| 摘要 |
Devices, methods and systems for providing electronic navigation are disclosed. Map data can be downloaded from a server through a network, such as the Internet or a cellular telephone network, onto a portable device. A route may be calculated based on the map data for a starting point and a destination provided by the user. The portable device may include a GPS-enabled module for determining the current positional data. The portable device is able to generate directional instructions based on the map data and the current positional information and to provide the user with directional instructions, such as instructions to turn left or right. In one aspect, a navigational system includes a map data server adapted to provide map data to requesting clients through a communication network and a portable device adapted to receive map data from the map data server through the communication network and to provide directional instructions to a user. The portable device includes a map data module adapted to receive the map data from the map data server and a navigational module adapted to receive current positional information and to generate directional instructions based on the map data and the current positional information.
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