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Geographical Information Systems: on modelling and representation

Rapid though developments in geographic information (GI) handling technologies continue to be, digital representations of the real world within GIS will almost always necessarily remain partial and incomplete. This point was implicit in my last report (Longley, 2003) with regard to digital data infrastructures that are becoming ever richer and more detailed, yet inevitably remain deficient in detail. Not just with respect to data per se, but also with respect to the methods and technologies that are used to assemble them into representations of the real world, there is a sense that the research horizon continues to recede ahead of us, until the realization dawns that attempts to built the perfect representation are almost inevitably doomed to failure. Research effort must therefore refocus upon effective management of the uncertainties that are inherent in incomplete representational models of reality (see Miller, 2003). In this report I would like to consider the interplay between networked computer technologies and new approaches to modelling that are helping to further this objective. For human geographers, it is nearly 40 years since the general notion of the ‘model’ as a simplification of reality – as opposed to the particular use of the term to describe scaled-down representations fashioned with physical materials – entered common parlance (Chorley and Haggett, 1967). The earliest models adapted a range of physical media to the representation of physical artifacts (as in planners’ block models of towns) or abstract relations (as in the embodiment of Weber’s model of industrial location in the Varignon Frame): however, as the digital revolution gathered pace, so simulation of mathematical relationships using computers increasingly became the norm. In considering the progress during the intervening decades, it remains helpful to revisit the distinction between iconic and symbolic models. Iconic models are best thought of as ‘scaled-down versions of the real thing’, and may have working parts that are similarly scaled down. The town planner’s block model or the hydrologist’s flume provide specific examples, but so too does the paper map. Symbolic models, by contrast, are Progress in Human Geography 28,1 (2004) pp. 108–116