Retrieval method of enormous POI in vehicle navigation system

In vehicle navigation system, POI(points of interest) retrieval is important. Since the restriction of the embedded system, the retrieval should deal with enormous POI data in limited external memory and internal memory, when the retrieval speed should fit for the vehicle navigation. The rapid retrieval method is designed for solving the problem. The method is based on Chinese Pinyin. It includes the storage method of search table with digital search tree and character compression. The method for retrieving in the compressed data is also designed. By the design, the size of the file for the POI retrieval is reduced, so the demand of external and internal memory is lower, when the retrieval is fast enough for the vehicle navigation.