基于网络地理信息服务的选线数字地形获取方法

针对道路前期规划阶段纸质地形图陈旧、数字地形信息获取困难且成本高的特点,在综合分析当前开放网络地理信息资源的基础上,利用航天飞机雷达地形测绘使命(shuttle radar topography mission, SRTM)数据和Google Maps影像,提出了获取构建道路数字化选线系统虚拟地理环境所需的数字高程模型 (digital elevation model, DEM)和数字正射影像 (digital orthophoto map, DOM)的方法,并设计了Google Maps影像瓦片快速下载方法;基于分治法的思想,提出了一种全局非线性、局部线性的Google Maps影像变换算法,实现了与SRTM数据的快速配准,并在此基础上进行了地形数据获取与建模测试.研究结果表明:通过自动计算瓦片URL地址,采用libcurl库函数和多线程下载技术,下载影像瓦片速度稳定、快捷、自动化程度高;获取的DOM分辨率可达0.2 m以上,与DEM数据配准后,构建的虚拟地理环境能满足道路前期规划阶段开展数字化选线设计的需要. 

Web Geographic Information Services-Based Acquisition Method of Digital Terrain Data for Highway Location

In the initial stage of a highway planning, obsolete topographic maps and the difficulty and high economic costs in acquiring digital terrain data always present challenges for digital location design. To address these challenges, a method based on comprehensive analysis of current geographic information resources available in the open network was proposed. It makes use of the shuttle radar topography mission (SRTM) data and Google Maps images to acquire the digital elevation model (DEM) and digital orthophoto map (DOM) for modeling in the virtual geographical environment (VGE) of highway digital location system. Then, a method for quick download of Google Maps image tiles was developed; a globally nonlinear and locally linear compression algorithm for the transformation of Google Maps images based on the divide-conquer method was proposed to realize quick match with SRTM data. Finally, terrain data acquisition and modeling test were conducted to verify the proposed method. The results show that stable, quick, and automatic download of image tiles can be achieved by automatically calculating tile URL address, using libcurl library functions and multithread downloading technology. The resolution of the acquired DOM is greater than 0.2 m. After data match with DEM, the constructed VGE meets the requirements of highway digital location design in the initial planning stage.