Mapping liminality: Critical frameworks for the GIS-based modelling of visibility.

Abstract

Since the widespread adoption of GIS by archaeologists in the early 1990s, analyses of visibility have steadily gained traction, becoming commonplace in landscape and regional analysis. This is in large part due to the routine way in which such products can be generated, bolstered by a raft of landscape-based studies that have placed varying degrees of emphasis upon human perception and direct bodily engagement in seeking to understand and explore the past. Despite this seeming popularity, two worrying trends stand out. The first is the lack of any coherent theoretical framework, applications preferring instead to seek justification in the very first wave of experiential landscape approaches that emerged in the early 1990s. Needless to say, the intervening 20 or so years have seen considerable development in the conceptual tools we draw upon in order to make sense of past landscapes, not to mention considerable finessing of the first-wave developments alluded to above. Second is the tendency to relegate viewshed analysis to certain types of predictable problem or question (i.e. viewshed analysis has become typecast). These trends have been compounded by a host of other issues. For example, whilst there have been refinements, tweaks and variations to the basic viewshed (and the frequency with which they are generated and combined), not to mention establishment of robust calibration criteria for controlling them and statistical approaches for assessing the patterns tendered, these have yet to be brought together in any coherent fashion and their veracity critically assessed. Likewise, a failure to establish an agreed vocabulary has resulted in a number of proverbial wheels being reinvented time and again. The argument presented here is that viewsheds have considerably more to offer archaeology but to realise this entails confronting these issues head on. That this is possible and desirable is illustrated through discussion of a new theoretical framework for visibility-studies that draws upon developments in assemblage theory and the author's own work on affordance and relationality. To demonstrate the value of this approach in encouraging different ways of thinking about what viewsheds are and how we might begin to draw creatively upon them, a case-study is described where viewsheds are folded into a detailed exploration of landscape liminality.