The Study Of Two-Dimensional Flow Hierarchical Search Algorithm Base On Navigation Path

GIS(Geographic information system) is used for acquisition, storage, management, processing, retrieval, analysis and presentation of geospatial data in the computer system,it is a common technology for analyzing and processing mass Geographic Data. With advances in computer science and technology and the development of social economy, GIS application is more and more used in daily lives. With the progress of era and development of social economic, making the road information more and more complex, the data of road information storing in external memory such as SD card is also increasingly large, the possibility of storing all the road network map data into memory in one time is becoming smaller and smaller, Therefore, the focus of this paper is how quickly and effectively block access to the data that is read into memory. This paper researches path planning based on block data retrieval mechanism which based on analyzing the external memory Road network data partitioned index-organized hierarchical storage mechanism. Proposes two-dimensional grid-based data flow block search algorithm.This paper studies the navigation path to retrieve the data block division theory and the optimal path search algorithm based on this theory, it mainly does the following researches:(1) Analyze the structure of navigation map's spatial data, and the storage format in electronic hard disk, and pretreatment the electronic map data.(2) Analyze the mechanism of massive electronic map data stored in the external storage, and research the embedded database retrieval theory. As the road path planning required for large road data, it is difficult to read all the data into memory in one time, so when do path planning, this paper research focus on finding the optimal path topology data(block) quickly and accurately from the external memory database. This paper will use a new index model"grid-based three-level Convergence index model",use this index model for retrieving data rapidly, it makes reading the path topology data into memory each time do not exceed the size of the memory limit. (3) Base on the above theory, propose appropriate search way to finding the optimal path in order to verify the correctness and reliability of theory. The amount of data reading into memory each time is limited, so the optimal path between two points using these topology data is not enough, the map topology data must be replaced several times, and find the optimal path eventually. The paper studies a new research way to find optimal path from the external memory database based on the previous path planning algorithm.