The Design And Implement Of Partial Database In Vehicle Navigation System

With the rapid development of socio-economic construction and the continuous expansion of the city scale, the traffic system in the city is becoming more and more complex, especially in recent years, the growth rate of the vehicle has been much faster than the road and other transport facilities. As the negative impact, the phenomenons such as road congestion, traffic accidents, environmental pollution and energy waste are becoming more and more serious in the world. In order to solve these problems, experts and scholars at home and abroad have put forth the Intelligent Transportation Systems(ITS), ITS is the real-time, accurate and efficient transported integrated management system that builded by effectively applied advanced information processing technology, data communication technology, electronic control technology and computer processing techniques into the whole integrated transported management system.Vehicle Navigation System (VNS) is an important component of ITS system, it is the high-tech integrated system that integrates automatic vehicle location technology , geographic information system technology, database technology, multimedia technology and modern communication technology and so on. VNS includes the functions such as path planning, map matching, route guidance, map display and target query, all these functions can not be separated from the support of navigation database. At present, the manufacturers can only provide some electronic maps supported by GIS development platform such as MapInfo because there are not yet the national vehicle navigation special map database standards. So what must be done is to read the data and build the navigation database from the electronic map file mentioned above. The information in the navigation database consists of the road network geometry, road hierarchy, road characteristics (such as the restrictions of single and two way, speed limits, turn, etc.), geo-political region, the interested target, servicing facilities, etc. They service the functions such as map-matching, route planning, map display and target query respectively.This paper makes research on the design of database in VNS, mainly includes the following: The storage structure of digital map data; the design of vehicle matching navigation database, the design of vehicle positioning module and the design of destination query database.1.Making research on the storage structure of digital map data. First introduces the model of electronic map, including the flat data model and non-flat data model, the data structure includes the vector data structure and raster data structure. Designing a simple network model by comparative analysis and combinating the actual needs of this paper. That is dividing the road network data into network node and sections category according to the theory of computer graphics, storing the digital map data by using the data structure of linked list. After that, designing two types of linked list according to the need of the navigation data, the node linked list and the section linked list. Finally, adding the rurning restriction class into the storage structure of adjacent linked list considering the rurning restriction.2.Making research on the establishment of vehicle matching navigation database. The key of the matching algorithm is looking for the current road. The basic idea is comparing the positioning information measured by vehicle sensor with the road in the electronic map and determining the road on which the vehicle is traveling. For a city vehicle navigation system, there may be hundreds of roads, it is impossible and unnecessary for map matching algorithm to compare every road in the map database with the measured location information. So, the determination to the scope of the candidate path is the key factor that affects the swiftness of the algorithm.So it is right to choose the roads that centered by the anchor point and is within a certain radius due to the error of the anchor point is always at a certain extent. When choosing the radius, not only taking into account the positioning error, but also the the width of road etc. It is easy to increase calculated amount and lead to the false justice, on the contrary, it is impossible to find the road on which the vehicle is traveling in the neighboring areas. As a better solution, the moving window technology can be used to solve this problem, achieving the fastness of the matching algorithm. Further more, making the improvement such as proposing the new moving window technology, researching the extraction and storage of grid road information, proposing the two index model on the base of original database mode. Finally, making the comparative analysis to the algorithms above in the aspects such as data storage capacity of the grid index table, the time of building a grid index file, the efficiency of data retrieval, the effective area of the candidate region etc.3.Making research on the design and implementation of vehicle positioning module. First, briefly introducing the principle of GPS navigation and positioning, studying the coordinate transformation principle of positioning data transmitted by the GPS location module. After that getting the work principle of the positioning module in VNS of this paper, taking the abstract method in the actual realization of the vehicle positioning module. That is abstracting the actual car into an point in the map to located the vehicle easily. Implementing by the VC+MapX widget: First, constructing the dialog box to receive the coordinates provided by GPS coordinates receiver. Second, finding the corresponding location according to the provided coordinate values. Finally, drawning the corresponding coordinate symbol in the finded lacation, which solving the problem of continuous vehicle positioning encountered in practical applications.4.The research to the method of building the spatial information query database. The fundamental task of spatial information query is to find the geometric spatial location of the object when the user specifies the destination name of the object. The spatial information query studied in this paper contains qualitative inquiry and location query. First, designing the database based on the inquiry function. Then illustrating the implementation method of spatial query function. Finally, developing the software program with the spatial information inquiry function using the VC programming language and MapX control, simulation completes the corresponding spatial information query function, further verifies the feasibility of this method.There are still some problems needing to be thoroughly studied and solved although some databases of VNS is designed in this paper. I hope that the research in this paper could make contribution to the development of VNS in our country.