ISHIGAKI Retrieval through Combinatorial Optimization

Ando, Shigehiro; Koutaki, Gou; Shirai, Kohji

doi:10.1145/3347317.3357241

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…Furthermore, the pre-collapse and post-collapse stones needed to be mapped on a one-to-one basis, and it was necessary to solve the problem similar to solving a jigsaw puzzle Ando et al (2019).…”

Section: Challenge and Our Contributionsmentioning

confidence: 99%

ISHIGAKI Retrieval System Using 3D Shape Matching and Combinatorial Optimization

et al. 2022

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In April 2016, a massive earthquake with a magnitude of 7.3 struck Kumamoto region, Japan, causing major devastation. One of the structures that were damaged in Kumamoto was Kumamoto Castle, a cultural asset of great significance in Japan. The stone retaining wall “ishigaki” that formed the foundation of the castle collapsed, and the superstructure was destroyed. The number of stones is estimated to be more than 70,000, and restoration work is anticipated to take more than 20 years. Since each of the stones is an important cultural asset, the broken stone structure needed to be restored to its original state in order not to lose its cultural value forever. In addition, the fallen stones need to be returned to their original positions in the ishigakis. In similar cases, non-automatic visual verification was used. However, for Kumamoto Castle, this would have been impossible because a large number of stones were displaced as a result of the collapse. The purpose of this project is to provide support for the restoration work by matching the stones that fell down after the collapse with those before the collapse using information technology, such as computer vision and optimization technologies. Specifically, we captured photographic images of the stones before and after the collapse to match them. The technical contributions of this study are as follows: (a) To estimate the scale and surface orientation of the stones, we exploit 3D model construction from the images. (b) To solve the jigsaw-puzzle-like problem of reassembling the stone fragments, we exploit the combination of a customized iterative closest point (ICP) algorithm for shape position matching and an assignment algorithm to find the best pairs of stones before and after the collapse by using the matching degree obtained from ICP. Here, only the 2D shape of the stones before the collapse can be used due to the small number of photos available. In contrast, a detailed 3D shape can be obtained from the stones after their collapse. We matched these asymmetric data in 2D and 3D to enable a comprehensive reconstruction. (c) We developed a user-friendly graphical user interface system that was used by actual masons without special knowledge. The developed system was used to match the ishigaki of a turret, Iidamaru. As a result, we succeeded in identifying 337 stones, or approximately 90% of the 370 images. These results are expected to be useful for and were used as a blueprint during actual restoration work.

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Section: Challenge and Our Contributionsmentioning

confidence: 99%

ISHIGAKI Retrieval System Using 3D Shape Matching and Combinatorial Optimization

et al. 2022

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Analysis of Measuring Precision of 3D Model of Ishigaki Stone in Kumamoto Castle Using Automatic CMG Crane System

Matsunaga¹,

Kuwahara²,

Okajima³

et al. 2022

JRM

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Kumamoto Castle, consisting of towers and stone walls called Ishigaki, was severely damaged by the 2016 Kumamoto earthquake. As this castle has cultural significance in Japan, the damaged stone walls of the castle need to be promptly and accurately restored. In recent years, the utilization of 3D stone data has been studied to determine the position of collapsed stones precisely. The 3D stone data needs to be measured automatically in a short period of time for the efficient restoration of stone walls. To control the attitude of the stone, a small control moment gyro (CMG) device was proposed, and a robust controller with a model error compensator was applied to the CMG device. In this study, the measurement precision of a 3D model of stones using the CMG crane system was analyzed. The automatic measuring system consists of a CMG device and an elevator for a 3D scanner to reduce the load on workers. The scanning motion was planned automatically based on the shape and position of stones using depth sensors. The effectiveness of the proposed measuring system was evaluated using the accuracy and measurement time including the data correction time of the 3D modeling.

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ISHIGAKI Retrieval through Combinatorial Optimization

Cited by 2 publications

References 3 publications

ISHIGAKI Retrieval System Using 3D Shape Matching and Combinatorial Optimization

ISHIGAKI Retrieval System Using 3D Shape Matching and Combinatorial Optimization

Analysis of Measuring Precision of 3D Model of Ishigaki Stone in Kumamoto Castle Using Automatic CMG Crane System

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