A novel measurement method based on silhouette for chimney quasi-static deformation monitoring

The monitoring of chimney quasi-static deformation is a difficult problem in that chimneys have the following characteristics; such as no direct way to survey, the rough surface and the lack of texture information. In this paper, we propose a novel method in surveying chimney horizontal quasi-static displacement based on the silhouette of chimney. The basic principle is that the tangent points of the sight lines and sections of the chimney are definitely projected at the outlines of the chimney in images. For a given elevation, space section’s circle radius and center point coordinates are easily surveyed by such silhouette-based method including steps such as chimney-oriented photography, outline detection, optimal-image selection, initial value estimation, and iteration for exact value. The experiment result shows that the relative accuracy of our method is superior to 1/25,000 and time consuming of field work is less than half a day. Compared with the existing techniques, the method proposed in this paper is not only more efficient and accurate, but also can realize the successive measurement of chimney section.