Web-based terrain and vector maps visualization for Wenchuan earthquake Liqiang Zhang a, *, Zhizhong Kang b , Jonathan Li c , Ling Yang a a State Key Laboratory of Remote Sensing Science, Jointly Sponsored by Beijing Normal University and the Institute of Remote Sensing Applications of Chinese Academy of Sciences, Beijing 100875, China b Department of Geomatics, School of Land Science and Technology, China University of Geosciences, Beijing 100083, China c Department of Geography & Environmental Management, Faculty of Environment, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada 1. Introduction On May 12, 2008, Wenchuan of China happened a serious earthquake. It caused much great damage in 42 counties in Sichuan province, 23 counties in Gansu province, and 19 counties in Shanxi province. Other provinces such as Chongqing, Yunnan, Shanxi, Guizhou and Hubei provinces also have been influenced in this earthquake. We have developed an earthquake application system which could provide functionalities for disaster information manage- ment, visualization and statistical analysis. It utilizes Web-based 3DGIS environments to manage the disaster database and visualize the monitored and analysis results. For earthquake disaster situation assessment, we need to integrate various remote sensed and aerial imagery and GIS data into an application for making decisions. The volume of these datasets is large, and is often distributed in remote computers. In order to visualize efficiently these earthquake-related spatial datasets and provide a good 3D user graphical interface for earthquake decision makers, transmis- sion and visualization of DEM and vector maps are discussed in this paper. 2. Related work 2.1. Multiple representations of 3D geographical models Lindstrom and Pascucci (2002) presented a method called SOAR for efficient out-of-core management and rendering of continuous adaptive terrain representation. The refinement framework is easy to display huge terrain datasets at high interactive frame rates. Cignoni et al. (2003) used a technique called P-BDAM for out-of- core management and interactive rendering of planet-sized terrain surfaces. It is said that it achieves better peak performance than SOAR on the same machine. Yang et al. (2005) combined TIN with Grid to construct multiresolution terrain models. They developed a method for encoding and storing vertex topological relationships in multiresolution terrain models. The connectivity among the triangulations needs to be stored and thus the method consumes lots of computation. Estkowsk and Mitchell (2001) presented the complexity for maintaining topological relations and used the ‘‘detours’’ to eliminate the wrong intersections based on Douglas–Peuker polyline simplification method. Mustafa et al. (2001, 2006) proposed a Voronoi-diagram-based algorithm, which took ad- vantage of the graphics hardware. It has a higher computational efficiency, and avoids the wrong intersections between the output lines, but this method cannot avoid self-intersections. Mantler and Snoeyink (2000) also presented an algorithm using the Voronoi diagram. They divided a complex polyline into a International Journal of Applied Earth Observation and Geoinformation 12 (2010) 439–447 ARTICLE INFO Article history: Received 3 August 2009 Accepted 12 January 2010 Keywords: Wenchuan earthquake Visualization Progressive transmission ABSTRACT This paper presents a Web-based three-dimensional Geographic Information System (3DGIS) for Wenchuan earthquake disaster assessment. With the help of information technology resources, geoscientists are in a position to learn more about the structure of the earthquake in efficient ways. Due to huge spatial datasets of Wenchuan, China and narrow network bandwidth, general-purpose applications are difficult to transmit and visualize these datasets on the network. The application aims to interactively represent and transfer large spatial objects of Wenchuan County, China, as well as for dynamically rendering them in networking environments. Level-of-detail (LOD) terrain models and vector maps are created, and the server–client architecture is presented. The application provides an effective way for powerful access and manipulation of large-scale Wenchuan datasets. ß 2010 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: zhanglq@bnu.edu.cn (L. Zhang). Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation journal homepage: www.elsevier.com/locate/jag 0303-2434/$ – see front matter ß 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jag.2010.01.001