Large-scale in-plane movement estimation of floating covers using UAV photogrammetry

Unmanned aerial vehicle (UAV) assisted photogrammetry has been used to perform a noncontact measurement of the covers on the anaerobic wastewater lagoons at Melbourne Water Corporation's Western Treatment Plant (WTP). These floating covers are a valuable asset that eliminate odour and greenhouse gas emissions and harvest the methane-rich biogas as a renewable resource to generate electricity. Hence, the state of deformation of the floating covers becomes an important engineering factor for structural integrity assessment. UAVs have been deployed to scan these covers and photogrammetry has been used to process the aerial images to construct the floating covers' orthophoto and digital elevation model (DEM). This paper proposes to adopt the finite element formulation to improve the quantification of the in-plane movement of a floating cover. Distinguishable features on the floating cover are first identified and their (x, y and z) coordinates are recorded over time. The results show that the technique can be used to quantify the short term and long term relative global lateral movement of the floating covers at WTP. More importantly, the results not only highlight the usefulness of this analysis for the integrity management of the floating cover, but also show the need for clearly defined markers on the floating cover to facilitate the calculation of the cover state of strain.