Browsing the WeChat official account “Hangzhou Historical Buildings” and scanning the quick response code, you will see the three-dimensional architectural model of the Hangzhou Society of Calligraphy and Painting in the Cultural and Historical Block of Wuliu Alley. This building was formerly the 33rd Building, Doufu 2nd Bridge constructed in the period of the Republic of China. In 2018, it became one of the 4th historical buildings in Hangzhou.

A few days ago, it was the first time that 3 historical buildings were surveyed, mapped, and archived in three dimensions in Hangzhou by three-dimensional laser scanning, oblique photography, panoramic imaging, and other technologies. Hangzhou has entered a new era of digital protection.

In January 2019, the Regulations on Surveying and Mapping Achievements in Historical Buildings were formally promulgated. "These standards have laid a foundation for digital surveying, mapping, and archiving of historical buildings so that regulations are available for digital surveying and mapping," said Lou Shu, who works as Senior Engineer in Hangzhou Center for Protecting and Managing Historical Buildings.

Compared with traditional surveying and mapping methods, digital surveying, mapping, and archiving are more efficient, precise, and complete. Take the 33rd Building in Doufu 2nd Bridge for example. This building is a two-story conventional residential building. It covers an area of 451m2 and a gross floor area of 527㎡. It approximately takes 6 hours to acquire data on the spot, and the efficiency is folded higher than that of traditional surveying and mapping. Besides, by three-dimensional laser scanning, three-dimensional data of historical buildings, including inclination angle of walls, pillar inclination, and flexural strength of beam frames, can be accurately acquired with a precision of millimeters. Compared with other surveying and mapping techniques, three-dimensional laser scanning can detect hidden hazards of structural deformation in historical buildings more easily, providing high-precision data for protection, repair, and routine maintenance of historical buildings.

As project team leader of Guangzhou Sikan Surveying and Mapping Technology Co., Ltd, Zhang Wenyang has reported that point cloud processing technology is useful for analysis of slices or physical conversion of models, and the models cannot only be used for drawing, but also for three-dimensional printing.  

Hangzhou is gradually constructing an information management system for historical buildings, in order to look up and statistically analyze basic information of historical buildings, including location, number, name, and address. This system will technologically guarantee future revitalization and utilization of historical buildings. It will be favorable for carrying forward and inheriting historical cultures.

(Compiled by Xu Yuhong)