Research On Web-based Wireless Navigation Service And Data Organization Technology

Being outside, all of us need navigation. This dissertation works over a novel navigation technology. Its objective is to provide us a kind of comprehensive and elaborate navigation service, that is, profound, real-time, personalized and intergrated navigation helps, anywhere and anytime.Today, there are mainly two kinds of land-use navigation systems: handheld navigation devices and car navigation systems (CNS). They both belong to autonomous systems, which can complete navigation tasks only with the help of positioning from outside. Autonomous systems store maps locally, execute all computations including complex tasks such as finding the best route. Their disadvantages include: (1) With limited memory capacity, handheld navigation devices cann't store detailed map, and so cann't provide profound navigation helps. (2) With limited CPU capability, executing complicated tasks are time-comsuming. (3) The map dataset can't be updated on time and maybe incorrect navigation hints result from out-of-date data. It is obvious that handheld navigation devices can not provide comprehensive and elaborate navigation service.Wireless navigation service (WNS) is a better solution than autonomous navigation. Serveral WNS systems are deployed now in French and America, etc.. Due to commercial secrecy, we only can learn the synopses of them. In China, there is not any successful WNS solution. So this dissertation presents a new technology called "Web-based Wireless Navigation Service (WWNS)". WWNS systems are composed of Internet map servers and mobile devices. Servers manage huge map dataset, complete most of computations and transmit all or part of maps to mobile devices through mobile telecommunication networks. The transport protocol is HTTP and all communications are XML-coded messages. A mobile device stores no or just a few maps, completes simple computations and interacts with users. WWNS are web-based and web browser, as is different from the foreign WNS solutions. Because almost all of mobile devices will be web-enabled in the future, the WWNS navigation service will be accessed by a variety of mobile devices.WWNS can provide comprehensive and elaborate navigation service. The reasons are: (1) WWNS servers with huge memory capacity can store as detailed map as needed and share information resources on Internet. (2) Complicated tasks are executed in servers with high CPU capability and the requests from users are responsed promptly. (3) The map dataset are updated online and are up-to-date at any time. (4) Serverssyncretize the real-time information and provide real-time information services. (5) Servers cany out personalized adaption and provide personalized services. (6) Servers intergrate other location-based services and provide intergrated services. WWNS systems have three problems that severely restrict their availability. The first one is map transmission, which results from the limited bandwidth of mobile networks. The second one is map access, which results from the huge map dataset. The third one is data processing, which results from the high cost of operations such as Map Generalization. The dissertation presents effective methods to deal with the three problems.For the data transmission problem, our researches focus on data transmission formats. By comparing the features of a series of transmission formats, the dissertation concludes that the XML-based SVG is the most appropriate one for WWNS. Original SVG documents are verbose, so we designed and implemented two methods to simplify SVG documents. Experiments based on actual map data set were made to measure the effectiveness of the two methods. Results indicate that when using GIF, JPEG and SVG to represent same maps, the simplified SVG documents are the compactest. Further, the following statistics were collected: for the transmission times of SVG-formatted maps through GPRS, whose resolution is 300*200 (pixel), 81% of them are less than one second. 97% of them compressed by gzip are less than one second. So it is feasible to transmit SVG-formatted maps throu...