| With the development of wireless network communication technology, computer technology and the improvement of performance of mobile devices, using wireless communications to combine the GIS and digital space, providing real-time mobile positioning and spatial information services has become an urgent requirement for GIS development. Mobile GIS is another fashion of GIS development after WebGIS. Mobile GIS based on GIS in embedded systems, takes mobile smart terminal as the information carrier and uses the integration of mobile computing technology, embedded GIS technology and the wireless network communication technology to change the geographical information acquisition and processing methods. Mobile GIS can make people enjoy the spatial information services provided by GIS in anytime on anywhere.This paper reviews the development background of Mobile GIS, introduces the research significance of vector data compression and transmission in Mobile GIS and the research results at home and abroad about the vector data compression and transmission. This paper also introduces the concept of Mobile GIS, architecture and its related technologies such as mobile positioning technology, wireless communication technology, embedded technology, and mobile computing technologies and so on. Through the related technologies of Mobile GIS, the characteristics of mobile smart terminal equipment and transmission environment are described, this paper analyses the importance of vector data compression in Mobile GIS. Combined with vector data compression algorithms and related optimized algorithms introduction, this paper analyses their advantages and disadvantages respectively and offers the improve algorithm for Douglas-Peucker algorithm which meets the requirements of compression, storage and transmission in Mobile GIS. The improved algorithm can solve the border distortion problem of Douglas-Peucker algorithm caused by it not considered the linear relationship in lines compression and also can control the area deviation in some extent, increase the accuracy of compression. The improved algorithm based on the compression of vector data, can better reserve the characteristics of the graph, and solve the problem of storage and display the vector data in the mobile smart terminal devices with limited hardware condition. This paper uses VC++ to realize the improved algorithm of Douglas-Peucker algorithm, using the vector data of MapInfo's MIF to compare with Douglas-Peucker algorithm by experiments, and then validates the Li-Openshaw algorithm which based on nature law.Finally, through studying the characteristics of vector data transmission by using wireless networks, combined with the development of wireless network technology currently and the requirements of mobile spatial information service, this paper introduces the idea of progressive transmission and discusses the principles and key technologies of the progressive transmission of spatial vector data. |
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