Inexpensive photogrammetry applied to displacement measurement of a gridshell

Abstract

Gridshells are unexploited structures, over which lengths measurement are difficult to do due to their size and complex curvature. To deformation measurement on a timber gridshell beam and on an entire gridshell, we used an affordable photogrammetry system that consisted of a consumer-level camera, a tripod, a mast with a gimbal to elevate the camera, a laptop, and two photogrammetric software: PhotoModeler Scanner and Metashape. The beam was subjected to a bending test, and the gridshell was loaded with 105 kg of dead load per node on its five central nodes. The maximum error in the measurement was 1.26 mm on the beam and 3.45 mm on the gridshell, which corresponded to 0.77 ‰ error relative to the span of the beam and 0.41 ‰ relative to the length of the gridshell. Three-dimensional models obtained through the proposed method serve as dimensional data with a uniform error around the object