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.