Strategies to model complex architectural objects using Unmanned Aerial Systems (UAS)

The use of Unmanned Aerial Systems (UAS) and photogrammetry are becoming attractive for creating three-dimensional (3D) models in many surveying applications of construction engineering. Although several researchers have introduced and evaluated UAS and photogrammetry technologies' potential in various applications such as earthwork surveying and building components modeling, there is still a lack of a comprehensive investigation of the UAS and photogrammetry applications from the perspective of practice. This paper aims at identifying and summarizing the optimal strategies of 3D mapping and modeling for existing buildings regarding the efficiency and accuracy from field experiments at a facility in Kentucky. The strategies discussed in this paper involve the development of the UAS images acquisition plans and the selection of data processing options for point cloud model using the Pix4D software program. For a complex structure, the efficiency relates to the number of image locations needed to model the object with its geometrically complex components and the number of subprojects that will be merged for faster processing. The accuracy is evaluated through the measurements comparisons and the effect of visualizations. The experiment results and illustrations are useful as a reference for researchers and practitioners in need of guidance to efficiently implement UAS and photogrammetry technology for their applications.