The Research Of Map Application Technology Of Vehicular Central Navigation Based On IPv6

With the rapid development of the economy, the sustained growth of the number of carsbrought a series of adverse to the lack of management of the traffic system, which severelylimited the safety and smooth travel of the majority of users. Facing the increasingly seriousproblem of the traffic congestion, the Intelligent Transportation System(ITS) is gradually re-vealed his importance, and as an important part of ITS, the Vehicle Navigation System(VNS)has also received the wide attention from all walks of life; at the same time, based on the con-tinuous improvement of cost-effective of the embedded equipment, and the widely use of thegeographical information system technology, and as well as the rapid development of thecommunication technology, the central navigation system is gradually become to be the keyresearch of the VNS.Be different with the traditional autonomous navigation system, the navigation terminalof central navigation system does not store any map data, but partition the map data at thecentral server by the map block strategy, and apply for downloading the data real-timethrough the wireless network; at the same time, rather than using the static storage of geo-graphic information and network topology relations, according to the real-time road condi-tions, the central navigation system can provide real time navigation service for users dynam-ically based on the traffic, so as to ensure the traffic system work real-time, accurately andefficiently, and alleviating the urban traffic congestion efficiently; in addition, through themonitor terminal, the central navigation system can monitor the Electronic Control Unit(ECU)of the vehicle all the time, and provide remote fault diagnosis and repair service by using thewireless network, and guarantee them working safely.As an important part of central navigation system, the map is related to the realization ofmany functions, so the purpose of this paper is to study the related techniques of the map ap-plication.In order to ensure the map data display in real time, the navigation terminal needs topre-fetch the map data under certain conditions. Through the analysis of simple pre-fetchstrategy found that due to the number of pre-fetched map unit is substantially constant, andsome of them may be discarded with no use, which led to a lower hit ratio of map unit, so inorder to improve the hit ratio, under the improved pre-fetch strategy, the navigation terminalconsiders the current road network information when it need to pre-fetch map unit, and dis-cusses the pre-fetch strategy on two cases according to the following circumstance of the road,which are unique path and multi-path, at the same time, there are inducer with path planning or not under the multi-path circumstance. When the successor of the road is unique or theterminal uses the path planning, the vehicle only can travel along this road, so the system onlyneed to pre-fetch the map unit which is associated with the road; otherwise, when the terminaldoes not use the path planning under the multi-path environment, the system can process eachsubsequent road as an unique path separately.The map display, as an important function of the navigation terminal system, through thetest we found that it is possible to ensure that the vehicle is always in the central position ofthe screen, but the direction of the map data refresh changes while the direction of the vehicletravels changing, when the user determines the direction, this way will add additional psy-chological burden. Therefore this paper puts forward the map data rotate, which manner isdetermined by the principle of “upward is forward”. Bases on the advantages and disadvan-tages of the bitmap and vector diagram, meanwhile, considers the running time complexity ofthe system, we design the vector map rotate, and redraw the map data under the fixed condi-tions, so as to the map data refresh downward, and the vehicle looks like driving toward theup of the screen, in order to provide convenience for user.The monitor terminal, as a part of the central navigation system, in order to monitoringthe vehicle and limit its driving area, so as to ensure it traffic safety, this paper pus forward thefunction of electronic fence based on the central monitoring, at the same time, in order tomeet the different requirements of industries, we design and implement three electronic fences,such as rectangle, round and polygon. In order to avoid the failure of the monitoring, when themonitor terminal updates the map data, the system updates the point coordinates simulta-neously, in order to ensure the range of the electronic fence is consistency with its initial set-ting which relatives to the map data.Finally, the simulation and test-bed test are given, in order to verify the validity and ra-tionality of the three kinds of map application technology. The result indicate that the im-proved pre-fetch strategy and map data rotate can improve the hit ratio of the map unit andsatisfy the real time requirement of the map display to some extent, at the same time, the elec-tronic fence of the monitor terminal has a good performance and can run inerrancy, whichprovides a reliable guarantee for the driving safety of the vehicle.