4.0 Archaeological Applications of Geographical Information Systems in Cultural Resource Management
Geographic Information Systems (GIS) are computer-based systems designed to input, store, transform, manipulate, analyze and display spatial data traditionally represented in the form of maps or plans. These systems are characterized by their ability to store many sets of location data, usually representing a series of map layers. The power of GIS lies in their ability to store not only location and attribute data for each spatial entity but also the topological relationships between them. This permits the different spatial features making up each map layer to be integrated with those of other map coverages, examined in the same analysis, and new component maps or information produced.
"It is this ability to handle spatially disparate data from several map layers, to seek relationships, to produce composite variables and maps, and to model the information, which makes GIS so potentially important to archaeology" (Lock/Harris 1992:90). GIS is well suited for "what if" types of queries encouraging an explanatory approach to data analysis.
A primary feature of GIS is the ability to select, integrate and analyze features from a combination of map coverages and to construct new composite variables or maps from these sources. GIS also possess operations which enable the "buffering" of either point, line or polygonal map features or the generation of separate overlay features. "The use of such operations for neighbourhood analysis and site catchment analysis of archaeological sites, along with the buffering of environmental or archaeological features which enable the exploration of various hypothesised relationships, provide a very powerful and useful tool to the archaeologist" (Lock/Harris 1992:91).
Finally, GIS provide an environment in which sophisticated modelling can be undertaken. Specifically, archaeological data often suffer from the problem of "white areas" in which no data is known to-exist, although it may not be clear whether this is due to some bias or represents a true absence of data. GIS offers a powerful modelling environment within which it is possible to generate models to predict and extrapolate beyond the available data and into these "white areas". "If, for example, multivariate relationships are known to exist which help explain the location of certain archaeological sites to a high degree, then the ability exists to use these relationships within a GIS to predict and map the location of possible, as yet unknown, sites" (Lock/Harris 1992:92).
In many ways GIS are similar to traditional database-management systems, but with the distinction that the data possess a spatial or mappable component. This characteristic of GIS provides a number of capabilities not found in traditional database-management systems. "Foremost among these is the ease with which maps of data can be produced, thereby offering a ready means to portray complex spatial relations and patterns. It is the ability of GIS to handle, generate, manipulate, and analyze spatial data types that is of importance for archaeological predictive modelling" (Kvamme 1990a:370).
There are three main areas of research currently conducted in CRM utilizing GIS:
The goal of an approach that utilizes a GIS as a cultural resource management tool is to locate areas that are sensitive to the presence of archaeological sites in advance of development. This would enable the plan of the development phase of a terrain altering project to incorporate and avoid sensitive archaeological areas. The majority of initial work with GIS in archaeology has centered on location analysis and predictive modelling. This is probably due to the emphasis on GIS as a management support tool, and the fact that many of the current GIS available have been developed by various government agencies (Savage 1990a:26).
In the absence of truly uniform data quality standards the results of current location models represent hypotheses to be tested in archaeological survey, not the end product of a process that creates archaeological "facts". "Many of the location analyses using GIS have been undertaken precisely to avoid a large survey, so it appears that the use of GIS in a CRM context may result in more harm than good if compliance is assumed on the end product of such analyses" (Savage 1990a:28).
The fundamental role that GIS plays in regional archaeological analysis is to provide the researcher with a means to obtain large amounts of environmental data in an easy and rapid manner (Kvamme 1990a:371). GIS technology easily and rapidly allows characterization of the nature of the distribution of a continuous variable across entire regions of study, with generally much greater accuracy than can be obtained by manual methods.
Finally, it should be emphasized that the region that is encoded within a GIS database can bias the results of analyses if it is not representative of some actual area of interest. For example, the region of interest ideally should correspond with the general area where habitation sites are located (Kvamme 1990a:379).