| The spatial and temporal databases have been studied widely and intensively over years. One of its applications is navigation system. In modern navigation systems, the essential problem is that how to compute the fastest path in the presence of varying traffic conditions on a road network. This dissertation contains researches on novel approaches for road network related problem The whole dissertation can be divided into five parts.;In the first chapter, We will introduce the the whole dissertation. Some brief ideas will be presented. In the second chapter, we mainly discuss computing the optimal fast path on dynamic road network. The road speed may be affected by weather, time of day, and vehicle types. These factors cannot be ignored in order to find the fastest path that match current traffic conditions. In this work, we present an A star based fastest path algorithm to answer queries of finding the best departure time and optimal path to reach the destination as early as possible, where the traffic conditions dynamically change from time to time. In the third chapter, we focus on computing an approximate result to reduce the time complexity. An acceptable result with quick response is much better than the optimal result which takes long time to compute. We will study how to compute the fast path from source to destination in a road network, using traffic mining method. The result should satisfy the following two requirements: take into account speed-affecting factors; the response time must be in an acceptable range. In the forth chapter, we will introduce existing methods to collect traffic information. We will use a sensor database. In this system, an user's query will be disseminated across the system. During this process, each sensor generates data that match the query from its covered area and then returns the data to the original sensor. In order to achieve an energy-efficient implementation, it will be useful to select a minimally sufficient subset of sensors to keep active at any given time. In the fifth chapter, we will conclude the whole dissertation and state the future work. |
