计算机毕业设计外文翻译--基于webgis的校园三维电子地图的设计与实现(编辑修改稿)

计算机毕业设计外文翻译--基于webgis的校园三维电子地图的设计与实现(编辑修改稿)内容摘要：

antage of JavaScript scripting language to realize the key functions such as loading maps, zooming maps, geographic location, and other related auxiliary functions, . map icon display, ranging, eagle eye, tags. Oracle database meets the need of the data which is used in backstage management, and together with the JSP, XML and HTML to realize the user39。 s authentication as well as adding, deleting, revising and inquiring information’s, etc. The main function of the system is to realize the three dimensional electronic map displayed in the browser through WEBGIS technology. Owing to the bination of JavaScript technology and WEBGIS development model, we can reduce the cost of the system, and at the same time improve the interoperability and system performance. Thanks 内蒙古工业大学 本科毕业设计 外文文献翻译 6 to the application of AJAX technology, we can make further improvement on loading dynamical map. All the technologies we use will reduce the reaction time, which will leave a quick and efficient impression on users. V. THE IMPLEMENTATION OF THE SYSTEM A. The fabrication of the threedimensional scene and scene rendering for map. The threedimensional electronic map of campus based on WEBGIS, is an electronic map system which takes the Northeast Petroleum University as the prototype. To realize this system, we should plete the fabrication of three dimensional scene and scene rendering for map, so we select 3DMAX whose operation is simple and flexible to model. Given the later needs of electronic map, the threedimension model should be delicate as much as possible. The three dimensional model39。 s construction would take up a great deal of time, due to so many plicated buildings of Northeast Petroleum University. To plete the threedimensional scene we should first prepare to render the scene well. Actually the grid picture which three dimensional electronic map used is the fixed angle of view swivel eye grid map. After modeling of three dimensional spatial entities, select the appropriate rendering method and make a fixed camera angle positioning in the render (Normally at 45degree angle ), and then set the render output parameters to render them into the camera from the perspective of fixed size picture[4]. B. Loading Map In the WEB, the maps are mainly shown through the Div layer which has three layers. One layer is used as a window the carrier of the map. The size of the layer is as large as the map which we usually see through the browser (referred to as the window layer). Another layer is the moving layer used to follow the drag of the mouse (referred to as the moving layer).The other is the covering layer which lies between the window layer and the moving layer. The map window operated by users is constituted by the three layers mentioned above. Basic operations of the map are realized through setting features in different layers [5]. When loading map, we use the raster data which we usually call image data. Raster data includes image data, two dimensional map, and threedimensional simulated 内蒙古工业大学 本科毕业设计 外文文献翻译 7 electronic map. The raster data in this system is threedimensional simulated electronic map. The abstract twodimensional map makes some ordinary users difficult to learn the information they need, but the threedimensional simulated map simulate the real world39。 s information exactly, so users can easily see the real world. This system mainly displays the map picture, when you view or drag the map, it just like a plete map picture of the current window, but in fact patchwork of small pictures. These small cards are cut from plete map by the specific cutting diagram program。 all the picture cards are the same size and have fixed naming rules, so the map is faster and easier to load. There are many methods to plete the map carving, the system use square slab method to cut the map to 256 pixels * 256 pixels. Then write the script which based on the naming rules to plete the picture load. C. The Basic Function of Map Dragging, zooming and translation are the basic functions of the map, and they are also important features of the map that differ from a simple picture. The following is a brief description of the implementation method. To realize dragging, the first thing is to set the mouse event functions. The events include mouse down and mouse up. So the two functions bined can plete the map navigation. The mouse down event is mainly used to record the drag state as well as the present location, while the mouse up function will capture the dragging pletion status, then use show map function to reload maps. Process of realizing zooming function as follows:  Gain ratio value before amplification and the proper ratio value needed to enlarge.  Cal。