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1、Research on key technologies ofembedded GPS navigationEmbedded GPS navigation, based on embedded platform technology, through GPS and GIS and combined with handheld devices, achieves target location, path calculation, route guidance and surrounding search functions of mobile users. This paper, Symbi
2、an OS mobile phones as the terminal, background Linux servers providing the mapping service, path calculation, route guidance, networking search, location query and other functions, using GPRS, WIFI and other wireless communication modes, achieves navigation services provided by professional navigat
3、ion mobile phones on light weight thin-client, and, at the same time, takes advantage of mobile phone communication to achieve a certain degree of user interaction. Thus, based on the user interface on Symbian platform, GPS, data persistence layer, audio and network programming, an overall solution
4、is proposed and the corresponding key technologies involved are discussed.With the development of 3G technology, the improvement of wireless network coverage, the embedded navigation of mobile phones, because of its good portability, low price, always online and more flexible ways to obtain such ser
5、vices, is more and more concerned about. However, due to wide sorts of mobile phones for different platforms, corresponding software needs to be developed, and therefore a suitable embedded operating system needs to be selected. Currently on the market there are more than 40 common embedded operatin
6、g systems, including Linux, Windows CE, Symbian, etc. These embedded systems have different characteristics, and there into Symbian system, developed by Nokia, because of its large user base and good network functions is a successful one. This paper realizes the Symbian-based GPS navigation system.
7、It involves techniques which can be divided into: server-side technology and client-side technology. Client-side technology is mainly related to Symbian programming, GPS module processing, network communication etc; server technology mainly involves Web server technology, database access, and geogra
8、phic information system technology. After server technology roughly introduced, this paper, mainly aiming at client-side technologies, discusses various technologies involved when building mobile phone GPS navigation software with the C/S structure.In order to improve the user experience, it is nece
9、ssary to convert the operations of high-latency and high memory requirements to the service side. Due to Linuxs open source and stability, this paper adopts Linux as the terminal server, uses Apache to build web services, and makes modular map services, POI queries, path calculationguidance services
10、, and built-in sub-services for the Apache. It shows the General framework of the embedded GPS navigation. Taking into account the mass characteristics of map data, tore duce real-time map data downloads when browsing the map, hierarchical block strategy about map data will be introduced in detail h
11、ereafter. Path calculation, as the core of GPS navigation services, supported by navigation data, adopts a dual-side A-Star algorithm to realize optimal path supporting the three kinds of calculation methods of the least time, the shortest distance and less fee. Route guidance, based on path calcula
12、tion module, analyzes the best sections of the calculated path and the node attributes, dynamically calculates the junction point in need of guidance information, loads on the display points of path calculation by index technology of matching, transfers to the client through the appropriate protocol
13、s, and consequently achieve navigation guidance. POI query service is based on full-text retrieval technology. A key technology of full-text Retrieval System to establish the inverted file of location index for each word in the article. Inverted index approach can not solve the problem about space s
14、earch. So the approach of inverted index combined with spatial segmentation is introduced. Firstly, using a grid method segments all POI information according to the relationship of spatial location. And then inverted index is built for the POI in the space after segmentation. Open extensible multi-
15、tier architecture, combined with search, index, cache and other key technologies for search services, greatly improve service stability and search efficiency Symbian OS, as a set of 32-bit operating system, with multi-tasking, multi-threaded, low-power, low occupation of memory, etc. is very suitabl
16、e for mobile communication equipment. It is not difficult to arrive at the following conclusion: In the Symbian client, there are map data mapping, GPS data reception and encryption, path computation and guidance analysis, voice broadcast and other modules. This test system is based on C/S mode, so the network communication module is the core module. Due to the transmission delay of network and unknown transmission errors, etc, multi-threaded scheduling download mechanism is used. And GPS, voi
