Research On Key Technologies For Cross-platform Embedded GIS

Embedded GIS is an important research field of GIS and it has a broad prospect of application. However, because of the diversity of platforms and the limit of resources, most embedded GIS are designed according to the specific embedded environment of software and hardware. As a result, their functions are relatively simple and it is impossible to realize the cross-platform application. In order to solve these problems, the dissertation conducts researches on the implementation methods of cross-platform embedded GIS and the key technologies in the implementing process. The main contents are as the following:1. The research background, relevant theories and current technologies of embedded GIS are analyzed. The significance of the research is elaborated, and the characteristics of embedded GIS, its technological differences with desktop GIS and implementing technologies and methods are summarized. The latest research achievements and development trends at home and abroad in the field are analyzed in depth, and the main problems are pointed out.2. The relevant technologies for cross-platform embedded GIS are researched in depth. Based on the research, the architecture of cross-platform embedded GIS is designed according to the hierarchical structure. The GIS middleware platform is added on the hardware platform and the operating system. In this way, the development of GIS software is no longer dependent on specific operating environment, which paves the way for crossing different platforms. A GIS functional component layer is built on the middleware platform, and each function of embedded GIS is packaged into the reusable component to improve the reusability of codes.3. An embedded GIS middleware platform named EGIS_MW is designed. The architecture of it can be divided into system abstract layer and GIS service framework layer. In the system abstract layer, EGIS_OSAdapter class is designed for operating system adapter, and EGIS_OSDrawlnterface class for graphic drawing. The graphic drawing function is packaged into the EGIS_OSAdapter class, and EGIS_OSAdapter class serves as the unified interface to various operation system services for GIS application.The GIS service framework layer is based on the system abstract layer. According to the characteristics of embedded system, the GUI interface, the extended graphic interface, the file processing interface and the fixed point calculation interface are designed in the GIS service framework layer. In this layer, the design method of GUI interface is object-oriented, windows and widgets are packaged into some classes, and the message transferring is managed in observer mode. The extended graphic interface mainly extends the graphic drawing interface such as point, line, surface and text in the system abstract layer, and it also provides more graphic interfaces. The cross-platform file processing interface achieves the cross-platform file reading by automatically converting the byte order of geospatial data to native byte order by EGIS_File class. The fixed point calculation interface greatly improves the real-time performance of embedded GIS analysis by converting floating point calculation to fixed point calculation by EGIS_FixedCalculate class.4. The map display technologies of cross-platform embedded GIS are researched. The characteristics of electronic map and the correspondence between map display and platforms are analyzed. Based on these research and analysis, it is concluded that the problems of cross-platforms and highly efficient displaying have to be solved in embedded environment. In order to solve the two problems, a map display engine architecture based on EGIS_MW platform is designed, and a cross-platform map symbol library is built, so that the map display engine is completely independent of platform. A hybrid organization model of multi-source data that is adapted to the multi-scale expression in embedded environment is designed, and a multilevel hybrid index for geospatial data is established according to the data organization model. A map data parallel display algorithm based on multi-buffer technique that can satisfy the requirement of embedded GIS map display is designed, and the high efficiency of the algorithm and data organization model are validated by experiments.5. The route programming technology is researched. By analyzing the characteristics of embedded GIS route programming, the design principles of the route programming module in embedded environment are established. An architecture based on EGIS_MW platform for route programming cross-platform application is designed. In the architecture construction, the main work is to design the route programming module based on the file processing interface and the fixed point calculation interface of the EGIS_MW. The physical storage and the memory structure of road network data are researched. The physical storage of road network data is organized and stored by adopting the multi-source data hybrid organization model adapted to embedded multi-scale expression. The road network data is organized and stored according to the forward star structure during the route programming. The A* algorithm for hierarchical search based on transformation network method is brought up to meet the requirement of real-time navigation. It has been validated by experiments that the algorithm can identify and deal with various traffic control information and the delay in the crossing, and it can achieve high calculation efficiency and fully meet the requirements of real-time navigation of embedded GIS.The theories and technologies have been applied to several embedded GIS in different software and hardware environment. It can be concluded that the research achievements based on the dissertation will promote the development of cross-platform embedded GIS application software that satisfy the need of practical use, and they are of great theoretical significance and practical value to the rapid explanting and expanding application of embedded GIS.