Application of a multi-smartphone measurement system in slope model tests

Physical model tests are considered to be useful tools and are widely used in landslide research. The three-dimensional (3D) surface deformation of slope models provides useful information for investigating the behaviour and mechanism of landslides. In this study, a measurement system called a multi-smartphone measurement (MSM) system was proposed and developed to measure the 3D surface deformation of slope models. This system includes nine identical smartphones, a USB hub, a control software package, and some postprocessing software. A series of high-quality images were simultaneously captured through the hardware devices and subsequently processed by using postprocessing software including 3D reconstruction and particle image velocimetry. A comparison with the results of a laser scanner was performed, and the performance of the MSM system was tested in two static models and one dynamic slope model. The system's accuracy was assessed using the root mean square error (RMSE) of the cloud-to-cloud distance. The results show that the accuracy of the MSM system for both the static and dynamic models is less than 1.1 mm. A short-period, low-cost, and easy-to-build system with millimetre accuracy has the potential to become a popular approach for measuring slope models. In addition, the performance of the MSM system is illustrated in three example applications.