Development of sampling moire camera for landslide prediction by small displacement measurement

Abstract

The ability to measure the small displacement caused by a landslide is important. If it were possible to measure the displacement before the landslide occurs, people would be able to evacuate before the landslide occurs and reach a safe area. Therefore, we developed a detection system using the small displacement measurement of a landslide. This system uses a displacement measurement technique known as the sampling moire method. This method is capable of analyzing the phase values from one image of a grating pattern. Because of this, the detection system is very simple and compact. In addition, it analyzes displacement very accurately. The phase is calculated from several phase-shifted method fringe patterns that are obtained by changing the sampling phase. The displacement is analyzed by determining the difference in the phase before and after displacement. However, the displacement results contain errors such as stir and air turbulence, which complicate landslide prediction. The level of error can be decreased by taking the averages of displacement that contain errors. Therefore, we developed a sampling moire camera that is capable of rapidly, acquiring images and performing a high-speed analysis. The sampling moire camera uses sampling moire method to analyzing the phase. In this paper, we describe the sampling moire camera's ability to predict landslides by measuring small displacement. We also conduct experiments that test the system.