Abstract
Recently, many spatio-temporal applications paid attention to the aggregative information of moving objects in road networks (e.g., the number of the vehicles, the average speed). Conventional sketch method can solve the distinct counting problem, but can’t guarantee on the approximate quality of aggregate queries over moving objects in road networks in masses of situations. This paper proposes an improved histogram method by dividing the query area to avoid some unnecessary drawbacks, and to improve the quality of the approximation. Evaluation shows this new method outperforms the traditional sketch method not only in sketch generation time, query time, and the memory requirements, but also in the approximation error of aggregate query which is in an appropriate range.
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