Infrastructure Engineering - Research Publications
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ItemSpatio-Temporal Event Detection Using Probabilistic Graphical Models (PGMs)(IEEE, 2013)Event detection concerns identifying occurrence of interesting events which are meaningful and understandable. In dynamic fields, as time passes the attribute of phenomenon varies in spatial locations. Detecting events in dynamic fields requires an approach to deal with the highly granular data arriving in real time. This paper proposes a spatiotemporal event detection algorithm in dynamic fields which are monitored by wireless sensor networks (WSNs). The algorithm provides a method using probabilistic graphical models (PGMs) in WSNs to cope with the uncertainty of sensor readings. The algorithm incorporates the ability of Markov chains in temporal dependency modelling and Markov random fields theory to model the spatial dependency of sensors in a distributed fashion. Experimental evaluation of the proposed algorithm demonstrates that the decentralized approach improves the F1-score to 82% and 29% better precision than simple threshold technique. In addition, the performance of the algorithm was evaluated and compared with respect to the scalability (in terms of communication complexity). In comparison with the centralized approach the decentralized algorithm can substantially improve the scalability of communication in wireless sensor networks.
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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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ItemQualitative reasoning about consistency in geographic information(Elsevier BV, 2006-03)
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ItemMonitoring qualitative spatiotemporal change for geosensor networks(Taylor & Francis, 2006)Recent technological advances in geosensor networks demand new models of distributed computation with dynamic spatial information. This paper presents a computational model of spatial change in dynamic regions (such as may be derived from discretizations of continuous fields) founded on embeddings of graphs in orientable surfaces. Continuous change, connectedness, and regularity of dynamic regions are defined and local transition rules are used to constrain region evolution and enable more efficient inference of a region’s state. The model provides a framework for the detection of global high-level events based on local low-level “snapshot” spatiotemporal data. The approach has particular relevance to environmental monitoring with geosensor networks, where technological constraints make the detection of global behavior from local conditions highly advantageous.
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ItemLocation privacy and location-aware computing(CRC Press, 2006)
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ItemAutomated geographic information fusion and ontology alignment(Springer, Berlin, 2007)
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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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Item"Simplest" paths: automated route selection for navigation(Springer, 2003)Numerous cognitive studies have indicated that the form andcomplexity of route instructions may be as important to human navigatorsas the overall length of route. Most automated navigation systemsrely on computing the solution to the shortest path problem, and not theproblem of finding the “simplest” path. This paper addresses the issueof finding the “simplest” paths through a network, in terms of the instructioncomplexity. We propose a “simplest” paths algorithm that hasquadratic computation time for a planar graph. An empirical study ofthe algorithm’s performance, based on an established cognitive model ofnavigation instruction complexity, revealed that the length of a simplestpath was on average only 16% longer than the length of the correspondingshortest path. In return for marginally longer routes, the simplest pathalgorithm seems to offer considerable advantages over shortest paths interms of their ease of description and execution. The conclusions indicateseveral areas for future research: in particular cognitive studies areneeded to verify these initial computational results. Potentially, the simplestpaths algorithm could be used to replace shortest paths algorithmsin any automated system for generating human navigation instructions,including in-car navigation systems, Internet driving direction servers,and other location-based services.