The Research Of Showing Speed Algorithm Of Embedded GIS Map Data

With the growing amount of map data and the improvment of GIS map function,GIS has more requirement to software and hardware conditions of computer.At present,it's increasing for GIS to be applied to the embedded equipment, but because of the limitations of existing hardware and software as well as the limited memory capacity, if all the map data can be stored at a time which can lead to extending the reading access time of map data, takeing too much memory space and the longer buffer time of map showing, which must affect the showing speed of GIS map data.As it is needed,combined GIS technology with the embedded technology may load part of data one time into the memory so as to solve the equipment memory insufficient and the slow showing speed of GIS map.The thesis mainly analysis and research R tree series and quadtree spatial index algorithm which are developed more maturer and make use of the respective characteristics of the R-tree and Quad-tree to improve their mixed structure QR-tree.Specifically,the GIS map is divided into four areas using the technology of Quad-tree and then R-tree is builded in each areas. At the same time,the stored region has been added in the improved QR-tree which mainly stores the nodes non-contained totally by region which are separated from contained completely in the modified QR-tree and the nodes are recorded in the root of the regions,which can not only save memory space,but also can be used to improve the efficiency of spatial operation and data retrieval speed during the data operation of searching,inserting and deleting.At last,the function modules of embedded GIS map have been designed and realized by using the Integrated Development Environment of Visual Studio 2005 and C# language and running in Windows Mobile 6.0 simulators.The realization of the basic functions include Opening the map, zooming in,zooming out,panning and layer control. After tests,by comparing the results show that the improved QR tree spatial index algorithm is applied to the GIS map,map displaying speed has been improved.