Infrastructure Engineering - Research Publications
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ItemA formal approach to imperfection in geographic information(Elsevier, 2001)Traditional computational models of geographic phenomena offer no room for imperfection. Underlying this tradition is the simplifying assumption that reality is certain, crisp, unambiguous, independent of context, and capable of quantitative representation. This paper reports on initial work which explicitly recognises that most geographic information is intrinsically imperfect. Based on an ontology of imperfection the paper explores a formal model of imperfect geographic information using multi-valued logic. The development of Java software able to assist with a geodemographic retail site assessment application is used to illustrate the utility of a formal approach.
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ItemImprecise Navigation(SpringerLink, 2003)Conventional models of navigation commonly assume a navigation agent's location can be precisely determined. This paper examines the more general case, where an agent's actual location cannot be precisely determined. This paper develops a formal model of navigation under imprecision using a graph. Two key strategies for dealing with imprecision are identified and defined: contingency and refinement. A contingency strategy aims to find an instruction sequence that maximizes an agent's chances of reaching its destination. A refinement strategy aims to use knowledge gained as an agent moves through the network to disambiguate location. Examples of both strategies are empirically tested using a simulation with computerized navigation agents moving through a road network at different levels of locational imprecision. The results of the simulation indicate that both the strategies, contingency and refinement, applied individually can produce significant improvements in navigation performance under imprecision, at least at relatively fine granularities. Using both strategies in concert produced significant improvements in performance across all granularities.
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ItemAn algebraic approach to automated information fusion(Taylor & Francis, 2005)This paper presents a new technique for information fusion. Unlike most previous work on information fusion, this paper explores the use of instance-level (extensional) information within the fusion process. This paper proposes an algorithm that can be used automatically to infer the schema-level structure necessary for information fusion from instance-level information. The approach is illustrated using the example of geospatial land cover data. The method is then extended to operate under uncertainty, such as in cases where the data is inaccurate or imprecise. The paper describes the implementation of the fusion method within a software prototype. Finally, the paper discusses several key topics for future research, including applications of this work to spatial data mining and the semantic web.
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ItemComputational structure in three-valued nearness relations(Springer, 2001)The development of cognitively plausible models of humanspatial reasoning may ultimately result in computational systems thatare better equipped to meet human needs. This paper explores how humansubjects perceive the qualitative spatial relation nearness within anenvironmental space. Based on experimental data, a three-valued nearnessrelation is analysed in two stages. First, the results are analysedwith special reference to the existence of subsets of candidate landmarkplaces, from which nearness relations between other places may be partiallyinferred. Second, the desirable properties of such landmark setsare considered and some of their formal properties are presented. Theseproperties are then considered in the light of the data furnished by theexperiment. The paper concludes with a discussion of the signicance ofthe analyses and the scope for further work in this area.
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ItemCommonsense notions of proximity and direction(Springer Verlag, 2004)It is desirable that formal theories of qualitative reasoning should be informed by the ways in which humans conceptualize the spaces in which they live. The work described in this paper uses data provided in experiments with human subjects to derive some regularities in such conceptualizations. The data concerns human conceptualization of proximity and direction within a university campus. The results are analyzed using several approaches. In particular, the relationship between geometric and human conceptual models of the space is explored; the structure and regularities of combinations of proximity and direction relations are examined; and the issue of granularity in vague spatial relations is considered. Overall, the results show that while individual differences between humans are important, there are striking regularities in the population’s notions of distance and direction in the space. The paper concentrates primarily on the formal foundations of commonsense notions of proximity and direction, but also identifies links to more applied domains, such as mobile and location-aware navigation systems.
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ItemMonitoring dynamic spatial fields using responsive geosensor networks(ACM, 2005-12-01)Information about dynamic spatial fields, such as temperature, windspeed, or the concentration of gas pollutant in the air, is important for many environmental applications. At the same time, the development of geosensor networks (wirelessly communicating, sensor-enabled small computing devices, distributed throughout a geographic environment) present new opportunities for monitoring of dynamic spatial fields in much more detail than ever before. This paper presents a new model for querying information about dynamic spatial fields using geosensor networks. In order to manage the inherent complexity of dynamic geographic phenomena, our approach in this paper is to focus on the qualitative representation of spatial entities, like regions, boundaries, and holes, and of events, like splitting, merging, appearance, and disappearance events. Based on combinatorial maps, we present a qualitative model as the underlying data management paradigm for geosensor networks that is capable of tracking salient changes in the network in a much more energy-efficient way. Further, our model enables reconfiguration of the communication in the geosensor network in response to changes in the environment. We present an algorithm capable of adapting sensor network granularity according to dynamic monitoring requirements. Regions of high variability can trigger increases in the geosensor network granularity, leading to more detailed information about the dynamic field. Conversely, regions of stability can trigger a coarsening of the sensor network, leading to efficiency increases in particular with respect to power consumption and longevity of the sensor nodes. Querying of this responsive geosensor network is also considered, and the paper concludes with a review of future research directions.