Applied photogrammetry for 3D modeling, quantity surveying, and augmented reality in construction.

摘要

This research establishes a 3D modeling method based on the mechanism of photogrammetry to ease the effort in providing model ingredients for visualizing main processes and major products in construction operations. Differing from the conventional computer-aided design (CAD) or virtual reality (VR) modeling, the proposed method utilizes a digital camera to capture site images and analytically processes the image data into a 3D model of an object, which largely alleviates the efforts of preparing the design drafts or geometry specifications of the modeling object. A precast facade is modeled under practical constraints to verify the method. The method is useful particularly when the design drafts or geometry specifications of the modeling objects are unavailable or the modeling objects are inaccessible for direct measurement due to safety concerns.;The photo-based 3D modeling method provides an alternative to taking geometric measurements on building products. In contrast with the conventional measurement tape, applying photogrammetry is cost-effective and safe as the measurements are conducted on the 3D model of an object resulting from photos, instead of on the object itself. Accordingly, the proposed method is conducive to measuring the building elements situated in hazardous areas and quickly checking the dimensions of prefabricated units on site for quality control purposes. The 95% limits of agreement are established to statistically characterize the accuracy level of the photo-based method against the measurement tape, resulting in [-15.30 mm, 11.39 mm]. The engineer makes the final decision on the applicability of the photo-based approach in a particular application.;Additionally, this research adapts the analytical algorithms of photogrammetry into a computationally simple yet practical method for incorporating computer-generated 3D as-built graphics of invisible underground infrastructure into site photos, resulting in a richer and more integral view of the site situation. Previous photo-augmenting methods require both the camera's position and orientation to be determined on site. The new method simplifies the superimposition of a view taken from a 3D virtual model onto an actual photo by analytically fixing the camera's orientation with the coordinates of two reference points only, namely, the camera station position and the object focus position. The new approach is applied to superimpose as-built models of infrastructure onto site photos in order to facilitate quality check of bored pile excavation and progress visualization of micro-tunneling construction.