Vector Graphics System Development For The Grassland Digital

Management of grassland resources is in the transfer direction from extensive tointensive period in China. We propose a set of "3S integration" as the technical meansof pasture resource management system. Pasture through the establishment ofregional geographic information system (GIS), remote sensing technology with (RS)and Global Positioning System (GPS), with high spatial and temporal resolution,multi-level, dynamic description of spatial and temporal distribution of grasslandresources, and provide a basis for Scientific and reasonable management to achievesustainable development of grassland resources and classification of business.Although in recent years, the number of domestic and foreign research institutionsconducted a number of grassland, and developed some practical systems. However,these studies and systems tend to concentrate on individual issues, such as grasslandfire prevention, pest and disease prevention. AS the digital study of grassland issueare in the early stages both at home and abroad, so the study of the issue has verygood prospects and space. Establishment an integrated WebGIS platform in theresearch of grassland become a more important aspect of the "resource-savinglivestock industry in the northeast digital management key technologies", and it is toprovide management and decision-making information technology systems.After 40 years development, it has become a relatively mature technology today,and has been a very wide range of applications. Is was widely used in resourcesurveys, environmental assessment, disaster prediction, land management, urbanplanning, post and telecommunications, transportation, military police, waterelectricity, public facilities management, agriculture, forestry, animal husbandry,statistics, almost all areas of commercial finance. GIS development model has alsogone through several developments, from the initial GIS module to the current component-based GIS and WebGIS. GIS has also appeared in the form of theperformance of two-dimensional and three-dimensional GIS. In the existing GISplatform, there are brought to-use sophisticated GIS platform, there are available forsecondary development of the GIS, and there are the professional GIS developmentpackage. After we investigated using a variety of existing GIS platform, exclude somemature professional GIS platforms with no copyright, and experience the languagebarriers in open source GIS platform secondary development, we finally choose theway to self-developed GIS based on the VC and MFC. Next, after we analyzedseveral development models of GIS, finally chose the way form component-basedGIS to the WebGIS. In the development process of GIS platform, through systematicanalysis, based on selected priority development strategies, object-oriented as theguiding ideology, to achieve the vector graphics system.Our article describes in detail the vector graphics system implementation process.From the most basic device draw class and basic coordinate system to the realizationof the basic GIS functions.In Chapter III of this article, mainly introduces the vector graphics system is basicdevice class, involving several brushes; device coordinates and logical coordinates,coordinate conversion between the user and relationships; and in accordance with theobject-oriented graphics are divided into point, line, surface and text class object. Topremise the project's needs, defines several graphics to use.In the fourth chapter, we achieved the drawing function which is the mostimportant and most basic portion of in each graphics system. Reference to othergraphics systems'function, in our system we use the mouse interaction mapping.Based on the mouse movement message handling functions which offered bywindows, we have chosen what our system needs. And added eight kinds of mousehandling functions in the MapEdit class, responsible for rendering and editinggraphics. Described the whole process of drawing graphic in detail, Combined withtiming diagram and the mouse information, we introduce Graphics initialization, startplotting, the moving graphics draw, the end of draw, graphics storage, editing graphicsand delete the object function. Then we realized some of the basic functions for the GIS, through the coordinatesystem conversion and the window proportional coefficient changes to achieve thezoom and selection function. In the realization of the process of selection functions,we achieve the function of bounding box settings for each graphic object, andcompleted a variety of graphic object is selectable marker drawing functions. Finallywe achieved point, round and rectangle three select object's ways. Grasslands GIS asa display of information systems, in order to meet project needs, defined some morecomplex linear and filling effects in the system.At present, under the joint efforts of students, the vector graphics system has beencompleted. We also achieved a number of GIS functions. And we implemented tomeet demand for a more complete grass vector graphics system. In dealing with thesome of the basic show issues in the project at this stage, has been able to play acertain role. Our system has been the base for the future WEBGIS'research anddevelopment, and supplied a data specification for other subsystems of the project.