Viability of Photogrammetry for As-built Surveys without Control Points in Building Renovation Projects

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2013-07-23

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In recent years, it is becoming more and more common to utilize 3D modeling technology to reconstruct cultural heritages. The most common way to deliver the 3D model of an existing object is based on hands-on surveys and CAD tools which could be impractical for large or complex structure in term of time consumption and cost. Recently, laser scanning technology and more automated photogrammetric modeling methods become available, and making the 3D reconstruction process of real world objects easier. Photogrammetry is one of the most cost-effective approaches we could use to gather the physical information of an object, such as size, location, and appearance. Also, the operation of the equipment of photogrammetry, which is a camera, is very easy and cost-effective. However, it also has its drawback, which is mainly caused the outcome?s low accuracy level. Accurate drawings or models only have been achieved with other approaches, such as 3D laser scanning or total station.

The 3D model of the Francis Hall at Texas A&M University, which will be renovated soon, was created in order to investigate whether the image-based 3D model produced using photogrammetry technology would be acceptable or not for the use in renovation projects. For this investigation, the elapsed time for data acquisition and 3D modeling was measured. The accuracy level of the image-based 3D model and the deficiencies of this approach were also recorded. Then, the image-based 3D model of Francis Hall was presented in the BIM CAVE to four industry professionals and one graduate student. The regular 3D model of the Francis Hall, which was created, using dimensions extracted from 2D drawings, was also presented to the interviewees in the BIM CAVE. After watching two different 3D models (image-based 3D model and regular 3D model) of the same Francis Hall, five interviewees were requested to describe the differences they noticed between image-based 3D model and regular 3D model presented in the BIM CAVE.

By reviewing and analyzing the data from interviews. Following conclusions could be made. First, the image-based 3D model of Francis Hall gave people more feeling of reality than the traditional CAD drawings or BIM models. Second, the image-based 3D model could be used for saving travels, showing details, improving coordination, improving design, facilities management tool, and marketing tool. Third, in order to make it practical for the industry, the time consumption and cost of generating the image-based 3D model should be at least equivalent to time consumption and cost for architects to conduct survey and generate CAD drawings or BIM model.

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