Application Of 3D Laser Geometry Acquiring Based On The Requirement Of Ancient Architecture Conservation And Renovation

The long history of Chinese culture left us with a wealth of historical architectural resources.As of 2016,the State Council announced a total of 4296 major historical and cultural sites protected at the national level,more than 10,000 sites at the provincial level,as well as hundreds of thousands of city and county level sites and immovable cultural relics.Meanwhile,China's cultural relics are widespread all over the country,which brought the problem of massive work requirements on conservation and renovation,as well as information collection.However,the number of professionals on cultural relic protection in China is obviously not enough.In addition,wood-based Chinese ancient architectures are difficult to save.Wood is perishable and flammable,in the event of natural damage or human damage,the loss on research and cultural value is immeasurable,and never reversible.Therefore,at this stage,to reduce the harm and risk of loss,it is necessary to manage the preservation of cultural relics,as well as surveying and mapping work.The traditional surveying and mapping for ancient architectures are taking the traditional tools such as ruler,tape and other traditional tools,as well as total station,laser range finder and other mapping tools to carry out single-point acquisition and mapping of the key location of the ancient architectures,the efficiency is low,and there are strong human intervention.3D laser scanning technology occurred in 1990 s,which can scan and measuring subjects through high-speed laser-intensive dotting,the spatial position information can be collected quickly and massively.At the same time,its features of non-contact,digital and automotive also have a natural advantage in the field of digital protection of ancient architecture and heritage.The technology has drawn more and more attention in the international cultural heritage protection industry,and successfully practiced in many cultural relics protection works.Although the technology has been introduced into Chinese ancient architecture surveying and mapping,and a large number of cultural relics have been collected and surveyed in recent ten years,due to the lack of professionals and industry standards,as well as the rapid upgrading of technology,3D laser scanning technology has not been applied to the ancient Chinese architectural protection work on the whole,as well as lacking of specific research.Especially in ancient Chinese architecture scanning surveying and mapping,the problem that method is not applicable and the results are not practical are generally exist.Therefore,it is very important and necessary to carry out the research on the appropriate method,process and application of 3D laser scanning technology in the face of the current contradiction of the large number of cultural relics and the serious lack of protection personnel.Based on the study of precision and station placement,which are often misused in the field of 3D laser technology,the paper classifies and studies the combination of theoretical research and experiment and the combination of actual demand and practice according to the surveying and mapping standard of ancient Chinese architectural protection:(1)Through the principle analysis and field experiment,to deeply understand the most important precision issue of 3D laser acquisition technology applied in the field of surveying and mapping,to find the factors that affect the measurement accuracy,and summarize the appropriate method to improve the accuracy of surveying and mapping.(2)According to the requirements of ancient Chinese wooden architectures protection,surveying and mapping,through the introduction of traditional measurement standards,on the basis of meeting the data preservation accuracy and authenticity,to study the systematic station placement scheme,and to develop three-dimensional acquisition scheme combined with equipment performance and characteristics for ancient architectures.(3)Through designing an experiment,to verify the influencing factors of the accuracy of the three-dimensional data stitching,and to study the influence of the point cloud format,the ratio of the extraction ratio on the precision of stitching,as well as the comparison of the automatic splicing precision of the different mainstream point cloud platform,and verifies the necessity of the applying of overall control network in the three-dimensional acquisition.(4)Through experiments to study the storage methods of cloud data in different formats,to understand the storage principle and compression method of massive data,and to choose the appropriate storage format and compression method.Using the displacement mapping technology to change the traditional data compression method,and through dimension reduction to improve the data compression ratio,for the effective optimization of massive data to make it suitable for ancient Chinese architecture,especially for the huge scale of the call,application and research for the official building.(5)According to the rigid requirements of ancient Chinese architectural protection and renovation,summarize current methods of transforming 3D scanning data to Auto CAD vector engineering drawing;strengthen the applicability and practicability of 3D scanning technology in the field of ancient architecture protection,to solve the storage needs of massive architectural materials at this stage.In the course of this research,Beijing University of Technology has the honor to undertake the digital collection and storage project of 85 key cultural relics protection units in Beijing,for a total of 1097 single buildings,which are led by Beijing Municipal Administration of Cultural Heritage.The project provides a wealth of valuable practical experience and research samples for optimization and research of data collection.