Fundamental study on the estimation of overturning ratio of tombstones by image analysis of aerial photographs

Abstract

As a method to estimate seismic intensity, the overturning ratio of tombstones in a cemetery has been used widely in Japan. In this study, the overturning ratio of tombstones due to an earthquake is estimated based on an image analysis of aerial photographs. It is possible to extract only notable edges from an image by removing noise. Then the displaced tombstones can be detected through the distribution of edge direction. In order to establish an estimation formula for the overturning ratio of tombstones, the direction of sunlight and the resolution of the photograph should be considered properly in a future research.