Tilt monitoring of tower based on video-photogrammetry

Abstract

The tilt of a tower is an important indicator in its health assessment. In particular, for an ancient tower, continuous tilt monitoring is necessary because of the long history of earthquakes and other factors. We propose a continuous tilt monitoring method for a tower based on video-photogrammetry. This method applies video-photogrammetric technology to obtain 3D coordinates of monitoring points, and then the inclination of the tower is estimated from the deflection of the space vector or space plane, which is fitted by suitable monitoring points. This inclination calculation method, which is a simple and convenient way to obtain the tilt of a tower during its monitoring, only uses the coordinate information of a limited number of monitoring points in images. To verify the effectiveness of the tilt monitoring method, an indoor experiment on a tower model and an outdoor experiment on Kuiguang Pagoda were carried out. In the indoor experiment, the tilting of a tower was simulated, and the whole process was photographed through a video-photogrammetric system. The tilt of the model tower was calculated to gradually increase from 0 to 2.5°, which was consistent with the actual tilt. The outdoor experiment involved the monitoring of the tilt of Kuiguang Pagoda in Dujiangyan City for about six months. It was found that Kuiguang Pagoda had no obvious tilt and was basically in a stable state during the monitoring period. The experimental results demonstrate the effectiveness of the method for tower tilt monitoring and show that video-photogrammetry is an alternative technique for tower tilt monitoring.