Infrastructure Engineering - Research Publications

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End date: 2009 × Author: Kulik, Lars × Subject: granularity ×

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    Imprecise Navigation
    Duckham, M ; Kulik, L ; Worboys, MF (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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    Commonsense notions of proximity and direction
    WORBOYS, MICHAEL ; DUCKHAM, MATT ; KULIK, LARS (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.