature has emphasized the extent to which disputes over territory, more than any other issue, have spurred interstate rivalry, military confrontation, and all-out war. Borders as territorial divisions are then analyzed as zero-sum manifestations of state competition for power, prestige, lebensraum, or an imagined historical identity.