Abstract
Abstract. A new way to document and visualize the as-built condition of an urban tunnel project with high accuracy is described in this paper, based on recent developments of laser scanning technology. In traditional surveying, the components of a tunnel are organized on the basis of the location of stations and offsets along the project alignment specified in the drawings. It is difficult for people without an engineering background to understand the information involved in surveying reports, drawings, and engineering data. However, in the interest of transparency, public agencies that commission construction projects have to make project information available to government officials and to the general public. This paper discusses the combined use of laser scanning technology and web mapping services to improve the documentation and visualization of an urban metro tunnel. Laser scanning technology is introduced to perform the surveyor's task, document the as-built condition, and geo-reference the construction elements. A set of panoramic pictures is generated by laser scanning that allows for taking measurements and extracting 3D coordinates. An XML file that contains geo-reference information is appended to each panoramic picture. Using application programming interface (API), this information is referenced to a web mapping service. A case study of the CTA Red line Tunnel in Chicago, IL demonstrates this method in a real life project.
Highlights
Good as-built documentation has the potential to be very valuable to the owners and operators of infrastructure facilities and to all stakeholders in large infrastructure projects
A set of panoramic pictures composed of point cloud data is generated by laser scanning that allows for taking measurements and extracting 3D coordinates
Using application programming interface (API), this information is referenced to a web mapping service
Summary
Good as-built documentation has the potential to be very valuable to the owners and operators of infrastructure facilities and to all stakeholders in large infrastructure projects. Compared with the traditional topographic survey method, such as total station and digital photogrammetric documentation, laser scanning technology has a great advantage. Documentation with a total station could be an option, but the advantage of laser scanning is that millions of points of the complete object are provided whereas measurements with a. By delivering millions of those accurate point clouds, it is easy to make a geo-referenced 3D model for better visualization This can be part of a system used onsite for functions like work order issuance or inventory management, or transferred to government agencies for use in their systems. The peer-review was conducted on the basis of the abstract Web mapping services such as Google Map and Bing Map have great potential to improve the construction activities and as-built documentation. A case study of the CTA Red line tunnel in Chicago, IL demonstrates this method in a real life project
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