Deformation Monitoring of Ancient Pagodas Based on Multi-Layer Central-Axis Point Fitting

This paper proposes a new method for tilt measurement and quality evaluation of ancient pagodas. To address the difficulty of determining deformation-measurement feature points caused by the tapering of successive pagoda tiers and the blurred edges of bracket sets and eaves, a circle-fitting method is proposed to determine the central-axis point of each pagoda tier. In fitting the pagoda’s central axis, the total least squares method is introduced for adjustment computation, overcoming the problem of errors in the coefficient matrix. In addition to computing the overall tilt of the pagoda, the tilt and torsion of each tier are also computed to reflect the pagoda’s deformation in detail. Compared with the traditional deformation-detection method that simply uses the relative displacement between the pagoda top and base together with the pagoda height to compute the tilt, the detection method based on multi-layer central-axis point fitting reflects the pagoda’s deformation more accurately and in greater detail.

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