本文在分析嵌入式环境下平台差异和计算、存储与显示等资源有限对数字地图可视化限制性的基础上,基于中间件思想,提出了跨嵌入式操作系统平台的数字地图可视化中间件EMD_MW(Embedded Map Display_MiddleWare),设计了操作系统抽象层、服务框架层和功能层中间件体系结构。利用操作系统抽象层,提取与数字地图可视化相关的操作系统消息转发和图形图像绘制接口进行抽象,屏蔽了不同嵌入式操作系统之间的异构性;利用服务框架层屏蔽了数据存储差异性,扩展了基本图形绘制接口;通过功能层提供数字地图显示各类接口,并详细阐述了EMD_MW的抽象层、服务框架和功能层的设计和实现,给出了基于EMD_MW的几种工程应用。本文设计的跨平台嵌入式数字地图可视化中间件,已在多个嵌入式地理信息应用系统中得到检验,表明该中间件具有良好的跨平台特性,较好地解决了不同嵌入式平台下的数字地图显示问题。
Along with the continuous development of computer technology, internet and wireless communication technology, digital map visualization, as the core of geographic information system, has been widely used. At the same time, with the increasing number of embedded software and hardware, a variety of heterogeneous plat- forms bring great challenges to the development of embedded geographic information system. Therefore, it is im- portant to study the digital map visualization method for cross-platform purpose. Firstly, after comparing the dif- ferences of middleware between the embedded system and desktop system, this paper summarizes the character- istics of the embedded middleware, and analyses the platform differences and resource restrictions for digital map visualization in the embedded environment. Based on the concept of middleware, a cross-platform middle- ware of digital map visualization with three layers: EMDMW was constructed. The middleware utilizes the op- erating system abstraction layer to prevent the heterogeneity from different embedded operating systems, and to abstract the operating system message forwarding and the graphic interfaces associated with the digital map visu- alization. Meanwhile, the model utilizes the framework layer to dispel the differences among data storage servic- es, to improve the base graphic interfaces, and to provide relevant digital map display interfaces through the func- tion layer. Then, the abstraction layer, service framework and function layer of EMD_WM were designed and re- alized. Finally, several engineering applications based on EMD_MW were presented. These examples indicate that, the embedded cross-platform middleware model for digital map visualization has a good cross-platform per- formance, and it can effectively solve the problem of digital map display on different embedded platforms.