基于OpenGL技术的多幅电子地图数据快速组织与表达

电子地图符号化的质量和绘制速度一直是地图工作者关注的重点。目前,地图符号化的质量基本能满足各类用户的需求,但是,电子地图绘制速度较慢的问题,特别是在涉及较大数据量的多幅电子地图显示时,系统响应用户操作时间比较长,影响用户操作体验。本研究分析比较了GDI与OpenGL的特点,提出使用OpenGL相关技术实现地图要素的符号化方法,并用内存池技术和共享显示列表的多线程调度技术实现多幅电子地图数据的快速组织与表达。实验表明,利用文中的方法能够实现地图点、线、面要素的符号化,并在地图数据的漫游、缩放操作的屏幕绘制速度基本保持在17帧/s以上,表明利用本文的方法和技术提高了系统的显示速度,保证了用户与电子地图良好的交互效果。

Fast Organization and Expression of Multi-sheet Electronic Map Based on OpenGL Technology

The quality of map symbolization and the display speed of the electronic map are always the hot issues for the cartographers.The availability of the electronic map mainly includes the effectiveness,efficiency and user subjective satisfaction.Currently,the map symbolization quality can meet to the basic needs of various user groups,but electronic map rendering speed has affected the feelings of map users.Since the electronic map involving large volumes of data,it needs a relatively long period of time to respond to user＇s operation,causing the user to generate anxiety and dissatisfaction because of waiting,so it is difficult to give map users more smooth operating experience.For the problem of improving the rendering speed,current studies mainly focused on data block processing,hierarchical processing and the establishment of efficient indexing model to improve the efficiency of electronic map display by reducing the amount of map data.Based on analysis and summary on the improved multi-sheet electronic map rendering speed,this research compares the characteristics between GDI and OpenGL.When we use GDI and OpenGL to draw 2D entities at the same time,if the number of primitive is small,the difference is not large.But if the number of primitive is large and primitives are static,the rendering speed using OpenGL is far faster than the GDI,because OpenGL can use display list technology,texture mapping and vertex data technology.In this paper we presented and implemented a symbolic method in three-dimensional interfaces for the different types of features.It proposes the way of expression and organization of multi-scale data in the three-dimensional space through multithreading technology and memory pool.The experimental results show that it is able to achieve the symbolization of point feature,line feature and area feature.And roaming,zooming in multi-sheet electronic map data,screen rendering speed remain at more than 17 frames per second.So,using methods and techniques mentioned in this paper can improve rendering speed and ensure the good interaction effect between user and map.