The Research And Implementation Of Map Symbols' Symbolization In GIS

Geographic Information System is refered to as GIS, and it is defined as the collection, management, operation, analysis and display of spatial data in computer software and hardware systems. GIS has a great ability to deal with spatial data, such as digitized maps, vector and image browser query, analysis based on spatial data, three-dimensional simulation, virtual reality, the map output and so on.The main feature of GIS is the management of geospatial data. one of the core issues is how to build geo-spatial database of GIS applications, map as one of the main data source in GIS, in geo-spatial data acquisition aspects of an extremely important position. Map is also the main form of product performance in GIS applications. The map symbols are the basic means to express the map content. it is not only to express things' spatial location, shape, quality and quantity features, but also the contact of the various objects and the overall features of the region.Map symbols are the language of the map. it expresses the variety spatial objects' graphic mark and note used with on the map. High-quality map symbols are necessary precondition for content-rich of maps, enhancing map legibility and convenience mapping. So map symbols occupy very important position in GIS. GIS using geometric form of point, line, surface or other form to express spatial data, which requires the corresponding geographic information systems support has a wealth symbols of points, lines and surface, that is necessary to establish a suit of perfect map symbols, by the map symbol library management. Therefore, design a comprehensive, systematic, precise map symbol library is of particular importance for GIS applications.At present, GIS software and mapping software contain their own symbol library system at home and abroad, but there are still a lot of deficiencies. In this paper, analysis the symbol types and functions of map symbol base on effective solution variety of questions, depth study the composition rule and construction theory of point, line, surface symbols, and designed data storage structure for point, line and surface symbol library, and design the structure to realize point, line, surface symbol library use object-oriented programming design method.In this paper, the map symbol library system is divided into symbols design management modules and symbol mapping module two parts, the symbols design management modules independent of the system exist as the symbols editor, Symbol mapping module is responsible for drawing symbols on the map based on actual need use the designed symbols. this design method mitigate of system platform running burden can expand the functions of the symbols design module. At the same time, it do not affect the structure of the platform system, in addition, the system for different platforms use the same symbol library provides a new idea. In order to enable more convenient and efficient for symbols design, this thesis design symbols using graphics element.For the distortion phenomenon of Overlap, Cross, rupture, Blank ,when we fill with line symbol, this paper do a certain improvement based on the ideal of horizontal circle filled linear symbols. It not only results in the very good visual effect but also improve the efficiency of the filling algorithm. At the same time, This paper presents a new polygon filling algorithm based on vertex storage types. The algorithm will divide the polygon vertex and the new nodes into three types of storage, and then the scan line through the vertex will divide the polygon into several regions to fill. This algorithm only refers to the scan line in the vertex and the pixel coordinates of the polygon edges can be directly calculated from the linear equation of the polygon edges. Consequently, the algorithm greatly reduces the computational complexity.