3D Data Acquisition by Terrestrial Laser Scanning for Protection of Historical Buildings Yinghui Xiao, Qingming Zhan School of Urban Design Research Center for Digital City Wuhan University Wuhan, China yhxiaoitc@126.com, qmzhan@whu.edu.cn Qiancong Pang School of Remote Sensing and Information Engineering Wuhan University Wuhan, China Abstract—With the development of information techniques and the need of digital earth and cyber city, the three dimensional (3D) information play much more important role in presentation and illustration of historical buildings. 3D modeling and virtual reality techniques have demonstrated the ability of visualizing the real world in three dimension space which provides a platform for better communication and understanding of historical buildings. This paper focuses on the acquisition of three dimensional data by using terrestrial laser scanners. Firstly, we review different approaches for acquiring 3D data and their advantages and disadvantages. Secondly we focus on a newly developed technology – terrestrial laser scanning. Thirdly, we present the practical use of a 3D laser scanning system: Riegl LMS-Z420i in a historical cultural heritage site, San Fan Qi Xiang, Fuzhou city, China. Finally, the testing results and the conclusions are provided. Keywords-3D data acquirsition; Terrestrial laser scanning; Historical heritage I. INTRODUCTION Digital city provides a framework to accommodate spatial and non-spatial information and provide powerful tools for 3D modeling and visualizing virtual 3D scenes of a cyber-city. It is required to have a fully understanding of a historical heritage before protecting or rebuilding it. In particular, 3D visualization and simulation play essential role in historical buildings. Due to its high historical value, it is important to measure and model a historical site including many ancient buildings with relatively high accuracy. Thus we aim at efficient approach for precision 3D data acquisition toward the establishment of measurable 3D models of the historical site, San Fan Qi Xiang (SFQX). In section 2, we give a review on available approaches for 3D data acquisition for 3D modeling. The testing site, instrument and the testing processes are introduced in section 3. The testing results and discussions are also presented in the same section. The conclusions and suggestions are provided in the last section. II. A REVIEW OF THE APPROACHES OF 3D DATA ACQUISITION A. Map-based approach Since the buildings are the dominating features of cities, reconstruction of 3D buildings is the main task in construction of a digital city. The map-based 3D data acquisition is a widely used conventional approach due to availability of the existing maps. The two dimensional data (X, Y) can be acquired from large scale topographic maps either in paper or in digital form. The height (Z) of building can be obtained based on the number of floors. By integrating these two, the 3D data can be collected. For the digital terrain model (DTM), contour lines are digitized from topographic maps for building DEM. This approach is usually applied by integrating 2D and 3D software packages such as AutoCAD and 3D max to build the 3 D models and other objects. With the development of geographic information system (GIS) and the enhancement of its 3D capability, this approach can be implemented relatively easily in a GIS environment and with a moderate accuracy in the Z dimension. However, it is done manually in most cases, thus it is labor-consuming. Additional work is required too to obtain the texture of buildings, which is essential in reconstruction of a realistic 3D model. B. Image-based approach The image-based 3D data acquisition is usually performed by using stereo image pairs. Both aerial-photogrammetry and close-rang photogrammetry are based on a block of overlapped images [8]. It has been proved to be a primary approach for 3D data acquisition and object reconstruction. Photogrammetry has been considered to be a classic and dominant approach for mapping of a large area. It is proven to be stable and accurate approach for 3D mapping in a moderate scale (1:5,000 to 1:50,000). With the development of digital imaging technology and the high-resolution space-borne sensors such as IKONOS, QuickBird, the image-based 3D data acquisition and modeling has been regarded as a cost effective approach in terms of large area mapping in a moderate scale. However, the obtained accuracy (decimeter) and the actual image resolution may not 1-4244-1312-5/07/$25.00 © 2007 IEEE